From 1ff511e35ed87cc2ebade9e678e4a2fe39b6f9c5 Mon Sep 17 00:00:00 2001 From: Masami Hiramatsu Date: Fri, 4 Feb 2011 21:52:05 +0900 Subject: tracing/kprobes: Add bitfield type Add bitfield type for tracing arguments on kprobe-tracer. The syntax of a bitfield type is: b@/ 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 Cc: Ingo Molnar Cc: Srikar Dronamraju Cc: Steven Rostedt LKML-Reference: <20110204125205.9507.11363.stgit@ltc236.sdl.hitachi.co.jp> Signed-off-by: Masami Hiramatsu Signed-off-by: Arnaldo Carvalho de Melo --- Documentation/trace/kprobetrace.txt | 16 +++++++++++++++- 1 file changed, 15 insertions(+), 1 deletion(-) (limited to 'Documentation/trace') 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@/ + Per-Probe Event Filtering ------------------------- -- cgit v1.2.3