[PATCH] ptrace.2: Mention that PTRACE_PEEK* libc API and kernel API are different

[PATCH] ptrace.2: Mention that PTRACE_PEEK* libc API and kernel API are different

[Denys Vlasenko]

By Oleg's request.

Signed-off-by: Denys Vlasenko <dvlasenk-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
CC: linux-man-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
CC: Oleg Nesterov <oleg-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
CC: Jan Kratochvil <jan.kratochvil-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
CC: Dmitry V. Levin <ldv-u2l5PoMzF/Vg9hUCZPvPmw@public.gmane.org>
---
 man2/ptrace.2 | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/man2/ptrace.2 b/man2/ptrace.2
index 55c4fe2..a6e01a0 100644
--- a/man2/ptrace.2
+++ b/man2/ptrace.2
@@ -1776,8 +1776,15 @@ the report is sent only once.
 .SH RETURN VALUE
 On success,
 .B PTRACE_PEEK*
-requests return the requested data,
-while other requests return zero.
+requests return the requested data, while other requests return zero.
+(On Linux, this is done in the libc wrapper around ptrace system call.
+On the system call level,
+.B PTRACE_PEEK*
+requests have a different API: they store the result
+at the address specified by
+.I data
+parameter, and return value is the error flag.)
+.LP
 On error, all requests return \-1, and
 .I errno
 is set appropriately.
-- 
1.8.1.4

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Re: [PATCH] ptrace.2: Mention that PTRACE_PEEK* libc API and kernel API are different

[Oleg Nesterov]

On 07/02, Denys Vlasenko wrote:
>
> By Oleg's request.

I spent several hours trying to understand why my test-case
doesn't work ;)

>  .B PTRACE_PEEK*
> -requests return the requested data,
> -while other requests return zero.
> +requests return the requested data, while other requests return zero.
> +(On Linux, this is done in the libc wrapper around ptrace system call.
> +On the system call level,
> +.B PTRACE_PEEK*
> +requests have a different API: they store the result
> +at the address specified by
> +.I data
> +parameter, and return value is the error flag.)
> +.LP

Thanks!

Oleg.

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Re: [PATCH] ptrace.2: Mention that PTRACE_PEEK* libc API and kernel API are different

[Michael Kerrisk]

Thanks, Denys. Applied.

On 07/02/13 13:20, Denys Vlasenko wrote:
> By Oleg's request.
> 
> Signed-off-by: Denys Vlasenko <dvlasenk-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
> CC: linux-man-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
> CC: Oleg Nesterov <oleg-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
> CC: Jan Kratochvil <jan.kratochvil-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
> CC: Dmitry V. Levin <ldv-u2l5PoMzF/Vg9hUCZPvPmw@public.gmane.org>
> ---
>  man2/ptrace.2 | 11 +++++++++--
>  1 file changed, 9 insertions(+), 2 deletions(-)
> 
> diff --git a/man2/ptrace.2 b/man2/ptrace.2
> index 55c4fe2..a6e01a0 100644
> --- a/man2/ptrace.2
> +++ b/man2/ptrace.2
> @@ -1776,8 +1776,15 @@ the report is sent only once.
>  .SH RETURN VALUE
>  On success,
>  .B PTRACE_PEEK*
> -requests return the requested data,
> -while other requests return zero.
> +requests return the requested data, while other requests return zero.
> +(On Linux, this is done in the libc wrapper around ptrace system call.
> +On the system call level,
> +.B PTRACE_PEEK*
> +requests have a different API: they store the result
> +at the address specified by
> +.I data
> +parameter, and return value is the error flag.)
> +.LP
>  On error, all requests return \-1, and
>  .I errno
>  is set appropriately.
> 

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