Introduce a method based on function tracer to trace any object and get the value of the object dynamically. the object can be obtained from the dynamic event (kprobe_event/uprobe_event) or the static event(tracepoint).
Usage: When using the kprobe event, only need to set the objtrace(a new trigger), we can get the value of the object. The object is from the setting of the kprobe event.
For example: For the function bio_add_page():
int bio_add_page(struct bio *bio, struct page *page, unsigned int len, unsigned int offset)
Firstly, we can set the base of the object, thus the first string "arg1" stands for the value of the first parameter of this function bio_add_gage(),
# echo 'p bio_add_page arg1=$arg1' > ./kprobe_events
Secondly, we can get the value dynamically based on above object.
find the offset of the bi_size in struct bio: $ gdb vmlinux (gdb) p &(((struct bio *)0)->bi_iter.bi_size) $1 = (unsigned int *) 0x28
# echo 'objtrace:add:arg1,0x28:u32:1 if comm == "cat"' > ./events/kprobes/ \ p_bio_add_page_0/trigger
# cd /sys/kernel/debug/tracing/ # echo 'p bio_add_page arg1=$arg1' > ./kprobe_events # echo 'objtrace:add:arg1,0x28:u32:1 if comm == "cat"' > ./events/kprobes/p_bio_add_page_0/trigger
# du -sh /test.txt 12.0K /test.txt
# cat /test.txt > /dev/null # cat ./trace # tracer: nop # # entries-in-buffer/entries-written: 128/128 #P:4 # # _-----=> irqs-off/BH-disabled # / _----=> need-resched # | / _---=> hardirq/softirq # || / _--=> preempt-depth # ||| / _-=> migrate-disable # |||| / delay # TASK-PID CPU# ||||| TIMESTAMP FUNCTION # | | | ||||| | | cat-117 [002] ...1. 1.602243: __bio_try_merge_page <-bio_add_page object:0xffff88811bee4000 value:0x0 cat-117 [002] ...1. 1.602244: __bio_add_page <-bio_add_page object:0xffff88811bee4000 value:0x0 cat-117 [002] ...2. 1.602244: bio_add_page <-ext4_mpage_readpages object:0xffff88811bee4000 value:0x1000 cat-117 [002] ...1. 1.602245: __bio_try_merge_page <-bio_add_page object:0xffff88811bee4000 value:0x1000 cat-117 [002] ...1. 1.602245: __bio_add_page <-bio_add_page object:0xffff88811bee4000 value:0x1000 cat-117 [002] ...2. 1.602245: bio_add_page <-ext4_mpage_readpages object:0xffff88811bee4000 value:0x2000 cat-117 [002] ...1. 1.602245: __bio_try_merge_page <-bio_add_page object:0xffff88811bee4000 value:0x2000 cat-117 [002] ...1. 1.602245: __bio_add_page <-bio_add_page object:0xffff88811bee4000 value:0x2000 cat-117 [002] ...1. 1.602245: submit_bio <-ext4_mpage_readpages object:0xffff88811bee4000 value:0x3000 cat-117 [002] ...1. 1.602245: submit_bio_noacct <-ext4_mpage_readpages object:0xffff88811bee4000 value:0x3000 cat-117 [002] ...1. 1.602246: __submit_bio <-submit_bio_noacct object:0xffff88811bee4000 value:0x3000 cat-117 [002] ...1. 1.602246: submit_bio_checks <-__submit_bio object:0xffff88811bee4000 value:0x3000 cat-117 [002] ...1. 1.602246: __cond_resched <-submit_bio_checks object:0xffff88811bee4000 value:0x3000 cat-117 [002] ...1. 1.602246: should_fail_bio <-submit_bio_checks object:0xffff88811bee4000 value:0x3000 cat-117 [002] ...1. 1.602246: blk_mq_submit_bio <-submit_bio_noacct object:0xffff88811bee4000 value:0x3000 cat-117 [002] ...1. 1.602246: blk_attempt_plug_merge <-blk_mq_submit_bio object:0xffff88811bee4000 value:0x3000 cat-117 [002] ...1. 1.602246: blk_mq_sched_bio_merge <-blk_mq_submit_bio object:0xffff88811bee4000 value:0x3000 cat-117 [002] ...1. 1.602247: __rcu_read_lock <-blk_mq_submit_bio object:0xffff88811bee4000 value:0x3000 cat-117 [002] ...1. 1.602247: __rcu_read_unlock <-blk_mq_submit_bio object:0xffff88811bee4000 value:0x3000 cat-117 [002] ...1. 1.602247: __blk_mq_alloc_requests <-blk_mq_submit_bio object:0xffff88811bee4000 value:0x3000 <idle>-0 [002] d..3. 1.602298: bio_endio <-blk_update_request object:0xffff88811bee4000 value:0x0 <idle>-0 [002] d..3. 1.602298: mpage_end_io <-blk_update_request object:0xffff88811bee4000 value:0x0 <idle>-0 [002] d..3. 1.602298: __read_end_io <-blk_update_request object:0xffff88811bee4000 value:0x0 <idle>-0 [002] d..3. 1.602300: bio_put <-blk_update_request object:0xffff88811bee4000 value:0x0 <idle>-0 [002] d..3. 1.602300: bio_free <-blk_update_request object:0xffff88811bee4000 value:0x0 <idle>-0 [002] d..3. 1.602300: mempool_free <-blk_update_request object:0xffff88811bee4000 value:0x0 <idle>-0 [002] d..3. 1.602300: mempool_free_slab <-blk_update_request object:0xffff88811bee4000 value:0x0 <idle>-0 [002] d..3. 1.602300: kmem_cache_free <-blk_update_request object:0xffff88811bee4000 value:0x0 ...
Almost all changelogs were suggested by Masami(mhiramat@kernel.org) and steve(rostedt@goodmis.org), thank you all so much.
v13: - remove the 's' type, since the objtrace event doesn't show the value with sign - change the [3/4] tag with 'selftests/ftrace' instead of 'trace/objtrace' - add 'Documentation:' tag for [4/4]
v12: - use the %zu to print the sizeof Reported-by: kernel test robot lkp@intel.com Suggested-by: Nathan Chancellor nathan@kernel.org
v11: - remove useless atomic counting methods for num_traced_obj - make array objtrace_fetch_types null terminated - add raw_spin_lock_init for obj_data_lock
v10: - support ftrace instances - use trace_buffer_lock_reserve instead of trace_event_buffer_lock_reserve - a lot of cleanup work has been done mainly for event_object_trigger_parse
v9: - fix objtrace trigger output was incomplete - fix the objtrace trigger was removed when using the existed parameter on event. - add testcase for the second fix above.
v8: - revert to use per-cpu recursion for the function trace_object_events_call - recover the filter when getting the value of the object - simplify the implementation for the function get_object_value - fix the build error
v7: - use fixed-size array for object pool instead of list structure - use ftrace_test_recursion_trylock for function trace hook function - fix trace_object_ref reference count in the init_trace_object - invoke exit_trace_object no matter whether data->ops->free is null in the unregister_object_trigger - release private_data of event_trigger_data in the trace_object_trigger_free - remove [RFC] tag
v6: - change the objtrace trigger syntax. - add patchset description - add <tracefs>/README
v5: - add testcasts - add check the field->size - add lockless to search object - describe the object trace more clearly in Kconfig
v4: - please ignore the v4 which is the same as v3
v3: - change the objfilter to objtrace - add a command to the objfilter syntax - change to get the value of the object - use trace_find_event_field to find the field instead of using argN - get data from @rec in the event trigger callback funciton
v2: - adding a "objfilter" trigger to update object
Jeff Xie (4): trace: Add trace any kernel object trace/objtrace: Get the value of the object selftests/ftrace: Add testcases for objtrace Documentation: trace/objtrace: Add documentation for objtrace
Documentation/trace/events.rst | 83 +++ include/linux/trace_events.h | 1 + kernel/trace/Kconfig | 10 + kernel/trace/Makefile | 1 + kernel/trace/trace.c | 11 + kernel/trace/trace.h | 21 + kernel/trace/trace_entries.h | 18 + kernel/trace/trace_events_trigger.c | 5 +- kernel/trace/trace_object.c | 611 ++++++++++++++++++ kernel/trace/trace_output.c | 40 ++ .../ftrace/test.d/trigger/trigger-objtrace.tc | 41 ++ 11 files changed, 840 insertions(+), 2 deletions(-) create mode 100644 kernel/trace/trace_object.c create mode 100644 tools/testing/selftests/ftrace/test.d/trigger/trigger-objtrace.tc
base-commit: 408d26e261b089596c0837e71d2fb4a80ea04ef3
Introduce objtrace trigger to get the call flow by tracing any kernel object in the function parameter.
The objtrace trigger makes a list of the target object address from the given event parameter, and records all kernel function calls which has the object address in its parameter.
Syntax: objtrace:add:obj[:count][if <filter>]
Usage: # echo 'p bio_add_page arg1=$arg1' > kprobe_events # cd events/kprobes/p_bio_add_page_0 # echo 'objtrace:add:arg1:1 if comm == "cat"' > ./trigger # cat /test.txt
Signed-off-by: Jeff Xie xiehuan09@gmail.com Acked-by: Masami Hiramatsu (Google) mhiramat@kernel.org --- include/linux/trace_events.h | 1 + kernel/trace/Kconfig | 10 + kernel/trace/Makefile | 1 + kernel/trace/trace.c | 11 + kernel/trace/trace.h | 21 ++ kernel/trace/trace_entries.h | 17 ++ kernel/trace/trace_events_trigger.c | 5 +- kernel/trace/trace_object.c | 450 ++++++++++++++++++++++++++++ kernel/trace/trace_output.c | 40 +++ 9 files changed, 554 insertions(+), 2 deletions(-) create mode 100644 kernel/trace/trace_object.c
diff --git a/include/linux/trace_events.h b/include/linux/trace_events.h index e6e95a9f07a5..f3645166b724 100644 --- a/include/linux/trace_events.h +++ b/include/linux/trace_events.h @@ -693,6 +693,7 @@ enum event_trigger_type { ETT_EVENT_HIST = (1 << 4), ETT_HIST_ENABLE = (1 << 5), ETT_EVENT_EPROBE = (1 << 6), + ETT_TRACE_OBJECT = (1 << 7), };
extern int filter_match_preds(struct event_filter *filter, void *rec); diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig index 2c43e327a619..30c34d43dc3f 100644 --- a/kernel/trace/Kconfig +++ b/kernel/trace/Kconfig @@ -276,6 +276,16 @@ config FUNCTION_PROFILER
If in doubt, say N.
+config TRACE_OBJECT + bool "Trace kernel object in function parameter" + depends on FUNCTION_TRACER + depends on HAVE_FUNCTION_ARG_ACCESS_API + select TRACING + default y + help + You can trace the kernel object in the kernel function parameter. + The kernel object is dynamically specified via event trigger. + config STACK_TRACER bool "Trace max stack" depends on HAVE_FUNCTION_TRACER diff --git a/kernel/trace/Makefile b/kernel/trace/Makefile index 0d261774d6f3..90ecc3c6c9d5 100644 --- a/kernel/trace/Makefile +++ b/kernel/trace/Makefile @@ -71,6 +71,7 @@ obj-$(CONFIG_FUNCTION_GRAPH_TRACER) += trace_functions_graph.o obj-$(CONFIG_TRACE_BRANCH_PROFILING) += trace_branch.o obj-$(CONFIG_BLK_DEV_IO_TRACE) += blktrace.o obj-$(CONFIG_FUNCTION_GRAPH_TRACER) += fgraph.o +obj-$(CONFIG_TRACE_OBJECT) += trace_object.o ifeq ($(CONFIG_BLOCK),y) obj-$(CONFIG_EVENT_TRACING) += blktrace.o endif diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index f400800bc910..7074ad8bc1a0 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -5627,6 +5627,9 @@ static const char readme_msg[] = "\t enable_hist:<system>:<event>\n" "\t disable_hist:<system>:<event>\n" #endif +#ifdef CONFIG_TRACE_OBJECT + "\t objtrace:add:obj[:count][if <filter>]\n" +#endif #ifdef CONFIG_STACKTRACE "\t\t stacktrace\n" #endif @@ -9272,6 +9275,9 @@ static struct trace_array *trace_array_create(const char *name) if (ftrace_allocate_ftrace_ops(tr) < 0) goto out_free_tr;
+ if (allocate_objtrace_data(tr) < 0) + goto out_free_tr; + ftrace_init_trace_array(tr);
init_trace_flags_index(tr); @@ -9291,6 +9297,7 @@ static struct trace_array *trace_array_create(const char *name)
out_free_tr: ftrace_free_ftrace_ops(tr); + free_objtrace_data(tr); free_trace_buffers(tr); free_cpumask_var(tr->tracing_cpumask); kfree(tr->name); @@ -9384,6 +9391,7 @@ static int __remove_instance(struct trace_array *tr) event_trace_del_tracer(tr); ftrace_clear_pids(tr); ftrace_destroy_function_files(tr); + free_objtrace_data(tr); tracefs_remove(tr->dir); free_percpu(tr->last_func_repeats); free_trace_buffers(tr); @@ -10118,6 +10126,9 @@ __init static int tracer_alloc_buffers(void) goto out_free_savedcmd; }
+ if (allocate_objtrace_data(&global_trace)) + goto out_free_savedcmd; + if (global_trace.buffer_disabled) tracing_off();
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h index ff816fb41e48..18220b659555 100644 --- a/kernel/trace/trace.h +++ b/kernel/trace/trace.h @@ -54,6 +54,7 @@ enum trace_type { TRACE_TIMERLAT, TRACE_RAW_DATA, TRACE_FUNC_REPEATS, + TRACE_OBJECT,
__TRACE_LAST_TYPE, }; @@ -363,6 +364,9 @@ struct trace_array { cpumask_var_t tracing_cpumask; /* only trace on set CPUs */ int ref; int trace_ref; +#ifdef CONFIG_TRACE_OBJECT + struct objtrace_data *obj_data; +#endif #ifdef CONFIG_FUNCTION_TRACER struct ftrace_ops *ops; struct trace_pid_list __rcu *function_pids; @@ -471,6 +475,7 @@ extern void __ftrace_bad_type(void); TRACE_GRAPH_RET); \ IF_ASSIGN(var, ent, struct func_repeats_entry, \ TRACE_FUNC_REPEATS); \ + IF_ASSIGN(var, ent, struct trace_object_entry, TRACE_OBJECT);\ __ftrace_bad_type(); \ } while (0)
@@ -1536,6 +1541,16 @@ static inline int register_trigger_hist_cmd(void) { return 0; } static inline int register_trigger_hist_enable_disable_cmds(void) { return 0; } #endif
+#ifdef CONFIG_TRACE_OBJECT +extern int register_trigger_object_cmd(void); +extern int allocate_objtrace_data(struct trace_array *tr); +extern void free_objtrace_data(struct trace_array *tr); +#else +static inline int register_trigger_object_cmd(void) { return 0; } +static inline int allocate_objtrace_data(struct trace_array *tr) { return 0; } +static inline void free_objtrace_data(struct trace_array *tr) { }; +#endif + extern int register_trigger_cmds(void); extern void clear_event_triggers(struct trace_array *tr);
