linux-kernel - RE: [PATCH 2/2] prctl.2: Document the new PR_GET_TASK

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Date:   Fri, 3 May 2019 11:20:32 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Joel Savitz' <jsavitz@...hat.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Waiman Long <longman@...hat.com>,
        Mauro Carvalho Chehab <mchehab+samsung@...nel.org>,
        Kristina Martsenko <kristina.martsenko@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Cyrill Gorcunov <gorcunov@...il.com>,
        Kees Cook <keescook@...omium.org>,
        "Gustavo A. R. Silva" <gustavo@...eddedor.com>,
        YueHaibing <yuehaibing@...wei.com>,
        Micah Morton <mortonm@...omium.org>,
        Yang Shi <yang.shi@...ux.alibaba.com>,
        Jann Horn <jannh@...gle.com>,
        Alexey Dobriyan <adobriyan@...il.com>,
        Rafael Aquini <aquini@...hat.com>,
        Michael Kerrisk <mtk.manpages@...il.com>
Subject: RE: [PATCH 2/2] prctl.2: Document the new PR_GET_TASK_SIZE option

From: Joel Savitz
> Sent: 02 May 2019 20:13
> Add a short explanation of the new PR_GET_TASK_SIZE option for the benefit
> of future generations.
> 
> Signed-off-by: Joel Savitz <jsavitz@...hat.com>
> ---
>  man2/prctl.2 | 9 +++++++++
>  1 file changed, 9 insertions(+)
> 
> diff --git a/man2/prctl.2 b/man2/prctl.2
> index 06d8e13c7..35a6a3919 100644
> --- a/man2/prctl.2
> +++ b/man2/prctl.2
> @@ -49,6 +49,7 @@
>  .\" 2013-01-10 Kees Cook, document PR_SET_PTRACER
>  .\" 2012-02-04 Michael Kerrisk, document PR_{SET,GET}_CHILD_SUBREAPER
>  .\" 2014-11-10 Dave Hansen, document PR_MPX_{EN,DIS}ABLE_MANAGEMENT
> +.\" 2019-05-02 Joel Savitz, document PR_GET_TASK_SIZE
>  .\"
>  .\"
>  .TH PRCTL 2 2019-03-06 "Linux" "Linux Programmer's Manual"
> @@ -1375,6 +1376,14 @@ system call on Tru64).
>  for information on versions and architectures)
>  Return unaligned access control bits, in the location pointed to by
>  .IR "(unsigned int\ *) arg2" .
> +.TP
> +.B PR_GET_TASK_SIZE
> +Copy the value of TASK_SIZE to the userspace address in
> +.IR "arg2" .
> +Return
> +.B EFAULT
> +if this operation fails.
> +

Shouldn't this say what the value is?
ISTR a recent patch to change the was the 'used to be constant' TASK_SIZE is defined.
I think it might be 'The highest userspace virtual address the current
process can use.' But I might be wrong.

	David

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