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authorMasami Hiramatsu <mhiramat@kernel.org>2018-04-25 15:21:55 +0300
committerSteven Rostedt (VMware) <rostedt@goodmis.org>2018-10-11 05:19:10 +0300
commit40b53b771806b1770837169cd32d1bf167fbccaf (patch)
treecd6a5bf5fee832a6169891ba07b347545dd03c47 /Documentation/trace
parent60c2e0cebfd01bd1bc5e8843f063264148d6b2bb (diff)
downloadlinux-40b53b771806b1770837169cd32d1bf167fbccaf.tar.xz
tracing: probeevent: Add array type support
Add array type support for probe events. This allows user to get arraied types from memory address. The array type syntax is TYPE[N] Where TYPE is one of types (u8/16/32/64,s8/16/32/64, x8/16/32/64, symbol, string) and N is a fixed value less than 64. The string array type is a bit different from other types. For other base types, <base-type>[1] is equal to <base-type> (e.g. +0(%di):x32[1] is same as +0(%di):x32.) But string[1] is not equal to string. The string type itself represents "char array", but string array type represents "char * array". So, for example, +0(%di):string[1] is equal to +0(+0(%di)):string. Link: http://lkml.kernel.org/r/152465891533.26224.6150658225601339931.stgit@devbox Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org> Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Diffstat (limited to 'Documentation/trace')
-rw-r--r--Documentation/trace/kprobetrace.rst11
1 files changed, 11 insertions, 0 deletions
diff --git a/Documentation/trace/kprobetrace.rst b/Documentation/trace/kprobetrace.rst
index 6224ddf34508..2dfed7a1ea6f 100644
--- a/Documentation/trace/kprobetrace.rst
+++ b/Documentation/trace/kprobetrace.rst
@@ -64,9 +64,20 @@ 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).
+These value types can be an array. To record array data, you can add '[N]'
+(where N is a fixed number, less than 64) to the base type.
+E.g. 'x16[4]' means an array of x16 (2bytes hex) with 4 elements.
+Note that the array can be applied to memory type fetchargs, you can not
+apply it to registers/stack-entries etc. (for example, '$stack1:x8[8]' is
+wrong, but '+8($stack):x8[8]' is OK.)
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.
+The string array type is a bit different from other types. For other base
+types, <base-type>[1] is equal to <base-type> (e.g. +0(%di):x32[1] is same
+as +0(%di):x32.) But string[1] is not equal to string. The string type itself
+represents "char array", but string array type represents "char * array".
+So, for example, +0(%di):string[1] is equal to +0(+0(%di)):string.
Bitfield is another special type, which takes 3 parameters, bit-width, bit-
offset, and container-size (usually 32). The syntax is::