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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>
authored by
Alexey Dobriyan
and committed by
Jonathan Corbet
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Documentation/userspace-api/ELF.rst
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Documentation/userspace-api/ELF.rst
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.. SPDX-License-Identifier: GPL-2.0
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=================================
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Linux-specific ELF idiosyncrasies
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=================================
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Definitions
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===========
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"First" program header is the one with the smallest offset in the file:
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e_phoff.
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"Last" program header is the one with the biggest offset in the file:
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e_phoff + (e_phnum - 1) * sizeof(Elf_Phdr).
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PT_INTERP
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=========
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First PT_INTERP program header is used to locate the filename of ELF
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interpreter. Other PT_INTERP headers are ignored (since Linux 2.4.11).
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PT_GNU_STACK
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============
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Last PT_GNU_STACK program header defines userspace stack executability
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(since Linux 2.6.6). Other PT_GNU_STACK headers are ignored.
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PT_GNU_PROPERTY
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===============
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ELF interpreter's last PT_GNU_PROPERTY program header is used (since
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Linux 5.8). If interpreter doesn't have one, then the last PT_GNU_PROPERTY
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program header of an executable is used. Other PT_GNU_PROPERTY headers
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are ignored.