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([email protected])
and steve([email protected]), thank you all so much.
v15:
- Add Shuah Khan's acked-by for [3/4]
https://lore.kernel.org/lkml/[email protected]/
- Add Bagas Sanjaya's reviewed-by for [4/4]
https://lore.kernel.org/lkml/[email protected]/
- Add syntax suggested by Joel for usage of objtrace in [4/4]
v14:
- make documentation more readable and fix literal code block by Bagas Sanjaya
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 <[email protected]>
Suggested-by: Nathan Chancellor <[email protected]>
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 | 90 +++
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, 847 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: 09794a5a6c348f629b35fc1687071a1622ef4265
--
2.25.1
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=$arg1' > kprobe_events
# cd events/kprobes/p_bio_add_page_0
# echo 'objtrace:add:arg1:1 if comm == "cat"' > ./trigger
# cat /test.txt
Signed-off-by: Jeff Xie <[email protected]>
Acked-by: Masami Hiramatsu (Google) <[email protected]>
---
include/linux/trace_events.h | 1 +
kernel/trace/Kconfig | 10 +
kernel/trace/Makefile | 1 +
kernel/trace/trace.c | 11 +
kernel/trace/trace.h | 21 ++
kernel/trace/trace_entries.h | 17 ++
kernel/trace/trace_events_trigger.c | 5 +-
kernel/trace/trace_object.c | 450 ++++++++++++++++++++++++++++
kernel/trace/trace_output.c | 40 +++
9 files changed, 554 insertions(+), 2 deletions(-)
create mode 100644 kernel/trace/trace_object.c
diff --git a/include/linux/trace_events.h b/include/linux/trace_events.h
index b18759a673c6..4c9a899fc041 100644
--- a/include/linux/trace_events.h
+++ b/include/linux/trace_events.h
@@ -693,6 +693,7 @@ enum event_trigger_type {
ETT_EVENT_HIST = (1 << 4),
ETT_HIST_ENABLE = (1 << 5),
ETT_EVENT_EPROBE = (1 << 6),
+ ETT_TRACE_OBJECT = (1 << 7),
};
extern int filter_match_preds(struct event_filter *filter, void *rec);
diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index 1052126bdca2..4a78e72a07df 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -278,6 +278,16 @@ config FUNCTION_PROFILER
If in doubt, say N.
+config TRACE_OBJECT
+ bool "Trace kernel object in function parameter"
+ depends on FUNCTION_TRACER
+ depends on HAVE_FUNCTION_ARG_ACCESS_API
+ select TRACING
+ default y
+ help
+ You can trace the kernel object in the kernel function parameter.
+ The kernel object is dynamically specified via event trigger.
+
config STACK_TRACER
bool "Trace max stack"
depends on HAVE_FUNCTION_TRACER
diff --git a/kernel/trace/Makefile b/kernel/trace/Makefile
index c6651e16b557..9bbd1ac22518 100644
--- a/kernel/trace/Makefile
+++ b/kernel/trace/Makefile
@@ -71,6 +71,7 @@ obj-$(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 27febd4ee33e..2c2477dea0f2 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -5621,6 +5621,9 @@ 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
@@ -9261,6 +9264,9 @@ 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);
@@ -9280,6 +9286,7 @@ 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);
@@ -9373,6 +9380,7 @@ 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);
@@ -10110,6 +10118,9 @@ __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 900e75d96c84..8da1ef78a09a 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 <[email protected]>
+ */
+
+#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
};
--
2.25.1
Add a series of testcases to illustrate correct and incorrect usage of
objtrace trigger.
Cc: Shuah Khan <[email protected]>
Cc: [email protected]
Signed-off-by: Jeff Xie <[email protected]>
Tested-by: Masami Hiramatsu (Google) <[email protected]>
Acked-by: Masami Hiramatsu (Google) <[email protected]>
Acked-by: Shuah Khan <[email protected]>
---
.../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
--
2.25.1
On Fri, 19 Aug 2022 11:27:02 +0800
Jeff Xie <[email protected]> wrote:
So on my way home from London, I tried to update it to use the fetch
instruction logic of kprobes (which will work), but I also ended up pretty
much rewriting most of it, which then I realized, I'm going much further
than I wanted to.
