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b2441318 | 1 | /* SPDX-License-Identifier: GPL-2.0 */ |
9c9b8b38 JF |
2 | #ifndef _LINUX_ELFNOTE_H |
3 | #define _LINUX_ELFNOTE_H | |
4 | /* | |
5 | * Helper macros to generate ELF Note structures, which are put into a | |
6 | * PT_NOTE segment of the final vmlinux image. These are useful for | |
7 | * including name-value pairs of metadata into the kernel binary (or | |
8 | * modules?) for use by external programs. | |
9 | * | |
10 | * Each note has three parts: a name, a type and a desc. The name is | |
11 | * intended to distinguish the note's originator, so it would be a | |
12 | * company, project, subsystem, etc; it must be in a suitable form for | |
13 | * use in a section name. The type is an integer which is used to tag | |
14 | * the data, and is considered to be within the "name" namespace (so | |
15 | * "FooCo"'s type 42 is distinct from "BarProj"'s type 42). The | |
16 | * "desc" field is the actual data. There are no constraints on the | |
17 | * desc field's contents, though typically they're fairly small. | |
18 | * | |
19 | * All notes from a given NAME are put into a section named | |
20 | * .note.NAME. When the kernel image is finally linked, all the notes | |
21 | * are packed into a single .notes section, which is mapped into the | |
22 | * PT_NOTE segment. Because notes for a given name are grouped into | |
23 | * the same section, they'll all be adjacent the output file. | |
24 | * | |
25 | * This file defines macros for both C and assembler use. Their | |
26 | * syntax is slightly different, but they're semantically similar. | |
27 | * | |
28 | * See the ELF specification for more detail about ELF notes. | |
29 | */ | |
30 | ||
31 | #ifdef __ASSEMBLER__ | |
32 | /* | |
33 | * Generate a structure with the same shape as Elf{32,64}_Nhdr (which | |
34 | * turn out to be the same size and shape), followed by the name and | |
5091e746 IC |
35 | * desc data with appropriate padding. The 'desctype' argument is the |
36 | * assembler pseudo op defining the type of the data e.g. .asciz while | |
37 | * 'descdata' is the data itself e.g. "hello, world". | |
38 | * | |
39 | * e.g. ELFNOTE(XYZCo, 42, .asciz, "forty-two") | |
40 | * ELFNOTE(XYZCo, 12, .long, 0xdeadbeef) | |
9c9b8b38 | 41 | */ |
810bab44 JF |
42 | #define ELFNOTE_START(name, type, flags) \ |
43 | .pushsection .note.name, flags,@note ; \ | |
44 | .balign 4 ; \ | |
5091e746 | 45 | .long 2f - 1f /* namesz */ ; \ |
810bab44 | 46 | .long 4484f - 3f /* descsz */ ; \ |
5091e746 | 47 | .long type ; \ |
03df4f6e | 48 | 1:.asciz #name ; \ |
810bab44 JF |
49 | 2:.balign 4 ; \ |
50 | 3: | |
51 | ||
52 | #define ELFNOTE_END \ | |
53 | 4484:.balign 4 ; \ | |
5091e746 | 54 | .popsection ; |
810bab44 JF |
55 | |
56 | #define ELFNOTE(name, type, desc) \ | |
51da9dfb | 57 | ELFNOTE_START(name, type, "a") \ |
810bab44 JF |
58 | desc ; \ |
59 | ELFNOTE_END | |
60 | ||
9c9b8b38 | 61 | #else /* !__ASSEMBLER__ */ |
b5580517 | 62 | #include <uapi/linux/elf.h> |
9c9b8b38 JF |
63 | /* |
64 | * Use an anonymous structure which matches the shape of | |
65 | * Elf{32,64}_Nhdr, but includes the name and desc data. The size and | |
66 | * type of name and desc depend on the macro arguments. "name" must | |
67 | * be a literal string, and "desc" must be passed by value. You may | |
68 | * only define one note per line, since __LINE__ is used to generate | |
69 | * unique symbols. | |
70 | */ | |
71 | #define _ELFNOTE_PASTE(a,b) a##b | |
72 | #define _ELFNOTE(size, name, unique, type, desc) \ | |
73 | static const struct { \ | |
74 | struct elf##size##_note _nhdr; \ | |
75 | unsigned char _name[sizeof(name)] \ | |
76 | __attribute__((aligned(sizeof(Elf##size##_Word)))); \ | |
77 | typeof(desc) _desc \ | |
78 | __attribute__((aligned(sizeof(Elf##size##_Word)))); \ | |
79 | } _ELFNOTE_PASTE(_note_, unique) \ | |
3ff6eecc | 80 | __used \ |
9c9b8b38 JF |
81 | __attribute__((section(".note." name), \ |
82 | aligned(sizeof(Elf##size##_Word)), \ | |
83 | unused)) = { \ | |
84 | { \ | |
85 | sizeof(name), \ | |
86 | sizeof(desc), \ | |
87 | type, \ | |
88 | }, \ | |
89 | name, \ | |
90 | desc \ | |
91 | } | |
92 | #define ELFNOTE(size, name, type, desc) \ | |
93 | _ELFNOTE(size, name, __LINE__, type, desc) | |
94 | ||
95 | #define ELFNOTE32(name, type, desc) ELFNOTE(32, name, type, desc) | |
96 | #define ELFNOTE64(name, type, desc) ELFNOTE(64, name, type, desc) | |
97 | #endif /* __ASSEMBLER__ */ | |
98 | ||
99 | #endif /* _LINUX_ELFNOTE_H */ |