Hi, On Mon, Jun 27, 2022 at 10:14 AM Bagas Sanjaya <bagasdotme@xxxxxxxxx> wrote: > > On Sun, Jun 26, 2022 at 10:56:04AM +0800, Jeff Xie wrote: > > Added documentation explaining how to use objtrace trigger to get the value > > of the object. > > > > Write "Add documentation..." instead. Thanks, I will change it. > > +- objtrace > > + > > + This command provides a way to get the value of any object, 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. > > + > > Did you mean "the object value can be obtained by only needing to set the > objtrace?" Yes, that's what it means. > > + 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 > > + > > Did you mean "the first parameter (arg1) is the parameter value of function > that is passed to kprobe_event, in this case the object base"? Yes, that's what it means. > > + 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 > > + ... > > + > > The output is messy, because for code example and output, literal code > blocks aren't used, hence trigger new warnings: > > Documentation/trace/events.rst:564: WARNING: Inline emphasis start-string without end-string. > Documentation/trace/events.rst:564: WARNING: Inline emphasis start-string without end-string. > Documentation/trace/events.rst:573: WARNING: Inline emphasis start-string without end-string. > Documentation/trace/events.rst:573: WARNING: Inline emphasis start-string without end-string. > Documentation/trace/events.rst:602: WARNING: Unexpected indentation. > Documentation/trace/events.rst:622: WARNING: Block quote ends without a blank line; unexpected unindent. > Documentation/trace/events.rst:630: WARNING: Unexpected indentation. > > I had to apply the following fixup (with rewording): Thank you so much for your help, It looks better ;-) > ---- >8 ---- > > diff --git a/Documentation/trace/events.rst b/Documentation/trace/events.rst > index 0dc47516013331..c15f1d25d4a071 100644 > --- a/Documentation/trace/events.rst > +++ b/Documentation/trace/events.rst > @@ -549,85 +549,89 @@ The following commands are supported: > - objtrace > > This command provides a way to get the value of any object, The object > - can be obtained from the dynamic event(kprobe_event/uprobe_event) or the > - static event(tracepoint). > + 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. > + When using the kprobe event, by only need to set the objtrace (a new > + trigger), we can get the value of object that is set by kprobe event. > > - For example: > - For the function bio_add_page(): > + For example, for the function bio_add_page(): > > - int bio_add_page(struct bio *bio, struct page *page, > - unsigned int len, unsigned int offset) > + .. code-block:: c > > - 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(), > + int bio_add_page(struct bio *bio, struct page *page, > + unsigned int len, unsigned int offset) > > - # echo 'p bio_add_page arg1=$arg1' > ./kprobe_events > + Firstly, we can set the base of the object as first parameter (arg1) to > + to the function: > > - Secondly, we can get the value dynamically based on above object. > + .. code-block:: > > - find the offset of the bi_size in struct bio: > - $ gdb vmlinux > - (gdb) p &(((struct bio *)0)->bi_iter.bi_size) > - $1 = (unsigned int *) 0x28 > + # echo 'p bio_add_page arg1=$arg1' > ./kprobe_events > > - # echo 'objtrace:add:arg1,0x28:u32:1 if comm == "cat"' > ./events/kprobes/ \ > - p_bio_add_page_0/trigger > + Secondly, we can get the value dynamically based on the object: > > - # 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 > + .. code-block:: > > - # du -sh /test.txt > - 12.0K /test.txt > + 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 > > - # 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 > - ... > + # 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 > + ... > > 7. In-kernel trace event API > ============================ > > > Thanks. > > -- > An old man doll... just what I always wanted! - Clara Thanks, JeffXie
