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

   1 /* Save current context and install the given one.
   2    Copyright (C) 2001-2016 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(__swapcontext)
  26         /* Load address of the context data structure we save in.  */
  27         movl    4(%esp), %eax
  28
  29         /* Return value of swapcontext.  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
  42         movl    %ecx, oESP(%eax)
  43         movl    %ebx, oEBX(%eax)
  44
  45         /* Save the FS segment register.  */
  46         xorl    %edx, %edx
  47         movw    %fs, %dx
  48         movl    %edx, oFS(%eax)
  49
  50         /* We have separate floating-point register content memory on the
  51            stack.  We use the __fpregs_mem block in the context.  Set the
  52            links up correctly.  */
  53         leal    oFPREGSMEM(%eax), %ecx
  54         movl    %ecx, oFPREGS(%eax)
  55         /* Save the floating-point context.  */
  56         fnstenv (%ecx)
  57
  58         /* Load address of the context data structure we have to load.  */
  59         movl    8(%esp), %ecx
  60
  61         /* Save the current signal mask and install the new one.  */
  62         pushl   %ebx
  63         leal    oSIGMASK(%eax), %edx
  64         leal    oSIGMASK(%ecx), %ecx
  65         movl    $SIG_SETMASK, %ebx
  66         movl    $__NR_sigprocmask, %eax
  67         ENTER_KERNEL
  68         popl    %ebx
  69         cmpl    $-4095, %eax            /* Check %eax for error.  */
  70         jae     SYSCALL_ERROR_LABEL     /* Jump to error handler if error.  */
  71
  72         /* EAX was modified, reload it.  */
  73         movl    8(%esp), %eax
  74
  75         /* Restore the floating-point context.  Not the registers, only the
  76            rest.  */
  77         movl    oFPREGS(%eax), %ecx
  78         fldenv  (%ecx)
  79
  80         /* Restore the FS segment register.  We don't touch the GS register
  81            since it is used for threads.  */
  82         movl    oFS(%eax), %edx
  83         movw    %dx, %fs
  84
  85         /* Fetch the address to return to.  */
  86         movl    oEIP(%eax), %ecx
  87
  88         /* Load the new stack pointer.  */
  89         movl    oESP(%eax), %esp
  90
  91         /* Push the return address on the new stack so we can return there.  */
  92         pushl   %ecx
  93
  94         /* Load the values of all the 32-bit registers (except ESP).
  95            Since we are loading from EAX, it must be last.  */
  96         movl    oEDI(%eax), %edi
  97         movl    oESI(%eax), %esi
  98         movl    oEBP(%eax), %ebp
  99         movl    oEBX(%eax), %ebx
 100         movl    oEDX(%eax), %edx
 101         movl    oECX(%eax), %ecx
 102         movl    oEAX(%eax), %eax
 103
 104         /* The following 'ret' will pop the address of the code and jump
 105            to it.  */
 106         ret
 107 PSEUDO_END(__swapcontext)
 108
 109 weak_alias (__swapcontext, swapcontext)