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Diffstat (limited to 'libc/sysdeps/linux/i386/makecontext.S')
-rw-r--r--libc/sysdeps/linux/i386/makecontext.S123
1 files changed, 123 insertions, 0 deletions
diff --git a/libc/sysdeps/linux/i386/makecontext.S b/libc/sysdeps/linux/i386/makecontext.S
new file mode 100644
index 000000000..d12799d80
--- /dev/null
+++ b/libc/sysdeps/linux/i386/makecontext.S
@@ -0,0 +1,123 @@
+/* Create new context.
+ Copyright (C) 2001,2002,2005,2007,2008,2009 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+ Contributed by Ulrich Drepper <drepper@redhat.com>, 2001.
+
+ 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
+ <http://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
+ /* 'makecontext' returns no value. */
+L(pseudo_end):
+ 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. */
+ cfi_endproc
+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
+
+#ifdef __PIC__
+ call 1f
+1: popl %ebx
+ addl $_GLOBAL_OFFSET_TABLE_+[.-1b], %ebx
+#endif
+ cmpl $0, (%esp) /* Check the next context. */
+ je 2f /* If it is zero exit. */
+
+ call JUMPTARGET(__setcontext)
+ /* If this returns (which can happen if the syscall fails) we'll
+ exit the program with the return error value (-1). */
+
+ movl %eax, (%esp)
+2: 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)