28 Jun
2022
28 Jun
'22
1:37 a.m.
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