Messages in this thread | | | From | Jeff Xie <> | Date | Wed, 19 Jan 2022 10:32:49 +0800 | Subject | Re: [PATCH v7 0/4] trace: Introduce objtrace trigger to trace the kernel object |
| |
Hi Masami,
On Tue, Jan 18, 2022 at 10:24 PM Masami Hiramatsu <mhiramat@kernel.org> wrote: > > On Thu, 13 Jan 2022 09:38:31 +0800 > Jeff Xie <xiehuan09@gmail.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 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 > > > > Almost all changelogs were suggested by Masami(mhiramat@kernel.org) > > and steve(rostedt@goodmis.org), thank you all so much. > > > > 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 > > > > Note: when change to use the ftrace_test_recursion_trylock, all the functions > > will call the copy_from_kernel_nofault, I don't know where this is the problem now, > > maybe should fall back to the usage in v6. > > > > for example: > > > > cat-118 [000] ...1. 1.458998: __bio_add_page <-bio_add_page object:0xffff88811a12e9e8 value:0x0 > > cat-118 [000] ...2. 1.458998: copy_from_kernel_nofault <-trace_object_events_call object:0xffff88811a12e9e8 value:0x1000 > > cat-118 [000] ...2. 1.458998: copy_from_kernel_nofault_allowed <-copy_from_kernel_nofault object:0xffff88811a12e9e8 value:0x1000 > > cat-118 [000] ...1. 1.458998: __rcu_read_lock <-xa_load object:0xffff88811a12e9e8 value:0x1000 > > cat-118 [000] ...2. 1.458998: copy_from_kernel_nofault <-trace_object_events_call object:0xffff88811a12e9e8 value:0x1000 > > cat-118 [000] ...2. 1.458998: copy_from_kernel_nofault_allowed <-copy_from_kernel_nofault object:0xffff88811a12e9e8 value:0x1000 > > cat-118 [000] ...1. 1.458998: __rcu_read_unlock <-xa_load object:0xffff88811a12e9e8 value:0x1000 > > cat-118 [000] ...3. 1.458998: copy_from_kernel_nofault <-trace_object_events_call object:0xffff88811a12e9e8 value:0x1000 > > cat-118 [000] ...3. 1.458998: copy_from_kernel_nofault_allowed <-copy_from_kernel_nofault object:0xffff88811a12e9e8 value:0x1000 > > .... > > Hmm, this is strange, but I got it is the expected behavior, since the > ftrace_test_recursion_trylock() accepts one stage recursion for the > first event in the interrupt as transition event. > Steve, any good way to limit probing this transition events? > > > BTW, I tried your series on the > git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace.git ftrace/core > and got below build errors. > > linux/kernel/trace/trace_object.c:266:3: error: ‘struct event_trigger_ops’ has no member named ‘func’ > 266 | .func = trace_object_trigger, > | ^~~~ > linux/kernel/trace/trace_object.c:273:3: error: ‘struct event_trigger_ops’ has no member named ‘func’ > 273 | .func = trace_object_count_trigger, > | ^~~~ > linux/kernel/trace/trace_object.c:535:3: error: ‘struct event_command’ has no member named ‘func’ > 535 | .func = event_object_trigger_callback, > | ^~~~ > CC net/ipv6/sysctl_net_ipv6.o > > This is because commit 7d28e1e7d4fa ("tracing: Change event_trigger_ops func() to trigger()") > and commit 4dfe5dff80a4 ("tracing: Change event_command func() to parse()") changed the field > names. Please update it. > Thanks, I will update it. > > Thank you, > > -- > Masami Hiramatsu <mhiramat@kernel.org> --- JeffXie
| |