linux-kernel - Re: [PATCH v2] ELF: document some de-facto PT

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Message-ID: <4de7483e-2240-5a81-e3e8-af7b658695eb@infradead.org>
Date:   Sun, 26 Mar 2023 12:51:37 -0700
From:   Randy Dunlap <rdunlap@...radead.org>
To:     Alexey Dobriyan <adobriyan@...il.com>, akpm@...ux-foundation.org
Cc:     linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
        Jonathan Corbet <corbet@....net>,
        Bagas Sanjaya <bagasdotme@...il.com>
Subject: Re: [PATCH v2] ELF: document some de-facto PT_* ABI quirks

Hi Alexey,

On 3/26/23 09:49, Alexey Dobriyan wrote:
> Turns out rules about PT_INTERP, PT_GNU_STACK and PT_GNU_PROPERTY
> program headers are slightly different.
> 
> Signed-off-by: Alexey Dobriyan <adobriyan@...il.com>
> ---
> 
> 	v2: integrate into documentation build system
> 
>  Documentation/ELF/ELF.rst   |   32 ++++++++++++++++++++++++++++++++
>  Documentation/ELF/index.rst |   10 ++++++++++
>  Documentation/index.rst     |    1 +
>  3 files changed, 43 insertions(+)

I'm not sure that ELF merits its own subdirectory or that each item here
should be a chapter,  but this fixes all of the issues that I pointed out. Thanks.

Reviewed-by: Randy Dunlap <rdunlap@...radead.org>

> new file mode 100644
> --- /dev/null
> +++ b/Documentation/ELF/ELF.rst
> @@ -0,0 +1,32 @@
> +.. SPDX-License-Identifier: GPL-2.0
> +
> +=================================
> +Linux-specific ELF idiosyncrasies
> +=================================
> +
> +Definitions
> +===========
> +
> +"First" program header is the one with the smallest offset in the file:
> +e_phoff. "Last" program header is the one with the biggest offset:
> +e_phoff + (e_phnum - 1) * sizeof(Elf_Phdr).
> +
> +PT_INTERP
> +=========
> +
> +First PT_INTERP program header is used to locate the filename of ELF
> +interpreter. Other PT_INTERP headers are ignored (since Linux 2.4.11).
> +
> +PT_GNU_STACK
> +============
> +
> +Last PT_GNU_STACK program header defines userspace stack executability
> +(since Linux 2.6.6). Other PT_GNU_STACK headers are ignored.
> +
> +PT_GNU_PROPERTY
> +===============
> +
> +ELF interpreter's last PT_GNU_PROPERTY program header is used (since
> +Linux 5.8). If interpreter doesn't have one, then the last PT_GNU_PROPERTY
> +program header of an executable is used. Other PT_GNU_PROPERTY headers
> +are ignored.
> new file mode 100644
> --- /dev/null
> +++ b/Documentation/ELF/index.rst
> @@ -0,0 +1,10 @@
> +.. SPDX-License-Identifier: GPL-2.0
> +
> +===
> +ELF
> +===
> +
> +.. toctree::
> +   :maxdepth: 1
> +
> +   ELF
> --- a/Documentation/index.rst
> +++ b/Documentation/index.rst
> @@ -113,6 +113,7 @@ to ReStructured Text format, or are simply too old.
>     :maxdepth: 1
>  
>     staging/index
> +   ELF/index
>  
>  
>  Translations

-- 
~Randy