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 'desc' argument includes 35 * the assembler pseudo op defining the type of the data: .asciz 36 * "hello, world" 37 */ 38 .macro ELFNOTE name type desc:vararg 39 .pushsection ".note.\name" 40 .align 4 41 .long 2f - 1f /* namesz */ 42 .long 4f - 3f /* descsz */ 43 .long \type 44 1:.asciz "\name" 45 2:.align 4 46 3:\desc 47 4:.align 4 48 .popsection 49 .endm 50 #else /* !__ASSEMBLER__ */ 51 #include <linux/elf.h> 52 /* 53 * Use an anonymous structure which matches the shape of 54 * Elf{32,64}_Nhdr, but includes the name and desc data. The size and 55 * type of name and desc depend on the macro arguments. "name" must 56 * be a literal string, and "desc" must be passed by value. You may 57 * only define one note per line, since __LINE__ is used to generate 58 * unique symbols. 59 */ 60 #define _ELFNOTE_PASTE(a,b) a##b 61 #define _ELFNOTE(size, name, unique, type, desc) \ 62 static const struct { \ 63 struct elf##size##_note _nhdr; \ 64 unsigned char _name[sizeof(name)] \ 65 __attribute__((aligned(sizeof(Elf##size##_Word)))); \ 66 typeof(desc) _desc \ 67 __attribute__((aligned(sizeof(Elf##size##_Word)))); \ 68 } _ELFNOTE_PASTE(_note_, unique) \ 69 __attribute_used__ \ 70 __attribute__((section(".note." name), \ 71 aligned(sizeof(Elf##size##_Word)), \ 72 unused)) = { \ 73 { \ 74 sizeof(name), \ 75 sizeof(desc), \ 76 type, \ 77 }, \ 78 name, \ 79 desc \ 80 } 81 #define ELFNOTE(size, name, type, desc) \ 82 _ELFNOTE(size, name, __LINE__, type, desc) 83 84 #define ELFNOTE32(name, type, desc) ELFNOTE(32, name, type, desc) 85 #define ELFNOTE64(name, type, desc) ELFNOTE(64, name, type, desc) 86 #endif /* __ASSEMBLER__ */ 87 88 #endif /* _LINUX_ELFNOTE_H */ 89