But know I have a much better idea of how this should work, and I'll try to
go through what I learned here and throughout the patches.
> 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).
Note, I can see the value of tracing only the value of the object, but that
to me would be "objfollow" not "objtrace". That is, to find out what
functions are calling the object. I guess that may have been your original
objective, but it was articulated more about knowing how the value changed
and not where the value is going (and the code was written more like that).
Having a objfollow may be nice, but reading the arguments of a function is
really a "best attempt" at most, and you can't really trust the arguments
are what you are tracing. I would hold off on that until we have a good BTF
tracing infrastructure in the function tracer.
So I'm going to continue with "objtrace" which is about tracing the
object's value throughout time.
>
> 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
So I was working to change the above to:
echo 'objtrace:add:+0x28($arg1):u32:1 if comm == "cat"'
>
> # 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
Now instead of searching the function arguments for "obj", we should just
read the obj value at every function and report when it changed, as well as
the last function it was still the same. The report will be like the
"func_repeats" entry. And instead we can print when the object changes,
something like this:
cat-117 [002] ...2. 1.602245: bio_add_page <-ext4_mpage_readpages object:0xffff88811bee4000 value:0x2000 (last value:0x1000 at [002] __bio_add_page <-bio_add_page ts: 1.602245)
This will tell us when a value changed.
It would need to store the CPU, ip and pip and timestamp of the last time
it was the same. And when it changes, it would then report it.
-- Steve
On Fri, 19 Aug 2022 11:27:03 +0800
Jeff Xie <[email protected]> wrote:
> index 27febd4ee33e..2c2477dea0f2 100644
> --- a/kernel/trace/trace.c
> +++ b/kernel/trace/trace.c
> @@ -5621,6 +5621,9 @@ 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
> @@ -9261,6 +9264,9 @@ 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;
When I was rewriting this, I found there's no reason to associate a objdata
with a tr. It should all be self contained (per event file). The objdata
can have a tr, but the tr doesn't care about the objdata.
> +
> ftrace_init_trace_array(tr);
>
> init_trace_flags_index(tr);
> @@ -9280,6 +9286,7 @@ 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);
> @@ -9373,6 +9380,7 @@ 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);
> @@ -10110,6 +10118,9 @@ __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 900e75d96c84..8da1ef78a09a 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
That means the above is not needed.
> #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 <[email protected]>
> + */
> +
> +#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;
The instance will need to hold the object, and last value.
> +};
> +
> +/* 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;
> +};
The objtrace_data and the objtrace_trigger_data could be merged into a
single instance that get's allocated when the trigger is written. The
object_instance array size can be the "count" passed in.
It will require initializing the entire instance at the time the trigger is
written into the trigger file.
> +
> +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;
> +}
I deleted the above function.
> +
> +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;
BTW, please use "upside-down x-mas tree" formatting for variables. That is:
struct object_instance *obj_ins;
struct objtrace_data *obj_data;
unsigned long flags;
And I have more to comment on about variable declarations.
> +
> + if (in_nmi())
> + return;
> +
> + if (!obj && object_exist(obj, tr))
If we are checking values, we do not test for object_exist here. Just !obj.
> + 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) {
No need for the READ_ONCE() in the spin locked area.
> + trace_array_printk_buf(tr->array_buffer.buffer, _THIS_IP_,
> + "object_pool is full, can't trace object:0x%px\n", obj);
Also, I'm not sure if we have a counter, that we are going to want to print
anything when it is full. Maybe for debugging?
> + 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;
We do not need the op->private for the tr. instead:
struct obj_data *obj_data;
> + struct trace_array_cpu *data;
> + unsigned long obj;
> + long disabled;
> + int cpu, n;
obj_data = container_of(op, struct obj_data, fops);
tr = obj_data->tr;
> +
> + 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,
As I mentioned, the above is best effort at best. Instead, we should get
the value and check if it changed. If it did, then we print, otherwise skip
it. Will need to be under the lock to do this check.
> + 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);
We are not going to have an "unlimited" here. I think the count should be
the number of objects we can trace.