@@ -1611,6 +1626,12 @@ extern bool event_trigger_check_remove(const char *glob); extern bool event_trigger_empty_param(const char *param); extern int event_trigger_separate_filter(char *param_and_filter, char **param, char **filter, bool param_required); +extern int register_trigger(char *glob, + struct event_trigger_data *data, + struct trace_event_file *file); +extern void unregister_trigger(char *glob, + struct event_trigger_data *test, + struct trace_event_file *file); extern struct event_trigger_data * event_trigger_alloc(struct event_command *cmd_ops, char *cmd, diff --git a/kernel/trace/trace_entries.h b/kernel/trace/trace_entries.h index cd41e863b51c..bb120d9498a9 100644 --- a/kernel/trace/trace_entries.h +++ b/kernel/trace/trace_entries.h @@ -401,3 +401,20 @@ FTRACE_ENTRY(timerlat, timerlat_entry, __entry->context, __entry->timer_latency) ); + +/* + * trace object entry: + */ +FTRACE_ENTRY(object, trace_object_entry, + + TRACE_OBJECT, + + F_STRUCT( + __field( unsigned long, ip ) + __field( unsigned long, parent_ip ) + __field( unsigned long, object ) + ), + + F_printk(" %ps <-- %ps object:%lx\n", + (void *)__entry->ip, (void *)__entry->parent_ip, __entry->object) +); diff --git a/kernel/trace/trace_events_trigger.c b/kernel/trace/trace_events_trigger.c index cb866c3141af..8bad4eb3b997 100644 --- a/kernel/trace/trace_events_trigger.c +++ b/kernel/trace/trace_events_trigger.c @@ -560,7 +560,7 @@ void update_cond_flag(struct trace_event_file *file) * * Return: 0 on success, errno otherwise */ -static int register_trigger(char *glob, +int register_trigger(char *glob, struct event_trigger_data *data, struct trace_event_file *file) { @@ -605,7 +605,7 @@ static int register_trigger(char *glob, * Usually used directly as the @unreg method in event command * implementations. */ -static void unregister_trigger(char *glob, +void unregister_trigger(char *glob, struct event_trigger_data *test, struct trace_event_file *file) { @@ -1976,6 +1976,7 @@ __init int register_trigger_cmds(void) register_trigger_enable_disable_cmds(); register_trigger_hist_enable_disable_cmds(); register_trigger_hist_cmd(); + register_trigger_object_cmd();
return 0; } diff --git a/kernel/trace/trace_object.c b/kernel/trace/trace_object.c new file mode 100644 index 000000000000..19ec4b1c0186 --- /dev/null +++ b/kernel/trace/trace_object.c @@ -0,0 +1,450 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * trace the kernel object in the kernel function parameter + * Copyright (C) 2021 Jeff Xie xiehuan09@gmail.com + */ + +#define pr_fmt(fmt) "trace_object: " fmt + +#include "trace_output.h" + +#define MAX_TRACED_OBJECT 5 +#define OBJTRACE_CMD_LEN 16 +#define OBJTRACE_CMD_ADD "add" +static LIST_HEAD(obj_data_head); +static const int max_args_num = 6; +static void exit_trace_object(struct trace_array *tr); +static int init_trace_object(struct trace_array *tr); + +struct object_instance { + void *obj; + struct trace_array *tr; +}; + +/* objtrace private data */ +struct objtrace_trigger_data { + struct ftrace_event_field *field; + char objtrace_cmd[OBJTRACE_CMD_LEN]; + struct trace_array *tr; +}; + +/* objtrace data with fops and objtrace_instances */ +struct objtrace_data { + struct list_head head; + struct trace_array *tr; + struct ftrace_ops fops; + int num_traced_obj; + struct object_instance traced_obj[MAX_TRACED_OBJECT]; + raw_spinlock_t obj_data_lock; +}; + +static struct objtrace_data *get_obj_data(struct trace_array *tr) +{ + struct objtrace_data *obj_data = NULL; + + list_for_each_entry(obj_data, &obj_data_head, head) { + if (obj_data->tr == tr) + break; + } + return obj_data; +} + +static bool object_exist(void *obj, struct trace_array *tr) +{ + int i, max; + struct objtrace_data *obj_data; + + obj_data = get_obj_data(tr); + if (!obj_data) + return false; + + max = READ_ONCE(obj_data->num_traced_obj); + smp_rmb(); + for (i = 0; i < max; i++) { + if (obj_data->traced_obj[i].obj == obj) + return true; + } + return false; +} + +static bool object_empty(struct trace_array *tr) +{ + struct objtrace_data *obj_data; + + obj_data = get_obj_data(tr); + if (!obj_data) + return false; + + return !READ_ONCE(obj_data->num_traced_obj); +} + +static void set_trace_object(void *obj, struct trace_array *tr) +{ + unsigned long flags; + struct object_instance *obj_ins; + struct objtrace_data *obj_data; + + if (in_nmi()) + return; + + if (!obj && object_exist(obj, tr)) + return; + + obj_data = get_obj_data(tr); + if (!obj_data) + return; + + /* only this place has write operations */ + raw_spin_lock_irqsave(&obj_data->obj_data_lock, flags); + if (READ_ONCE(obj_data->num_traced_obj) == MAX_TRACED_OBJECT) { + trace_array_printk_buf(tr->array_buffer.buffer, _THIS_IP_, + "object_pool is full, can't trace object:0x%px\n", obj); + goto out; + } + obj_ins = &obj_data->traced_obj[READ_ONCE(obj_data->num_traced_obj)]; + obj_ins->obj = obj; + obj_ins->tr = tr; + /* make sure the num_traced_obj update always appears after traced_obj update */ + smp_wmb(); + obj_data->num_traced_obj++; +out: + raw_spin_unlock_irqrestore(&obj_data->obj_data_lock, flags); +} + +static void submit_trace_object(unsigned long ip, unsigned long parent_ip, + unsigned long object, struct trace_array *tr) +{ + + struct trace_buffer *buffer = tr->array_buffer.buffer; + struct ring_buffer_event *event; + struct trace_object_entry *entry; + unsigned int trace_ctx = 0; + + trace_ctx = tracing_gen_ctx(); + event = trace_buffer_lock_reserve(buffer, TRACE_OBJECT, + sizeof(*entry), trace_ctx); + if (!event) + return; + entry = ring_buffer_event_data(event); + entry->ip = ip; + entry->parent_ip = parent_ip; + entry->object = object; + + trace_buffer_unlock_commit(tr, buffer, event, trace_ctx); +} + +static void +trace_object_events_call(unsigned long ip, unsigned long parent_ip, + struct ftrace_ops *op, struct ftrace_regs *fregs) +{ + struct pt_regs *pt_regs = ftrace_get_regs(fregs); + struct trace_array *tr = op->private; + struct trace_array_cpu *data; + unsigned long obj; + long disabled; + int cpu, n; + + preempt_disable_notrace(); + + cpu = raw_smp_processor_id(); + data = per_cpu_ptr(tr->array_buffer.data, cpu); + disabled = atomic_inc_return(&data->disabled); + if (likely(disabled == 1)) { + if (object_empty(tr)) + goto out; + for (n = 0; n < max_args_num; n++) { + obj = regs_get_kernel_argument(pt_regs, n); + if (object_exist((void *)obj, tr)) + submit_trace_object(ip, parent_ip, obj, tr); + /* The parameters of a function may match multiple objects */ + } + } +out: + atomic_dec(&data->disabled); + preempt_enable_notrace(); +} + +static void +trace_object_trigger(struct event_trigger_data *data, + struct trace_buffer *buffer, void *rec, + struct ring_buffer_event *event) +{ + struct objtrace_trigger_data *obj_data = data->private_data; + struct trace_array *tr = obj_data->tr; + struct ftrace_event_field *field; + void *obj = NULL; + + field = obj_data->field; + memcpy(&obj, rec + field->offset, sizeof(obj)); + set_trace_object(obj, tr); +} + +static void +trace_object_trigger_free(struct event_trigger_data *data) +{ + struct objtrace_trigger_data *obj_data = data->private_data; + + if (WARN_ON_ONCE(data->ref <= 0)) + return; + + data->ref--; + if (!data->ref) { + exit_trace_object(obj_data->tr); + kfree(data->private_data); + trigger_data_free(data); + } +} + +static void +trace_object_count_trigger(struct event_trigger_data *data, + struct trace_buffer *buffer, void *rec, + struct ring_buffer_event *event) +{ + if (!data->count) + return; + + if (data->count != -1) + (data->count)--; + + trace_object_trigger(data, buffer, rec, event); +} + +static int +event_trigger_print(const char *name, struct seq_file *m, + void *data, char *filter_str, void *objtrace_data) +{ + long count = (long)data; + struct objtrace_trigger_data *obj_data = objtrace_data; + + seq_puts(m, name); + + seq_printf(m, ":%s", obj_data->objtrace_cmd); + seq_printf(m, ":%s", obj_data->field->name); + + if (count == -1) + seq_puts(m, ":unlimited"); + else + seq_printf(m, ":count=%ld", count); + + if (filter_str) + seq_printf(m, " if %s\n", filter_str); + else + seq_putc(m, '\n'); + + return 0; +} + +static int event_object_trigger_init(struct event_trigger_data *data) +{ + struct objtrace_trigger_data *obj_data = data->private_data; + int ret; + + if (!data->ref) { + ret = init_trace_object(obj_data->tr); + if (ret) + return ret; + } + data->ref++; + return 0; +} + +static int +trace_object_trigger_print(struct seq_file *m, struct event_trigger_data *data) +{ + return event_trigger_print("objtrace", m, (void *)data->count, + data->filter_str, data->private_data); +} + +static struct event_trigger_ops objecttrace_trigger_ops = { + .trigger = trace_object_trigger, + .print = trace_object_trigger_print, + .init = event_object_trigger_init, + .free = trace_object_trigger_free, +}; + +static struct event_trigger_ops objecttrace_count_trigger_ops = { + .trigger = trace_object_count_trigger, + .print = trace_object_trigger_print, + .init = event_object_trigger_init, + .free = trace_object_trigger_free, +}; + +static struct event_trigger_ops * +objecttrace_get_trigger_ops(char *cmd, char *param) +{ + return param ? &objecttrace_count_trigger_ops : &objecttrace_trigger_ops; +} + +static bool field_exist(struct trace_event_file *file, + struct event_command *cmd_ops, + const char *field_name) +{ + struct event_trigger_data *data; + struct objtrace_trigger_data *obj_data; + + lockdep_assert_held(&event_mutex); + + list_for_each_entry(data, &file->triggers, list) { + if (data->cmd_ops->trigger_type == cmd_ops->trigger_type) { + obj_data = data->private_data; + if (!strcmp(obj_data->field->name, field_name)) + return true; + } + } + + return false; +} + +static int +event_object_trigger_parse(struct event_command *cmd_ops, + struct trace_event_file *file, + char *glob, char *cmd, char *param_and_filter) +{ + struct event_trigger_data *trigger_data; + struct objtrace_trigger_data *obj_data; + struct ftrace_event_field *field; + char *objtrace_cmd, *arg; + char *param, *filter; + int ret; + bool remove; + + remove = event_trigger_check_remove(glob); + + /* + * separate the param and the filter: + * objtrace:add:OBJ[:COUNT] [if filter] + */ + ret = event_trigger_separate_filter(param_and_filter, ¶m, &filter, true); + if (ret) + return ret; + + objtrace_cmd = strsep(¶m, ":"); + if (!objtrace_cmd || strcmp(objtrace_cmd, OBJTRACE_CMD_ADD)) { + pr_err("error objtrace command\n"); + return -EINVAL; + } + + arg = strsep(¶m, ":"); + if (!arg) + return -EINVAL; + + field = trace_find_event_field(file->event_call, arg); + if (!field) + return -EINVAL; + + if (field->size != sizeof(void *)) { + pr_err("the size of the %s should be:%zu\n", field->name, sizeof(void *)); + return -EINVAL; + } + + if (remove && !field_exist(file, cmd_ops, field->name)) + return -ENOENT; + + obj_data = kzalloc(sizeof(*obj_data), GFP_KERNEL); + if (!obj_data) + return -ENOMEM; + + obj_data->field = field; + obj_data->tr = file->tr; + snprintf(obj_data->objtrace_cmd, OBJTRACE_CMD_LEN, objtrace_cmd); + + trigger_data = event_trigger_alloc(cmd_ops, cmd, param, obj_data); + if (!trigger_data) { + kfree(obj_data); + return -ENOMEM; + } + if (remove) { + event_trigger_unregister(cmd_ops, file, glob+1, trigger_data); + kfree(obj_data); + kfree(trigger_data); + return 0; + } + + ret = event_trigger_parse_num(param, trigger_data); + if (ret) + goto out_free; + + ret = event_trigger_set_filter(cmd_ops, file, filter, trigger_data); + if (ret < 0) + goto out_free; + + ret = event_trigger_register(cmd_ops, file, glob, trigger_data); + if (ret) + goto out_free; + + return ret; + + out_free: + event_trigger_reset_filter(cmd_ops, trigger_data); + kfree(obj_data); + kfree(trigger_data); + return ret; +} + +static struct event_command trigger_object_cmd = { + .name = "objtrace", + .trigger_type = ETT_TRACE_OBJECT, + .flags = EVENT_CMD_FL_NEEDS_REC, + .parse = event_object_trigger_parse, + .reg = register_trigger, + .unreg = unregister_trigger, + .get_trigger_ops = objecttrace_get_trigger_ops, + .set_filter = set_trigger_filter, +}; + +__init int register_trigger_object_cmd(void) +{ + int ret; + + ret = register_event_command(&trigger_object_cmd); + WARN_ON(ret < 0); + + return ret; +} + +int allocate_objtrace_data(struct trace_array *tr) +{ + struct objtrace_data *obj_data; + struct ftrace_ops *fops; + + obj_data = kzalloc(sizeof(*obj_data), GFP_KERNEL); + if (!obj_data) + return -ENOMEM; + + raw_spin_lock_init(&obj_data->obj_data_lock); + obj_data->tr = tr; + fops = &obj_data->fops; + fops->func = trace_object_events_call; + fops->flags = FTRACE_OPS_FL_SAVE_REGS; + fops->private = tr; + list_add(&obj_data->head, &obj_data_head); + + tr->obj_data = obj_data; + + return 0; +} + +static int init_trace_object(struct trace_array *tr) +{ + int ret; + + ret = register_ftrace_function(&tr->obj_data->fops); + WARN_ON(ret < 0); + + return ret; +} + +void free_objtrace_data(struct trace_array *tr) +{ + kfree(tr->obj_data); + tr->obj_data = NULL; +} + +static void exit_trace_object(struct trace_array *tr) +{ + struct objtrace_data *obj_data = tr->obj_data; + + obj_data->num_traced_obj = 0; + WARN_ONCE(unregister_ftrace_function(&obj_data->fops), + "can't unregister ftrace for trace object\n"); +} diff --git a/kernel/trace/trace_output.c b/kernel/trace/trace_output.c index 67f47ea27921..34ff7b4dc521 100644 --- a/kernel/trace/trace_output.c +++ b/kernel/trace/trace_output.c @@ -1551,6 +1551,45 @@ static struct trace_event trace_func_repeats_event = { .funcs = &trace_func_repeats_funcs, };
+/* TRACE_OBJECT */ +static enum print_line_t trace_object_print(struct trace_iterator *iter, int flags, + struct trace_event *event) +{ + struct trace_object_entry *field; + struct trace_seq *s = &iter->seq; + + trace_assign_type(field, iter->ent); + print_fn_trace(s, field->ip, field->parent_ip, flags); + trace_seq_printf(s, " object:0x%lx", field->object); + trace_seq_putc(s, '\n'); + + return trace_handle_return(s); +} + +static enum print_line_t trace_object_raw(struct trace_iterator *iter, int flags, + struct trace_event *event) +{ + struct trace_object_entry *field; + + trace_assign_type(field, iter->ent); + + trace_seq_printf(&iter->seq, "%lx %lx\n", + field->ip, + field->parent_ip); + + return trace_handle_return(&iter->seq); +} + +static struct trace_event_functions trace_object_funcs = { + .trace = trace_object_print, + .raw = trace_object_raw, +}; + +static struct trace_event trace_object_event = { + .type = TRACE_OBJECT, + .funcs = &trace_object_funcs, +}; + static struct trace_event *events[] __initdata = { &trace_fn_event, &trace_ctx_event, @@ -1565,6 +1604,7 @@ static struct trace_event *events[] __initdata = { &trace_timerlat_event, &trace_raw_data_event, &trace_func_repeats_event, + &trace_object_event, NULL };
Using objtrace trigger to get the value of the object which from the kernel function parameter.
