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Message-ID: <CAEr6+EDVhMwF1cok1StkYPSd_AMdMsn9Kw9U+Bt5p9i7CYZG4A@mail.gmail.com>
Date: Tue, 5 Jul 2022 23:30:46 +0800
From: Jeff Xie <xiehuan09@...il.com>
To: Steven Rostedt <rostedt@...dmis.org>
Cc: mingo@...hat.com, Masami Hiramatsu <mhiramat@...nel.org>,
Tom Zanussi <zanussi@...nel.org>, linux-kernel@...r.kernel.org,
Song Chen <chensong_2000@....cn>
Subject: Re: [PATCH v14 0/4] trace: Introduce objtrace trigger to trace the
kernel object
Hi Steve,
I'm curious if you have any comments on this patchset ;-)
On Tue, Jun 28, 2022 at 10:56 PM Jeff Xie <xiehuan09@...il.com> wrote:
>
> 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@...nel.org)
> and steve(rostedt@...dmis.org), thank you all so much.
>
> 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 <lkp@...el.com>
> Suggested-by: Nathan Chancellor <nathan@...nel.org>
>
> v11:
> - remove useless atomic counting methods for num_traced_obj
> - make array objtrace_fetch_types null terminated
> - add raw_spin_lock_init for obj_data_lock
>
> v10:
> - support ftrace instances
> - use trace_buffer_lock_reserve instead of trace_event_buffer_lock_reserve
> - a lot of cleanup work has been done mainly for event_object_trigger_parse
>
> v9:
> - fix objtrace trigger output was incomplete
> - fix the objtrace trigger was removed when using the existed parameter on
> event.
> - add testcase for the second fix above.
>
> v8:
> - revert to use per-cpu recursion for the function trace_object_events_call
> - recover the filter when getting the value of the object
> - simplify the implementation for the function get_object_value
> - fix the build error
>
> v7:
> - use fixed-size array for object pool instead of list structure
> - use ftrace_test_recursion_trylock for function trace hook function
> - fix trace_object_ref reference count in the init_trace_object
> - invoke exit_trace_object no matter whether data->ops->free is null
> in the unregister_object_trigger
> - release private_data of event_trigger_data in the trace_object_trigger_free
> - remove [RFC] tag
>
> v6:
> - change the objtrace trigger syntax.
> - add patchset description
> - add <tracefs>/README
>
> v5:
> - add testcasts
> - add check the field->size
> - add lockless to search object
> - describe the object trace more clearly in Kconfig
>
> v4:
> - please ignore the v4 which is the same as v3
>
> v3:
> - change the objfilter to objtrace
> - add a command to the objfilter syntax
> - change to get the value of the object
> - use trace_find_event_field to find the field instead of using argN
> - get data from @rec in the event trigger callback funciton
>
> v2:
> - adding a "objfilter" trigger to update object
>
> Jeff Xie (4):
> trace: Add trace any kernel object
> trace/objtrace: Get the value of the object
> selftests/ftrace: Add testcases for objtrace
> Documentation: trace/objtrace: Add documentation for objtrace
>
> Documentation/trace/events.rst | 87 +++
> 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, 844 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
>
Thanks,
JeffXie
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