Introduce a method based on function tracer to trace any object and get
the value of the object dynamically. the object can be obtained from the
dynamic event (kprobe_event/uprobe_event) or the static event(tracepoint).
Usage:
When using the kprobe event, only need to set the objtrace(a new trigger),
we can get the value of the object. The object is from the setting of the
kprobe event.
For example:
For the function bio_add_page():
int bio_add_page(struct bio *bio, struct page *page,
unsigned int len, unsigned int offset)
Firstly, we can set the base of the object, thus the first string "arg1"
stands for the value of the first parameter of this function bio_add_gage(),
# echo 'p bio_add_page arg1=$arg1' > ./kprobe_events
Secondly, we can get the value dynamically based on above object.
find the offset of the bi_size in struct bio:
$ gdb vmlinux
(gdb) p &(((struct bio *)0)->bi_iter.bi_size)
$1 = (unsigned int *) 0x28
# echo 'objtrace:add:arg1,0x28:u32:1 if comm == "cat"' > ./events/kprobes/ \
p_bio_add_page_0/trigger
# cd /sys/kernel/debug/tracing/
# echo 'p bio_add_page arg1=$arg1' > ./kprobe_events
# echo 'objtrace:add:arg1,0x28:u32:1 if comm == "cat"' > ./events/kprobes/p_bio_add_page_0/trigger
# du -sh /test.txt
12.0K /test.txt
# cat /test.txt > /dev/null
# cat ./trace
# tracer: nop
#
# entries-in-buffer/entries-written: 128/128 #P:4
#
# _-----=> irqs-off/BH-disabled
# / _----=> need-resched
# | / _---=> hardirq/softirq
# || / _--=> preempt-depth
# ||| / _-=> migrate-disable
# |||| / delay
# TASK-PID CPU# ||||| TIMESTAMP FUNCTION
# | | | ||||| | |
cat-117 [002] ...1. 1.602243: __bio_try_merge_page <-bio_add_page object:0xffff88811bee4000 value:0x0
cat-117 [002] ...1. 1.602244: __bio_add_page <-bio_add_page object:0xffff88811bee4000 value:0x0
cat-117 [002] ...2. 1.602244: bio_add_page <-ext4_mpage_readpages object:0xffff88811bee4000 value:0x1000
cat-117 [002] ...1. 1.602245: __bio_try_merge_page <-bio_add_page object:0xffff88811bee4000 value:0x1000
cat-117 [002] ...1. 1.602245: __bio_add_page <-bio_add_page object:0xffff88811bee4000 value:0x1000
cat-117 [002] ...2. 1.602245: bio_add_page <-ext4_mpage_readpages object:0xffff88811bee4000 value:0x2000
cat-117 [002] ...1. 1.602245: __bio_try_merge_page <-bio_add_page object:0xffff88811bee4000 value:0x2000
cat-117 [002] ...1. 1.602245: __bio_add_page <-bio_add_page object:0xffff88811bee4000 value:0x2000
cat-117 [002] ...1. 1.602245: submit_bio <-ext4_mpage_readpages object:0xffff88811bee4000 value:0x3000
cat-117 [002] ...1. 1.602245: submit_bio_noacct <-ext4_mpage_readpages object:0xffff88811bee4000 value:0x3000
cat-117 [002] ...1. 1.602246: __submit_bio <-submit_bio_noacct object:0xffff88811bee4000 value:0x3000
cat-117 [002] ...1. 1.602246: submit_bio_checks <-__submit_bio object:0xffff88811bee4000 value:0x3000
cat-117 [002] ...1. 1.602246: __cond_resched <-submit_bio_checks object:0xffff88811bee4000 value:0x3000
cat-117 [002] ...1. 1.602246: should_fail_bio <-submit_bio_checks object:0xffff88811bee4000 value:0x3000
cat-117 [002] ...1. 1.602246: blk_mq_submit_bio <-submit_bio_noacct object:0xffff88811bee4000 value:0x3000
cat-117 [002] ...1. 1.602246: blk_attempt_plug_merge <-blk_mq_submit_bio object:0xffff88811bee4000 value:0x3000
cat-117 [002] ...1. 1.602246: blk_mq_sched_bio_merge <-blk_mq_submit_bio object:0xffff88811bee4000 value:0x3000
cat-117 [002] ...1. 1.602247: __rcu_read_lock <-blk_mq_submit_bio object:0xffff88811bee4000 value:0x3000
cat-117 [002] ...1. 1.602247: __rcu_read_unlock <-blk_mq_submit_bio object:0xffff88811bee4000 value:0x3000
cat-117 [002] ...1. 1.602247: __blk_mq_alloc_requests <-blk_mq_submit_bio object:0xffff88811bee4000 value:0x3000
<idle>-0 [002] d..3. 1.602298: bio_endio <-blk_update_request object:0xffff88811bee4000 value:0x0
<idle>-0 [002] d..3. 1.602298: mpage_end_io <-blk_update_request object:0xffff88811bee4000 value:0x0
<idle>-0 [002] d..3. 1.602298: __read_end_io <-blk_update_request object:0xffff88811bee4000 value:0x0
<idle>-0 [002] d..3. 1.602300: bio_put <-blk_update_request object:0xffff88811bee4000 value:0x0
<idle>-0 [002] d..3. 1.602300: bio_free <-blk_update_request object:0xffff88811bee4000 value:0x0
<idle>-0 [002] d..3. 1.602300: mempool_free <-blk_update_request object:0xffff88811bee4000 value:0x0
<idle>-0 [002] d..3. 1.602300: mempool_free_slab <-blk_update_request object:0xffff88811bee4000 value:0x0
<idle>-0 [002] d..3. 1.602300: kmem_cache_free <-blk_update_request object:0xffff88811bee4000 value:0x0
...
