sysdeps/unix/sysv/linux/i386/getcontext.S

   1 /* Save current context.
   2    Copyright (C) 2001-2017 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4    Contributed by Ulrich Drepper <drepper@redhat.com>, 2001.
   5
   6    The GNU C Library is free software; you can redistribute it and/or
   7    modify it under the terms of the GNU Lesser General Public
   8    License as published by the Free Software Foundation; either
   9    version 2.1 of the License, or (at your option) any later version.
  10
  11    The GNU C Library is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14    Lesser General Public License for more details.
  15
  16    You should have received a copy of the GNU Lesser General Public
  17    License along with the GNU C Library; if not, see
  18    <http://www.gnu.org/licenses/>.  */
  19
  20 #include <sysdep.h>
  21
  22 #include "ucontext_i.h"
  23
  24
  25 ENTRY(__getcontext)
  26         /* Load address of the context data structure.  */
  27         movl    4(%esp), %eax
  28
  29         /* Return value of getcontext.  EAX is the only register whose
  30            value is not preserved.  */
  31         movl    $0, oEAX(%eax)
  32
  33         /* Save the 32-bit register values and the return address.  */
  34         movl    %ecx, oECX(%eax)
  35         movl    %edx, oEDX(%eax)
  36         movl    %edi, oEDI(%eax)
  37         movl    %esi, oESI(%eax)
  38         movl    %ebp, oEBP(%eax)
  39         movl    (%esp), %ecx
  40         movl    %ecx, oEIP(%eax)
  41         leal    4(%esp), %ecx           /* Exclude the return address.  */
  42         movl    %ecx, oESP(%eax)
  43         movl    %ebx, oEBX(%eax)
  44
  45         /* Save the FS segment register.  We don't touch the GS register
  46            since it is used for threads.  */
  47         xorl    %edx, %edx
  48         movw    %fs, %dx
  49         movl    %edx, oFS(%eax)
  50
  51         /* We have separate floating-point register content memory on the
  52            stack.  We use the __fpregs_mem block in the context.  Set the
  53            links up correctly.  */
  54         leal    oFPREGSMEM(%eax), %ecx
  55         movl    %ecx, oFPREGS(%eax)
  56         /* Save the floating-point context.  */
  57         fnstenv (%ecx)
  58         /* And load it right back since the processor changes the mask.
  59            Intel thought this opcode to be used in interrupt handlers which
  60            would block all exceptions.  */
  61         fldenv  (%ecx)
  62
  63         /* Save the current signal mask.  */
  64         pushl   %ebx
  65         cfi_adjust_cfa_offset (4)
  66         cfi_rel_offset (ebx, 0)
  67         leal    oSIGMASK(%eax), %edx
  68         xorl    %ecx, %ecx
  69         movl    $SIG_BLOCK, %ebx
  70         movl    $__NR_sigprocmask, %eax
  71         ENTER_KERNEL
  72         popl    %ebx
  73         cfi_adjust_cfa_offset (-4)
  74         cfi_restore (ebx)
  75         cmpl    $-4095, %eax            /* Check %eax for error.  */
  76         jae     SYSCALL_ERROR_LABEL     /* Jump to error handler if error.  */
  77
  78         /* All done, return 0 for success.  */
  79         xorl    %eax, %eax
  80         ret
  81 PSEUDO_END(__getcontext)
  82
  83 weak_alias (__getcontext, getcontext)