path: root/Documentation/trace
diff options
authorMasami Hiramatsu <masami.hiramatsu.pt@hitachi.com>2011-02-04 21:52:05 +0900
committerArnaldo Carvalho de Melo <acme@redhat.com>2011-02-07 09:18:11 -0200
commit1ff511e35ed87cc2ebade9e678e4a2fe39b6f9c5 (patch)
treeb16cff475673db75aef773cc1118734a2172066a /Documentation/trace
parente3745369986ddcdaa19f70e2d24e658876b97e84 (diff)
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')
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.
+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