sysdeps/unix/sysv/linux/x86_64/__start_context.S

   1 /* Copyright (C) 2002-2015 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3    Contributed by Andreas Jaeger <aj@suse.de>, 2002.
   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
  21 /* This is the helper code which gets called if a function which is
  22    registered with 'makecontext' returns.  In this case we have to
  23    install the context listed in the uc_link element of the context
  24    'makecontext' manipulated at the time of the 'makecontext' call.
  25    If the pointer is NULL the process must terminate.  */
  26
  27
  28 ENTRY(__start_context)
  29         /* This removes the parameters passed to the function given to
  30            'makecontext' from the stack.  RBX contains the address
  31            on the stack pointer for the next context.  */
  32         movq    %rbx, %rsp
  33
  34         popq    %rdi                    /* This is the next context.  */
  35         cfi_adjust_cfa_offset(-8)
  36         testq   %rdi, %rdi
  37         je      2f                      /* If it is zero exit.  */
  38
  39         call    JUMPTARGET(__setcontext)
  40         /* If this returns (which can happen if the syscall fails) we'll
  41            exit the program with the return error value (-1).  */
  42         movq    %rax,%rdi
  43
  44 2:
  45         call    HIDDEN_JUMPTARGET(exit)
  46         /* The 'exit' call should never return.  In case it does cause
  47            the process to terminate.  */
  48         hlt
  49 END(__start_context)