#ifndef _LINUX_ELFNOTE_H #define _LINUX_ELFNOTE_H /* * Helper macros to generate ELF Note structures, which are put into a * PT_NOTE segment of the final vmlinux image. These are useful for * including name-value pairs of metadata into the kernel binary (or * modules?) for use by external programs. * * Each note has three parts: a name, a type and a desc. The name is * intended to distinguish the note's originator, so it would be a * company, project, subsystem, etc; it must be in a suitable form for * use in a section name. The type is an integer which is used to tag * the data, and is considered to be within the "name" namespace (so * "FooCo"'s type 42 is distinct from "BarProj"'s type 42). The * "desc" field is the actual data. There are no constraints on the * desc field's contents, though typically they're fairly small. * * All notes from a given NAME are put into a section named * .note.NAME. When the kernel image is finally linked, all the notes * are packed into a single .notes section, which is mapped into the * PT_NOTE segment. Because notes for a given name are grouped into * the same section, they'll all be adjacent the output file. * * This file defines macros for both C and assembler use. Their * syntax is slightly different, but they're semantically similar. * * See the ELF specification for more detail about ELF notes. */ #ifdef __ASSEMBLER__ /* * Generate a structure with the same shape as Elf{32,64}_Nhdr (which * turn out to be the same size and shape), followed by the name and * desc data with appropriate padding. The 'desctype' argument is the * assembler pseudo op defining the type of the data e.g. .asciz while * 'descdata' is the data itself e.g. "hello, world". * * e.g. ELFNOTE(XYZCo, 42, .asciz, "forty-two") * ELFNOTE(XYZCo, 12, .long, 0xdeadbeef) */ #define ELFNOTE_START(name, type, flags) \ .pushsection .note.name, flags,@note ; \ .balign 4 ; \ .long 2f - 1f /* namesz */ ; \ .long 4484f - 3f /* descsz */ ; \ .long type ; \ 1:.asciz #name ; \ 2:.balign 4 ; \ 3: #define ELFNOTE_END \ 4484:.balign 4 ; \ .popsection ; #define ELFNOTE(name, type, desc) \ ELFNOTE_START(name, type, "") \ desc ; \ ELFNOTE_END #else /* !__ASSEMBLER__ */ #include <linux/elf.h> /* * Use an anonymous structure which matches the shape of * Elf{32,64}_Nhdr, but includes the name and desc data. The size and * type of name and desc depend on the macro arguments. "name" must * be a literal string, and "desc" must be passed by value. You may * only define one note per line, since __LINE__ is used to generate * unique symbols. */ #define _ELFNOTE_PASTE(a,b) a##b #define _ELFNOTE(size, name, unique, type, desc) \ static const struct { \ struct elf##size##_note _nhdr; \ unsigned char _name[sizeof(name)] \ __attribute__((aligned(sizeof(Elf##size##_Word)))); \ typeof(desc) _desc \ __attribute__((aligned(sizeof(Elf##size##_Word)))); \ } _ELFNOTE_PASTE(_note_, unique) \ __attribute_used__ \ __attribute__((section(".note." name), \ aligned(sizeof(Elf##size##_Word)), \ unused)) = { \ { \ sizeof(name), \ sizeof(desc), \ type, \ }, \ name, \ desc \ } #define ELFNOTE(size, name, type, desc) \ _ELFNOTE(size, name, __LINE__, type, desc) #define ELFNOTE32(name, type, desc) ELFNOTE(32, name, type, desc) #define ELFNOTE64(name, type, desc) ELFNOTE(64, name, type, desc) #endif /* __ASSEMBLER__ */ #endif /* _LINUX_ELFNOTE_H */