Syntax: objtrace:add:obj[,offset][:type][:count][if <filter>]
Usage: # echo 'p bio_add_page arg1=$arg1' > ./kprobe_events # gdb vmlinux (gdb) p &(((struct bio *)0)->bi_iter.bi_size) $1 = (unsigned int *) 0x28 # echo 'objtrace:add:arg1,0x28:u32:1 if comm == "cat"' > ./events/kprobes/ \ p_bio_add_page_0/trigger # cat /test.txt
Signed-off-by: Jeff Xie xiehuan09@gmail.com --- kernel/trace/trace.c | 2 +- kernel/trace/trace_entries.h | 5 +- kernel/trace/trace_object.c | 187 ++++++++++++++++++++++++++++++++--- kernel/trace/trace_output.c | 6 +- 4 files changed, 181 insertions(+), 19 deletions(-)
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 7074ad8bc1a0..37f5cbfa5347 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -5628,7 +5628,7 @@ static const char readme_msg[] = "\t disable_hist:<system>:<event>\n" #endif #ifdef CONFIG_TRACE_OBJECT - "\t objtrace:add:obj[:count][if <filter>]\n" + "\t objtrace:add:obj[,offset][:type][:count][if <filter>]\n" #endif #ifdef CONFIG_STACKTRACE "\t\t stacktrace\n" diff --git a/kernel/trace/trace_entries.h b/kernel/trace/trace_entries.h index bb120d9498a9..2407c45a568c 100644 --- a/kernel/trace/trace_entries.h +++ b/kernel/trace/trace_entries.h @@ -413,8 +413,9 @@ FTRACE_ENTRY(object, trace_object_entry, __field( unsigned long, ip ) __field( unsigned long, parent_ip ) __field( unsigned long, object ) + __field( unsigned long, value ) ),
- F_printk(" %ps <-- %ps object:%lx\n", - (void *)__entry->ip, (void *)__entry->parent_ip, __entry->object) + F_printk(" %ps <-- %ps object:%lx value:%lx\n", (void *)__entry->ip, + (void *)__entry->parent_ip, __entry->object, __entry->value) ); diff --git a/kernel/trace/trace_object.c b/kernel/trace/trace_object.c index 19ec4b1c0186..611341abeb7c 100644 --- a/kernel/trace/trace_object.c +++ b/kernel/trace/trace_object.c @@ -16,8 +16,14 @@ static const int max_args_num = 6; static void exit_trace_object(struct trace_array *tr); static int init_trace_object(struct trace_array *tr);
+/* + * get the offset from the special object and + * the type size of the value + */ struct object_instance { void *obj; + int obj_offset; + int obj_value_type_size; struct trace_array *tr; };
@@ -25,9 +31,23 @@ struct object_instance { struct objtrace_trigger_data { struct ftrace_event_field *field; char objtrace_cmd[OBJTRACE_CMD_LEN]; + int obj_offset; + int obj_value_type_size; struct trace_array *tr; };
+/* get the type size for the special object */ +struct objtrace_fetch_type { + char *name; + int type_size; +}; + +enum objattr { + OBJ_OFFSET, + OBJ_VAL_TYPE_SIZE, + MAX_OBJ_ATTR +}; + /* objtrace data with fops and objtrace_instances */ struct objtrace_data { struct list_head head; @@ -67,6 +87,35 @@ static bool object_exist(void *obj, struct trace_array *tr) return false; }
+static int get_object_attr(void *obj, int objattr, + struct trace_array *tr, int *result) +{ + int i, max; + struct objtrace_data *obj_data; + + obj_data = get_obj_data(tr); + if (!obj_data) + return -EINVAL; + + max = READ_ONCE(obj_data->num_traced_obj); + smp_rmb(); + for (i = 0; i < max; i++) { + if (obj_data->traced_obj[i].obj == obj) { + switch (objattr) { + case OBJ_OFFSET: + *result = obj_data->traced_obj[i].obj_offset; + return 0; + case OBJ_VAL_TYPE_SIZE: + *result = obj_data->traced_obj[i].obj_value_type_size; + return 0; + default: + return -EINVAL; + } + } + } + return -EINVAL; +} + static bool object_empty(struct trace_array *tr) { struct objtrace_data *obj_data; @@ -78,7 +127,8 @@ static bool object_empty(struct trace_array *tr) return !READ_ONCE(obj_data->num_traced_obj); }
-static void set_trace_object(void *obj, struct trace_array *tr) +static void set_trace_object(void *obj, int obj_offset, + int obj_value_type_size, struct trace_array *tr) { unsigned long flags; struct object_instance *obj_ins; @@ -103,6 +153,8 @@ static void set_trace_object(void *obj, struct trace_array *tr) } obj_ins = &obj_data->traced_obj[READ_ONCE(obj_data->num_traced_obj)]; obj_ins->obj = obj; + obj_ins->obj_value_type_size = obj_value_type_size; + obj_ins->obj_offset = obj_offset; obj_ins->tr = tr; /* make sure the num_traced_obj update always appears after traced_obj update */ smp_wmb(); @@ -112,7 +164,7 @@ static void set_trace_object(void *obj, struct trace_array *tr) }
static void submit_trace_object(unsigned long ip, unsigned long parent_ip, - unsigned long object, struct trace_array *tr) + unsigned long object, unsigned long value, struct trace_array *tr) {
struct trace_buffer *buffer = tr->array_buffer.buffer; @@ -129,10 +181,43 @@ static void submit_trace_object(unsigned long ip, unsigned long parent_ip, entry->ip = ip; entry->parent_ip = parent_ip; entry->object = object; + entry->value = value;
trace_buffer_unlock_commit(tr, buffer, event, trace_ctx); }
+static inline long get_object_value(unsigned long *val, void *obj, int type_size) +{ + char tmp[sizeof(u64)]; + long ret = 0; + + ret = copy_from_kernel_nofault(tmp, obj, sizeof(tmp)); + if (ret) + return ret; + switch (type_size) { + case 1: { + *val = (unsigned long)*(u8 *)tmp; + break; + } + case 2: { + *val = (unsigned long)*(u16 *)tmp; + break; + } + case 4: { + *val = (unsigned long)*(u32 *)tmp; + break; + } + case 8: { + *val = (unsigned long)*(u64 *)tmp; + break; + } + default: + return -EINVAL; + } + + return 0; +} + static void trace_object_events_call(unsigned long ip, unsigned long parent_ip, struct ftrace_ops *op, struct ftrace_regs *fregs) @@ -140,7 +225,8 @@ trace_object_events_call(unsigned long ip, unsigned long parent_ip, struct pt_regs *pt_regs = ftrace_get_regs(fregs); struct trace_array *tr = op->private; struct trace_array_cpu *data; - unsigned long obj; + int ret, val_type_size, obj_offset; + unsigned long obj, val; long disabled; int cpu, n;
@@ -154,8 +240,21 @@ trace_object_events_call(unsigned long ip, unsigned long parent_ip, goto out; for (n = 0; n < max_args_num; n++) { obj = regs_get_kernel_argument(pt_regs, n); - if (object_exist((void *)obj, tr)) - submit_trace_object(ip, parent_ip, obj, tr); + if (object_exist((void *)obj, tr)) { + ret = get_object_attr((void *)obj, OBJ_OFFSET, + tr, &obj_offset); + if (unlikely(ret) < 0) + goto out; + ret = get_object_attr((void *)obj, OBJ_VAL_TYPE_SIZE, + tr, &val_type_size); + if (unlikely(ret) < 0) + goto out; + if (get_object_value(&val, (void *)(obj + obj_offset), + val_type_size)) + continue; + + submit_trace_object(ip, parent_ip, obj, val, tr); + } /* The parameters of a function may match multiple objects */ } } @@ -176,9 +275,23 @@ trace_object_trigger(struct event_trigger_data *data,
field = obj_data->field; memcpy(&obj, rec + field->offset, sizeof(obj)); - set_trace_object(obj, tr); + /* set the offset from the special object and the type size of the value*/ + set_trace_object(obj, obj_data->obj_offset, + obj_data->obj_value_type_size, tr); }
+static const struct objtrace_fetch_type objtrace_fetch_types[] = { + {"u8", 1}, + {"x8", 1}, + {"u16", 2}, + {"x16", 2}, + {"u32", 4}, + {"x32", 4}, + {"u64", 8}, + {"x64", 8}, + {NULL, 0}, +}; + static void trace_object_trigger_free(struct event_trigger_data *data) { @@ -213,14 +326,25 @@ static int event_trigger_print(const char *name, struct seq_file *m, void *data, char *filter_str, void *objtrace_data) { + int i; long count = (long)data; struct objtrace_trigger_data *obj_data = objtrace_data; + const char *value_type_name;
seq_puts(m, name);
seq_printf(m, ":%s", obj_data->objtrace_cmd); seq_printf(m, ":%s", obj_data->field->name); + if (obj_data->obj_offset) + seq_printf(m, ",0x%x", obj_data->obj_offset);
+ for (i = 0; objtrace_fetch_types[i].name; i++) { + if (objtrace_fetch_types[i].type_size == obj_data->obj_value_type_size) { + value_type_name = objtrace_fetch_types[i].name; + break; + } + } + seq_printf(m, ":%s", value_type_name); if (count == -1) seq_puts(m, ":unlimited"); else @@ -303,16 +427,18 @@ event_object_trigger_parse(struct event_command *cmd_ops, struct event_trigger_data *trigger_data; struct objtrace_trigger_data *obj_data; struct ftrace_event_field *field; - char *objtrace_cmd, *arg; - char *param, *filter; - int ret; + char *objtrace_cmd, *obj; + char *param, *filter, *str, *type; + int ret, i, def_type_size, obj_value_type_size = 0; + char *tmp_saved_param; + long offset = 0; bool remove;
remove = event_trigger_check_remove(glob);
/* * separate the param and the filter: - * objtrace:add:OBJ[:COUNT] [if filter] + * objtrace:add:OBJ[,OFFS][:TYPE][:COUNT] [if filter] */ ret = event_trigger_separate_filter(param_and_filter, ¶m, &filter, true); if (ret) @@ -324,11 +450,44 @@ event_object_trigger_parse(struct event_command *cmd_ops, return -EINVAL; }
- arg = strsep(¶m, ":"); - if (!arg) + obj = strsep(¶m, ":"); + if (!obj) return -EINVAL;
- field = trace_find_event_field(file->event_call, arg); + str = strchr(obj, ','); + if (!str) + offset = 0; + else { + *str++ = '\0'; + ret = kstrtol(str, 0, &offset); + if (ret) + return -EINVAL; + } + def_type_size = sizeof(void *); + if (!param) { + obj_value_type_size = def_type_size; + goto skip_get_type; + } + tmp_saved_param = param; + type = strsep(¶m, ":"); + if (!type) + obj_value_type_size = def_type_size; + /* if this is the trigger count */ + else if (isdigit(type[0])) { + obj_value_type_size = def_type_size; + param = tmp_saved_param; + } else { + for (i = 0; objtrace_fetch_types[i].name; i++) { + if (strcmp(objtrace_fetch_types[i].name, type) == 0) { + obj_value_type_size = objtrace_fetch_types[i].type_size; + break; + } + } + } + if (!obj_value_type_size) + return -EINVAL; +skip_get_type: + field = trace_find_event_field(file->event_call, obj); if (!field) return -EINVAL;
@@ -345,6 +504,8 @@ event_object_trigger_parse(struct event_command *cmd_ops, return -ENOMEM;
obj_data->field = field; + obj_data->obj_offset = offset; + obj_data->obj_value_type_size = obj_value_type_size; obj_data->tr = file->tr; snprintf(obj_data->objtrace_cmd, OBJTRACE_CMD_LEN, objtrace_cmd);
diff --git a/kernel/trace/trace_output.c b/kernel/trace/trace_output.c index 34ff7b4dc521..a45871b52dcc 100644 --- a/kernel/trace/trace_output.c +++ b/kernel/trace/trace_output.c @@ -1561,6 +1561,7 @@ static enum print_line_t trace_object_print(struct trace_iterator *iter, int fla trace_assign_type(field, iter->ent); print_fn_trace(s, field->ip, field->parent_ip, flags); trace_seq_printf(s, " object:0x%lx", field->object); + trace_seq_printf(s, " value:0x%lx", field->value); trace_seq_putc(s, '\n');
return trace_handle_return(s); @@ -1573,9 +1574,8 @@ static enum print_line_t trace_object_raw(struct trace_iterator *iter, int flags
trace_assign_type(field, iter->ent);
- trace_seq_printf(&iter->seq, "%lx %lx\n", - field->ip, - field->parent_ip); + trace_seq_printf(&iter->seq, "%lx %lx %lx %lx\n", field->ip, + field->parent_ip, field->object, field->value);
return trace_handle_return(&iter->seq); }
On Sun, 26 Jun 2022 10:56:02 +0800 Jeff Xie xiehuan09@gmail.com wrote:
Using objtrace trigger to get the value of the object which from the kernel function parameter.
Syntax: objtrace:add:obj[,offset][:type][:count][if <filter>]
Usage: # echo 'p bio_add_page arg1=$arg1' > ./kprobe_events # gdb vmlinux (gdb) p &(((struct bio *)0)->bi_iter.bi_size) $1 = (unsigned int *) 0x28 # echo 'objtrace:add:arg1,0x28:u32:1 if comm == "cat"' > ./events/kprobes/ \ p_bio_add_page_0/trigger # cat /test.txt
Thanks for update! This looks good to me.
