linux/include/linux/elfnote.h
<<
>>
Prefs
   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
lxr.linux.no kindly hosted by Redpill Linpro AS, provider of Linux consulting and operations services since 1995.