100 lines
3.5 KiB
C
100 lines
3.5 KiB
C
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/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _LINUX_ELFNOTE_H
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#define _LINUX_ELFNOTE_H
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/*
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* Helper macros to generate ELF Note structures, which are put into a
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* PT_NOTE segment of the final vmlinux image. These are useful for
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* including name-value pairs of metadata into the kernel binary (or
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* modules?) for use by external programs.
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*
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* Each note has three parts: a name, a type and a desc. The name is
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* intended to distinguish the note's originator, so it would be a
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* company, project, subsystem, etc; it must be in a suitable form for
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* use in a section name. The type is an integer which is used to tag
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* the data, and is considered to be within the "name" namespace (so
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* "FooCo"'s type 42 is distinct from "BarProj"'s type 42). The
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* "desc" field is the actual data. There are no constraints on the
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* desc field's contents, though typically they're fairly small.
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*
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* All notes from a given NAME are put into a section named
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* .note.NAME. When the kernel image is finally linked, all the notes
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* are packed into a single .notes section, which is mapped into the
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* PT_NOTE segment. Because notes for a given name are grouped into
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* the same section, they'll all be adjacent the output file.
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*
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* This file defines macros for both C and assembler use. Their
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* syntax is slightly different, but they're semantically similar.
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*
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* See the ELF specification for more detail about ELF notes.
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*/
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#ifdef __ASSEMBLER__
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/*
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* Generate a structure with the same shape as Elf{32,64}_Nhdr (which
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* turn out to be the same size and shape), followed by the name and
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* desc data with appropriate padding. The 'desctype' argument is the
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* assembler pseudo op defining the type of the data e.g. .asciz while
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* 'descdata' is the data itself e.g. "hello, world".
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*
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* e.g. ELFNOTE(XYZCo, 42, .asciz, "forty-two")
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* ELFNOTE(XYZCo, 12, .long, 0xdeadbeef)
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*/
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#define ELFNOTE_START(name, type, flags) \
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.pushsection .note.name, flags,@note ; \
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.balign 4 ; \
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.long 2f - 1f /* namesz */ ; \
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.long 4484f - 3f /* descsz */ ; \
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.long type ; \
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1:.asciz #name ; \
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2:.balign 4 ; \
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3:
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#define ELFNOTE_END \
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4484:.balign 4 ; \
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.popsection ;
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#define ELFNOTE(name, type, desc) \
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ELFNOTE_START(name, type, "a") \
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desc ; \
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ELFNOTE_END
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#else /* !__ASSEMBLER__ */
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#include <uapi/linux/elf.h>
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/*
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* Use an anonymous structure which matches the shape of
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* Elf{32,64}_Nhdr, but includes the name and desc data. The size and
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* type of name and desc depend on the macro arguments. "name" must
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* be a literal string, and "desc" must be passed by value. You may
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* only define one note per line, since __LINE__ is used to generate
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* unique symbols.
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*/
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#define _ELFNOTE_PASTE(a,b) a##b
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#define _ELFNOTE(size, name, unique, type, desc) \
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static const struct { \
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struct elf##size##_note _nhdr; \
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unsigned char _name[sizeof(name)] \
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__attribute__((aligned(sizeof(Elf##size##_Word)))); \
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typeof(desc) _desc \
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__attribute__((aligned(sizeof(Elf##size##_Word)))); \
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} _ELFNOTE_PASTE(_note_, unique) \
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__used \
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__attribute__((section(".note." name), \
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aligned(sizeof(Elf##size##_Word)), \
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unused)) = { \
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{ \
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sizeof(name), \
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sizeof(desc), \
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type, \
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}, \
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name, \
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desc \
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}
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#define ELFNOTE(size, name, type, desc) \
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_ELFNOTE(size, name, __LINE__, type, desc)
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#define ELFNOTE32(name, type, desc) ELFNOTE(32, name, type, desc)
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#define ELFNOTE64(name, type, desc) ELFNOTE(64, name, type, desc)
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#endif /* __ASSEMBLER__ */
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#endif /* _LINUX_ELFNOTE_H */
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