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Date: Thu, 16 Dec 2021 23:50:17 +0900
From: Masami Hiramatsu <mhiramat@...nel.org>
To: Jeff Xie <xiehuan09@...il.com>
Cc: rostedt@...dmis.org, mhiramat@...nel.org, mingo@...hat.com,
zanussi@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC][PATCH v6 0/5] trace: Introduce objtrace trigger to trace
the kernel object
Hi Jeff,
On Tue, 30 Nov 2021 00:49:46 +0800
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).
Now you can remove [RFC] tag from this series, I think.
And can you also add a changelog (short description of the changes) from
the previous version, so that reviewers can find the difference
point easily? Unless that, I need to make a diff from your previous version. :(
Thank you,
>
> 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 base the above object.
>
> find the offset of the bi_size in struct bio:
> $ gdb vmlinux
> (gdb) p &(((struct bio *)0)->bi_iter.bi_size)
> $1 = (unsigned int *) 0x28
>
> # echo 'objtrace:add:arg1,0x28:u32:1 if comm == "cat"' > ./events/kprobes/ \
> p_bio_add_page_0/trigger
>
> The best way to use this is that we can set the entrance event and exit
> event, for example, the following example is to set the read_papes as
> the entrance event, and set the __blk_account_io_start as the exit event.
>
> # cd /sys/kernel/debug/tracing/
> # echo 0 > ./tracing_on
> # echo 'p read_pages' >> ./kprobe_events
> # echo 'p __blk_account_io_start' >> ./kprobe_events
> # echo 'traceon if comm == "cat"' > ./events/kprobes/p_read_pages_0/trigger
> # echo 'traceoff if comm == "cat"' > ./events/kprobes/p___blk_account_io_start_0/trigger
> # echo 'p bio_add_page arg1=$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: 50/50 #P:1
> #
> # _-----=> irqs-off
> # / _----=> need-resched
> # | / _---=> hardirq/softirq
> # || / _--=> preempt-depth
> # ||| / _-=> migrate-disable
> # |||| / delay
> # TASK-PID CPU# ||||| TIMESTAMP FUNCTION
> # | | | ||||| | |
> cat-95 [000] ..... 1.412065: _raw_spin_unlock_irqrestore <-event_triggers_call object:0xffff888108af6328 value:0x0
> cat-95 [000] ..... 1.412066: __bio_try_merge_page <-bio_add_page object:0xffff888108af6328 value:0x0
> cat-95 [000] ..... 1.412066: __bio_add_page <-bio_add_page object:0xffff888108af6328 value:0x0
> cat-95 [000] ..... 1.412066: rcu_read_unlock_strict <-xa_load object:0xffff888108af6328 value:0x1000
> cat-95 [000] ..... 1.412066: bio_add_page <-ext4_mpage_readpages object:0xffff888108af6328 value:0x1000
> cat-95 [000] ..... 1.412066: kprobe_ftrace_handler <-ftrace_ops_list_func object:0xffff888108af6328 value:0x1000
> cat-95 [000] ..... 1.412067: get_kprobe <-kprobe_ftrace_handler object:0xffff888108af6328 value:0x1000
> cat-95 [000] ..... 1.412067: __bio_try_merge_page <-bio_add_page object:0xffff888108af6328 value:0x1000
> cat-95 [000] ..... 1.412067: __bio_add_page <-bio_add_page object:0xffff888108af6328 value:0x1000
> cat-95 [000] ..... 1.412067: rcu_read_unlock_strict <-xa_load object:0xffff888108af6328 value:0x2000
> cat-95 [000] ..... 1.412067: bio_add_page <-ext4_mpage_readpages object:0xffff888108af6328 value:0x2000
> cat-95 [000] ..... 1.412067: kprobe_ftrace_handler <-ftrace_ops_list_func object:0xffff888108af6328 value:0x2000
> cat-95 [000] ..... 1.412067: get_kprobe <-kprobe_ftrace_handler object:0xffff888108af6328 value:0x2000
> cat-95 [000] ..... 1.412067: __bio_try_merge_page <-bio_add_page object:0xffff888108af6328 value:0x2000
> cat-95 [000] ..... 1.412068: submit_bio <-ext4_mpage_readpages object:0xffff888108af6328 value:0x3000
> cat-95 [000] ..... 1.412068: submit_bio_noacct <-ext4_mpage_readpages object:0xffff888108af6328 value:0x3000
> cat-95 [000] ..... 1.412068: __submit_bio <-submit_bio_noacct object:0xffff888108af6328 value:0x3000
> cat-95 [000] ..... 1.412068: blk_try_enter_queue <-__submit_bio object:0xffff888108af6328 value:0x3000
> cat-95 [000] ..... 1.412068: rcu_read_unlock_strict <-blk_try_enter_queue object:0xffff888108af6328 value:0x3000
> cat-95 [000] ..... 1.412068: rcu_read_unlock_strict <-blk_try_enter_queue object:0xffff888108af6328 value:0x3000
