Apply same basic fix for getcontext(2) as for i386. Store the return

value for getcontext() in a preserved register rather than on the stack.
The second time around, the stack value would likely have changed so we
can't depend on it for the return value.

2 files changed, 56 insertions, 2 deletions

diff --git a/lib/libc/amd64/sys/Makefile.inc b/lib/libc/amd64/sys/Makefile.inc
index 897ed4f7fc62..43c6c11a09f6 100644
--- a/lib/libc/amd64/sys/Makefile.inc
+++ b/lib/libc/amd64/sys/Makefile.inc
@@ -1,8 +1,8 @@
 #	from: Makefile.inc,v 1.1 1993/09/03 19:04:23 jtc Exp
 # $FreeBSD$
 
-MDASM=	vfork.S brk.S cerror.S exect.S pipe.S ptrace.S reboot.S sbrk.S \
-	setlogin.S sigreturn.S
+MDASM=	vfork.S brk.S cerror.S exect.S getcontext.S pipe.S ptrace.S \
+	reboot.S sbrk.S setlogin.S sigreturn.S
 
 # Don't generate default code for these syscalls:
 NOASM=	break.o exit.o ftruncate.o getdomainname.o getlogin.o \
diff --git a/lib/libc/amd64/sys/getcontext.S b/lib/libc/amd64/sys/getcontext.S
new file mode 100644
index 000000000000..a0a77c0e4a1e
--- /dev/null
+++ b/lib/libc/amd64/sys/getcontext.S
@@ -0,0 +1,54 @@
+/*-
+ * Copyright (c) 2003 Peter Wemm <peter@FreeBSD.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <machine/asm.h>
+__FBSDID("$FreeBSD$");
+
+#include <SYS.h>
+
+/*
+ * This has to be magic to handle the multiple returns.
+ * Otherwise, the setcontext() syscall will return here and we'll
+ * pop off the return address and go to the *setcontext* call.
+ */
+	.weak	_getcontext
+	.set	_getcontext,__sys_getcontext
+	.weak	getcontext
+	.set	getcontext,__sys_getcontext
+ENTRY(__sys_getcontext)
+	movq	(%rsp),%rsi	/* save getcontext return address */
+	mov	$SYS_getcontext,%rax
+	KERNCALL
+	jb	1f
+	addl	$8,%rsp		/* remove stale (setcontext) return address */
+	jmp	*%rsi		/* restore return address */
+1:
+#ifdef PIC
+	movq	PIC_GOT(HIDENAME(cerror)),%rdx
+	jmp	*%rdx
+#else
+	jmp	HIDENAME(cerror)
+#endif