From: Cherry Mui <cherryyz@google.com>
Date: Wed, 2 Jun 2021 23:43:28 +0000 (-0400)
Subject: [dev.typeparams] runtime: call cgocallbackg indirectly on ARM64
X-Git-Tag: go1.18beta1~1818^2^2~432
X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=3de4986852;p=gostls13.git

[dev.typeparams] runtime: call cgocallbackg indirectly on ARM64

This is CL 312669, for ARM64.

cgocallback calls cgocallbackg after switching the stack. Call it
indirectly to bypass the linker's nosplit check. In particular,
this avoids a nosplit stack overflow on Windows when register ABI
is enabled.

Change-Id: I7054a750fb0ec2579d46004f94b46b6f7b9e3a21
Reviewed-on: https://go-review.googlesource.com/c/go/+/324734
Trust: Cherry Mui <cherryyz@google.com>
Run-TryBot: Cherry Mui <cherryyz@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
---

diff --git a/src/runtime/asm_arm64.s b/src/runtime/asm_arm64.s
index 4babcc7fcb..be4313d35d 100644
--- a/src/runtime/asm_arm64.s
+++ b/src/runtime/asm_arm64.s
@@ -1196,7 +1196,8 @@ havem:
 	MOVD	R1, 8(RSP)
 	MOVD	R2, 16(RSP)
 	MOVD	R3, 24(RSP)
-	BL	runtime·cgocallbackg(SB)
+	MOVD	$runtime·cgocallbackg(SB), R0
+	CALL	(R0) // indirect call to bypass nosplit check. We're on a different stack now.
 
 	// Restore g->sched (== m->curg->sched) from saved values.
 	MOVD	0(RSP), R5