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authorAlexey Dobriyan <adobriyan@gmail.com>2023-04-15 20:37:29 +0300
committerJonathan Corbet <corbet@lwn.net>2023-04-21 02:53:38 +0300
commit5c2c34a49be8fa534379c64579671feea52432b9 (patch)
treeb6f032031ad2d620043c1ca0be82bfb3a89e6348 /Documentation/userspace-api
parent4de3790a6313dd6596ba7d0391ade94a21ee10b5 (diff)
downloadlinux-5c2c34a49be8fa534379c64579671feea52432b9.tar.xz
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>
Diffstat (limited to 'Documentation/userspace-api')
-rw-r--r--Documentation/userspace-api/ELF.rst34
-rw-r--r--Documentation/userspace-api/index.rst1
2 files changed, 35 insertions, 0 deletions
diff --git a/Documentation/userspace-api/ELF.rst b/Documentation/userspace-api/ELF.rst
new file mode 100644
index 000000000000..ac8aeacd458d
--- /dev/null
+++ b/Documentation/userspace-api/ELF.rst
@@ -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.
diff --git a/Documentation/userspace-api/index.rst b/Documentation/userspace-api/index.rst
index f16337bdb852..72a65db0c498 100644
--- a/Documentation/userspace-api/index.rst
+++ b/Documentation/userspace-api/index.rst
@@ -23,6 +23,7 @@ place where this information is gathered.
spec_ctrl
accelerators/ocxl
ebpf/index
+ ELF
ioctl/index
iommu
iommufd