import syscall from glibc

1 files changed, 71 insertions, 0 deletions

diff --git a/libc/sysdeps/linux/alpha/syscall.S b/libc/sysdeps/linux/alpha/syscall.S
new file mode 100644
index 000000000..1ccb5815f
--- /dev/null
+++ b/libc/sysdeps/linux/alpha/syscall.S
@@ -0,0 +1,71 @@
+/* Copyright (C) 1996 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+   Contributed by David Mosberger <davidm@azstarnet.com>, 1996.
+
+   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.  */
+
+#include <features.h>
+#include <asm/regdef.h>
+#include <asm/pal.h>
+
+/*
+ * This is for COMPATIBILITY with Linux/x86 only.  Linux/Alpha system
+ * calls return an error indication in a3.  This allows arbitrary 64bit 
+ * values to be returned in v0 (because negative values are not
+ * mistaken as error numbers).  However, C allows only one value to
+ * be returned, so the interface below folds the error indication passed in
+ * a3 back into v0: it sets v0 to -errno if an error occurs.  Thus,
+ * no negative 64bit numbers can be returned.  To avoid this problem,
+ * use assembly stubs wherever possible/convenient.
+ *
+ * Usage:
+ *
+ * long	syscall(syscall_number, arg1, arg2, arg3, arg4, arg5)
+ *
+ * syscall_number = the index of the system call we're invoking
+ * arg1-arg5 = up to 5 integer arguments to the system call
+ *
+ * We need to do some arg shifting: the kernel expects the
+ * syscall number in v0 and the first five args in a0-a4.
+ *
+ */
+
+.globl __syscall;
+.align 4;
+.ent __syscall, 0;
+__syscall:
+.frame sp, 0, ra
+	.prologue 0
+
+	mov	a0, v0		/* Syscall number -> v0 */
+	mov	a1, a0		/* arg1-arg5 -> a0-a4 */
+	mov	a2, a1
+	mov	a3, a2
+	mov	a4, a3
+	mov	a5, a4
+
+	call_pal PAL_callsys	/* Invoke system call */
+	bne	a3, $error
+	ret
+
+$error:
+	br	gp, 2f
+2:	ldgp	gp, 0(gp)
+	jmp	zero,__syscall_error
+
+.end __syscall
+
+weak_alias (__syscall, syscall)