> cat-95 [000] ..... 1.412068: submit_bio_checks <-__submit_bio object:0xffff888108af6328 value:0x3000
> cat-95 [000] ..... 1.412068: __cond_resched <-submit_bio_checks object:0xffff888108af6328 value:0x3000
> cat-95 [000] ..... 1.412068: rcu_all_qs <-__cond_resched object:0xffff888108af6328 value:0x3000
> cat-95 [000] ..... 1.412068: should_fail_bio <-submit_bio_checks object:0xffff888108af6328 value:0x3000
> cat-95 [000] ..... 1.412069: create_task_io_context <-submit_bio_checks object:0xffff888108af6328 value:0x3000
> cat-95 [000] ..... 1.412069: kmem_cache_alloc_node <-create_task_io_context object:0xffff888108af6328 value:0x3000
> cat-95 [000] ..... 1.412069: should_failslab <-kmem_cache_alloc_node object:0xffff888108af6328 value:0x3000
> cat-95 [000] ..... 1.412069: _raw_spin_lock <-create_task_io_context object:0xffff888108af6328 value:0x3000
> cat-95 [000] ..... 1.412069: blk_mq_submit_bio <-__submit_bio object:0xffff888108af6328 value:0x3000
> cat-95 [000] ..... 1.412069: __blk_queue_split <-blk_mq_submit_bio object:0xffff888108af6328 value:0x3000
> cat-95 [000] ..... 1.412069: bvec_split_segs <-__blk_queue_split object:0xffff888108af6328 value:0x3000
> cat-95 [000] ..... 1.412069: blk_attempt_plug_merge <-blk_mq_submit_bio object:0xffff888108af6328 value:0x3000
> cat-95 [000] ..... 1.412070: __blk_mq_sched_bio_merge <-blk_mq_submit_bio object:0xffff888108af6328 value:0x3000
> cat-95 [000] ..... 1.412070: dd_bio_merge <-blk_mq_submit_bio object:0xffff888108af6328 value:0x3000
> cat-95 [000] ..... 1.412070: _raw_spin_lock <-dd_bio_merge object:0xffff888108af6328 value:0x3000
> cat-95 [000] ..... 1.412070: blk_mq_sched_try_merge <-dd_bio_merge object:0xffff888108af6328 value:0x3000
> cat-95 [000] ..... 1.412070: elv_merge <-blk_mq_sched_try_merge object:0xffff888108af6328 value:0x3000
> cat-95 [000] ..... 1.412070: elv_rqhash_find <-elv_merge object:0xffff888108af6328 value:0x3000
> cat-95 [000] ..... 1.412070: dd_request_merge <-blk_mq_sched_try_merge object:0xffff888108af6328 value:0x3000
> cat-95 [000] ..... 1.412070: elv_rb_find <-dd_request_merge object:0xffff888108af6328 value:0x3000
> cat-95 [000] ..... 1.412070: __blk_mq_alloc_request <-blk_mq_submit_bio object:0xffff888108af6328 value:0x3000
> cat-95 [000] ..... 1.412071: dd_limit_depth <-__blk_mq_alloc_request object:0xffff888108af6328 value:0x3000
> cat-95 [000] ..... 1.412071: blk_mq_get_tag <-__blk_mq_alloc_request object:0xffff888108af6328 value:0x3000
> cat-95 [000] ..... 1.412071: __blk_mq_get_tag <-blk_mq_get_tag object:0xffff888108af6328 value:0x3000
> cat-95 [000] ..... 1.412071: blk_mq_rq_ctx_init.isra.0 <-blk_mq_submit_bio object:0xffff888108af6328 value:0x3000
> cat-95 [000] ..... 1.412071: ktime_get <-blk_mq_rq_ctx_init.isra.0 object:0xffff888108af6328 value:0x3000
> cat-95 [000] ..... 1.412071: dd_prepare_request <-blk_mq_rq_ctx_init.isra.0 object:0xffff888108af6328 value:0x3000
> cat-95 [000] ..... 1.412071: __blk_account_io_start <-blk_mq_submit_bio object:0xffff888108af6328 value:0x3000
> cat-95 [000] ..... 1.412071: kprobe_ftrace_handler <-ftrace_ops_list_func object:0xffff888108af6328 value:0x3000
> cat-95 [000] ..... 1.412071: get_kprobe <-kprobe_ftrace_handler object:0xffff888108af6328 value:0x3000
>
> Jeff Xie (5):
> trace: Add trace any kernel object
> trace/objtrace: get the value of the object
> trace/README: Document objtrace trigger syntax
> trace/objtrace: Add testcases for objtrace
> trace/objtrace: Add documentation for objtrace
>
> Documentation/trace/events.rst | 114 +++
> include/linux/trace_events.h | 1 +
> kernel/trace/Kconfig | 10 +
> kernel/trace/Makefile | 1 +
> kernel/trace/trace.c | 3 +
> kernel/trace/trace.h | 8 +
> kernel/trace/trace_entries.h | 18 +
> kernel/trace/trace_events_trigger.c | 1 +
> kernel/trace/trace_object.c | 660 ++++++++++++++++++
> kernel/trace/trace_output.c | 40 ++
> .../ftrace/test.d/trigger/trigger-objtrace.tc | 39 ++
> 11 files changed, 895 insertions(+)
> create mode 100644 kernel/trace/trace_object.c
> create mode 100644 tools/testing/selftests/ftrace/test.d/trigger/trigger-objtrace.tc
>
> --
> 2.25.1
>
--
Masami Hiramatsu <mhiramat@...nel.org>
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