linux-kernel - Re: [PATCH v2 1/3] tracing: document "string

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Message-Id: <20160607152911.976e1c922ae334f8b8675c86@kernel.org>
Date:	Tue, 7 Jun 2016 15:29:11 +0900
From:	Masami Hiramatsu <mhiramat@...nel.org>
To:	Omar Sandoval <osandov@...ndov.com>
Cc:	Steven Rostedt <rostedt@...dmis.org>,
	Ingo Molnar <mingo@...hat.com>,
	Namhyung Kim <namhyung@...il.com>,
	linux-kernel@...r.kernel.org, kernel-team@...com,
	Omar Sandoval <osandov@...com>
Subject: Re: [PATCH v2 1/3] tracing: document "string_size" [ku]probe type

On Thu,  2 Jun 2016 18:11:01 -0700
Omar Sandoval <osandov@...ndov.com> wrote:

> From: Omar Sandoval <osandov@...com>
> 
> It has been undocumented since it was introduced in commit e09c8614b329
> ("tracing/kprobes: Support "string" type").

Ah, actually, string_size is a support fetch function for string.
So please ignore it. Or would you have any idea to use it?

Thank you,

> 
> Signed-off-by: Omar Sandoval <osandov@...com>
> ---
>  Documentation/trace/kprobetrace.txt  | 11 ++++++-----
>  Documentation/trace/uprobetracer.txt |  9 +++++----
>  2 files changed, 11 insertions(+), 9 deletions(-)
> 
> diff --git a/Documentation/trace/kprobetrace.txt b/Documentation/trace/kprobetrace.txt
> index d68ea5fc812b..4b3f5293b7bf 100644
> --- a/Documentation/trace/kprobetrace.txt
> +++ b/Documentation/trace/kprobetrace.txt
> @@ -43,8 +43,8 @@ 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), "string", "string_size", and
> +		  bitfield are supported.
>  
>    (*) only for return probe.
>    (**) this is useful for fetching a field of data structures.
> @@ -54,9 +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).
> -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.
> +"string" 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. "string_size" is the length of a null-terminated string including
> +the NUL byte.
>  Bitfield is another special type, which takes 3 parameters, bit-width, bit-
>  offset, and container-size (usually 32). The syntax is;
>  
> diff --git a/Documentation/trace/uprobetracer.txt b/Documentation/trace/uprobetracer.txt
> index f1cf9a34ad9d..7e0480263c2f 100644
> --- a/Documentation/trace/uprobetracer.txt
> +++ b/Documentation/trace/uprobetracer.txt
> @@ -39,8 +39,8 @@ Synopsis of uprobe_tracer
>     +|-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), "string",
> +		       "string_size", and bitfield are supported.
>  
>    (*) only for return probe.
>    (**) this is useful for fetching a field of data structures.
> @@ -50,8 +50,9 @@ Types
>  Several types are supported for fetch-args. Uprobe 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
> -user space.
> +"string" is a special type which fetches a null-terminated string from user
> +space. "string_size" is the length of a null-terminated string including the
> +NUL byte.
>  Bitfield is another special type, which takes 3 parameters, bit-width, bit-
>  offset, and container-size (usually 32). The syntax is;
>  
> -- 
> 2.8.3
> 


-- 
Masami Hiramatsu <mhiramat@...nel.org>