summaryrefslogtreecommitdiff
path: root/libc/sysdeps/linux/xtensa/vfork.S
diff options
context:
space:
mode:
Diffstat (limited to 'libc/sysdeps/linux/xtensa/vfork.S')
-rw-r--r--libc/sysdeps/linux/xtensa/vfork.S170
1 files changed, 170 insertions, 0 deletions
diff --git a/libc/sysdeps/linux/xtensa/vfork.S b/libc/sysdeps/linux/xtensa/vfork.S
new file mode 100644
index 000000000..830a0cd4d
--- /dev/null
+++ b/libc/sysdeps/linux/xtensa/vfork.S
@@ -0,0 +1,170 @@
+/* Copyright (C) 2005, 2007 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, write to the Free
+ Software Foundation, Inc., 51 Franklin Street - Fifth Floor,
+ Boston, MA 02110-1301, USA. */
+
+#include "sysdep.h"
+#include <sys/syscall.h>
+#define _SIGNAL_H
+#include <bits/signum.h>
+
+
+/* Clone the calling process, but without copying the whole address space.
+ The calling process is suspended until the new process exits or is
+ replaced by a call to `execve'. Return -1 for errors, 0 to the new process,
+ and the process ID of the new process to the old process.
+
+ Note that it is important that we don't create a new stack frame for the
+ caller. */
+
+
+/* The following are defined in linux/sched.h, which unfortunately
+ is not safe for inclusion in an assembly file. */
+#define CLONE_VM 0x00000100 /* set if VM shared between processes */
+#define CLONE_VFORK 0x00004000 /* set if the parent wants the child to
+ wake it up on mm_release */
+
+#ifndef SAVE_PID
+#define SAVE_PID
+#endif
+
+#ifndef RESTORE_PID
+#define RESTORE_PID
+#endif
+
+
+/* pid_t vfork(void);
+ Implemented as __clone_syscall(CLONE_VFORK | CLONE_VM | SIGCHLD, 0) */
+
+ENTRY (__vfork)
+
+ movi a6, .Ljumptable
+ extui a2, a0, 30, 2 // call-size: call4/8/12 = 1/2/3
+ addx4 a4, a2, a6 // find return address in jumptable
+ l32i a4, a4, 0
+ add a4, a4, a6
+
+ slli a2, a2, 30
+ xor a3, a0, a2 // remove call-size from return address
+ extui a5, a4, 30, 2 // get high bits of jump target
+ slli a5, a5, 30
+ or a3, a3, a5 // stuff them into the return address
+ xor a4, a4, a5 // clear high bits of jump target
+ or a0, a4, a2 // create temporary return address
+ retw // "return" to .L4, .L8, or .L12
+
+ .align 4
+.Ljumptable:
+ .word 0
+ .word .L4 - .Ljumptable
+ .word .L8 - .Ljumptable
+ .word .L12 - .Ljumptable
+
+ /* a7: return address */
+.L4: mov a12, a2
+ mov a13, a3
+
+ SAVE_PID
+
+ /* Use syscall 'clone'. Set new stack pointer to the same address. */
+ movi a2, SYS_ify (clone)
+ movi a3, 0
+ movi a6, CLONE_VM | CLONE_VFORK | SIGCHLD
+ syscall
+
+ RESTORE_PID
+
+ movi a5, -4096
+
+ mov a6, a2
+ mov a2, a12
+ mov a3, a13
+
+ bgeu a6, a5, 1f
+ jx a7
+1: call4 .Lerr // returns to original caller
+
+
+ /* a11: return address */
+.L8: mov a12, a2
+ mov a13, a3
+ mov a14, a6
+
+ SAVE_PID
+
+ movi a2, SYS_ify (clone)
+ movi a3, 0
+ movi a6, CLONE_VM | CLONE_VFORK | SIGCHLD
+ syscall
+
+ RESTORE_PID
+
+ movi a9, -4096
+
+ mov a10, a2
+ mov a2, a12
+ mov a3, a13
+ mov a6, a14
+
+ bgeu a10, a9, 1f
+ jx a11
+1: call8 .Lerr // returns to original caller
+
+
+ /* a15: return address */
+.L12: mov a12, a2
+ mov a13, a3
+ mov a14, a6
+
+ SAVE_PID
+
+ movi a2, SYS_ify (clone)
+ movi a3, 0
+ movi a6, CLONE_VM | CLONE_VFORK | SIGCHLD
+ syscall
+
+ RESTORE_PID
+
+ mov a3, a13
+ movi a13, -4096
+
+ mov a6, a14
+ mov a14, a2
+
+ mov a2, a12
+
+ bgeu a14, a13, 1f
+ jx a15
+1: call12 .Lerr // returns to original caller
+
+
+ .align 4
+.Lerr: entry a1, 16
+
+ /* Restore the return address. */
+ extui a4, a0, 30, 2 // get the call-size bits
+ slli a4, a4, 30
+ slli a3, a3, 2 // clear high bits of target address
+ srli a3, a3, 2
+ or a0, a3, a4 // combine them
+
+ PSEUDO_END (__vfork)
+.Lpseudo_end:
+ retw
+
+libc_hidden_def (__vfork)
+
+weak_alias (__vfork, vfork)