Almost all changelogs were suggested by Masami(mhiramat@xxxxxxxxxx)
and steve(rostedt@xxxxxxxxxxx), thank you all so much.
v13:
- remove the 's' type, since the objtrace event doesn't show the value with sign
- change the [3/4] tag with 'selftests/ftrace' instead of 'trace/objtrace'
- add 'Documentation:' tag for [4/4]
v12:
- use the %zu to print the sizeof
Reported-by: kernel test robot <lkp@xxxxxxxxx>
Suggested-by: Nathan Chancellor <nathan@xxxxxxxxxx>
v11:
- remove useless atomic counting methods for num_traced_obj
- make array objtrace_fetch_types null terminated
- add raw_spin_lock_init for obj_data_lock
v10:
- support ftrace instances
- use trace_buffer_lock_reserve instead of trace_event_buffer_lock_reserve
- a lot of cleanup work has been done mainly for event_object_trigger_parse
v9:
- fix objtrace trigger output was incomplete
- fix the objtrace trigger was removed when using the existed parameter on
event.
- add testcase for the second fix above.
v8:
- revert to use per-cpu recursion for the function trace_object_events_call
- recover the filter when getting the value of the object
- simplify the implementation for the function get_object_value
- fix the build error
v7:
- use fixed-size array for object pool instead of list structure
- use ftrace_test_recursion_trylock for function trace hook function
- fix trace_object_ref reference count in the init_trace_object
- invoke exit_trace_object no matter whether data->ops->free is null
in the unregister_object_trigger
- release private_data of event_trigger_data in the trace_object_trigger_free
- remove [RFC] tag
v6:
- change the objtrace trigger syntax.
- add patchset description
- add <tracefs>/README
v5:
- add testcasts
- add check the field->size
- add lockless to search object
- describe the object trace more clearly in Kconfig
v4:
- please ignore the v4 which is the same as v3
v3:
- change the objfilter to objtrace
- add a command to the objfilter syntax
- change to get the value of the object
- use trace_find_event_field to find the field instead of using argN
- get data from @rec in the event trigger callback funciton
v2:
- adding a "objfilter" trigger to update object
Jeff Xie (4):
trace: Add trace any kernel object
trace/objtrace: Get the value of the object
selftests/ftrace: Add testcases for objtrace
Documentation: trace/objtrace: Add documentation for objtrace
Documentation/trace/events.rst | 83 +++
include/linux/trace_events.h | 1 +
kernel/trace/Kconfig | 10 +
kernel/trace/Makefile | 1 +
kernel/trace/trace.c | 11 +
kernel/trace/trace.h | 21 +
kernel/trace/trace_entries.h | 18 +
kernel/trace/trace_events_trigger.c | 5 +-
kernel/trace/trace_object.c | 611 ++++++++++++++++++
kernel/trace/trace_output.c | 40 ++
.../ftrace/test.d/trigger/trigger-objtrace.tc | 41 ++
11 files changed, 840 insertions(+), 2 deletions(-)
create mode 100644 kernel/trace/trace_object.c
create mode 100644 tools/testing/selftests/ftrace/test.d/trigger/trigger-objtrace.tc
base-commit: 408d26e261b089596c0837e71d2fb4a80ea04ef3
--
2.25.1
