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1#ifndef _LINUX_ELFNOTE_H
2#define _LINUX_ELFNOTE_H
3/*
4 * Helper macros to generate ELF Note structures, which are put into a
5 * PT_NOTE segment of the final vmlinux image. These are useful for
6 * including name-value pairs of metadata into the kernel binary (or
7 * modules?) for use by external programs.
8 *
9 * Each note has three parts: a name, a type and a desc. The name is
10 * intended to distinguish the note's originator, so it would be a
11 * company, project, subsystem, etc; it must be in a suitable form for
12 * use in a section name. The type is an integer which is used to tag
13 * the data, and is considered to be within the "name" namespace (so
14 * "FooCo"'s type 42 is distinct from "BarProj"'s type 42). The
15 * "desc" field is the actual data. There are no constraints on the
16 * desc field's contents, though typically they're fairly small.
17 *
18 * All notes from a given NAME are put into a section named
19 * .note.NAME. When the kernel image is finally linked, all the notes
20 * are packed into a single .notes section, which is mapped into the
21 * PT_NOTE segment. Because notes for a given name are grouped into
22 * the same section, they'll all be adjacent the output file.
23 *
24 * This file defines macros for both C and assembler use. Their
25 * syntax is slightly different, but they're semantically similar.
26 *
27 * See the ELF specification for more detail about ELF notes.
28 */
29
30#ifdef __ASSEMBLER__
31/*
32 * Generate a structure with the same shape as Elf{32,64}_Nhdr (which
33 * turn out to be the same size and shape), followed by the name and
34 * desc data with appropriate padding. The 'desctype' argument is the
35 * assembler pseudo op defining the type of the data e.g. .asciz while
36 * 'descdata' is the data itself e.g. "hello, world".
37 *
38 * e.g. ELFNOTE(XYZCo, 42, .asciz, "forty-two")
39 * ELFNOTE(XYZCo, 12, .long, 0xdeadbeef)
40 */
41#define ELFNOTE(name, type, desctype, descdata) \
42.pushsection .note.name, "",@note ; \
43 .align 4 ; \
44 .long 2f - 1f /* namesz */ ; \
45 .long 4f - 3f /* descsz */ ; \
46 .long type ; \
471:.asciz #name ; \
482:.align 4 ; \
493:desctype descdata ; \
504:.align 4 ; \
51.popsection ;
52#else /* !__ASSEMBLER__ */
53#include <linux/elf.h>
54/*
55 * Use an anonymous structure which matches the shape of
56 * Elf{32,64}_Nhdr, but includes the name and desc data. The size and
57 * type of name and desc depend on the macro arguments. "name" must
58 * be a literal string, and "desc" must be passed by value. You may
59 * only define one note per line, since __LINE__ is used to generate
60 * unique symbols.
61 */
62#define _ELFNOTE_PASTE(a,b) a##b
63#define _ELFNOTE(size, name, unique, type, desc) \
64 static const struct { \
65 struct elf##size##_note _nhdr; \
66 unsigned char _name[sizeof(name)] \
67 __attribute__((aligned(sizeof(Elf##size##_Word)))); \
68 typeof(desc) _desc \
69 __attribute__((aligned(sizeof(Elf##size##_Word)))); \
70 } _ELFNOTE_PASTE(_note_, unique) \
71 __attribute_used__ \
72 __attribute__((section(".note." name), \
73 aligned(sizeof(Elf##size##_Word)), \
74 unused)) = { \
75 { \
76 sizeof(name), \
77 sizeof(desc), \
78 type, \
79 }, \
80 name, \
81 desc \
82 }
83#define ELFNOTE(size, name, type, desc) \
84 _ELFNOTE(size, name, __LINE__, type, desc)
85
86#define ELFNOTE32(name, type, desc) ELFNOTE(32, name, type, desc)
87#define ELFNOTE64(name, type, desc) ELFNOTE(64, name, type, desc)
88#endif /* __ASSEMBLER__ */
89
90#endif /* _LINUX_ELFNOTE_H */