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Diffstat (limited to 'include/linux/elfnote.h')
| -rw-r--r-- | include/linux/elfnote.h | 90 |
1 files changed, 90 insertions, 0 deletions
diff --git a/include/linux/elfnote.h b/include/linux/elfnote.h new file mode 100644 index 000000000000..67396db141e8 --- /dev/null +++ b/include/linux/elfnote.h @@ -0,0 +1,90 @@ +#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(name, type, desctype, descdata) \ +.pushsection .note.name ; \ + .align 4 ; \ + .long 2f - 1f /* namesz */ ; \ + .long 4f - 3f /* descsz */ ; \ + .long type ; \ +1:.asciz "name" ; \ +2:.align 4 ; \ +3:desctype descdata ; \ +4:.align 4 ; \ +.popsection ; +#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 */ |