Acked-by: Masami Hiramatsu (Google) mhiramat@kernel.org
Signed-off-by: Jeff Xie xiehuan09@gmail.com
kernel/trace/trace.c | 2 +- kernel/trace/trace_entries.h | 5 +- kernel/trace/trace_object.c | 187 ++++++++++++++++++++++++++++++++--- kernel/trace/trace_output.c | 6 +- 4 files changed, 181 insertions(+), 19 deletions(-)
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 7074ad8bc1a0..37f5cbfa5347 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -5628,7 +5628,7 @@ static const char readme_msg[] = "\t disable_hist:<system>:<event>\n" #endif #ifdef CONFIG_TRACE_OBJECT
- "\t objtrace:add:obj[:count][if <filter>]\n"
- "\t objtrace:add:obj[,offset][:type][:count][if <filter>]\n"
#endif #ifdef CONFIG_STACKTRACE "\t\t stacktrace\n" diff --git a/kernel/trace/trace_entries.h b/kernel/trace/trace_entries.h index bb120d9498a9..2407c45a568c 100644 --- a/kernel/trace/trace_entries.h +++ b/kernel/trace/trace_entries.h @@ -413,8 +413,9 @@ FTRACE_ENTRY(object, trace_object_entry, __field( unsigned long, ip ) __field( unsigned long, parent_ip ) __field( unsigned long, object )
__field( unsigned long, value )
- F_printk(" %ps <-- %ps object:%lx\n",
(void *)__entry->ip, (void *)__entry->parent_ip, __entry->object)
- F_printk(" %ps <-- %ps object:%lx value:%lx\n", (void *)__entry->ip,
(void *)__entry->parent_ip, __entry->object, __entry->value)); diff --git a/kernel/trace/trace_object.c b/kernel/trace/trace_object.c index 19ec4b1c0186..611341abeb7c 100644 --- a/kernel/trace/trace_object.c +++ b/kernel/trace/trace_object.c @@ -16,8 +16,14 @@ static const int max_args_num = 6; static void exit_trace_object(struct trace_array *tr); static int init_trace_object(struct trace_array *tr); +/*
- get the offset from the special object and
- the type size of the value
- */
struct object_instance { void *obj;
- int obj_offset;
- int obj_value_type_size; struct trace_array *tr;
}; @@ -25,9 +31,23 @@ struct object_instance { struct objtrace_trigger_data { struct ftrace_event_field *field; char objtrace_cmd[OBJTRACE_CMD_LEN];
- int obj_offset;
- int obj_value_type_size; struct trace_array *tr;
}; +/* get the type size for the special object */ +struct objtrace_fetch_type {
- char *name;
- int type_size;
+};
+enum objattr {
- OBJ_OFFSET,
- OBJ_VAL_TYPE_SIZE,
- MAX_OBJ_ATTR
+};
/* objtrace data with fops and objtrace_instances */ struct objtrace_data { struct list_head head; @@ -67,6 +87,35 @@ static bool object_exist(void *obj, struct trace_array *tr) return false; } +static int get_object_attr(void *obj, int objattr,
struct trace_array *tr, int *result)+{
- int i, max;
- struct objtrace_data *obj_data;
- obj_data = get_obj_data(tr);
- if (!obj_data)
return -EINVAL;- max = READ_ONCE(obj_data->num_traced_obj);
- smp_rmb();
- for (i = 0; i < max; i++) {
if (obj_data->traced_obj[i].obj == obj) {switch (objattr) {case OBJ_OFFSET:*result = obj_data->traced_obj[i].obj_offset;return 0;case OBJ_VAL_TYPE_SIZE:*result = obj_data->traced_obj[i].obj_value_type_size;return 0;default:return -EINVAL;}}- }
- return -EINVAL;
+}
static bool object_empty(struct trace_array *tr) { struct objtrace_data *obj_data; @@ -78,7 +127,8 @@ static bool object_empty(struct trace_array *tr) return !READ_ONCE(obj_data->num_traced_obj); } -static void set_trace_object(void *obj, struct trace_array *tr) +static void set_trace_object(void *obj, int obj_offset,
int obj_value_type_size, struct trace_array *tr){ unsigned long flags; struct object_instance *obj_ins; @@ -103,6 +153,8 @@ static void set_trace_object(void *obj, struct trace_array *tr) } obj_ins = &obj_data->traced_obj[READ_ONCE(obj_data->num_traced_obj)]; obj_ins->obj = obj;
- obj_ins->obj_value_type_size = obj_value_type_size;
- obj_ins->obj_offset = obj_offset; obj_ins->tr = tr; /* make sure the num_traced_obj update always appears after traced_obj update */ smp_wmb();
@@ -112,7 +164,7 @@ static void set_trace_object(void *obj, struct trace_array *tr) } static void submit_trace_object(unsigned long ip, unsigned long parent_ip,
unsigned long object, struct trace_array *tr)
unsigned long object, unsigned long value, struct trace_array *tr){ struct trace_buffer *buffer = tr->array_buffer.buffer; @@ -129,10 +181,43 @@ static void submit_trace_object(unsigned long ip, unsigned long parent_ip, entry->ip = ip; entry->parent_ip = parent_ip; entry->object = object;
- entry->value = value;
trace_buffer_unlock_commit(tr, buffer, event, trace_ctx); } +static inline long get_object_value(unsigned long *val, void *obj, int type_size) +{
- char tmp[sizeof(u64)];
- long ret = 0;
- ret = copy_from_kernel_nofault(tmp, obj, sizeof(tmp));
- if (ret)
return ret;- switch (type_size) {
- case 1: {
*val = (unsigned long)*(u8 *)tmp;break;- }
- case 2: {
*val = (unsigned long)*(u16 *)tmp;break;- }
- case 4: {
*val = (unsigned long)*(u32 *)tmp;break;- }
- case 8: {
*val = (unsigned long)*(u64 *)tmp;break;- }
- default:
return -EINVAL;- }
- return 0;
+}
static void trace_object_events_call(unsigned long ip, unsigned long parent_ip, struct ftrace_ops *op, struct ftrace_regs *fregs) @@ -140,7 +225,8 @@ trace_object_events_call(unsigned long ip, unsigned long parent_ip, struct pt_regs *pt_regs = ftrace_get_regs(fregs); struct trace_array *tr = op->private; struct trace_array_cpu *data;
- unsigned long obj;
- int ret, val_type_size, obj_offset;
- unsigned long obj, val; long disabled; int cpu, n;
@@ -154,8 +240,21 @@ trace_object_events_call(unsigned long ip, unsigned long parent_ip, goto out; for (n = 0; n < max_args_num; n++) { obj = regs_get_kernel_argument(pt_regs, n);
if (object_exist((void *)obj, tr))submit_trace_object(ip, parent_ip, obj, tr);
if (object_exist((void *)obj, tr)) {ret = get_object_attr((void *)obj, OBJ_OFFSET,tr, &obj_offset);if (unlikely(ret) < 0)goto out;ret = get_object_attr((void *)obj, OBJ_VAL_TYPE_SIZE,tr, &val_type_size);if (unlikely(ret) < 0)goto out;if (get_object_value(&val, (void *)(obj + obj_offset),val_type_size))continue;submit_trace_object(ip, parent_ip, obj, val, tr);}@@ -176,9 +275,23 @@ trace_object_trigger(struct event_trigger_data *data, field = obj_data->field; memcpy(&obj, rec + field->offset, sizeof(obj));
- set_trace_object(obj, tr);
- /* set the offset from the special object and the type size of the value*/
- set_trace_object(obj, obj_data->obj_offset,
obj_data->obj_value_type_size, tr);} +static const struct objtrace_fetch_type objtrace_fetch_types[] = {
- {"u8", 1},
- {"x8", 1},
- {"u16", 2},
- {"x16", 2},
- {"u32", 4},
- {"x32", 4},
- {"u64", 8},
- {"x64", 8},
- {NULL, 0},
+};
static void trace_object_trigger_free(struct event_trigger_data *data) { @@ -213,14 +326,25 @@ static int event_trigger_print(const char *name, struct seq_file *m, void *data, char *filter_str, void *objtrace_data) {
- int i; long count = (long)data; struct objtrace_trigger_data *obj_data = objtrace_data;
- const char *value_type_name;
seq_puts(m, name); seq_printf(m, ":%s", obj_data->objtrace_cmd); seq_printf(m, ":%s", obj_data->field->name);
- if (obj_data->obj_offset)
seq_printf(m, ",0x%x", obj_data->obj_offset);
- for (i = 0; objtrace_fetch_types[i].name; i++) {
if (objtrace_fetch_types[i].type_size == obj_data->obj_value_type_size) {value_type_name = objtrace_fetch_types[i].name;break;}- }
- seq_printf(m, ":%s", value_type_name); if (count == -1) seq_puts(m, ":unlimited"); else
@@ -303,16 +427,18 @@ event_object_trigger_parse(struct event_command *cmd_ops, struct event_trigger_data *trigger_data; struct objtrace_trigger_data *obj_data; struct ftrace_event_field *field;
- char *objtrace_cmd, *arg;
- char *param, *filter;
- int ret;
- char *objtrace_cmd, *obj;
- char *param, *filter, *str, *type;
- int ret, i, def_type_size, obj_value_type_size = 0;
- char *tmp_saved_param;
- long offset = 0; bool remove;
remove = event_trigger_check_remove(glob); /* * separate the param and the filter:
* objtrace:add:OBJ[:COUNT] [if filter]
* objtrace:add:OBJ[,OFFS][:TYPE][:COUNT] [if filter]@@ -324,11 +450,44 @@ event_object_trigger_parse(struct event_command *cmd_ops, return -EINVAL; }
- arg = strsep(¶m, ":");
- if (!arg)
- obj = strsep(¶m, ":");
- if (!obj) return -EINVAL;
- field = trace_find_event_field(file->event_call, arg);
- str = strchr(obj, ',');
- if (!str)
offset = 0;- else {
*str++ = '\0';ret = kstrtol(str, 0, &offset);if (ret)return -EINVAL;- }
- def_type_size = sizeof(void *);
- if (!param) {
obj_value_type_size = def_type_size;goto skip_get_type;- }
- tmp_saved_param = param;
- type = strsep(¶m, ":");
- if (!type)
obj_value_type_size = def_type_size;- /* if this is the trigger count */
- else if (isdigit(type[0])) {
obj_value_type_size = def_type_size;param = tmp_saved_param;- } else {
for (i = 0; objtrace_fetch_types[i].name; i++) {if (strcmp(objtrace_fetch_types[i].name, type) == 0) {obj_value_type_size = objtrace_fetch_types[i].type_size;break;}}- }
- if (!obj_value_type_size)
return -EINVAL;+skip_get_type:
- field = trace_find_event_field(file->event_call, obj); if (!field) return -EINVAL;
@@ -345,6 +504,8 @@ event_object_trigger_parse(struct event_command *cmd_ops, return -ENOMEM; obj_data->field = field;
- obj_data->obj_offset = offset;
- obj_data->obj_value_type_size = obj_value_type_size; obj_data->tr = file->tr; snprintf(obj_data->objtrace_cmd, OBJTRACE_CMD_LEN, objtrace_cmd);
diff --git a/kernel/trace/trace_output.c b/kernel/trace/trace_output.c index 34ff7b4dc521..a45871b52dcc 100644 --- a/kernel/trace/trace_output.c +++ b/kernel/trace/trace_output.c @@ -1561,6 +1561,7 @@ static enum print_line_t trace_object_print(struct trace_iterator *iter, int fla trace_assign_type(field, iter->ent); print_fn_trace(s, field->ip, field->parent_ip, flags); trace_seq_printf(s, " object:0x%lx", field->object);
- trace_seq_printf(s, " value:0x%lx", field->value); trace_seq_putc(s, '\n');
return trace_handle_return(s); @@ -1573,9 +1574,8 @@ static enum print_line_t trace_object_raw(struct trace_iterator *iter, int flags trace_assign_type(field, iter->ent);
- trace_seq_printf(&iter->seq, "%lx %lx\n",
field->ip,field->parent_ip);
- trace_seq_printf(&iter->seq, "%lx %lx %lx %lx\n", field->ip,
field->parent_ip, field->object, field->value);return trace_handle_return(&iter->seq); } -- 2.25.1
Add a series of testcases to illustrate correct and incorrect usage of objtrace trigger.
Signed-off-by: Jeff Xie xiehuan09@gmail.com Tested-by: Masami Hiramatsu (Google) mhiramat@kernel.org Acked-by: Masami Hiramatsu (Google) mhiramat@kernel.org --- .../ftrace/test.d/trigger/trigger-objtrace.tc | 41 +++++++++++++++++++ 1 file changed, 41 insertions(+) create mode 100644 tools/testing/selftests/ftrace/test.d/trigger/trigger-objtrace.tc
diff --git a/tools/testing/selftests/ftrace/test.d/trigger/trigger-objtrace.tc b/tools/testing/selftests/ftrace/test.d/trigger/trigger-objtrace.tc new file mode 100644 index 000000000000..d894442b6a30 --- /dev/null +++ b/tools/testing/selftests/ftrace/test.d/trigger/trigger-objtrace.tc @@ -0,0 +1,41 @@ +#!/bin/sh +# SPDX-License-Identifier: GPL-2.0 +# description: event trigger - test objtrace-trigger +# requires: kprobe_events "objtrace":README + +fail() { #msg + echo $1 + exit_fail +} + +echo 'p bio_add_page arg1=$arg1 arg2=$arg2' > kprobe_events + +FEATURE=`grep objtrace events/kprobes/p_bio_add_page_0/trigger` +if [ -z "$FEATURE" ]; then + echo "objtrace trigger is not supported" + exit_unsupported +fi + +echo "Test objtrace trigger" +echo 'objtrace:add:arg1,0x28:u32:1 if comm == "cat"' > \ + events/kprobes/p_bio_add_page_0/trigger +if [ -z $? ]; then + fail "objtrace trigger syntax error" +fi + +echo "Test objtrace semantic errors" + +# Being lack of objtrace command +! echo 'objtrace:arg1,0x28:u32:1' > events/kprobes/p_bio_add_page_0/trigger +# Bad parameter name +! echo 'objtrace:add:argx:u32:1' > events/kprobes/p_bio_add_page_0/trigger +# The parameter existed on event +! echo 'objtrace:add:arg2:u32:1' > events/kprobes/p_bio_add_page_0/trigger + +echo "reset objtrace trigger" + +echo '!objtrace:add:arg1,0x28:u32' > \ + events/kprobes/p_bio_add_page_0/trigger +echo '-:p_bio_add_page_0' >> ./kprobe_events + +exit 0
On 6/25/22 8:56 PM, Jeff Xie wrote:
Add a series of testcases to illustrate correct and incorrect usage of objtrace trigger.
Signed-off-by: Jeff Xie xiehuan09@gmail.com Tested-by: Masami Hiramatsu (Google) mhiramat@kernel.org Acked-by: Masami Hiramatsu (Google) mhiramat@kernel.org
.../ftrace/test.d/trigger/trigger-objtrace.tc | 41 +++++++++++++++++++ 1 file changed, 41 insertions(+) create mode 100644 tools/testing/selftests/ftrace/test.d/trigger/trigger-objtrace.tc
Assuming this patch depends on the other kernel/trace changes in this series, here is my Ack for this series to go through tracing tree
Acked-by: Shuah Khan skhan@linuxfoundation.org
thanks, -- Shuah
Added documentation explaining how to use objtrace trigger to get the value of the object.
Signed-off-by: Jeff Xie xiehuan09@gmail.com Reviewed-by: Masami Hiramatsu (Google) mhiramat@kernel.org --- Documentation/trace/events.rst | 83 ++++++++++++++++++++++++++++++++++ 1 file changed, 83 insertions(+)
diff --git a/Documentation/trace/events.rst b/Documentation/trace/events.rst index c47f381d0c00..0dc475160133 100644 --- a/Documentation/trace/events.rst +++ b/Documentation/trace/events.rst @@ -546,6 +546,89 @@ The following commands are supported:
See Documentation/trace/histogram.rst for details and examples.
