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tracing: probeevent: Add array type support

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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>
This commit is contained in:
Masami Hiramatsu
2018-04-25 21:21:55 +09:00
committed by Steven Rostedt (VMware)
parent 60c2e0cebf
commit 40b53b7718
5 changed files with 180 additions and 39 deletions
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11
Documentation/trace/kprobetrace.rst
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@@ -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::