ELF: document some de-facto PT_* ABI quirks

Turns out rules about PT_INTERP, PT_GNU_STACK and PT_GNU_PROPERTY
program headers are slightly different.

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Link: https://lore.kernel.org/r/88d3f1bb-f4e0-4c40-9304-3843513a1262@p183
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
This commit is contained in:
Alexey Dobriyan 2023-04-15 20:37:29 +03:00 committed by Jonathan Corbet
parent 4de3790a63
commit 5c2c34a49b
2 changed files with 35 additions and 0 deletions

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@ -0,0 +1,34 @@
.. 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 in the file:
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.

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@ -23,6 +23,7 @@ place where this information is gathered.
spec_ctrl spec_ctrl
accelerators/ocxl accelerators/ocxl
ebpf/index ebpf/index
ELF
ioctl/index ioctl/index
iommu iommu
iommufd iommufd