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/* Create new context.
Copyright (C) 2001-2023 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
#include <sysdep.h>
#include "ucontext_i.h"
ENTRY(__makecontext)
movl 4(%esp), %eax
/* Load the address of the function we are supposed to run. */
movl 8(%esp), %ecx
/* Compute the address of the stack. The information comes from
to us_stack element. */
movl oSS_SP(%eax), %edx
movl %ecx, oEIP(%eax)
addl oSS_SIZE(%eax), %edx
/* Remember the number of parameters for the exit handler since
it has to remove them. We store the number in the EBX register
which the function we will call must preserve. */
movl 12(%esp), %ecx
movl %ecx, oEBX(%eax)
/* Make room on the new stack for the parameters.
Room for the arguments, return address (== L(exitcode)) and
oLINK pointer is needed. One of the pointer sizes is subtracted
after aligning the stack. */
negl %ecx
leal -4(%edx,%ecx,4), %edx
negl %ecx
/* Align the stack. */
andl $0xfffffff0, %edx
subl $4, %edx
/* Store the future stack pointer. */
movl %edx, oESP(%eax)
/* Put the next context on the new stack (from the uc_link
element). */
movl oLINK(%eax), %eax
movl %eax, 4(%edx,%ecx,4)
/* Copy all the parameters. */
jecxz 2f
1: movl 12(%esp,%ecx,4), %eax
movl %eax, (%edx,%ecx,4)
decl %ecx
jnz 1b
2:
/* If the function we call returns we must continue with the
context which is given in the uc_link element. To do this
set the return address for the function the user provides
to a little bit of helper code which does the magic (see
below). */
#ifdef PIC
call 1f
cfi_adjust_cfa_offset (4)
1: popl %ecx
cfi_adjust_cfa_offset (-4)
addl $L(exitcode)-1b, %ecx
movl %ecx, (%edx)
#else
movl $L(exitcode), (%edx)
#endif
/* We need to terminate the FDE here instead of after ret because
the unwinder looks at ra-1 for unwind information. */
cfi_endproc
/* 'makecontext' returns no value. */
ret
/* This is the helper code which gets called if a function which
is registered with 'makecontext' returns. In this case we
have to install the context listed in the uc_link element of
the context 'makecontext' manipulated at the time of the
'makecontext' call. If the pointer is NULL the process must
terminate. */
L(exitcode):
/* This removes the parameters passed to the function given to
'makecontext' from the stack. EBX contains the number of
parameters (see above). */
leal (%esp,%ebx,4), %esp
cmpl $0, (%esp) /* Check the next context. */
je 2f /* If it is zero exit. */
call HIDDEN_JUMPTARGET(__setcontext)
/* If this returns (which can happen if the syscall fails) we'll
exit the program with the return error value (-1). */
jmp L(call_exit)
2:
/* Exit with status 0. */
xorl %eax, %eax
L(call_exit):
/* Align the stack and pass the exit code (from %eax). */
andl $0xfffffff0, %esp
subl $12, %esp
pushl %eax
call HIDDEN_JUMPTARGET(exit)
/* The 'exit' call should never return. In case it does cause
the process to terminate. */
hlt
cfi_startproc
END(__makecontext)
weak_alias (__makecontext, makecontext)
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