csu/abi-note.c

   1 /* Special .init and .fini section support.
   2    Copyright (C) 1997-2022 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    In addition to the permissions in the GNU Lesser General Public
  11    License, the Free Software Foundation gives you unlimited
  12    permission to link the compiled version of this file with other
  13    programs, and to distribute those programs without any restriction
  14    coming from the use of this file.  (The Lesser General Public
  15    License restrictions do apply in other respects; for example, they
  16    cover modification of the file, and distribution when not linked
  17    into another program.)
  18
  19    The GNU C Library is distributed in the hope that it will be useful,
  20    but WITHOUT ANY WARRANTY; without even the implied warranty of
  21    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  22    Lesser General Public License for more details.
  23
  24    You should have received a copy of the GNU Lesser General Public
  25    License along with the GNU C Library; if not, see
  26    <https://www.gnu.org/licenses/>.  */
  27
  28 /* Define an ELF note identifying the operating-system ABI that the
  29    executable was created for.  The ELF note information identifies a
  30    particular OS or coordinated development effort within which the
  31    ELF header's e_machine value plus (for dynamically linked programs)
  32    the PT_INTERP dynamic linker name and DT_NEEDED shared library
  33    names fully identify the runtime environment required by an
  34    executable.
  35
  36    The general format of ELF notes is as follows.
  37    Offsets and lengths are bytes or (parenthetical references) to the
  38    values in other fields.
  39
  40 offset  length  contents
  41 0       4       length of name
  42 4       4       length of data
  43 8       4       note type
  44 12      (0)     vendor name
  45                 - null-terminated ASCII string, padded to 4-byte alignment
  46 12+(0)  (4)     note data,
  47
  48    The GNU project and cooperating development efforts (including the
  49    Linux community) use note type 1 and a vendor name string of "GNU"
  50    for a note descriptor that indicates ABI requirements.  The note data
  51    is four 32-bit words.  The first of these is an operating system
  52    number (0=Linux, 1=Hurd, 2=Solaris, ...) and the remaining three
  53    identify the earliest release of that OS that supports this ABI.
  54    See abi-tags (top level) for details. */
  55
  56 #include <link.h>
  57 #include <stdint.h>
  58 #include <config.h>
  59 #include <abi-tag.h>            /* OS-specific ABI tag value */
  60
  61 /* The linker (GNU ld 2.8 and later) recognizes an allocated section whose
  62    name begins with `.note' and creates a PT_NOTE program header entry
  63    pointing at it. */
  64
  65 __attribute__ ((used, aligned (4), section (".note.ABI-tag")))
  66 static const struct
  67 {
  68   ElfW(Nhdr) nhdr;
  69   char name[4];
  70   int32_t desc[4];
  71 } __abi_tag = {
  72   { .n_namesz = sizeof __abi_tag.name,
  73     .n_descsz = sizeof __abi_tag.desc,
  74     .n_type = 1 },
  75   "GNU",
  76   { __ABI_TAG_OS, __ABI_TAG_VERSION }
  77 };