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| author | Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> | 2011-02-04 21:52:05 +0900 |
|---|---|---|
| committer | Arnaldo Carvalho de Melo <acme@redhat.com> | 2011-02-07 09:18:11 -0200 |
| commit | 1ff511e35ed87cc2ebade9e678e4a2fe39b6f9c5 (patch) | |
| tree | b16cff475673db75aef773cc1118734a2172066a /Documentation/trace | |
| parent | e3745369986ddcdaa19f70e2d24e658876b97e84 (diff) | |
| download | lwn-1ff511e35ed87cc2ebade9e678e4a2fe39b6f9c5.tar.gz lwn-1ff511e35ed87cc2ebade9e678e4a2fe39b6f9c5.zip | |
tracing/kprobes: Add bitfield type
Add bitfield type for tracing arguments on kprobe-tracer. The syntax of
a bitfield type is:
b<bit-size>@<bit-offset>/<container-size>
e.g.
Accessing 2 bits-width field with 4 bits-offset in 32 bits-width data at
4 bytes offseted from the address pointed by AX register:
+4(%ax):b2@4/32
Since the width of container data depends on the arch, so I just added
the container-size at the end.
Cc: 2nddept-manager@sdl.hitachi.co.jp
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
LKML-Reference: <20110204125205.9507.11363.stgit@ltc236.sdl.hitachi.co.jp>
Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Diffstat (limited to 'Documentation/trace')
| -rw-r--r-- | Documentation/trace/kprobetrace.txt | 16 |
1 files changed, 15 insertions, 1 deletions
diff --git a/Documentation/trace/kprobetrace.txt b/Documentation/trace/kprobetrace.txt index 5f77d94598dd..6d27ab8d6e9f 100644 --- a/Documentation/trace/kprobetrace.txt +++ b/Documentation/trace/kprobetrace.txt @@ -42,11 +42,25 @@ Synopsis of kprobe_events +|-offs(FETCHARG) : Fetch memory at FETCHARG +|- offs address.(**) NAME=FETCHARG : Set NAME as the argument name of FETCHARG. FETCHARG:TYPE : Set TYPE as the type of FETCHARG. Currently, basic types - (u8/u16/u32/u64/s8/s16/s32/s64) and string are supported. + (u8/u16/u32/u64/s8/s16/s32/s64), "string" and bitfield + are supported. (*) only for return probe. (**) this is useful for fetching a field of data structures. +Types +----- +Several types are supported for fetch-args. Kprobe tracer will access memory +by given type. Prefix 's' and 'u' means those types are signed and unsigned +respectively. Traced arguments are shown in decimal (signed) or hex (unsigned). +String type is a special type, which fetches a "null-terminated" string from +kernel space. This means it will fail and store NULL if the string container +has been paged out. +Bitfield is another special type, which takes 3 parameters, bit-width, bit- +offset, and container-size (usually 32). The syntax is; + + b<bit-width>@<bit-offset>/<container-size> + Per-Probe Event Filtering ------------------------- |