> +
> + 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;
BTW, do not declare more than one variable on the same line. It makes it
hard to know what is declared, makes diffs harder to know what changed, and
makes it annoying when the compiler says a variable is unused to delete it.
The above should be:
struct event_trigger_data *trigger_data;
struct objtrace_trigger_data *obj_data;
struct ftrace_event_field *field;
char *objtrace_cmd;
char *filter;
char *param;
char *arg;
bool remove;
int ret;
Although, when I changed this to use the fetch instruction, most of it was
removed anyway (which is why I found the above to be annoying due to all the
"unused variable" warnings I had).
-- Steve
> +
> + 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;
> +
>
On Tue, Oct 18, 2022 at 3:40 AM Steven Rostedt <[email protected]> wrote:
>
> On Fri, 19 Aug 2022 11:27:02 +0800
> Jeff Xie <[email protected]> wrote:
>
> So on my way home from London, I tried to update it to use the fetch
> instruction logic of kprobes (which will work), but I also ended up pretty
> much rewriting most of it, which then I realized, I'm going much further
> than I wanted to.
Very excited to hear it will work. Thank you for your hard work.
> But know I have a much better idea of how this should work, and I'll try to
> go through what I learned here and throughout the patches.
>
>
> > 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).
>
> Note, I can see the value of tracing only the value of the object, but that
> to me would be "objfollow" not "objtrace". That is, to find out what
> functions are calling the object. I guess that may have been your original
> objective, but it was articulated more about knowing how the value changed
Yes, It actually was my original objective -;) and I also really love
your idea of getting its value.
> and not where the value is going (and the code was written more like that).
> Having a objfollow may be nice, but reading the arguments of a function is
> really a "best attempt" at most, and you can't really trust the arguments
> are what you are tracing.
It's true, you spoke to my heart ;-)
>I would hold off on that until we have a good BTF
> tracing infrastructure in the function tracer.
>
> So I'm going to continue with "objtrace" which is about tracing the
> object's value throughout time.
Thanks.
>
> >
> > 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
>
> So I was working to change the above to:
>
> echo 'objtrace:add:+0x28($arg1):u32:1 if comm == "cat"'
It seems easier to use, I like it.
>
>
> >
> > # 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
>
> Now instead of searching the function arguments for "obj", we should just
> read the obj value at every function and report when it changed, as well as
> the last function it was still the same. The report will be like the
> "func_repeats" entry. And instead we can print when the object changes,
> something like this:
>
> cat-117 [002] ...2. 1.602245: bio_add_page <-ext4_mpage_readpages object:0xffff88811bee4000 value:0x2000 (last value:0x1000 at [002] __bio_add_page <-bio_add_page ts: 1.602245)
This output is better than I expected.
>
> This will tell us when a value changed.
>
> It would need to store the CPU, ip and pip and timestamp of the last time
> it was the same. And when it changes, it would then report it.
>
> -- Steve
--
Thanks,
JeffXie
Hi steve,
Thank you very much for your patient reply, very happy and very welcome to
rewrite the patch series with fetch instructions.
On Tue, Oct 18, 2022 at 3:58 AM Steven Rostedt <[email protected]> wrote:>
> On Fri, 19 Aug 2022 11:27:03 +0800
> Jeff Xie <[email protected]> wrote:
>
>
> > index 27febd4ee33e..2c2477dea0f2 100644
> > --- a/kernel/trace/trace.c
> > +++ b/kernel/trace/trace.c
> > @@ -5621,6 +5621,9 @@ 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
> > @@ -9261,6 +9264,9 @@ 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;
>
> When I was rewriting this, I found there's no reason to associate a objdata
> with a tr. It should all be self contained (per event file). The objdata
> can have a tr, but the tr doesn't care about the objdata.
I'm so glad you can rewrite it. okay, you should have removed the
object_exist(),
so the tr doesn't care about the objdata.
>
> > +
> > ftrace_init_trace_array(tr);
> >
> > init_trace_flags_index(tr);
> > @@ -9280,6 +9286,7 @@ 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);
> > @@ -9373,6 +9380,7 @@ 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);
> > @@ -10110,6 +10118,9 @@ __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 900e75d96c84..8da1ef78a09a 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
>
> That means the above is not needed.
