runtime: mlock top of signal stack on both amd64 and 386

CL 209899 worked around an issue that corrupts vector registers in
recent versions of the Linux kernel by mlocking the top page of every
signal stack on amd64. However, the underlying issue also affects the
XMM registers on 386. This CL applies the mlock fix to both amd64 and
386.

Fixes #35777 (again).

Change-Id: I9886f2dc4c23625421296bd5518d5fd3288bfe48
Reviewed-on: https://go-review.googlesource.com/c/go/+/210345
Run-TryBot: Austin Clements <austin@google.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: David Chase <drchase@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/runtime/defs_linux_386.go

@@ -227,3 +227,14 @@ type sockaddr_un struct {
 	family uint16
 	path   [108]byte
 }
+
+const __NEW_UTS_LEN = 64
+
+type new_utsname struct {
+	sysname    [__NEW_UTS_LEN + 1]byte
+	nodename   [__NEW_UTS_LEN + 1]byte
+	release    [__NEW_UTS_LEN + 1]byte
+	version    [__NEW_UTS_LEN + 1]byte
+	machine    [__NEW_UTS_LEN + 1]byte
+	domainname [__NEW_UTS_LEN + 1]byte
+}

src/runtime/os_linux_386.go

-// Copyright 2019 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-package runtime
-
-func osArchInit() {}

src/runtime/os_linux_amd64.go → src/runtime/os_linux_x86.go

@@ -2,6 +2,9 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+// +build linux
+// +build 386 amd64
+
 package runtime
 
 //go:noescape

src/runtime/sys_linux_386.s

@@ -39,6 +39,8 @@
 #define SYS_socketcall		102
 #define SYS_setittimer		104
 #define SYS_clone		120
+#define SYS_uname		122
+#define SYS_mlock		150
 #define SYS_sched_yield 	158
 #define SYS_nanosleep		162
 #define SYS_rt_sigreturn	173
@@ -776,3 +778,20 @@ TEXT runtime·sbrk0(SB),NOSPLIT,$0-4
 	INVOKE_SYSCALL
 	MOVL	AX, ret+0(FP)
 	RET
+
+// func uname(utsname *new_utsname) int
+TEXT ·uname(SB),NOSPLIT,$0-8
+	MOVL    $SYS_uname, AX
+	MOVL    utsname+0(FP), BX
+	INVOKE_SYSCALL
+	MOVL	AX, ret+4(FP)
+	RET
+
+// func mlock(addr, len uintptr) int
+TEXT ·mlock(SB),NOSPLIT,$0-12
+	MOVL    $SYS_mlock, AX
+	MOVL    addr+0(FP), BX
+	MOVL    len+4(FP), CX
+	INVOKE_SYSCALL
+	MOVL	AX, ret+8(FP)
+	RET