runtime: mlock top of signal stack on Linux 5.2–5.4.1

Linux 5.2 introduced a bug that can corrupt vector registers on return
from a signal if the signal stack isn't faulted in:
https://bugzilla.kernel.org/show_bug.cgi?id=205663

This CL works around this by mlocking the top page of all Go signal
stacks on the affected kernels.

Fixes #35326, #35777

Change-Id: I77c80a2baa4780827633f92f464486caa222295d
Reviewed-on: https://go-review.googlesource.com/c/go/+/209899
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: David Chase <drchase@google.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/src/runtime/os_linux_ppc64x.go b/src/runtime/os_linux_ppc64x.go
index cc79cc4a66..3aedc23ef9 100644
--- a/src/runtime/os_linux_ppc64x.go
+++ b/src/runtime/os_linux_ppc64x.go
@@ -20,3 +20,5 @@ func archauxv(tag, val uintptr) {
 		cpu.HWCap2 = uint(val)
 	}
 }
+
+func osArchInit() {}