From cad6629144ddb79401f90bd0388da14294f9131a Mon Sep 17 00:00:00 2001
From: Mauri de Souza Meneguzzo <mauri870@gmail.com>
Date: Sat, 2 Dec 2023 15:04:52 +0000
Subject: [PATCH] runtime: add crash stack support for s390x

Change-Id: Ie923f7bbe5ef22e381ae4f421387fbd570622a28
GitHub-Last-Rev: f8f21635025eb6e26c6994679995ade501e870cf
GitHub-Pull-Request: golang/go#63908
Reviewed-on: https://go-review.googlesource.com/c/go/+/539296
Run-TryBot: Joel Sing <joel@sing.id.au>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Cherry Mui <cherryyz@google.com>
Reviewed-by: Carlos Amedee <carlos@golang.org>
Run-TryBot: Mauri de Souza Meneguzzo <mauri870@gmail.com>
Reviewed-by: Joel Sing <joel@sing.id.au>
---
 src/runtime/asm.s       |  2 ++
 src/runtime/asm_s390x.s | 39 +++++++++++++++++++++++++++++++--------
 src/runtime/proc.go     |  2 +-
 3 files changed, 34 insertions(+), 9 deletions(-)

diff --git a/src/runtime/asm.s b/src/runtime/asm.s
index 24cd0c95db6..74ae8789abc 100644
--- a/src/runtime/asm.s
+++ b/src/runtime/asm.s
@@ -20,6 +20,7 @@ TEXT ·mapinitnoop<ABIInternal>(SB),NOSPLIT,$0-0
 #ifndef GOARCH_ppc64
 #ifndef GOARCH_ppc64le
 #ifndef GOARCH_riscv64
+#ifndef GOARCH_s390x
 #ifndef GOARCH_wasm
 // stub to appease shared build mode.
 TEXT ·switchToCrashStack0<ABIInternal>(SB),NOSPLIT,$0-0
@@ -32,3 +33,4 @@ TEXT ·switchToCrashStack0<ABIInternal>(SB),NOSPLIT,$0-0
 #endif
 #endif
 #endif
+#endif
diff --git a/src/runtime/asm_s390x.s b/src/runtime/asm_s390x.s
index a8e1424bf18..f2354a6d536 100644
--- a/src/runtime/asm_s390x.s
+++ b/src/runtime/asm_s390x.s
@@ -292,6 +292,29 @@ noswitch:
 	ADD	$8, R15
 	BR	(R3)
 
+// func switchToCrashStack0(fn func())
+TEXT runtime·switchToCrashStack0<ABIInternal>(SB), NOSPLIT, $0-8
+	MOVD	fn+0(FP), R12	// context
+	MOVD	g_m(g), R4	// curm
+
+	// set g to gcrash
+	MOVD	$runtime·gcrash(SB), g	// g = &gcrash
+	BL	runtime·save_g(SB)
+	MOVD	R4, g_m(g)	// g.m = curm
+	MOVD	g, m_g0(R4)	// curm.g0 = g
+
+	// switch to crashstack
+	MOVD	(g_stack+stack_hi)(g), R4
+	ADD	$(-4*8), R4, R15
+
+	// call target function
+	MOVD	0(R12), R3	// code pointer
+	BL	(R3)
+
+	// should never return
+	BL	runtime·abort(SB)
+	UNDEF
+
 /*
  * support for morestack
  */
@@ -305,6 +328,14 @@ noswitch:
 // calling the scheduler calling newm calling gc), so we must
 // record an argument size. For that purpose, it has no arguments.
 TEXT runtime·morestack(SB),NOSPLIT|NOFRAME,$0-0
+	// Called from f.
+	// Set g->sched to context in f.
+	MOVD	R15, (g_sched+gobuf_sp)(g)
+	MOVD	LR, R8
+	MOVD	R8, (g_sched+gobuf_pc)(g)
+	MOVD	R5, (g_sched+gobuf_lr)(g)
+	MOVD	R12, (g_sched+gobuf_ctxt)(g)
+
 	// Cannot grow scheduler stack (m->g0).
 	MOVD	g_m(g), R7
 	MOVD	m_g0(R7), R8
@@ -319,14 +350,6 @@ TEXT runtime·morestack(SB),NOSPLIT|NOFRAME,$0-0
 	BL	runtime·badmorestackgsignal(SB)
 	BL	runtime·abort(SB)
 
-	// Called from f.
-	// Set g->sched to context in f.
-	MOVD	R15, (g_sched+gobuf_sp)(g)
-	MOVD	LR, R8
-	MOVD	R8, (g_sched+gobuf_pc)(g)
-	MOVD	R5, (g_sched+gobuf_lr)(g)
-	MOVD	R12, (g_sched+gobuf_ctxt)(g)
-
 	// Called from f.
 	// Set m->morebuf to f's caller.
 	MOVD	R5, (m_morebuf+gobuf_pc)(R7)	// f's caller's PC
diff --git a/src/runtime/proc.go b/src/runtime/proc.go
index c2676c43b2c..b3caeb9a7c2 100644
--- a/src/runtime/proc.go
+++ b/src/runtime/proc.go
@@ -579,7 +579,7 @@ func switchToCrashStack(fn func()) {
 // Disable crash stack on Windows for now. Apparently, throwing an exception
 // on a non-system-allocated crash stack causes EXCEPTION_STACK_OVERFLOW and
 // hangs the process (see issue 63938).
-const crashStackImplemented = (GOARCH == "amd64" || GOARCH == "arm64" || GOARCH == "mips64" || GOARCH == "mips64le" || GOARCH == "ppc64" || GOARCH == "ppc64le" || GOARCH == "riscv64" || GOARCH == "wasm") && GOOS != "windows"
+const crashStackImplemented = (GOARCH == "amd64" || GOARCH == "arm64" || GOARCH == "mips64" || GOARCH == "mips64le" || GOARCH == "ppc64" || GOARCH == "ppc64le" || GOARCH == "riscv64" || GOARCH == "s390x" || GOARCH == "wasm") && GOOS != "windows"
 
 //go:noescape
 func switchToCrashStack0(fn func()) // in assembly