syscall: use CLONE_VFORK (WIP)

neelance · Feb 24, 2017 · f207709 · f207709
1 parent a1ea912
commit f207709
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Showing 3 changed files with 32 additions and 2 deletions.
diff --git a/src/syscall/asm_linux_amd64.s b/src/syscall/asm_linux_amd64.s
@@ -111,6 +111,31 @@ ok2:
 	MOVQ	$0, err+72(FP)
 	RET
 
+// func rawSyscall6PreserveRet(trap, a1, a2, a3, a4, a5, a6 uintptr) (r1, r2, err uintptr)
+TEXT ·rawSyscall6PreserveRet(SB),NOSPLIT,$0-80
+	MOVQ	a1+8(FP), DI
+	MOVQ	a2+16(FP), SI
+	MOVQ	a3+24(FP), DX
+	MOVQ	a4+32(FP), R10
+	MOVQ	a5+40(FP), R8
+	MOVQ	a6+48(FP), R9
+	MOVQ	trap+0(FP), AX	// syscall entry
+	POPQ	R12 // preserve return address
+	SYSCALL
+	PUSHQ	R12
+	CMPQ	AX, $0xfffffffffffff001
+	JLS	ok2
+	MOVQ	$-1, r1+56(FP)
+	MOVQ	$0, r2+64(FP)
+	NEGQ	AX
+	MOVQ	AX, err+72(FP)
+	RET
+ok2:
+	MOVQ	AX, r1+56(FP)
+	MOVQ	DX, r2+64(FP)
+	MOVQ	$0, err+72(FP)
+	RET
+
 // func gettimeofday(tv *Timeval) (err uintptr)
 TEXT ·gettimeofday(SB),NOSPLIT,$0-16
 	MOVQ	tv+0(FP), DI

diff --git a/src/syscall/exec_linux.go b/src/syscall/exec_linux.go
@@ -95,9 +95,12 @@ func forkAndExecInChild(argv0 *byte, argv, envv []*byte, chroot, dir *byte, attr
 	// About to call fork.
 	// No more allocation or calls of non-assembly functions.
 	runtime_BeforeFork()
-	if runtime.GOARCH == "s390x" {
+	switch {
+	case runtime.GOARCH == "amd64" && sys.Cloneflags&CLONE_NEWUSER == 0:
+		r1, _, err1 = rawSyscall6PreserveRet(SYS_CLONE, uintptr(SIGCHLD|CLONE_VFORK|CLONE_VM)|sys.Cloneflags, 0, 0, 0, 0, 0)
+	case runtime.GOARCH == "s390x":
 		r1, _, err1 = RawSyscall6(SYS_CLONE, 0, uintptr(SIGCHLD)|sys.Cloneflags, 0, 0, 0, 0)
-	} else {
+	default:
 		r1, _, err1 = RawSyscall6(SYS_CLONE, uintptr(SIGCHLD)|sys.Cloneflags, 0, 0, 0, 0, 0)
 	}
 	if err1 != 0 {

diff --git a/src/syscall/syscall_linux_amd64.go b/src/syscall/syscall_linux_amd64.go
@@ -134,3 +134,5 @@ func (msghdr *Msghdr) SetControllen(length int) {
 func (cmsg *Cmsghdr) SetLen(length int) {
 	cmsg.Len = uint64(length)
 }
+
+func rawSyscall6PreserveRet(trap, a1, a2, a3, a4, a5, a6 uintptr) (r1, r2 uintptr, err Errno)