From: Damien Neil <dneil@google.com>
Date: Tue, 19 Nov 2024 17:04:11 +0000 (-0800)
Subject: runtime: use indirect call in adjustSignalStack to avoid nosplit overflow
X-Git-Tag: go1.24rc1~249
X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=944df9a7516021f0405cd8adb1e6894ae9872cb5;p=gostls13.git

runtime: use indirect call in adjustSignalStack to avoid nosplit overflow

Avoids a nosplit stack overflow on OpenBSD after CL 591997
increases the adjustSignalStack stack by 16 bytes.

Change-Id: I2c990de6c7cd8d2aca6e6b98133da120c8a4174b
Reviewed-on: https://go-review.googlesource.com/c/go/+/629696
Reviewed-by: Cherry Mui <cherryyz@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
---

diff --git a/src/runtime/signal_unix.go b/src/runtime/signal_unix.go
index a056e21a2f..96628d6baa 100644
--- a/src/runtime/signal_unix.go
+++ b/src/runtime/signal_unix.go
@@ -584,15 +584,23 @@ func adjustSignalStack(sig uint32, mp *m, gsigStack *gsignalStack) bool {
 	}
 
 	// sp is not within gsignal stack, g0 stack, or sigaltstack. Bad.
+	// Call indirectly to avoid nosplit stack overflow on OpenBSD.
+	adjustSignalStack2Indirect(sig, sp, mp, st.ss_flags&_SS_DISABLE != 0)
+	return false
+}
+
+var adjustSignalStack2Indirect = adjustSignalStack2
+
+//go:nosplit
+func adjustSignalStack2(sig uint32, sp uintptr, mp *m, ssDisable bool) {
 	setg(nil)
 	needm(true)
-	if st.ss_flags&_SS_DISABLE != 0 {
+	if ssDisable {
 		noSignalStack(sig)
 	} else {
 		sigNotOnStack(sig, sp, mp)
 	}
 	dropm()
-	return false
 }
 
 // crashing is the number of m's we have waited for when implementing