Yes, thanks.
>
> > #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 <[email protected]>
> > + */
> > +
> > +#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;
>
> The instance will need to hold the object, and last value.
Thanks, I got it.
>
> > +};
> > +
> > +/* 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;
> > +};
>
> The objtrace_data and the objtrace_trigger_data could be merged into a
> single instance that get's allocated when the trigger is written. The
> object_instance array size can be the "count" passed in.
>
> It will require initializing the entire instance at the time the trigger is
> written into the trigger file.
>
It does look better;-)
> > +
> > +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;
> > +}
>
> I deleted the above function.
Thanks.
>
> > +
> > +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;
>
> BTW, please use "upside-down x-mas tree" formatting for variables. That is:
Thanks for your reminder.
>
> struct object_instance *obj_ins;
> struct objtrace_data *obj_data;
> unsigned long flags;
>
> And I have more to comment on about variable declarations.
>
> > +
> > + if (in_nmi())
> > + return;
> > +
> > + if (!obj && object_exist(obj, tr))
>
> If we are checking values, we do not test for object_exist here. Just !obj.
>
> > + 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) {
>
> No need for the READ_ONCE() in the spin locked area.
Thanks.
>
> > + trace_array_printk_buf(tr->array_buffer.buffer, _THIS_IP_,
> > + "object_pool is full, can't trace object:0x%px\n", obj);
>
> Also, I'm not sure if we have a counter, that we are going to want to print
> anything when it is full. Maybe for debugging?
I was worried that if there is no counter, there needs to be a refill logic,
and the implementation will become more complicated ;-)
> > + 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;
>
> We do not need the op->private for the tr. instead:
>
> struct obj_data *obj_data;
>
> > + struct trace_array_cpu *data;
> > + unsigned long obj;
> > + long disabled;
> > + int cpu, n;
>
> obj_data = container_of(op, struct obj_data, fops);
>
> tr = obj_data->tr;
learned, thanks.
>
> > +
> > + 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,
>
> As I mentioned, the above is best effort at best. Instead, we should get
> the value and check if it changed. If it did, then we print, otherwise skip
> it. Will need to be under the lock to do this check.
Although this is not my original intention, I am also very happy to
accept your idea.
>
>
> > + 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);
>
> We are not going to have an "unlimited" here. I think the count should be
> the number of objects we can trace.
Thanks, I agree.
>
> > +
> > + 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;
>
> BTW, do not declare more than one variable on the same line. It makes it
> hard to know what is declared, makes diffs harder to know what changed, and
> makes it annoying when the compiler says a variable is unused to delete it.
>
> The above should be:
>
> struct event_trigger_data *trigger_data;
> struct objtrace_trigger_data *obj_data;
> struct ftrace_event_field *field;
> char *objtrace_cmd;
> char *filter;
> char *param;
> char *arg;
> bool remove;
> int ret;
Thanks for your reminder .
> Although, when I changed this to use the fetch instruction, most of it was
> removed anyway (which is why I found the above to be annoying due to all the
> "unused variable" warnings I had).
>
> -- Steve
>
> > +
> > + 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;
> > +
> >
--
Thanks,
JeffXie
Hi Steven,
On Tue, Oct 18, 2022 at 3:40 AM Steven Rostedt <[email protected]> wrote:
>
> On Fri, 19 Aug 2022 11:27:02 +0800
> Jeff Xie <[email protected]> wrote:
>
> So on my way home from London, I tried to update it to use the fetch
> instruction logic of kprobes (which will work), but I also ended up pretty
> much rewriting most of it, which then I realized, I'm going much further
> than I wanted to.
>
> But know I have a much better idea of how this should work, and I'll try to
> go through what I learned here and throughout the patches.
>
>
> > 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).
>
> Note, I can see the value of tracing only the value of the object, but that
> to me would be "objfollow" not "objtrace". That is, to find out what
> functions are calling the object. I guess that may have been your original
> objective, but it was articulated more about knowing how the value changed
> and not where the value is going (and the code was written more like that).
