From fbdfa99246ecbb04954a042a5809c4748415574d Mon Sep 17 00:00:00 2001
From: Ian Lance Taylor <iant@golang.org>
Date: Wed, 16 Dec 2015 12:16:17 -0800
Subject: runtime: for c-archive/c-shared, don't install unnecessary signal
 handlers

Only install signal handlers for synchronous signals that become
run-time panics.  Set the SA_ONSTACK flag for other signal handlers as
needed.

Fixes #13028.
Update #12465.
Update #13034.
Update #13042.

Change-Id: I28375e70641f60630e10f3c86e24b6e4f8a35cc9
Reviewed-on: https://go-review.googlesource.com/17903
Reviewed-by: Russ Cox <rsc@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
---
 src/runtime/signal1_unix.go    |  8 ++++++++
 src/runtime/signal2_unix.go    | 11 +++++++++--
 src/runtime/sys_darwin_amd64.s |  6 +++++-
 src/runtime/sys_linux_arm.s    |  4 ++++
 4 files changed, 26 insertions(+), 3 deletions(-)

(limited to 'src/runtime')

diff --git a/src/runtime/signal1_unix.go b/src/runtime/signal1_unix.go
index 405713b371..2a325bb9fc 100644
--- a/src/runtime/signal1_unix.go
+++ b/src/runtime/signal1_unix.go
@@ -65,6 +65,14 @@ func initsig() {
 			continue
 		}
 
+		// When built using c-archive or c-shared, only
+		// install signal handlers for synchronous signals.
+		// Set SA_ONSTACK for other signals if necessary.
+		if (isarchive || islibrary) && t.flags&_SigPanic == 0 {
+			setsigstack(i)
+			continue
+		}
+
 		t.flags |= _SigHandling
 		setsig(i, funcPC(sighandler), true)
 	}
diff --git a/src/runtime/signal2_unix.go b/src/runtime/signal2_unix.go
index 8b0bd42206..0633a51900 100644
--- a/src/runtime/signal2_unix.go
+++ b/src/runtime/signal2_unix.go
@@ -16,8 +16,6 @@ func sigfwd(fn uintptr, sig uint32, info *siginfo, ctx unsafe.Pointer)
 // signal was forwarded.
 //go:nosplit
 func sigfwdgo(sig uint32, info *siginfo, ctx unsafe.Pointer) bool {
-	g := getg()
-	c := &sigctxt{info, ctx}
 	if sig >= uint32(len(sigtable)) {
 		return false
 	}
@@ -28,13 +26,22 @@ func sigfwdgo(sig uint32, info *siginfo, ctx unsafe.Pointer) bool {
 	if fwdFn == _SIG_DFL {
 		return false
 	}
+
+	// If we aren't handling the signal, forward it.
+	if flags&_SigHandling == 0 {
+		sigfwd(fwdFn, sig, info, ctx)
+		return true
+	}
+
 	// Only forward synchronous signals.
+	c := &sigctxt{info, ctx}
 	if c.sigcode() == _SI_USER || flags&_SigPanic == 0 {
 		return false
 	}
 	// Determine if the signal occurred inside Go code.  We test that:
 	//   (1) we were in a goroutine (i.e., m.curg != nil), and
 	//   (2) we weren't in CGO (i.e., m.curg.syscallsp == 0).
+	g := getg()
 	if g != nil && g.m != nil && g.m.curg != nil && g.m.curg.syscallsp == 0 {
 		return false
 	}
diff --git a/src/runtime/sys_darwin_amd64.s b/src/runtime/sys_darwin_amd64.s
index 692dbca580..7b9cf6a3bc 100644
--- a/src/runtime/sys_darwin_amd64.s
+++ b/src/runtime/sys_darwin_amd64.s
@@ -214,10 +214,14 @@ TEXT runtime·sigaction(SB),NOSPLIT,$0-24
 
 TEXT runtime·sigfwd(SB),NOSPLIT,$0-32
 	MOVQ fn+0(FP),    AX
-	MOVQ sig+8(FP),   DI
+	MOVL sig+8(FP),   DI
 	MOVQ info+16(FP), SI
 	MOVQ ctx+24(FP),  DX
+	MOVQ SP, BP
+	SUBQ $64, SP
+	ANDQ $~15, SP     // alignment for x86_64 ABI
 	CALL AX
+	MOVQ BP, SP
 	RET
 
 TEXT runtime·sigreturn(SB),NOSPLIT,$0-12
diff --git a/src/runtime/sys_linux_arm.s b/src/runtime/sys_linux_arm.s
index 216781ef7a..6a3b924330 100644
--- a/src/runtime/sys_linux_arm.s
+++ b/src/runtime/sys_linux_arm.s
@@ -339,7 +339,11 @@ TEXT runtime·sigfwd(SB),NOSPLIT,$0-16
 	MOVW	info+8(FP), R1
 	MOVW	ctx+12(FP), R2
 	MOVW	fn+0(FP), R11
+	MOVW	R13, R4
+	SUB	$24, R13
+	BIC	$0x7, R13 // alignment for ELF ABI
 	BL	(R11)
+	MOVW	R4, R13
 	RET
 
 TEXT runtime·sigtramp(SB),NOSPLIT,$12
-- 
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