diff mbox series

[v13,4/4] Documentation: trace/objtrace: Add documentation for objtrace

Message ID 20220626025604.277413-5-xiehuan09@gmail.com (mailing list archive)
State New
Headers show
Series trace: Introduce objtrace trigger to trace the kernel object | expand

Commit Message

Jeff Xie June 26, 2022, 2:56 a.m. UTC 
Added documentation explaining how to use objtrace trigger to get the value
of the object.

Signed-off-by: Jeff Xie <xiehuan09@gmail.com>
Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
---
 Documentation/trace/events.rst | 83 ++++++++++++++++++++++++++++++++++
 1 file changed, 83 insertions(+)

Comments

Bagas Sanjaya June 27, 2022, 2:14 a.m. UTC | #1 
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.

> +- 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?"

> +  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"?

> +  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):

---- >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.
Jeff Xie June 27, 2022, 7:45 a.m. UTC | #2 
Hi,

On Mon, Jun 27, 2022 at 10:14 AM Bagas Sanjaya <bagasdotme@gmail.com> 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
Jeff Xie June 28, 2022, 1:37 a.m. UTC | #3 
Hi Masami,

I would like to ask if I change the document like "Bagas Sanjaya"
rewording in the next version.
I don't know if I can add your Reviewed-by again, I don't know the
rules very well ;-)

On Mon, Jun 27, 2022 at 3:45 PM Jeff Xie <xiehuan09@gmail.com> wrote:
>
> Hi,
>
> On Mon, Jun 27, 2022 at 10:14 AM Bagas Sanjaya <bagasdotme@gmail.com> 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

Thanks,
JeffXie
Bagas Sanjaya June 28, 2022, 2:31 a.m. UTC | #4 
On 6/28/22 08:37, Jeff Xie wrote:
> Hi Masami,
> 
> I would like to ask if I change the document like "Bagas Sanjaya"
> rewording in the next version.
> I don't know if I can add your Reviewed-by again, I don't know the
> rules very well ;-)
> 

In the next version roll, just mention the feedback in the patch
changelog (but not in the patch message as would appear on git log).
Jeff Xie June 28, 2022, 2:48 a.m. UTC | #5 
On Tue, Jun 28, 2022 at 10:31 AM Bagas Sanjaya <bagasdotme@gmail.com> wrote:
>
> On 6/28/22 08:37, Jeff Xie wrote:
> > Hi Masami,
> >
> > I would like to ask if I change the document like "Bagas Sanjaya"
> > rewording in the next version.
> > I don't know if I can add your Reviewed-by again, I don't know the
> > rules very well ;-)
> >
>
> In the next version roll, just mention the feedback in the patch
> changelog (but not in the patch message as would appear on git log).

Okay, thank you for your reply ;-)

> --
> An old man doll... just what I always wanted! - Clara

Thanks,
JeffXie
diff mbox series

Patch

diff --git a/Documentation/trace/events.rst b/Documentation/trace/events.rst
index c47f381d0c00..0dc475160133 100644
--- a/Documentation/trace/events.rst
+++ b/Documentation/trace/events.rst
@@ -546,6 +546,89 @@  The following commands are supported:
 
   See Documentation/trace/histogram.rst for details and examples.
 
+- 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.
+
+  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
+             ...
+
 7. In-kernel trace event API
 ============================