>
> Having a objfollow may be nice, but reading the arguments of a function is
> really a "best attempt" at most, and you can't really trust the arguments
> are what you are tracing. I would hold off on that until we have a good BTF
> tracing infrastructure in the function tracer.
>
> So I'm going to continue with "objtrace" which is about tracing the
> object's value throughout time.
>
> >
> > 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
>
> So I was working to change the above to:
>
> echo 'objtrace:add:+0x28($arg1):u32:1 if comm == "cat"'
>
>
>
> >
> > # 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
>
> Now instead of searching the function arguments for "obj", we should just
> read the obj value at every function and report when it changed, as well as
> the last function it was still the same. The report will be like the
> "func_repeats" entry. And instead we can print when the object changes,
> something like this:
>
> cat-117 [002] ...2. 1.602245: bio_add_page <-ext4_mpage_readpages object:0xffff88811bee4000 value:0x2000 (last value:0x1000 at [002] __bio_add_page <-bio_add_page ts: 1.602245)
I'm just curious if we'll see this rewritten version in the next merge
window ;-)
> This will tell us when a value changed.
>
> It would need to store the CPU, ip and pip and timestamp of the last time
> it was the same. And when it changes, it would then report it.
>
> -- Steve
--
Thanks,
JeffXie
On Wed, 30 Nov 2022 00:09:51 +0800
Jeff Xie <[email protected]> wrote:
> > Now instead of searching the function arguments for "obj", we should just
> > read the obj value at every function and report when it changed, as well as
> > the last function it was still the same. The report will be like the
> > "func_repeats" entry. And instead we can print when the object changes,
> > something like this:
> >
> > cat-117 [002] ...2. 1.602245: bio_add_page <-ext4_mpage_readpages object:0xffff88811bee4000 value:0x2000 (last value:0x1000 at [002] __bio_add_page <-bio_add_page ts: 1.602245)
>
>
> I'm just curious if we'll see this rewritten version in the next merge
> window ;-)
Unfortunately, this ended up getting dropped in priority, as my workload
increased internally. :-/
-- Steve
On Wed, Nov 30, 2022 at 12:30 AM Steven Rostedt <[email protected]> wrote:
>
> On Wed, 30 Nov 2022 00:09:51 +0800
> Jeff Xie <[email protected]> wrote:
>
> > > Now instead of searching the function arguments for "obj", we should just
> > > read the obj value at every function and report when it changed, as well as
> > > the last function it was still the same. The report will be like the
> > > "func_repeats" entry. And instead we can print when the object changes,
> > > something like this:
> > >
> > > cat-117 [002] ...2. 1.602245: bio_add_page <-ext4_mpage_readpages object:0xffff88811bee4000 value:0x2000 (last value:0x1000 at [002] __bio_add_page <-bio_add_page ts: 1.602245)
> >
> >
> > I'm just curious if we'll see this rewritten version in the next merge
> > window ;-)
>
> Unfortunately, this ended up getting dropped in priority, as my workload
> increased internally. :-/
Hope you have multiple trips to London and more time on the plane to
get this done ;-)
>
> -- Steve
--
Thanks,
JeffXie
Hi Steve,
On Sat, Dec 17, 2022 at 4:27 PM Jeff Xie <[email protected]> wrote:
>
> On Wed, Nov 30, 2022 at 12:30 AM Steven Rostedt <[email protected]> wrote:
> >
> > On Wed, 30 Nov 2022 00:09:51 +0800
> > Jeff Xie <[email protected]> wrote:
> >
> > > > Now instead of searching the function arguments for "obj", we should just
> > > > read the obj value at every function and report when it changed, as well as
> > > > the last function it was still the same. The report will be like the
> > > > "func_repeats" entry. And instead we can print when the object changes,
> > > > something like this:
> > > >
> > > > cat-117 [002] ...2. 1.602245: bio_add_page <-ext4_mpage_readpages object:0xffff88811bee4000 value:0x2000 (last value:0x1000 at [002] __bio_add_page <-bio_add_page ts: 1.602245)
> > >
> > >
> > > I'm just curious if we'll see this rewritten version in the next merge
> > > window ;-)
> >
> > Unfortunately, this ended up getting dropped in priority, as my workload
> > increased internally. :-/
>
I would like to ask if there is any hope that this patchset can be
merged into the linux kernel in the end.
