From: Elias Naur <mail@eliasnaur.com>
Date: Tue, 16 Apr 2019 06:52:42 +0000 (+0200)
Subject: runtime: avoid getg in preinit on Android
X-Git-Tag: go1.13beta1~681
X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=ae85ae5db2d3b6a3dfb75ade74e0f11234375594;p=gostls13.git

runtime: avoid getg in preinit on Android

sigaction is called as part of library mode initializers
(_rt0_*_lib). Sigaction in turn calls getg, but on Android the TLS
offset for g has not been initialized and getg might return garbage.

Add a check for initialization before calling getg.

Fixes the golang.org/x/mobile/bind/java tests on amd64 and 386.

Fixes #31476

Change-Id: Id2c41fdc983239eca039b49a54b8853c5669d127
Reviewed-on: https://go-review.googlesource.com/c/go/+/172158
Reviewed-by: Ian Lance Taylor <iant@golang.org>
---

diff --git a/src/runtime/cgo_sigaction.go b/src/runtime/cgo_sigaction.go
index 3ef6800cd9..bc5e0786d9 100644
--- a/src/runtime/cgo_sigaction.go
+++ b/src/runtime/cgo_sigaction.go
@@ -39,7 +39,10 @@ func sigaction(sig uint32, new, old *sigactiont) {
 
 		var ret int32
 
-		g := getg()
+		var g *g
+		if mainStarted {
+			g = getg()
+		}
 		sp := uintptr(unsafe.Pointer(&sig))
 		switch {
 		case g == nil: