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Jeremy Fitzhardinge9c9b8b32006-09-25 23:32:26 -07001#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
Ian Campbell5091e742006-09-25 23:32:28 -070034 * 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)
Jeremy Fitzhardinge9c9b8b32006-09-25 23:32:26 -070040 */
Jeremy Fitzhardinge810bab42007-07-17 18:37:03 -070041#define ELFNOTE_START(name, type, flags) \
42.pushsection .note.name, flags,@note ; \
43 .balign 4 ; \
Ian Campbell5091e742006-09-25 23:32:28 -070044 .long 2f - 1f /* namesz */ ; \
Jeremy Fitzhardinge810bab42007-07-17 18:37:03 -070045 .long 4484f - 3f /* descsz */ ; \
Ian Campbell5091e742006-09-25 23:32:28 -070046 .long type ; \
Jeremy Fitzhardinge03df4f62007-05-02 19:27:17 +0200471:.asciz #name ; \
Jeremy Fitzhardinge810bab42007-07-17 18:37:03 -0700482:.balign 4 ; \
493:
50
51#define ELFNOTE_END \
524484:.balign 4 ; \
Ian Campbell5091e742006-09-25 23:32:28 -070053.popsection ;
Jeremy Fitzhardinge810bab42007-07-17 18:37:03 -070054
55#define ELFNOTE(name, type, desc) \
56 ELFNOTE_START(name, type, "") \
57 desc ; \
58 ELFNOTE_END
59
Jeremy Fitzhardinge9c9b8b32006-09-25 23:32:26 -070060#else /* !__ASSEMBLER__ */
61#include <linux/elf.h>
62/*
63 * Use an anonymous structure which matches the shape of
64 * Elf{32,64}_Nhdr, but includes the name and desc data. The size and
65 * type of name and desc depend on the macro arguments. "name" must
66 * be a literal string, and "desc" must be passed by value. You may
67 * only define one note per line, since __LINE__ is used to generate
68 * unique symbols.
69 */
70#define _ELFNOTE_PASTE(a,b) a##b
71#define _ELFNOTE(size, name, unique, type, desc) \
72 static const struct { \
73 struct elf##size##_note _nhdr; \
74 unsigned char _name[sizeof(name)] \
75 __attribute__((aligned(sizeof(Elf##size##_Word)))); \
76 typeof(desc) _desc \
77 __attribute__((aligned(sizeof(Elf##size##_Word)))); \
78 } _ELFNOTE_PASTE(_note_, unique) \
79 __attribute_used__ \
80 __attribute__((section(".note." name), \
81 aligned(sizeof(Elf##size##_Word)), \
82 unused)) = { \
83 { \
84 sizeof(name), \
85 sizeof(desc), \
86 type, \
87 }, \
88 name, \
89 desc \
90 }
91#define ELFNOTE(size, name, type, desc) \
92 _ELFNOTE(size, name, __LINE__, type, desc)
93
94#define ELFNOTE32(name, type, desc) ELFNOTE(32, name, type, desc)
95#define ELFNOTE64(name, type, desc) ELFNOTE(64, name, type, desc)
96#endif /* __ASSEMBLER__ */
97
98#endif /* _LINUX_ELFNOTE_H */