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-rw-r--r--Documentation/trace/kprobetrace.txt9
1 files changed, 6 insertions, 3 deletions
diff --git a/Documentation/trace/kprobetrace.txt b/Documentation/trace/kprobetrace.txt
index ea52ec1f8484..e4991fb1eedc 100644
--- a/Documentation/trace/kprobetrace.txt
+++ b/Documentation/trace/kprobetrace.txt
@@ -44,8 +44,8 @@ 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), "string" and bitfield
- are supported.
+ (u8/u16/u32/u64/s8/s16/s32/s64), hexadecimal types
+ (x8/x16/x32/x64), "string" and bitfield are supported.
(*) only for return probe.
(**) this is useful for fetching a field of data structures.
@@ -54,7 +54,10 @@ 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).
+respectively. 'x' prefix implies it is unsigned. Traced arguments are shown
+in decimal ('s' and 'u') or hexadecimal ('x'). Without type casting, 'x32'
+or 'x64' is used depends on the architecture (e.g. x86-32 uses x32, and
+x86-64 uses x64).
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.