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9c9b8b38 JF |
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 | |
5091e746 IC |
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) | |
9c9b8b38 | 40 | */ |
810bab44 JF |
41 | #define ELFNOTE_START(name, type, flags) \ |
42 | .pushsection .note.name, flags,@note ; \ | |
43 | .balign 4 ; \ | |
5091e746 | 44 | .long 2f - 1f /* namesz */ ; \ |
810bab44 | 45 | .long 4484f - 3f /* descsz */ ; \ |
5091e746 | 46 | .long type ; \ |
03df4f6e | 47 | 1:.asciz #name ; \ |
810bab44 JF |
48 | 2:.balign 4 ; \ |
49 | 3: | |
50 | ||
51 | #define ELFNOTE_END \ | |
52 | 4484:.balign 4 ; \ | |
5091e746 | 53 | .popsection ; |
810bab44 JF |
54 | |
55 | #define ELFNOTE(name, type, desc) \ | |
56 | ELFNOTE_START(name, type, "") \ | |
57 | desc ; \ | |
58 | ELFNOTE_END | |
59 | ||
9c9b8b38 JF |
60 | #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) \ | |
3ff6eecc | 79 | __used \ |
9c9b8b38 JF |
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 */ |