diff options
| author | Masami Hiramatsu (Google) <mhiramat@kernel.org> | 2026-07-02 21:12:41 +0900 |
|---|---|---|
| committer | Masami Hiramatsu (Google) <mhiramat@kernel.org> | 2026-07-14 22:43:16 +0900 |
| commit | f2183452402508ad68ea01eed18ae8eecfcd8f0a (patch) | |
| tree | a7ae00c583a20ab6f56fb9e270f659d7211a9d3a /Documentation/trace | |
| parent | 52c76ec18ebacdcf7e227c06f4215bc49e5d284c (diff) | |
tracing/probes: Support field specifier option for typecast
Add a field specifier option for the typecast. This works like
container_of() macro.
(STRUCT[,FIELD[.FIELD2...]])VAR
This is equivalent to :
container_of(VAR, struct STRUCT, FIELD[.FIELD2...])
For example:
echo "f tick_nohz_handler next_tick=(tick_sched,sched_timer)timer->next_tick" >> dynamic_events
This will trace tick_nohz_handler() with its tick_sched::next_tick which
is converted from @timer by contianer_of(tick, struct tick_sched, sched_timer).
So, if you enabkle both fprobes:tick_nohz_handler__entry and
timer:hrtimer_expire_entry events, we will see something like:
<idle>-0 [002] d.h1. 3778.087272: hrtimer_expire_entry: hrtimer=00000000d63db328 f
unction=tick_nohz_handler now=3777450051040
<idle>-0 [002] d.h1. 3778.087281: tick_nohz_handler__entry: (tick_nohz_handler+0x4
/0x140) next_tick=3777450000000
Link: https://lore.kernel.org/all/178271365745.1176915.725923927180862257.stgit@devnote2/
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Diffstat (limited to 'Documentation/trace')
| -rw-r--r-- | Documentation/trace/eprobetrace.rst | 5 | ||||
| -rw-r--r-- | Documentation/trace/fprobetrace.rst | 8 | ||||
| -rw-r--r-- | Documentation/trace/kprobetrace.rst | 8 |
3 files changed, 14 insertions, 7 deletions
diff --git a/Documentation/trace/eprobetrace.rst b/Documentation/trace/eprobetrace.rst index cd0b4aa7f896..680e0af43d5d 100644 --- a/Documentation/trace/eprobetrace.rst +++ b/Documentation/trace/eprobetrace.rst @@ -49,7 +49,10 @@ Synopsis of eprobe_events (STRUCT)FIELD->MEMBER[->MEMBER] : If BTF is supported, typecast FIELD to a pointer to STRUCT and then derference the pointer defined by ->MEMBER. Note that when this is used, the FIELD name does not - need to be prefixed with a '$'. + need to be prefixed with a '$'. ASGN can be specified optionally. + If ASGN is specified, FIELD will be cast to the same offset + position as the ASGN member, rather than to the beginning of + the STRUCT. (STRUCT)(FETCHARG)->MEMBER[->MEMBER] : typecast can nest, so the above can also be used with another FETCHARG instead of FIELD. diff --git a/Documentation/trace/fprobetrace.rst b/Documentation/trace/fprobetrace.rst index 6b8bb27bb62d..290a9e6f7491 100644 --- a/Documentation/trace/fprobetrace.rst +++ b/Documentation/trace/fprobetrace.rst @@ -57,10 +57,12 @@ Synopsis of fprobe-events (u8/u16/u32/u64/s8/s16/s32/s64), hexadecimal types (x8/x16/x32/x64), "char", "string", "ustring", "symbol", "symstr" and bitfield are supported. - (STRUCT)FIELD->MEMBER[->MEMBER] : If BTF is supported, typecast FIELD to + (STRUCT[,ASGN])FIELD->MEMBER[->MEMBER] : If BTF is supported, typecast FIELD to a pointer to STRUCT and then derference the pointer defined by - ->MEMBER. - (STRUCT)(FETCHARG)->MEMBER[->MEMBER] : typecast can nest, so the above can + ->MEMBER. ASGN can be specified optionally. If ASGN is specified, + FIELD will be cast to the same offset position as the ASGN member, + rather than to the beginning of the STRUCT. + (STRUCT[,ASGN])(FETCHARG)->MEMBER[->MEMBER] : typecast can nest, so the above can also be used with another FETCHARG instead of FIELD. (\*1) This is available only when BTF is enabled. diff --git a/Documentation/trace/kprobetrace.rst b/Documentation/trace/kprobetrace.rst index c4382765d5b2..a62707e6a9f2 100644 --- a/Documentation/trace/kprobetrace.rst +++ b/Documentation/trace/kprobetrace.rst @@ -61,11 +61,13 @@ Synopsis of kprobe_events (x8/x16/x32/x64), VFS layer common type(%pd/%pD), "char", "string", "ustring", "symbol", "symstr" and bitfield are supported. - (STRUCT)FIELD->MEMBER[->MEMBER] : If BTF is supported, typecast FIELD to + (STRUCT[,ASGN])FIELD->MEMBER[->MEMBER] : If BTF is supported, typecast FIELD to a pointer to STRUCT and then derference the pointer defined by ->MEMBER. Note that this is available only when the probe is - on function entry. - (STRUCT)(FETCHARG)->MEMBER[->MEMBER] : typecast can nest, so the above can + on function entry. ASGN can be specified optionally. If ASGN + is specified, FIELD will be cast to the same offset position + as the ASGN member, rather than to the beginning of the STRUCT. + (STRUCT[,ASGN])(FETCHARG)->MEMBER[->MEMBER] : typecast can nest, so the above can also be used with another FETCHARG instead of FIELD. (\*1) only for the probe on function entry (offs == 0). Note, this argument access |