+- objtrace + + This command provides a way to get the value of any object, The object + can be obtained from the dynamic event(kprobe_event/uprobe_event) or the + static event(tracepoint). + + Usage: + When using the kprobe event, only need to set the objtrace(a new trigger), + we can get the value of the object. The object is from the setting of the + kprobe event. + + For example: + For the function bio_add_page(): + + int bio_add_page(struct bio *bio, struct page *page, + unsigned int len, unsigned int offset) + + Firstly, we can set the base of the object, thus the first string "arg1" + stands for the value of the first parameter of this function bio_add_gage(), + + # echo 'p bio_add_page arg1=$arg1' > ./kprobe_events + + Secondly, we can get the value dynamically based on above object. + + find the offset of the bi_size in struct bio: + $ gdb vmlinux + (gdb) p &(((struct bio *)0)->bi_iter.bi_size) + $1 = (unsigned int *) 0x28 + + # echo 'objtrace:add:arg1,0x28:u32:1 if comm == "cat"' > ./events/kprobes/ \ + p_bio_add_page_0/trigger + + # cd /sys/kernel/debug/tracing/ + # echo 'p bio_add_page arg1=$arg1' > ./kprobe_events + # echo 'objtrace:add:arg1,0x28:u32:1 if comm == "cat"' > ./events/kprobes/p_bio_add_page_0/trigger + + # du -sh /test.txt + 12.0K /test.txt + + # cat /test.txt > /dev/null + # cat ./trace + # tracer: nop + # + # entries-in-buffer/entries-written: 128/128 #P:4 + # + # _-----=> irqs-off/BH-disabled + # / _----=> need-resched + # | / _---=> hardirq/softirq + # || / _--=> preempt-depth + # ||| / _-=> migrate-disable + # |||| / delay + # TASK-PID CPU# ||||| TIMESTAMP FUNCTION + # | | | ||||| | | + cat-117 [002] ...1. 1.602243: __bio_try_merge_page <-bio_add_page object:0xffff88811bee4000 value:0x0 + cat-117 [002] ...1. 1.602244: __bio_add_page <-bio_add_page object:0xffff88811bee4000 value:0x0 + cat-117 [002] ...2. 1.602244: bio_add_page <-ext4_mpage_readpages object:0xffff88811bee4000 value:0x1000 + cat-117 [002] ...1. 1.602245: __bio_try_merge_page <-bio_add_page object:0xffff88811bee4000 value:0x1000 + cat-117 [002] ...1. 1.602245: __bio_add_page <-bio_add_page object:0xffff88811bee4000 value:0x1000 + cat-117 [002] ...2. 1.602245: bio_add_page <-ext4_mpage_readpages object:0xffff88811bee4000 value:0x2000 + cat-117 [002] ...1. 1.602245: __bio_try_merge_page <-bio_add_page object:0xffff88811bee4000 value:0x2000 + cat-117 [002] ...1. 1.602245: __bio_add_page <-bio_add_page object:0xffff88811bee4000 value:0x2000 + cat-117 [002] ...1. 1.602245: submit_bio <-ext4_mpage_readpages object:0xffff88811bee4000 value:0x3000 + cat-117 [002] ...1. 1.602245: submit_bio_noacct <-ext4_mpage_readpages object:0xffff88811bee4000 value:0x3000 + cat-117 [002] ...1. 1.602246: __submit_bio <-submit_bio_noacct object:0xffff88811bee4000 value:0x3000 + cat-117 [002] ...1. 1.602246: submit_bio_checks <-__submit_bio object:0xffff88811bee4000 value:0x3000 + cat-117 [002] ...1. 1.602246: __cond_resched <-submit_bio_checks object:0xffff88811bee4000 value:0x3000 + cat-117 [002] ...1. 1.602246: should_fail_bio <-submit_bio_checks object:0xffff88811bee4000 value:0x3000 + cat-117 [002] ...1. 1.602246: blk_mq_submit_bio <-submit_bio_noacct object:0xffff88811bee4000 value:0x3000 + cat-117 [002] ...1. 1.602246: blk_attempt_plug_merge <-blk_mq_submit_bio object:0xffff88811bee4000 value:0x3000 + cat-117 [002] ...1. 1.602246: blk_mq_sched_bio_merge <-blk_mq_submit_bio object:0xffff88811bee4000 value:0x3000 + cat-117 [002] ...1. 1.602247: __rcu_read_lock <-blk_mq_submit_bio object:0xffff88811bee4000 value:0x3000 + cat-117 [002] ...1. 1.602247: __rcu_read_unlock <-blk_mq_submit_bio object:0xffff88811bee4000 value:0x3000 + cat-117 [002] ...1. 1.602247: __blk_mq_alloc_requests <-blk_mq_submit_bio object:0xffff88811bee4000 value:0x3000 + <idle>-0 [002] d..3. 1.602298: bio_endio <-blk_update_request object:0xffff88811bee4000 value:0x0 + <idle>-0 [002] d..3. 1.602298: mpage_end_io <-blk_update_request object:0xffff88811bee4000 value:0x0 + <idle>-0 [002] d..3. 1.602298: __read_end_io <-blk_update_request object:0xffff88811bee4000 value:0x0 + <idle>-0 [002] d..3. 1.602300: bio_put <-blk_update_request object:0xffff88811bee4000 value:0x0 + <idle>-0 [002] d..3. 1.602300: bio_free <-blk_update_request object:0xffff88811bee4000 value:0x0 + <idle>-0 [002] d..3. 1.602300: mempool_free <-blk_update_request object:0xffff88811bee4000 value:0x0 + <idle>-0 [002] d..3. 1.602300: mempool_free_slab <-blk_update_request object:0xffff88811bee4000 value:0x0 + <idle>-0 [002] d..3. 1.602300: kmem_cache_free <-blk_update_request object:0xffff88811bee4000 value:0x0 + ... + 7. In-kernel trace event API ============================
On Sun, Jun 26, 2022 at 10:56:04AM +0800, Jeff Xie wrote:
Added documentation explaining how to use objtrace trigger to get the value of the object.
Write "Add documentation..." instead.
+- objtrace
- This command provides a way to get the value of any object, The object
- can be obtained from the dynamic event(kprobe_event/uprobe_event) or the
- static event(tracepoint).
- Usage:
- When using the kprobe event, only need to set the objtrace(a new trigger),
- we can get the value of the object. The object is from the setting of the
- kprobe event.
Did you mean "the object value can be obtained by only needing to set the objtrace?"
- For example:
- For the function bio_add_page():
- int bio_add_page(struct bio *bio, struct page *page,
- unsigned int len, unsigned int offset)
- Firstly, we can set the base of the object, thus the first string "arg1"
- stands for the value of the first parameter of this function bio_add_gage(),
- # echo 'p bio_add_page arg1=$arg1' > ./kprobe_events
Did you mean "the first parameter (arg1) is the parameter value of function that is passed to kprobe_event, in this case the object base"?
- Secondly, we can get the value dynamically based on above object.
- find the offset of the bi_size in struct bio:
- $ gdb vmlinux
- (gdb) p &(((struct bio *)0)->bi_iter.bi_size)
- $1 = (unsigned int *) 0x28
- # echo 'objtrace:add:arg1,0x28:u32:1 if comm == "cat"' > ./events/kprobes/ \
- p_bio_add_page_0/trigger
- # cd /sys/kernel/debug/tracing/
- # echo 'p bio_add_page arg1=$arg1' > ./kprobe_events
- # echo 'objtrace:add:arg1,0x28:u32:1 if comm == "cat"' > ./events/kprobes/p_bio_add_page_0/trigger
- # du -sh /test.txt
- 12.0K /test.txt
- # cat /test.txt > /dev/null
- # cat ./trace
- # tracer: nop
- #
- # entries-in-buffer/entries-written: 128/128 #P:4
- #
- # _-----=> irqs-off/BH-disabled
- # / _----=> need-resched
- # | / _---=> hardirq/softirq
- # || / _--=> preempt-depth
- # ||| / _-=> migrate-disable
- # |||| / delay
- # TASK-PID CPU# ||||| TIMESTAMP FUNCTION
- # | | | ||||| | |
cat-117 [002] ...1. 1.602243: __bio_try_merge_page <-bio_add_page object:0xffff88811bee4000 value:0x0cat-117 [002] ...1. 1.602244: __bio_add_page <-bio_add_page object:0xffff88811bee4000 value:0x0cat-117 [002] ...2. 1.602244: bio_add_page <-ext4_mpage_readpages object:0xffff88811bee4000 value:0x1000cat-117 [002] ...1. 1.602245: __bio_try_merge_page <-bio_add_page object:0xffff88811bee4000 value:0x1000cat-117 [002] ...1. 1.602245: __bio_add_page <-bio_add_page object:0xffff88811bee4000 value:0x1000cat-117 [002] ...2. 1.602245: bio_add_page <-ext4_mpage_readpages object:0xffff88811bee4000 value:0x2000cat-117 [002] ...1. 1.602245: __bio_try_merge_page <-bio_add_page object:0xffff88811bee4000 value:0x2000cat-117 [002] ...1. 1.602245: __bio_add_page <-bio_add_page object:0xffff88811bee4000 value:0x2000cat-117 [002] ...1. 1.602245: submit_bio <-ext4_mpage_readpages object:0xffff88811bee4000 value:0x3000cat-117 [002] ...1. 1.602245: submit_bio_noacct <-ext4_mpage_readpages object:0xffff88811bee4000 value:0x3000cat-117 [002] ...1. 1.602246: __submit_bio <-submit_bio_noacct object:0xffff88811bee4000 value:0x3000cat-117 [002] ...1. 1.602246: submit_bio_checks <-__submit_bio object:0xffff88811bee4000 value:0x3000cat-117 [002] ...1. 1.602246: __cond_resched <-submit_bio_checks object:0xffff88811bee4000 value:0x3000cat-117 [002] ...1. 1.602246: should_fail_bio <-submit_bio_checks object:0xffff88811bee4000 value:0x3000cat-117 [002] ...1. 1.602246: blk_mq_submit_bio <-submit_bio_noacct object:0xffff88811bee4000 value:0x3000cat-117 [002] ...1. 1.602246: blk_attempt_plug_merge <-blk_mq_submit_bio object:0xffff88811bee4000 value:0x3000cat-117 [002] ...1. 1.602246: blk_mq_sched_bio_merge <-blk_mq_submit_bio object:0xffff88811bee4000 value:0x3000cat-117 [002] ...1. 1.602247: __rcu_read_lock <-blk_mq_submit_bio object:0xffff88811bee4000 value:0x3000cat-117 [002] ...1. 1.602247: __rcu_read_unlock <-blk_mq_submit_bio object:0xffff88811bee4000 value:0x3000cat-117 [002] ...1. 1.602247: __blk_mq_alloc_requests <-blk_mq_submit_bio object:0xffff88811bee4000 value:0x3000<idle>-0 [002] d..3. 1.602298: bio_endio <-blk_update_request object:0xffff88811bee4000 value:0x0<idle>-0 [002] d..3. 1.602298: mpage_end_io <-blk_update_request object:0xffff88811bee4000 value:0x0<idle>-0 [002] d..3. 1.602298: __read_end_io <-blk_update_request object:0xffff88811bee4000 value:0x0<idle>-0 [002] d..3. 1.602300: bio_put <-blk_update_request object:0xffff88811bee4000 value:0x0<idle>-0 [002] d..3. 1.602300: bio_free <-blk_update_request object:0xffff88811bee4000 value:0x0<idle>-0 [002] d..3. 1.602300: mempool_free <-blk_update_request object:0xffff88811bee4000 value:0x0<idle>-0 [002] d..3. 1.602300: mempool_free_slab <-blk_update_request object:0xffff88811bee4000 value:0x0<idle>-0 [002] d..3. 1.602300: kmem_cache_free <-blk_update_request object:0xffff88811bee4000 value:0x0...
The output is messy, because for code example and output, literal code blocks aren't used, hence trigger new warnings:
Documentation/trace/events.rst:564: WARNING: Inline emphasis start-string without end-string. Documentation/trace/events.rst:564: WARNING: Inline emphasis start-string without end-string. Documentation/trace/events.rst:573: WARNING: Inline emphasis start-string without end-string. Documentation/trace/events.rst:573: WARNING: Inline emphasis start-string without end-string. Documentation/trace/events.rst:602: WARNING: Unexpected indentation. Documentation/trace/events.rst:622: WARNING: Block quote ends without a blank line; unexpected unindent. Documentation/trace/events.rst:630: WARNING: Unexpected indentation.
I had to apply the following fixup (with rewording):
---- >8 ----
diff --git a/Documentation/trace/events.rst b/Documentation/trace/events.rst index 0dc47516013331..c15f1d25d4a071 100644 --- a/Documentation/trace/events.rst +++ b/Documentation/trace/events.rst @@ -549,85 +549,89 @@ The following commands are supported: - objtrace
This command provides a way to get the value of any object, The object - can be obtained from the dynamic event(kprobe_event/uprobe_event) or the - static event(tracepoint). + can be obtained from the dynamic event (kprobe_event/uprobe_event) or the + static event (tracepoint).
Usage: - When using the kprobe event, only need to set the objtrace(a new trigger), - we can get the value of the object. The object is from the setting of the - kprobe event. + When using the kprobe event, by only need to set the objtrace (a new + trigger), we can get the value of object that is set by kprobe event.
