From aa9dd50095efd2bb0e3b6fcf75859904f3f80d03 Mon Sep 17 00:00:00 2001
From: Joel Sing <joel@sing.id.au>
Date: Sun, 12 Nov 2023 23:01:34 +1100
Subject: [PATCH] runtime: add support for crash stack on ppc64/ppc64le

Change-Id: I8d1011509c4f0f529e97055280606603747a2e1a
Reviewed-on: https://go-review.googlesource.com/c/go/+/541775
Reviewed-by: Mauri de Souza Meneguzzo <mauri870@gmail.com>
Reviewed-by: Paul Murphy <murp@ibm.com>
Reviewed-by: David Chase <drchase@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Cherry Mui <cherryyz@google.com>
Run-TryBot: Joel Sing <joel@sing.id.au>
---
 src/runtime/asm.s        |  4 ++++
 src/runtime/asm_ppc64x.s | 41 ++++++++++++++++++++++++++++++++--------
 src/runtime/proc.go      |  2 +-
 3 files changed, 38 insertions(+), 9 deletions(-)

diff --git a/src/runtime/asm.s b/src/runtime/asm.s
index 012a6a095d..45ba467806 100644
--- a/src/runtime/asm.s
+++ b/src/runtime/asm.s
@@ -17,6 +17,8 @@ TEXT ·mapinitnoop<ABIInternal>(SB),NOSPLIT,$0-0
 #ifndef GOARCH_arm64
 #ifndef GOARCH_mips64
 #ifndef GOARCH_mips64le
+#ifndef GOARCH_ppc64
+#ifndef GOARCH_ppc64le
 #ifndef GOARCH_riscv64
 // stub to appease shared build mode.
 TEXT ·switchToCrashStack0<ABIInternal>(SB),NOSPLIT,$0-0
@@ -26,3 +28,5 @@ TEXT ·switchToCrashStack0<ABIInternal>(SB),NOSPLIT,$0-0
 #endif
 #endif
 #endif
+#endif
+#endif
diff --git a/src/runtime/asm_ppc64x.s b/src/runtime/asm_ppc64x.s
index 922c50dc4f..ff9b736430 100644
--- a/src/runtime/asm_ppc64x.s
+++ b/src/runtime/asm_ppc64x.s
@@ -284,6 +284,31 @@ noswitch:
 #endif
 	RET
 
+// func switchToCrashStack0(fn func())
+TEXT runtime·switchToCrashStack0<ABIInternal>(SB), NOSPLIT, $0-8
+	MOVD	R3, R11				// context register
+	MOVD	g_m(g), R3			// curm
+
+	// set g to gcrash
+	MOVD	$runtime·gcrash(SB), g	// g = &gcrash
+	CALL	runtime·save_g(SB)	// clobbers R31
+	MOVD	R3, g_m(g)			// g.m = curm
+	MOVD	g, m_g0(R3)			// curm.g0 = g
+
+	// switch to crashstack
+	MOVD	(g_stack+stack_hi)(g), R3
+	SUB	$(4*8), R3
+	MOVD	R3, R1
+
+	// call target function
+	MOVD	0(R11), R12			// code pointer
+	MOVD	R12, CTR
+	BL	(CTR)
+
+	// should never return
+	CALL	runtime·abort(SB)
+	UNDEF
+
 /*
  * support for morestack
  */
@@ -297,6 +322,14 @@ 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	R1, (g_sched+gobuf_sp)(g)
+	MOVD	LR, R8
+	MOVD	R8, (g_sched+gobuf_pc)(g)
+	MOVD	R5, (g_sched+gobuf_lr)(g)
+	MOVD	R11, (g_sched+gobuf_ctxt)(g)
+
 	// Cannot grow scheduler stack (m->g0).
 	MOVD	g_m(g), R7
 	MOVD	m_g0(R7), R8
@@ -312,14 +345,6 @@ 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	R1, (g_sched+gobuf_sp)(g)
-	MOVD	LR, R8
-	MOVD	R8, (g_sched+gobuf_pc)(g)
-	MOVD	R5, (g_sched+gobuf_lr)(g)
-	MOVD	R11, (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 6b13d3b2f6..66d7da887e 100644
--- a/src/runtime/proc.go
+++ b/src/runtime/proc.go
@@ -576,7 +576,7 @@ func switchToCrashStack(fn func()) {
 	abort()
 }
 
-const crashStackImplemented = GOARCH == "amd64" || GOARCH == "arm64" || GOARCH == "mips64" || GOARCH == "mips64le" || GOARCH == "riscv64"
+const crashStackImplemented = GOARCH == "amd64" || GOARCH == "arm64" || GOARCH == "mips64" || GOARCH == "mips64le" || GOARCH == "ppc64" || GOARCH == "ppc64le" || GOARCH == "riscv64"
 
 //go:noescape
 func switchToCrashStack0(fn func()) // in assembly
-- 
2.50.0