[PATCH v13 2/4] trace/objtrace: Get the value of the object

26 Jun 2022

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, &param, &filter, true);
    if (ret)
@@ -324,11 +450,44 @@ event_object_trigger_parse(struct event_command *cmd_ops,
    	return -EINVAL;
    }
-	arg = strsep(&param, ":");
-	if (!arg)
+	obj = strsep(&param, ":");
+	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(&param, ":");
+	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


    

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[PATCH v13 2/4] trace/objtrace: Get the value of the object