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/* Copyright (C) 2002 Free Software Foundation, Inc.
This file is part of the GNU C Library.
Contributed by Bruno Haible <bruno@clisp.org>, 2002.
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, write to the Free
Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
02111-1307 USA. */
/* __start_thread (flags, stack, func, arg)
calls __rfork (flags), and in the child sets the stack pointer and then
calls _exit (func (arg)).
It cannot be done in portable C. */
#include <sysdep.h>
#include <asm-syntax.h>
#define SIG_SETMASK 3
.text
ENTRY (__start_thread)
/* End FDE now, because in the child the unwind info will be
wrong. */
cfi_endproc
/* There is a window of a few instructions, right after the rfork
system call, where the handling of a signal would write garbage
into the stack shared by the parent and the child (assuming
RFMEM is set in flags). To solve this: 1. We block all signals
around the rfork system call and unblock them afterwards in
the parent and in the child (but only after changing the stack
pointer). 2. The child accesses only values passed in registers
and on its own stack. This way, if the parent is scheduled to
run first, and handles a signal, it will not affect the child;
and if the child runs first, and handles a signal, it will use
the child's stack and not affect the parent.
We need to pass 7 words of info to the child: stack, func, arg,
and the signal mask to restore. Since we have only 4 call-saved
registers available (%ebx, %esi, %edi, %ebp), we pass only the
stack pointer in a register, and the rest through the child's
stack. */
pushl %ebp
movl %esp, %ebp
subl $36, %esp
movl %ebx, 32(%esp)
movl 8(%ebp), %eax /* flags */
testl $32, %eax /* flags & RFMEM */
jz L(simple)
/* Block all signals. */
movl $-1, %eax
movl %eax, 16(%esp)
movl %eax, 20(%esp)
movl %eax, 24(%esp)
movl %eax, 28(%esp)
leal 16(%esp), %eax
movl $SIG_SETMASK, 4(%esp)
movl %eax, 8(%esp)
movl %eax, 12(%esp)
DO_CALL (sigprocmask, 3)
jb L(error)
/* Copy all info to the child's stack. */
movl 12(%ebp), %ebx /* stack */
subl $32, %ebx /* room for func, arg, sigset_t */
andl $-16, %ebx /* make it 16-bytes aligned */
movl 16(%ebp), %eax /* func */
movl 20(%ebp), %edx /* arg */
movl %eax, 4(%ebx)
movl %edx, (%ebx)
movl 16(%esp), %eax /* sigset_t word 0 */
movl 20(%esp), %edx /* sigset_t word 1 */
movl %eax, 16(%ebx)
movl %edx, 20(%ebx)
movl 24(%esp), %eax /* sigset_t word 2 */
movl 28(%esp), %edx /* sigset_t word 3 */
movl %eax, 24(%ebx)
movl %edx, 28(%ebx)
/* Perform the rfork system call. */
movl 8(%ebp), %eax /* flags */
movl %eax, 4(%esp)
DO_CALL (rfork, 1)
jb L(error_unmask)
/* %edx is now 0 for the parent and 1 for the child. */
testl %edx, %edx
jnz L(child)
/* Save the child pid, currently in %eax. */
movl %eax, %ebx
/* Restore the previous signal mask. */
leal 16(%esp), %eax
movl $SIG_SETMASK, 4(%esp)
movl %eax, 8(%esp)
movl $0, 12(%esp)
DO_CALL (sigprocmask, 3)
/* Return the child pid, currently in %ebx. */
movl %ebx, %eax
addl $32, %esp
popl %ebx
popl %ebp
ret
L(child):/* Here we are in the child thread. */
/* Set the stack pointer. */
movl %ebx, %esp
/* Terminate the stack frame. */
subl %ebp, %ebp
movl 4(%esp), %edi
/* Restore the previous signal mask. */
leal 16(%esp), %eax
movl $SIG_SETMASK, 4(%esp)
movl %eax, 8(%esp)
movl $0, 12(%esp)
DO_CALL (sigprocmask, 3)
L(child1):
/* Call func (arg). */
call *%edi
/* Call _exit. */
#ifdef PIC
call L(here)
L(here):
popl %ebx
addl $_GLOBAL_OFFSET_TABLE_+[.-L(here)], %ebx
#endif
pushl %eax
call HIDDEN_JUMPTARGET (_exit)
L(simple):/* Simple case without signal mask handling. */
/* Copy all info to the child's stack. */
movl 12(%ebp), %ebx /* stack */
subl $8, %ebx /* room for func, arg */
andl $-16, %ebx /* make it 16-bytes aligned */
movl 16(%ebp), %eax /* func */
movl 20(%ebp), %edx /* arg */
movl %eax, 4(%ebx)
movl %edx, (%ebx)
/* Perform the rfork system call. */
movl 8(%ebp), %eax /* flags */
movl %eax, 4(%esp)
DO_CALL (rfork, 1)
jb L(error)
/* %edx is now 0 for the parent and 1 for the child. */
testl %edx, %edx
jnz L(simple_child)
/* Return the child pid, currently in %eax. */
addl $32, %esp
popl %ebx
popl %ebp
L(pseudo_end):
ret
L(simple_child):/* Here we are in the child thread. */
/* Set the stack pointer. */
movl %ebx, %esp
/* Terminate the stack frame. */
subl %ebp, %ebp
movl 4(%esp), %edi
jmp L(child1)
L(error_unmask):
/* Save the error code, currently in %eax. */
movl %eax, %ebx
/* Restore the previous signal mask. */
leal 16(%esp), %eax
movl $SIG_SETMASK, 4(%esp)
movl %eax, 8(%esp)
movl $0, 12(%esp)
DO_CALL (sigprocmask, 3)
/* load saved error code */
movl %ebx, %eax
L(error):
addl $32, %esp
popl %ebx
popl %ebp
jmp SYSCALL_ERROR_LABEL
cfi_startproc
PSEUDO_END (__start_thread)
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