sysdeps/unix/alpha/sysdep.S

   1 /* Copyright (C) 1993-2019 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3    Contributed by Brendan Kehoe (brendan@zen.org).
   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 <sysdep.h>
  20 #include <features.h>
  21
  22 #if defined(PIC)
  23         /* Put this at the end of libc's text segment so that all of
  24            the direct branches from the syscalls are forward, and
  25            thus predicted not taken.  */
  26         .section .text.last, "ax", @progbits
  27 #else
  28         .text
  29 #endif
  30
  31 #if IS_IN (libc)
  32 # define SYSCALL_ERROR_ERRNO __libc_errno
  33 #else
  34 # define SYSCALL_ERROR_ERRNO errno
  35 #endif
  36
  37         .align 4
  38         .globl  __syscall_error
  39         .ent    __syscall_error
  40 __syscall_error:
  41         /* When building a shared library, we branch here without having
  42            loaded the GP.  Nor, since it was a direct branch, have we
  43            loaded PV with our address.
  44
  45            When building a static library, we tail call here from another
  46            object file, possibly with a different GP, and must return with
  47            the GP of our caller in place so that linker relaxation works.
  48
  49            Both issues are solved by computing the GP into T1 instead of
  50            clobbering the traditional GP register.  */
  51         .prologue 0
  52         mov     v0, t0
  53         br      t1, 1f
  54 1:      ldah    t1, 0(t1) !gpdisp!1
  55         call_pal PAL_rduniq
  56
  57         lda     t1, 0(t1) !gpdisp!1
  58         ldq     t1, SYSCALL_ERROR_ERRNO(t1) !gottprel
  59         addq    v0, t1, t1
  60         lda     v0, -1
  61
  62         stl     t0, 0(t1)
  63         ret
  64
  65         .end __syscall_error