- For example: - For the function bio_add_page(): + For example, for the function bio_add_page():
- int bio_add_page(struct bio *bio, struct page *page, - unsigned int len, unsigned int offset) + .. code-block:: c
- Firstly, we can set the base of the object, thus the first string "arg1" - stands for the value of the first parameter of this function bio_add_gage(), + int bio_add_page(struct bio *bio, struct page *page, + unsigned int len, unsigned int offset)
- # echo 'p bio_add_page arg1=$arg1' > ./kprobe_events + Firstly, we can set the base of the object as first parameter (arg1) to + to the function:
- Secondly, we can get the value dynamically based on above object. + .. code-block::
- find the offset of the bi_size in struct bio: - $ gdb vmlinux - (gdb) p &(((struct bio *)0)->bi_iter.bi_size) - $1 = (unsigned int *) 0x28 + # echo 'p bio_add_page arg1=$arg1' > ./kprobe_events
- # echo 'objtrace:add:arg1,0x28:u32:1 if comm == "cat"' > ./events/kprobes/ \ - p_bio_add_page_0/trigger + Secondly, we can get the value dynamically based on the object:
- # cd /sys/kernel/debug/tracing/ - # echo 'p bio_add_page arg1=$arg1' > ./kprobe_events - # echo 'objtrace:add:arg1,0x28:u32:1 if comm == "cat"' > ./events/kprobes/p_bio_add_page_0/trigger + .. code-block::
- # du -sh /test.txt - 12.0K /test.txt + find the offset of the bi_size in struct bio: + $ gdb vmlinux + (gdb) p &(((struct bio *)0)->bi_iter.bi_size) + $1 = (unsigned int *) 0x28
- # cat /test.txt > /dev/null - # cat ./trace - # tracer: nop - # - # entries-in-buffer/entries-written: 128/128 #P:4 - # - # _-----=> irqs-off/BH-disabled - # / _----=> need-resched - # | / _---=> hardirq/softirq - # || / _--=> preempt-depth - # ||| / _-=> migrate-disable - # |||| / delay - # TASK-PID CPU# ||||| TIMESTAMP FUNCTION - # | | | ||||| | | - cat-117 [002] ...1. 1.602243: __bio_try_merge_page <-bio_add_page object:0xffff88811bee4000 value:0x0 - cat-117 [002] ...1. 1.602244: __bio_add_page <-bio_add_page object:0xffff88811bee4000 value:0x0 - cat-117 [002] ...2. 1.602244: bio_add_page <-ext4_mpage_readpages object:0xffff88811bee4000 value:0x1000 - cat-117 [002] ...1. 1.602245: __bio_try_merge_page <-bio_add_page object:0xffff88811bee4000 value:0x1000 - cat-117 [002] ...1. 1.602245: __bio_add_page <-bio_add_page object:0xffff88811bee4000 value:0x1000 - cat-117 [002] ...2. 1.602245: bio_add_page <-ext4_mpage_readpages object:0xffff88811bee4000 value:0x2000 - cat-117 [002] ...1. 1.602245: __bio_try_merge_page <-bio_add_page object:0xffff88811bee4000 value:0x2000 - cat-117 [002] ...1. 1.602245: __bio_add_page <-bio_add_page object:0xffff88811bee4000 value:0x2000 - cat-117 [002] ...1. 1.602245: submit_bio <-ext4_mpage_readpages object:0xffff88811bee4000 value:0x3000 - cat-117 [002] ...1. 1.602245: submit_bio_noacct <-ext4_mpage_readpages object:0xffff88811bee4000 value:0x3000 - cat-117 [002] ...1. 1.602246: __submit_bio <-submit_bio_noacct object:0xffff88811bee4000 value:0x3000 - cat-117 [002] ...1. 1.602246: submit_bio_checks <-__submit_bio object:0xffff88811bee4000 value:0x3000 - cat-117 [002] ...1. 1.602246: __cond_resched <-submit_bio_checks object:0xffff88811bee4000 value:0x3000 - cat-117 [002] ...1. 1.602246: should_fail_bio <-submit_bio_checks object:0xffff88811bee4000 value:0x3000 - cat-117 [002] ...1. 1.602246: blk_mq_submit_bio <-submit_bio_noacct object:0xffff88811bee4000 value:0x3000 - cat-117 [002] ...1. 1.602246: blk_attempt_plug_merge <-blk_mq_submit_bio object:0xffff88811bee4000 value:0x3000 - cat-117 [002] ...1. 1.602246: blk_mq_sched_bio_merge <-blk_mq_submit_bio object:0xffff88811bee4000 value:0x3000 - cat-117 [002] ...1. 1.602247: __rcu_read_lock <-blk_mq_submit_bio object:0xffff88811bee4000 value:0x3000 - cat-117 [002] ...1. 1.602247: __rcu_read_unlock <-blk_mq_submit_bio object:0xffff88811bee4000 value:0x3000 - cat-117 [002] ...1. 1.602247: __blk_mq_alloc_requests <-blk_mq_submit_bio object:0xffff88811bee4000 value:0x3000 - <idle>-0 [002] d..3. 1.602298: bio_endio <-blk_update_request object:0xffff88811bee4000 value:0x0 - <idle>-0 [002] d..3. 1.602298: mpage_end_io <-blk_update_request object:0xffff88811bee4000 value:0x0 - <idle>-0 [002] d..3. 1.602298: __read_end_io <-blk_update_request object:0xffff88811bee4000 value:0x0 - <idle>-0 [002] d..3. 1.602300: bio_put <-blk_update_request object:0xffff88811bee4000 value:0x0 - <idle>-0 [002] d..3. 1.602300: bio_free <-blk_update_request object:0xffff88811bee4000 value:0x0 - <idle>-0 [002] d..3. 1.602300: mempool_free <-blk_update_request object:0xffff88811bee4000 value:0x0 - <idle>-0 [002] d..3. 1.602300: mempool_free_slab <-blk_update_request object:0xffff88811bee4000 value:0x0 - <idle>-0 [002] d..3. 1.602300: kmem_cache_free <-blk_update_request object:0xffff88811bee4000 value:0x0 - ... + # echo 'objtrace:add:arg1,0x28:u32:1 if comm == "cat"' > ./events/kprobes/ \ + p_bio_add_page_0/trigger + + # cd /sys/kernel/debug/tracing/ + # echo 'p bio_add_page arg1=$arg1' > ./kprobe_events + # echo 'objtrace:add:arg1,0x28:u32:1 if comm == "cat"' > ./events/kprobes/p_bio_add_page_0/trigger + + # du -sh /test.txt + 12.0K /test.txt + + # cat /test.txt > /dev/null + # cat ./trace + # tracer: nop + # + # entries-in-buffer/entries-written: 128/128 #P:4 + # + # _-----=> irqs-off/BH-disabled + # / _----=> need-resched + # | / _---=> hardirq/softirq + # || / _--=> preempt-depth + # ||| / _-=> migrate-disable + # |||| / delay + # TASK-PID CPU# ||||| TIMESTAMP FUNCTION + # | | | ||||| | | + cat-117 [002] ...1. 1.602243: __bio_try_merge_page <-bio_add_page object:0xffff88811bee4000 value:0x0 + cat-117 [002] ...1. 1.602244: __bio_add_page <-bio_add_page object:0xffff88811bee4000 value:0x0 + cat-117 [002] ...2. 1.602244: bio_add_page <-ext4_mpage_readpages object:0xffff88811bee4000 value:0x1000 + cat-117 [002] ...1. 1.602245: __bio_try_merge_page <-bio_add_page object:0xffff88811bee4000 value:0x1000 + cat-117 [002] ...1. 1.602245: __bio_add_page <-bio_add_page object:0xffff88811bee4000 value:0x1000 + cat-117 [002] ...2. 1.602245: bio_add_page <-ext4_mpage_readpages object:0xffff88811bee4000 value:0x2000 + cat-117 [002] ...1. 1.602245: __bio_try_merge_page <-bio_add_page object:0xffff88811bee4000 value:0x2000 + cat-117 [002] ...1. 1.602245: __bio_add_page <-bio_add_page object:0xffff88811bee4000 value:0x2000 + cat-117 [002] ...1. 1.602245: submit_bio <-ext4_mpage_readpages object:0xffff88811bee4000 value:0x3000 + cat-117 [002] ...1. 1.602245: submit_bio_noacct <-ext4_mpage_readpages object:0xffff88811bee4000 value:0x3000 + cat-117 [002] ...1. 1.602246: __submit_bio <-submit_bio_noacct object:0xffff88811bee4000 value:0x3000 + cat-117 [002] ...1. 1.602246: submit_bio_checks <-__submit_bio object:0xffff88811bee4000 value:0x3000 + cat-117 [002] ...1. 1.602246: __cond_resched <-submit_bio_checks object:0xffff88811bee4000 value:0x3000 + cat-117 [002] ...1. 1.602246: should_fail_bio <-submit_bio_checks object:0xffff88811bee4000 value:0x3000 + cat-117 [002] ...1. 1.602246: blk_mq_submit_bio <-submit_bio_noacct object:0xffff88811bee4000 value:0x3000 + cat-117 [002] ...1. 1.602246: blk_attempt_plug_merge <-blk_mq_submit_bio object:0xffff88811bee4000 value:0x3000 + cat-117 [002] ...1. 1.602246: blk_mq_sched_bio_merge <-blk_mq_submit_bio object:0xffff88811bee4000 value:0x3000 + cat-117 [002] ...1. 1.602247: __rcu_read_lock <-blk_mq_submit_bio object:0xffff88811bee4000 value:0x3000 + cat-117 [002] ...1. 1.602247: __rcu_read_unlock <-blk_mq_submit_bio object:0xffff88811bee4000 value:0x3000 + cat-117 [002] ...1. 1.602247: __blk_mq_alloc_requests <-blk_mq_submit_bio object:0xffff88811bee4000 value:0x3000 + <idle>-0 [002] d..3. 1.602298: bio_endio <-blk_update_request object:0xffff88811bee4000 value:0x0 + <idle>-0 [002] d..3. 1.602298: mpage_end_io <-blk_update_request object:0xffff88811bee4000 value:0x0 + <idle>-0 [002] d..3. 1.602298: __read_end_io <-blk_update_request object:0xffff88811bee4000 value:0x0 + <idle>-0 [002] d..3. 1.602300: bio_put <-blk_update_request object:0xffff88811bee4000 value:0x0 + <idle>-0 [002] d..3. 1.602300: bio_free <-blk_update_request object:0xffff88811bee4000 value:0x0 + <idle>-0 [002] d..3. 1.602300: mempool_free <-blk_update_request object:0xffff88811bee4000 value:0x0 + <idle>-0 [002] d..3. 1.602300: mempool_free_slab <-blk_update_request object:0xffff88811bee4000 value:0x0 + <idle>-0 [002] d..3. 1.602300: kmem_cache_free <-blk_update_request object:0xffff88811bee4000 value:0x0 + ...
7. In-kernel trace event API ============================
Thanks.
Hi,
On Mon, Jun 27, 2022 at 10:14 AM Bagas Sanjaya bagasdotme@gmail.com wrote:
On Sun, Jun 26, 2022 at 10:56:04AM +0800, Jeff Xie wrote:
Added documentation explaining how to use objtrace trigger to get the value of the object.
Write "Add documentation..." instead.
Thanks, I will change it.
+- objtrace
- This command provides a way to get the value of any object, The object
- can be obtained from the dynamic event(kprobe_event/uprobe_event) or the
- static event(tracepoint).
- Usage:
- When using the kprobe event, only need to set the objtrace(a new trigger),
- we can get the value of the object. The object is from the setting of the
- kprobe event.
Did you mean "the object value can be obtained by only needing to set the objtrace?"
Yes, that's what it means.
- For example:
- For the function bio_add_page():
- int bio_add_page(struct bio *bio, struct page *page,
unsigned int len, unsigned int offset)- Firstly, we can set the base of the object, thus the first string "arg1"
- stands for the value of the first parameter of this function bio_add_gage(),
- # echo 'p bio_add_page arg1=$arg1' > ./kprobe_events
Did you mean "the first parameter (arg1) is the parameter value of function that is passed to kprobe_event, in this case the object base"?
Yes, that's what it means.
- Secondly, we can get the value dynamically based on above object.
- find the offset of the bi_size in struct bio:
- $ gdb vmlinux
- (gdb) p &(((struct bio *)0)->bi_iter.bi_size)
- $1 = (unsigned int *) 0x28
- # echo 'objtrace:add:arg1,0x28:u32:1 if comm == "cat"' > ./events/kprobes/ \
p_bio_add_page_0/trigger- # cd /sys/kernel/debug/tracing/
- # echo 'p bio_add_page arg1=$arg1' > ./kprobe_events
- # echo 'objtrace:add:arg1,0x28:u32:1 if comm == "cat"' > ./events/kprobes/p_bio_add_page_0/trigger
- # du -sh /test.txt
- 12.0K /test.txt
- # cat /test.txt > /dev/null
- # cat ./trace
- # tracer: nop
- #
- # entries-in-buffer/entries-written: 128/128 #P:4
- #
- # _-----=> irqs-off/BH-disabled
- # / _----=> need-resched
- # | / _---=> hardirq/softirq
- # || / _--=> preempt-depth
- # ||| / _-=> migrate-disable
- # |||| / delay
- # TASK-PID CPU# ||||| TIMESTAMP FUNCTION
- # | | | ||||| | |
cat-117 [002] ...1. 1.602243: __bio_try_merge_page <-bio_add_page object:0xffff88811bee4000 value:0x0cat-117 [002] ...1. 1.602244: __bio_add_page <-bio_add_page object:0xffff88811bee4000 value:0x0cat-117 [002] ...2. 1.602244: bio_add_page <-ext4_mpage_readpages object:0xffff88811bee4000 value:0x1000cat-117 [002] ...1. 1.602245: __bio_try_merge_page <-bio_add_page object:0xffff88811bee4000 value:0x1000cat-117 [002] ...1. 1.602245: __bio_add_page <-bio_add_page object:0xffff88811bee4000 value:0x1000cat-117 [002] ...2. 1.602245: bio_add_page <-ext4_mpage_readpages object:0xffff88811bee4000 value:0x2000cat-117 [002] ...1. 1.602245: __bio_try_merge_page <-bio_add_page object:0xffff88811bee4000 value:0x2000cat-117 [002] ...1. 1.602245: __bio_add_page <-bio_add_page object:0xffff88811bee4000 value:0x2000cat-117 [002] ...1. 1.602245: submit_bio <-ext4_mpage_readpages object:0xffff88811bee4000 value:0x3000cat-117 [002] ...1. 1.602245: submit_bio_noacct <-ext4_mpage_readpages object:0xffff88811bee4000 value:0x3000cat-117 [002] ...1. 1.602246: __submit_bio <-submit_bio_noacct object:0xffff88811bee4000 value:0x3000cat-117 [002] ...1. 1.602246: submit_bio_checks <-__submit_bio object:0xffff88811bee4000 value:0x3000cat-117 [002] ...1. 1.602246: __cond_resched <-submit_bio_checks object:0xffff88811bee4000 value:0x3000cat-117 [002] ...1. 1.602246: should_fail_bio <-submit_bio_checks object:0xffff88811bee4000 value:0x3000cat-117 [002] ...1. 1.602246: blk_mq_submit_bio <-submit_bio_noacct object:0xffff88811bee4000 value:0x3000cat-117 [002] ...1. 1.602246: blk_attempt_plug_merge <-blk_mq_submit_bio object:0xffff88811bee4000 value:0x3000cat-117 [002] ...1. 1.602246: blk_mq_sched_bio_merge <-blk_mq_submit_bio object:0xffff88811bee4000 value:0x3000cat-117 [002] ...1. 1.602247: __rcu_read_lock <-blk_mq_submit_bio object:0xffff88811bee4000 value:0x3000cat-117 [002] ...1. 1.602247: __rcu_read_unlock <-blk_mq_submit_bio object:0xffff88811bee4000 value:0x3000cat-117 [002] ...1. 1.602247: __blk_mq_alloc_requests <-blk_mq_submit_bio object:0xffff88811bee4000 value:0x3000<idle>-0 [002] d..3. 1.602298: bio_endio <-blk_update_request object:0xffff88811bee4000 value:0x0<idle>-0 [002] d..3. 1.602298: mpage_end_io <-blk_update_request object:0xffff88811bee4000 value:0x0<idle>-0 [002] d..3. 1.602298: __read_end_io <-blk_update_request object:0xffff88811bee4000 value:0x0<idle>-0 [002] d..3. 1.602300: bio_put <-blk_update_request object:0xffff88811bee4000 value:0x0<idle>-0 [002] d..3. 1.602300: bio_free <-blk_update_request object:0xffff88811bee4000 value:0x0<idle>-0 [002] d..3. 1.602300: mempool_free <-blk_update_request object:0xffff88811bee4000 value:0x0<idle>-0 [002] d..3. 1.602300: mempool_free_slab <-blk_update_request object:0xffff88811bee4000 value:0x0<idle>-0 [002] d..3. 1.602300: kmem_cache_free <-blk_update_request object:0xffff88811bee4000 value:0x0...The output is messy, because for code example and output, literal code blocks aren't used, hence trigger new warnings:
Documentation/trace/events.rst:564: WARNING: Inline emphasis start-string without end-string. Documentation/trace/events.rst:564: WARNING: Inline emphasis start-string without end-string. Documentation/trace/events.rst:573: WARNING: Inline emphasis start-string without end-string. Documentation/trace/events.rst:573: WARNING: Inline emphasis start-string without end-string. Documentation/trace/events.rst:602: WARNING: Unexpected indentation. Documentation/trace/events.rst:622: WARNING: Block quote ends without a blank line; unexpected unindent. Documentation/trace/events.rst:630: WARNING: Unexpected indentation.
I had to apply the following fixup (with rewording):
Thank you so much for your help, It looks better ;-)
---- >8 ----
diff --git a/Documentation/trace/events.rst b/Documentation/trace/events.rst index 0dc47516013331..c15f1d25d4a071 100644 --- a/Documentation/trace/events.rst +++ b/Documentation/trace/events.rst @@ -549,85 +549,89 @@ The following commands are supported:
objtrace
This command provides a way to get the value of any object, The object
can be obtained from the dynamic event(kprobe_event/uprobe_event) or the
static event(tracepoint).
can be obtained from the dynamic event (kprobe_event/uprobe_event) or the
static event (tracepoint).
