nptl/pt-vfork.c

   1 /* vfork ABI-compatibility entry points for libpthread.
   2    Copyright (C) 2014-2015 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    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <http://www.gnu.org/licenses/>.  */
  18
  19 #include <unistd.h>
  20 #include <shlib-compat.h>
  21
  22 /* libpthread used to have its own vfork implementation that differed
  23    from libc's only in having a pointless micro-optimization.  There
  24    is no longer any use to having a separate copy in libpthread, but
  25    the historical ABI requires it.  For static linking, there is no
  26    need to provide anything here--the libc version will be linked in.
  27    For shared library ABI compatibility, there must be __vfork and
  28    vfork symbols in libpthread.so; so we define them using IFUNC to
  29    redirect to the libc function.  */
  30
  31 /* Note! If the architecture doesn't support IFUNC, then we need an
  32    alternate target-specific mechanism to implement this.  So we just
  33    assume IFUNC here and require that the target override this file
  34    if necessary.
  35
  36    If the architecture can assume all supported versions of gcc will
  37    produce a tail-call to __libc_vfork, consider including the version
  38    in sysdeps/unix/sysv/linux/aarch64/pt-vfork.c.  */
  39
  40 #if !HAVE_IFUNC
  41 # error "must write pt-vfork for this machine or get IFUNC support"
  42 #endif
  43
  44 #if (SHLIB_COMPAT (libpthread, GLIBC_2_0, GLIBC_2_20) \
  45      || SHLIB_COMPAT (libpthread, GLIBC_2_1_2, GLIBC_2_20))
  46
  47 extern __typeof (vfork) __libc_vfork;   /* Defined in libc.  */
  48
  49 static __typeof (vfork) *
  50 __attribute__ ((used))
  51 vfork_resolve (void)
  52 {
  53   return &__libc_vfork;
  54 }
  55
  56 # ifdef HAVE_ASM_SET_DIRECTIVE
  57 #  define DEFINE_VFORK(name) \
  58   asm (".set " #name ", vfork_resolve\n" \
  59        ".globl " #name "\n" \
  60        ".type " #name ", %gnu_indirect_function");
  61 # else
  62 #  define DEFINE_VFORK(name) \
  63   asm (#name " = vfork_resolve\n" \
  64        ".globl " #name "\n" \
  65        ".type " #name ", %gnu_indirect_function");
  66 # endif
  67 #endif
  68
  69 #if SHLIB_COMPAT (libpthread, GLIBC_2_0, GLIBC_2_20)
  70 DEFINE_VFORK (vfork_ifunc)
  71 compat_symbol (libpthread, vfork_ifunc, vfork, GLIBC_2_0);
  72 #endif
  73
  74 #if SHLIB_COMPAT (libpthread, GLIBC_2_1_2, GLIBC_2_20)
  75 DEFINE_VFORK (__vfork_ifunc)
  76 compat_symbol (libpthread, __vfork_ifunc, __vfork, GLIBC_2_1_2);
  77 #endif