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_START(name, type, flags) \ 42.pushsection .note.name, flags,@note ; \ 43 .balign 4 ; \ 44 .long 2f - 1f /* namesz */ ; \ 45 .long 4484f - 3f /* descsz */ ; \ 46 .long type ; \ 471:.asciz #name ; \ 482:.balign 4 ; \ 493: 50 51#define ELFNOTE_END \ 524484:.balign 4 ; \ 53.popsection ; 54 55#define ELFNOTE(name, type, desc) \ 56 ELFNOTE_START(name, type, "") \ 57 desc ; \ 58 ELFNOTE_END 59 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) \ 79 __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 */ 99