Usage:
- When using the kprobe event, only need to set the objtrace(a new trigger),
- we can get the value of the object. The object is from the setting of the
- kprobe event.
- When using the kprobe event, by only need to set the objtrace (a new
- trigger), we can get the value of object that is set by kprobe event.
- For example:
- For the function bio_add_page():
- For example, for the function bio_add_page():
- int bio_add_page(struct bio *bio, struct page *page,
unsigned int len, unsigned int offset)
- .. code-block:: c
- Firstly, we can set the base of the object, thus the first string "arg1"
- stands for the value of the first parameter of this function bio_add_gage(),
int bio_add_page(struct bio *bio, struct page *page,unsigned int len, unsigned int offset)
- # echo 'p bio_add_page arg1=$arg1' > ./kprobe_events
- Firstly, we can set the base of the object as first parameter (arg1) to
- to the function:
- Secondly, we can get the value dynamically based on above object.
- .. code-block::
- find the offset of the bi_size in struct bio:
- $ gdb vmlinux
- (gdb) p &(((struct bio *)0)->bi_iter.bi_size)
- $1 = (unsigned int *) 0x28
# echo 'p bio_add_page arg1=$arg1' > ./kprobe_events
- # echo 'objtrace:add:arg1,0x28:u32:1 if comm == "cat"' > ./events/kprobes/ \
p_bio_add_page_0/trigger
- Secondly, we can get the value dynamically based on the object:
- # cd /sys/kernel/debug/tracing/
- # echo 'p bio_add_page arg1=$arg1' > ./kprobe_events
- # echo 'objtrace:add:arg1,0x28:u32:1 if comm == "cat"' > ./events/kprobes/p_bio_add_page_0/trigger
- .. code-block::
- # du -sh /test.txt
- 12.0K /test.txt
find the offset of the bi_size in struct bio:$ gdb vmlinux(gdb) p &(((struct bio *)0)->bi_iter.bi_size)$1 = (unsigned int *) 0x28
- # cat /test.txt > /dev/null
- # cat ./trace
- # tracer: nop
- #
- # entries-in-buffer/entries-written: 128/128 #P:4
- #
- # _-----=> irqs-off/BH-disabled
- # / _----=> need-resched
- # | / _---=> hardirq/softirq
- # || / _--=> preempt-depth
- # ||| / _-=> migrate-disable
- # |||| / delay
- # TASK-PID CPU# ||||| TIMESTAMP FUNCTION
- # | | | ||||| | |
cat-117 [002] ...1. 1.602243: __bio_try_merge_page <-bio_add_page object:0xffff88811bee4000 value:0x0cat-117 [002] ...1. 1.602244: __bio_add_page <-bio_add_page object:0xffff88811bee4000 value:0x0cat-117 [002] ...2. 1.602244: bio_add_page <-ext4_mpage_readpages object:0xffff88811bee4000 value:0x1000cat-117 [002] ...1. 1.602245: __bio_try_merge_page <-bio_add_page object:0xffff88811bee4000 value:0x1000cat-117 [002] ...1. 1.602245: __bio_add_page <-bio_add_page object:0xffff88811bee4000 value:0x1000cat-117 [002] ...2. 1.602245: bio_add_page <-ext4_mpage_readpages object:0xffff88811bee4000 value:0x2000cat-117 [002] ...1. 1.602245: __bio_try_merge_page <-bio_add_page object:0xffff88811bee4000 value:0x2000cat-117 [002] ...1. 1.602245: __bio_add_page <-bio_add_page object:0xffff88811bee4000 value:0x2000cat-117 [002] ...1. 1.602245: submit_bio <-ext4_mpage_readpages object:0xffff88811bee4000 value:0x3000cat-117 [002] ...1. 1.602245: submit_bio_noacct <-ext4_mpage_readpages object:0xffff88811bee4000 value:0x3000cat-117 [002] ...1. 1.602246: __submit_bio <-submit_bio_noacct object:0xffff88811bee4000 value:0x3000cat-117 [002] ...1. 1.602246: submit_bio_checks <-__submit_bio object:0xffff88811bee4000 value:0x3000cat-117 [002] ...1. 1.602246: __cond_resched <-submit_bio_checks object:0xffff88811bee4000 value:0x3000cat-117 [002] ...1. 1.602246: should_fail_bio <-submit_bio_checks object:0xffff88811bee4000 value:0x3000cat-117 [002] ...1. 1.602246: blk_mq_submit_bio <-submit_bio_noacct object:0xffff88811bee4000 value:0x3000cat-117 [002] ...1. 1.602246: blk_attempt_plug_merge <-blk_mq_submit_bio object:0xffff88811bee4000 value:0x3000cat-117 [002] ...1. 1.602246: blk_mq_sched_bio_merge <-blk_mq_submit_bio object:0xffff88811bee4000 value:0x3000cat-117 [002] ...1. 1.602247: __rcu_read_lock <-blk_mq_submit_bio object:0xffff88811bee4000 value:0x3000cat-117 [002] ...1. 1.602247: __rcu_read_unlock <-blk_mq_submit_bio object:0xffff88811bee4000 value:0x3000cat-117 [002] ...1. 1.602247: __blk_mq_alloc_requests <-blk_mq_submit_bio object:0xffff88811bee4000 value:0x3000<idle>-0 [002] d..3. 1.602298: bio_endio <-blk_update_request object:0xffff88811bee4000 value:0x0<idle>-0 [002] d..3. 1.602298: mpage_end_io <-blk_update_request object:0xffff88811bee4000 value:0x0<idle>-0 [002] d..3. 1.602298: __read_end_io <-blk_update_request object:0xffff88811bee4000 value:0x0<idle>-0 [002] d..3. 1.602300: bio_put <-blk_update_request object:0xffff88811bee4000 value:0x0<idle>-0 [002] d..3. 1.602300: bio_free <-blk_update_request object:0xffff88811bee4000 value:0x0<idle>-0 [002] d..3. 1.602300: mempool_free <-blk_update_request object:0xffff88811bee4000 value:0x0<idle>-0 [002] d..3. 1.602300: mempool_free_slab <-blk_update_request object:0xffff88811bee4000 value:0x0<idle>-0 [002] d..3. 1.602300: kmem_cache_free <-blk_update_request object:0xffff88811bee4000 value:0x0...
# echo 'objtrace:add:arg1,0x28:u32:1 if comm == "cat"' > ./events/kprobes/ \p_bio_add_page_0/trigger# cd /sys/kernel/debug/tracing/# echo 'p bio_add_page arg1=$arg1' > ./kprobe_events# echo 'objtrace:add:arg1,0x28:u32:1 if comm == "cat"' > ./events/kprobes/p_bio_add_page_0/trigger# du -sh /test.txt12.0K /test.txt# cat /test.txt > /dev/null# cat ./trace# tracer: nop## entries-in-buffer/entries-written: 128/128 #P:4## _-----=> irqs-off/BH-disabled# / _----=> need-resched# | / _---=> hardirq/softirq# || / _--=> preempt-depth# ||| / _-=> migrate-disable# |||| / delay# TASK-PID CPU# ||||| TIMESTAMP FUNCTION# | | | ||||| | |cat-117 [002] ...1. 1.602243: __bio_try_merge_page <-bio_add_page object:0xffff88811bee4000 value:0x0cat-117 [002] ...1. 1.602244: __bio_add_page <-bio_add_page object:0xffff88811bee4000 value:0x0cat-117 [002] ...2. 1.602244: bio_add_page <-ext4_mpage_readpages object:0xffff88811bee4000 value:0x1000cat-117 [002] ...1. 1.602245: __bio_try_merge_page <-bio_add_page object:0xffff88811bee4000 value:0x1000cat-117 [002] ...1. 1.602245: __bio_add_page <-bio_add_page object:0xffff88811bee4000 value:0x1000cat-117 [002] ...2. 1.602245: bio_add_page <-ext4_mpage_readpages object:0xffff88811bee4000 value:0x2000cat-117 [002] ...1. 1.602245: __bio_try_merge_page <-bio_add_page object:0xffff88811bee4000 value:0x2000cat-117 [002] ...1. 1.602245: __bio_add_page <-bio_add_page object:0xffff88811bee4000 value:0x2000cat-117 [002] ...1. 1.602245: submit_bio <-ext4_mpage_readpages object:0xffff88811bee4000 value:0x3000cat-117 [002] ...1. 1.602245: submit_bio_noacct <-ext4_mpage_readpages object:0xffff88811bee4000 value:0x3000cat-117 [002] ...1. 1.602246: __submit_bio <-submit_bio_noacct object:0xffff88811bee4000 value:0x3000cat-117 [002] ...1. 1.602246: submit_bio_checks <-__submit_bio object:0xffff88811bee4000 value:0x3000cat-117 [002] ...1. 1.602246: __cond_resched <-submit_bio_checks object:0xffff88811bee4000 value:0x3000cat-117 [002] ...1. 1.602246: should_fail_bio <-submit_bio_checks object:0xffff88811bee4000 value:0x3000cat-117 [002] ...1. 1.602246: blk_mq_submit_bio <-submit_bio_noacct object:0xffff88811bee4000 value:0x3000cat-117 [002] ...1. 1.602246: blk_attempt_plug_merge <-blk_mq_submit_bio object:0xffff88811bee4000 value:0x3000cat-117 [002] ...1. 1.602246: blk_mq_sched_bio_merge <-blk_mq_submit_bio object:0xffff88811bee4000 value:0x3000cat-117 [002] ...1. 1.602247: __rcu_read_lock <-blk_mq_submit_bio object:0xffff88811bee4000 value:0x3000cat-117 [002] ...1. 1.602247: __rcu_read_unlock <-blk_mq_submit_bio object:0xffff88811bee4000 value:0x3000cat-117 [002] ...1. 1.602247: __blk_mq_alloc_requests <-blk_mq_submit_bio object:0xffff88811bee4000 value:0x3000<idle>-0 [002] d..3. 1.602298: bio_endio <-blk_update_request object:0xffff88811bee4000 value:0x0<idle>-0 [002] d..3. 1.602298: mpage_end_io <-blk_update_request object:0xffff88811bee4000 value:0x0<idle>-0 [002] d..3. 1.602298: __read_end_io <-blk_update_request object:0xffff88811bee4000 value:0x0<idle>-0 [002] d..3. 1.602300: bio_put <-blk_update_request object:0xffff88811bee4000 value:0x0<idle>-0 [002] d..3. 1.602300: bio_free <-blk_update_request object:0xffff88811bee4000 value:0x0<idle>-0 [002] d..3. 1.602300: mempool_free <-blk_update_request object:0xffff88811bee4000 value:0x0<idle>-0 [002] d..3. 1.602300: mempool_free_slab <-blk_update_request object:0xffff88811bee4000 value:0x0<idle>-0 [002] d..3. 1.602300: kmem_cache_free <-blk_update_request object:0xffff88811bee4000 value:0x0...
- In-kernel trace event API
============================
Thanks.
-- An old man doll... just what I always wanted! - Clara
Thanks, JeffXie
Hi Masami,
I would like to ask if I change the document like "Bagas Sanjaya" rewording in the next version. I don't know if I can add your Reviewed-by again, I don't know the rules very well ;-)
On Mon, Jun 27, 2022 at 3:45 PM Jeff Xie xiehuan09@gmail.com wrote:
Hi,
On Mon, Jun 27, 2022 at 10:14 AM Bagas Sanjaya bagasdotme@gmail.com wrote:
On Sun, Jun 26, 2022 at 10:56:04AM +0800, Jeff Xie wrote:
Added documentation explaining how to use objtrace trigger to get the value of the object.
Write "Add documentation..." instead.
Thanks, I will change it.
+- objtrace
- This command provides a way to get the value of any object, The object
- can be obtained from the dynamic event(kprobe_event/uprobe_event) or the
- static event(tracepoint).
- Usage:
- When using the kprobe event, only need to set the objtrace(a new trigger),
- we can get the value of the object. The object is from the setting of the
- kprobe event.
Did you mean "the object value can be obtained by only needing to set the objtrace?"
Yes, that's what it means.
- For example:
- For the function bio_add_page():
- int bio_add_page(struct bio *bio, struct page *page,
unsigned int len, unsigned int offset)- Firstly, we can set the base of the object, thus the first string "arg1"
- stands for the value of the first parameter of this function bio_add_gage(),
- # echo 'p bio_add_page arg1=$arg1' > ./kprobe_events
Did you mean "the first parameter (arg1) is the parameter value of function that is passed to kprobe_event, in this case the object base"?
Yes, that's what it means.
- Secondly, we can get the value dynamically based on above object.