We spent a lot of time on this patchset, I don't want to give up so easily ;-)
--
Thanks,
JeffXie
On Tue, 31 Jan 2023 17:55:16 +0800
Jeff Xie <[email protected]> wrote:
> Hi Steve,
>
> On Sat, Dec 17, 2022 at 4:27 PM Jeff Xie <[email protected]> wrote:
> >
> > On Wed, Nov 30, 2022 at 12:30 AM Steven Rostedt <[email protected]> wrote:
> > >
> > > On Wed, 30 Nov 2022 00:09:51 +0800
> > > Jeff Xie <[email protected]> wrote:
> > >
> > > > > Now instead of searching the function arguments for "obj", we should just
> > > > > read the obj value at every function and report when it changed, as well as
> > > > > the last function it was still the same. The report will be like the
> > > > > "func_repeats" entry. And instead we can print when the object changes,
> > > > > something like this:
> > > > >
> > > > > cat-117 [002] ...2. 1.602245: bio_add_page <-ext4_mpage_readpages object:0xffff88811bee4000 value:0x2000 (last value:0x1000 at [002] __bio_add_page <-bio_add_page ts: 1.602245)
> > > >
> > > >
> > > > I'm just curious if we'll see this rewritten version in the next merge
> > > > window ;-)
> > >
> > > Unfortunately, this ended up getting dropped in priority, as my workload
> > > increased internally. :-/
> >
>
> I would like to ask if there is any hope that this patchset can be
> merged into the linux kernel in the end.
>
> We spent a lot of time on this patchset, I don't want to give up so easily ;-)
>
I think we were near the end, but it wasn't quite done, as I want it to be
integrated with the kprobes indirection interface:
https://lore.kernel.org/all/[email protected]/
Which I started to work on but didn't have time to finish, nor even get
very far with it.
I think once we can get that implemented, then this can get in. I don't
want to give up on it either.
-- Steve
On Tue, Jan 31, 2023 at 11:36 PM Steven Rostedt <[email protected]> wrote:
>
> On Tue, 31 Jan 2023 17:55:16 +0800
> Jeff Xie <[email protected]> wrote:
>
> > Hi Steve,
> >
> > On Sat, Dec 17, 2022 at 4:27 PM Jeff Xie <[email protected]> wrote:
> > >
> > > On Wed, Nov 30, 2022 at 12:30 AM Steven Rostedt <[email protected]> wrote:
> > > >
> > > > On Wed, 30 Nov 2022 00:09:51 +0800
> > > > Jeff Xie <[email protected]> wrote:
> > > >
> > > > > > Now instead of searching the function arguments for "obj", we should just
> > > > > > read the obj value at every function and report when it changed, as well as
> > > > > > the last function it was still the same. The report will be like the
> > > > > > "func_repeats" entry. And instead we can print when the object changes,
> > > > > > something like this:
> > > > > >
> > > > > > cat-117 [002] ...2. 1.602245: bio_add_page <-ext4_mpage_readpages object:0xffff88811bee4000 value:0x2000 (last value:0x1000 at [002] __bio_add_page <-bio_add_page ts: 1.602245)
> > > > >
> > > > >
> > > > > I'm just curious if we'll see this rewritten version in the next merge
> > > > > window ;-)
> > > >
> > > > Unfortunately, this ended up getting dropped in priority, as my workload
> > > > increased internally. :-/
> > >
> >
> > I would like to ask if there is any hope that this patchset can be
> > merged into the linux kernel in the end.
> >
> > We spent a lot of time on this patchset, I don't want to give up so easily ;-)
> >
>
> I think we were near the end, but it wasn't quite done, as I want it to be
> integrated with the kprobes indirection interface:
>
> https://lore.kernel.org/all/[email protected]/
>
> Which I started to work on but didn't have time to finish, nor even get
> very far with it.
>
> I think once we can get that implemented, then this can get in. I don't
> want to give up on it either.
Thank you for your positive and fast feedback.
>
> -- Steve
--
Thanks,
JeffXie