- find the offset of the bi_size in struct bio:
- $ gdb vmlinux
- (gdb) p &(((struct bio *)0)->bi_iter.bi_size)
- $1 = (unsigned int *) 0x28
- # echo 'objtrace:add:arg1,0x28:u32:1 if comm == "cat"' > ./events/kprobes/ \
p_bio_add_page_0/trigger- # cd /sys/kernel/debug/tracing/
- # echo 'p bio_add_page arg1=$arg1' > ./kprobe_events
- # echo 'objtrace:add:arg1,0x28:u32:1 if comm == "cat"' > ./events/kprobes/p_bio_add_page_0/trigger
- # du -sh /test.txt
- 12.0K /test.txt
- # cat /test.txt > /dev/null
- # cat ./trace
- # tracer: nop
- #
- # entries-in-buffer/entries-written: 128/128 #P:4
- #
- # _-----=> irqs-off/BH-disabled
- # / _----=> need-resched
- # | / _---=> hardirq/softirq
- # || / _--=> preempt-depth
- # ||| / _-=> migrate-disable
- # |||| / delay
- # TASK-PID CPU# ||||| TIMESTAMP FUNCTION
- # | | | ||||| | |
cat-117 [002] ...1. 1.602243: __bio_try_merge_page <-bio_add_page object:0xffff88811bee4000 value:0x0cat-117 [002] ...1. 1.602244: __bio_add_page <-bio_add_page object:0xffff88811bee4000 value:0x0cat-117 [002] ...2. 1.602244: bio_add_page <-ext4_mpage_readpages object:0xffff88811bee4000 value:0x1000cat-117 [002] ...1. 1.602245: __bio_try_merge_page <-bio_add_page object:0xffff88811bee4000 value:0x1000cat-117 [002] ...1. 1.602245: __bio_add_page <-bio_add_page object:0xffff88811bee4000 value:0x1000cat-117 [002] ...2. 1.602245: bio_add_page <-ext4_mpage_readpages object:0xffff88811bee4000 value:0x2000cat-117 [002] ...1. 1.602245: __bio_try_merge_page <-bio_add_page object:0xffff88811bee4000 value:0x2000cat-117 [002] ...1. 1.602245: __bio_add_page <-bio_add_page object:0xffff88811bee4000 value:0x2000cat-117 [002] ...1. 1.602245: submit_bio <-ext4_mpage_readpages object:0xffff88811bee4000 value:0x3000cat-117 [002] ...1. 1.602245: submit_bio_noacct <-ext4_mpage_readpages object:0xffff88811bee4000 value:0x3000cat-117 [002] ...1. 1.602246: __submit_bio <-submit_bio_noacct object:0xffff88811bee4000 value:0x3000cat-117 [002] ...1. 1.602246: submit_bio_checks <-__submit_bio object:0xffff88811bee4000 value:0x3000cat-117 [002] ...1. 1.602246: __cond_resched <-submit_bio_checks object:0xffff88811bee4000 value:0x3000cat-117 [002] ...1. 1.602246: should_fail_bio <-submit_bio_checks object:0xffff88811bee4000 value:0x3000cat-117 [002] ...1. 1.602246: blk_mq_submit_bio <-submit_bio_noacct object:0xffff88811bee4000 value:0x3000cat-117 [002] ...1. 1.602246: blk_attempt_plug_merge <-blk_mq_submit_bio object:0xffff88811bee4000 value:0x3000cat-117 [002] ...1. 1.602246: blk_mq_sched_bio_merge <-blk_mq_submit_bio object:0xffff88811bee4000 value:0x3000cat-117 [002] ...1. 1.602247: __rcu_read_lock <-blk_mq_submit_bio object:0xffff88811bee4000 value:0x3000cat-117 [002] ...1. 1.602247: __rcu_read_unlock <-blk_mq_submit_bio object:0xffff88811bee4000 value:0x3000cat-117 [002] ...1. 1.602247: __blk_mq_alloc_requests <-blk_mq_submit_bio object:0xffff88811bee4000 value:0x3000<idle>-0 [002] d..3. 1.602298: bio_endio <-blk_update_request object:0xffff88811bee4000 value:0x0<idle>-0 [002] d..3. 1.602298: mpage_end_io <-blk_update_request object:0xffff88811bee4000 value:0x0<idle>-0 [002] d..3. 1.602298: __read_end_io <-blk_update_request object:0xffff88811bee4000 value:0x0<idle>-0 [002] d..3. 1.602300: bio_put <-blk_update_request object:0xffff88811bee4000 value:0x0<idle>-0 [002] d..3. 1.602300: bio_free <-blk_update_request object:0xffff88811bee4000 value:0x0<idle>-0 [002] d..3. 1.602300: mempool_free <-blk_update_request object:0xffff88811bee4000 value:0x0<idle>-0 [002] d..3. 1.602300: mempool_free_slab <-blk_update_request object:0xffff88811bee4000 value:0x0<idle>-0 [002] d..3. 1.602300: kmem_cache_free <-blk_update_request object:0xffff88811bee4000 value:0x0...The output is messy, because for code example and output, literal code blocks aren't used, hence trigger new warnings:
Documentation/trace/events.rst:564: WARNING: Inline emphasis start-string without end-string. Documentation/trace/events.rst:564: WARNING: Inline emphasis start-string without end-string. Documentation/trace/events.rst:573: WARNING: Inline emphasis start-string without end-string. Documentation/trace/events.rst:573: WARNING: Inline emphasis start-string without end-string. Documentation/trace/events.rst:602: WARNING: Unexpected indentation. Documentation/trace/events.rst:622: WARNING: Block quote ends without a blank line; unexpected unindent. Documentation/trace/events.rst:630: WARNING: Unexpected indentation.
I had to apply the following fixup (with rewording):
Thank you so much for your help, It looks better ;-)
---- >8 ----
diff --git a/Documentation/trace/events.rst b/Documentation/trace/events.rst index 0dc47516013331..c15f1d25d4a071 100644 --- a/Documentation/trace/events.rst +++ b/Documentation/trace/events.rst @@ -549,85 +549,89 @@ The following commands are supported:
objtrace
This command provides a way to get the value of any object, The object
can be obtained from the dynamic event(kprobe_event/uprobe_event) or the
static event(tracepoint).
can be obtained from the dynamic event (kprobe_event/uprobe_event) or the
static event (tracepoint).
Usage:
- When using the kprobe event, only need to set the objtrace(a new trigger),
- we can get the value of the object. The object is from the setting of the
- kprobe event.
- When using the kprobe event, by only need to set the objtrace (a new
- trigger), we can get the value of object that is set by kprobe event.
- For example:
- For the function bio_add_page():
- For example, for the function bio_add_page():
- int bio_add_page(struct bio *bio, struct page *page,
unsigned int len, unsigned int offset)
- .. code-block:: c
- Firstly, we can set the base of the object, thus the first string "arg1"
- stands for the value of the first parameter of this function bio_add_gage(),
int bio_add_page(struct bio *bio, struct page *page,unsigned int len, unsigned int offset)
- # echo 'p bio_add_page arg1=$arg1' > ./kprobe_events
- Firstly, we can set the base of the object as first parameter (arg1) to
- to the function:
- Secondly, we can get the value dynamically based on above object.
- .. code-block::
- find the offset of the bi_size in struct bio:
- $ gdb vmlinux
- (gdb) p &(((struct bio *)0)->bi_iter.bi_size)
- $1 = (unsigned int *) 0x28
# echo 'p bio_add_page arg1=$arg1' > ./kprobe_events
- # echo 'objtrace:add:arg1,0x28:u32:1 if comm == "cat"' > ./events/kprobes/ \
p_bio_add_page_0/trigger
- Secondly, we can get the value dynamically based on the object:
- # cd /sys/kernel/debug/tracing/
- # echo 'p bio_add_page arg1=$arg1' > ./kprobe_events
- # echo 'objtrace:add:arg1,0x28:u32:1 if comm == "cat"' > ./events/kprobes/p_bio_add_page_0/trigger
- .. code-block::
- # du -sh /test.txt
- 12.0K /test.txt
find the offset of the bi_size in struct bio:$ gdb vmlinux(gdb) p &(((struct bio *)0)->bi_iter.bi_size)$1 = (unsigned int *) 0x28
- # cat /test.txt > /dev/null
- # cat ./trace
- # tracer: nop
- #
- # entries-in-buffer/entries-written: 128/128 #P:4
- #
- # _-----=> irqs-off/BH-disabled
- # / _----=> need-resched
- # | / _---=> hardirq/softirq
- # || / _--=> preempt-depth
- # ||| / _-=> migrate-disable
- # |||| / delay
- # TASK-PID CPU# ||||| TIMESTAMP FUNCTION
- # | | | ||||| | |
cat-117 [002] ...1. 1.602243: __bio_try_merge_page <-bio_add_page object:0xffff88811bee4000 value:0x0cat-117 [002] ...1. 1.602244: __bio_add_page <-bio_add_page object:0xffff88811bee4000 value:0x0cat-117 [002] ...2. 1.602244: bio_add_page <-ext4_mpage_readpages object:0xffff88811bee4000 value:0x1000cat-117 [002] ...1. 1.602245: __bio_try_merge_page <-bio_add_page object:0xffff88811bee4000 value:0x1000cat-117 [002] ...1. 1.602245: __bio_add_page <-bio_add_page object:0xffff88811bee4000 value:0x1000cat-117 [002] ...2. 1.602245: bio_add_page <-ext4_mpage_readpages object:0xffff88811bee4000 value:0x2000cat-117 [002] ...1. 1.602245: __bio_try_merge_page <-bio_add_page object:0xffff88811bee4000 value:0x2000cat-117 [002] ...1. 1.602245: __bio_add_page <-bio_add_page object:0xffff88811bee4000 value:0x2000cat-117 [002] ...1. 1.602245: submit_bio <-ext4_mpage_readpages object:0xffff88811bee4000 value:0x3000cat-117 [002] ...1. 1.602245: submit_bio_noacct <-ext4_mpage_readpages object:0xffff88811bee4000 value:0x3000cat-117 [002] ...1. 1.602246: __submit_bio <-submit_bio_noacct object:0xffff88811bee4000 value:0x3000cat-117 [002] ...1. 1.602246: submit_bio_checks <-__submit_bio object:0xffff88811bee4000 value:0x3000cat-117 [002] ...1. 1.602246: __cond_resched <-submit_bio_checks object:0xffff88811bee4000 value:0x3000cat-117 [002] ...1. 1.602246: should_fail_bio <-submit_bio_checks object:0xffff88811bee4000 value:0x3000cat-117 [002] ...1. 1.602246: blk_mq_submit_bio <-submit_bio_noacct object:0xffff88811bee4000 value:0x3000cat-117 [002] ...1. 1.602246: blk_attempt_plug_merge <-blk_mq_submit_bio object:0xffff88811bee4000 value:0x3000cat-117 [002] ...1. 1.602246: blk_mq_sched_bio_merge <-blk_mq_submit_bio object:0xffff88811bee4000 value:0x3000cat-117 [002] ...1. 1.602247: __rcu_read_lock <-blk_mq_submit_bio object:0xffff88811bee4000 value:0x3000cat-117 [002] ...1. 1.602247: __rcu_read_unlock <-blk_mq_submit_bio object:0xffff88811bee4000 value:0x3000cat-117 [002] ...1. 1.602247: __blk_mq_alloc_requests <-blk_mq_submit_bio object:0xffff88811bee4000 value:0x3000<idle>-0 [002] d..3. 1.602298: bio_endio <-blk_update_request object:0xffff88811bee4000 value:0x0<idle>-0 [002] d..3. 1.602298: mpage_end_io <-blk_update_request object:0xffff88811bee4000 value:0x0<idle>-0 [002] d..3. 1.602298: __read_end_io <-blk_update_request object:0xffff88811bee4000 value:0x0<idle>-0 [002] d..3. 1.602300: bio_put <-blk_update_request object:0xffff88811bee4000 value:0x0<idle>-0 [002] d..3. 1.602300: bio_free <-blk_update_request object:0xffff88811bee4000 value:0x0<idle>-0 [002] d..3. 1.602300: mempool_free <-blk_update_request object:0xffff88811bee4000 value:0x0<idle>-0 [002] d..3. 1.602300: mempool_free_slab <-blk_update_request object:0xffff88811bee4000 value:0x0<idle>-0 [002] d..3. 1.602300: kmem_cache_free <-blk_update_request object:0xffff88811bee4000 value:0x0...
# echo 'objtrace:add:arg1,0x28:u32:1 if comm == "cat"' > ./events/kprobes/ \p_bio_add_page_0/trigger# cd /sys/kernel/debug/tracing/# echo 'p bio_add_page arg1=$arg1' > ./kprobe_events# echo 'objtrace:add:arg1,0x28:u32:1 if comm == "cat"' > ./events/kprobes/p_bio_add_page_0/trigger# du -sh /test.txt12.0K /test.txt# cat /test.txt > /dev/null# cat ./trace# tracer: nop## entries-in-buffer/entries-written: 128/128 #P:4## _-----=> irqs-off/BH-disabled# / _----=> need-resched# | / _---=> hardirq/softirq# || / _--=> preempt-depth# ||| / _-=> migrate-disable# |||| / delay# TASK-PID CPU# ||||| TIMESTAMP FUNCTION# | | | ||||| | |cat-117 [002] ...1. 1.602243: __bio_try_merge_page <-bio_add_page object:0xffff88811bee4000 value:0x0cat-117 [002] ...1. 1.602244: __bio_add_page <-bio_add_page object:0xffff88811bee4000 value:0x0cat-117 [002] ...2. 1.602244: bio_add_page <-ext4_mpage_readpages object:0xffff88811bee4000 value:0x1000cat-117 [002] ...1. 1.602245: __bio_try_merge_page <-bio_add_page object:0xffff88811bee4000 value:0x1000cat-117 [002] ...1. 1.602245: __bio_add_page <-bio_add_page object:0xffff88811bee4000 value:0x1000cat-117 [002] ...2. 1.602245: bio_add_page <-ext4_mpage_readpages object:0xffff88811bee4000 value:0x2000cat-117 [002] ...1. 1.602245: __bio_try_merge_page <-bio_add_page object:0xffff88811bee4000 value:0x2000cat-117 [002] ...1. 1.602245: __bio_add_page <-bio_add_page object:0xffff88811bee4000 value:0x2000cat-117 [002] ...1. 1.602245: submit_bio <-ext4_mpage_readpages object:0xffff88811bee4000 value:0x3000cat-117 [002] ...1. 1.602245: submit_bio_noacct <-ext4_mpage_readpages object:0xffff88811bee4000 value:0x3000cat-117 [002] ...1. 1.602246: __submit_bio <-submit_bio_noacct object:0xffff88811bee4000 value:0x3000cat-117 [002] ...1. 1.602246: submit_bio_checks <-__submit_bio object:0xffff88811bee4000 value:0x3000cat-117 [002] ...1. 1.602246: __cond_resched <-submit_bio_checks object:0xffff88811bee4000 value:0x3000cat-117 [002] ...1. 1.602246: should_fail_bio <-submit_bio_checks object:0xffff88811bee4000 value:0x3000cat-117 [002] ...1. 1.602246: blk_mq_submit_bio <-submit_bio_noacct object:0xffff88811bee4000 value:0x3000cat-117 [002] ...1. 1.602246: blk_attempt_plug_merge <-blk_mq_submit_bio object:0xffff88811bee4000 value:0x3000cat-117 [002] ...1. 1.602246: blk_mq_sched_bio_merge <-blk_mq_submit_bio object:0xffff88811bee4000 value:0x3000cat-117 [002] ...1. 1.602247: __rcu_read_lock <-blk_mq_submit_bio object:0xffff88811bee4000 value:0x3000cat-117 [002] ...1. 1.602247: __rcu_read_unlock <-blk_mq_submit_bio object:0xffff88811bee4000 value:0x3000cat-117 [002] ...1. 1.602247: __blk_mq_alloc_requests <-blk_mq_submit_bio object:0xffff88811bee4000 value:0x3000<idle>-0 [002] d..3. 1.602298: bio_endio <-blk_update_request object:0xffff88811bee4000 value:0x0<idle>-0 [002] d..3. 1.602298: mpage_end_io <-blk_update_request object:0xffff88811bee4000 value:0x0<idle>-0 [002] d..3. 1.602298: __read_end_io <-blk_update_request object:0xffff88811bee4000 value:0x0<idle>-0 [002] d..3. 1.602300: bio_put <-blk_update_request object:0xffff88811bee4000 value:0x0<idle>-0 [002] d..3. 1.602300: bio_free <-blk_update_request object:0xffff88811bee4000 value:0x0<idle>-0 [002] d..3. 1.602300: mempool_free <-blk_update_request object:0xffff88811bee4000 value:0x0<idle>-0 [002] d..3. 1.602300: mempool_free_slab <-blk_update_request object:0xffff88811bee4000 value:0x0<idle>-0 [002] d..3. 1.602300: kmem_cache_free <-blk_update_request object:0xffff88811bee4000 value:0x0...
- In-kernel trace event API
============================
Thanks.
-- An old man doll... just what I always wanted! - Clara
Thanks, JeffXie
Thanks, JeffXie
On 6/28/22 08:37, Jeff Xie wrote:
Hi Masami,
I would like to ask if I change the document like "Bagas Sanjaya" rewording in the next version. I don't know if I can add your Reviewed-by again, I don't know the rules very well ;-)
In the next version roll, just mention the feedback in the patch changelog (but not in the patch message as would appear on git log).
On Tue, Jun 28, 2022 at 10:31 AM Bagas Sanjaya bagasdotme@gmail.com wrote:
On 6/28/22 08:37, Jeff Xie wrote:
Hi Masami,
I would like to ask if I change the document like "Bagas Sanjaya" rewording in the next version. I don't know if I can add your Reviewed-by again, I don't know the rules very well ;-)
In the next version roll, just mention the feedback in the patch changelog (but not in the patch message as would appear on git log).
Okay, thank you for your reply ;-)
-- An old man doll... just what I always wanted! - Clara
Thanks, JeffXie
linux-kselftest-mirror@lists.linaro.org
-
Bagas Sanjaya -
Jeff Xie -
Masami Hiramatsu -
Shuah Khan