[release-branch.go1.18] runtime: mark morestack_noctxt SPWRITE on LR architectures

On LR architectures, morestack (and morestack_noctxt) are called
with a special calling convention, where the caller doesn't save
LR on stack but passes it as a register, which morestack will save
to g.sched.lr. The stack unwinder currently doesn't understand it,
and would fail to unwind from it. morestack already writes SP (as
it switches stack), but morestack_noctxt (which tailcalls
morestack) doesn't. If a profiling signal lands right in
morestack_noctxt, the unwinder will try to unwind the stack and
go off, and possibly crash.

Marking morestack_noctxt SPWRITE stops the unwinding.

Ideally we could teach the unwinder about the special calling
convention, or change the calling convention to be less special
(so the unwinder doesn't need to fetch a register from the signal
context). This is a stop-gap solution, to stop the unwinder from
crashing.

Updates #54332.
Fixes #54674.

Change-Id: I75295f2e27ddcf05f1ea0b541aedcb9000ae7576
Reviewed-on: https://go-review.googlesource.com/c/go/+/425396
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Cherry Mui <cherryyz@google.com>
Reviewed-by: Michael Pratt <mpratt@google.com>
(cherry picked from commit e4be2ac79f3cc7219ae1cf8334463d11cae24e01)
Reviewed-on: https://go-review.googlesource.com/c/go/+/425616

7 files changed, 51 insertions, 2 deletions

diff --git a/src/runtime/asm_arm.s b/src/runtime/asm_arm.s
index b47184e36b..591ef2a399 100644
--- a/src/runtime/asm_arm.s
+++ b/src/runtime/asm_arm.s
@@ -387,6 +387,13 @@ TEXT runtime·morestack(SB),NOSPLIT|NOFRAME,$0-0
 	RET
 
 TEXT runtime·morestack_noctxt(SB),NOSPLIT|NOFRAME,$0-0
+	// Force SPWRITE. This function doesn't actually write SP,
+	// but it is called with a special calling convention where
+	// the caller doesn't save LR on stack but passes it as a
+	// register (R3), and the unwinder currently doesn't understand.
+	// Make it SPWRITE to stop unwinding. (See issue 54332)
+	MOVW	R13, R13
+
 	MOVW	$0, R7
 	B runtime·morestack(SB)
 
diff --git a/src/runtime/asm_arm64.s b/src/runtime/asm_arm64.s
index fd65969b62..64121b11aa 100644
--- a/src/runtime/asm_arm64.s
+++ b/src/runtime/asm_arm64.s
@@ -318,6 +318,13 @@ TEXT runtime·morestack(SB),NOSPLIT|NOFRAME,$0-0
 	UNDEF
 
 TEXT runtime·morestack_noctxt(SB),NOSPLIT|NOFRAME,$0-0
+	// Force SPWRITE. This function doesn't actually write SP,
+	// but it is called with a special calling convention where
+	// the caller doesn't save LR on stack but passes it as a
+	// register (R3), and the unwinder currently doesn't understand.
+	// Make it SPWRITE to stop unwinding. (See issue 54332)
+	MOVD	RSP, RSP
+
 	MOVW	$0, R26
 	B runtime·morestack(SB)
 
diff --git a/src/runtime/asm_mips64x.s b/src/runtime/asm_mips64x.s
index 3597ebec57..1abadb9c7d 100644
--- a/src/runtime/asm_mips64x.s
+++ b/src/runtime/asm_mips64x.s
@@ -258,6 +258,13 @@ TEXT runtime·morestack(SB),NOSPLIT|NOFRAME,$0-0
 	UNDEF
 
 TEXT runtime·morestack_noctxt(SB),NOSPLIT|NOFRAME,$0-0
+	// Force SPWRITE. This function doesn't actually write SP,
+	// but it is called with a special calling convention where
+	// the caller doesn't save LR on stack but passes it as a
+	// register (R3), and the unwinder currently doesn't understand.
+	// Make it SPWRITE to stop unwinding. (See issue 54332)
+	MOVV	R29, R29
+
 	MOVV	R0, REGCTXT
 	JMP	runtime·morestack(SB)
 
diff --git a/src/runtime/asm_mipsx.s b/src/runtime/asm_mipsx.s
index 4a086b8eb3..877c1bb97b 100644
--- a/src/runtime/asm_mipsx.s
+++ b/src/runtime/asm_mipsx.s
@@ -257,6 +257,13 @@ TEXT runtime·morestack(SB),NOSPLIT|NOFRAME,$0-0
 	UNDEF
 
 TEXT runtime·morestack_noctxt(SB),NOSPLIT,$0-0
+	// Force SPWRITE. This function doesn't actually write SP,
+	// but it is called with a special calling convention where
+	// the caller doesn't save LR on stack but passes it as a
+	// register (R3), and the unwinder currently doesn't understand.
+	// Make it SPWRITE to stop unwinding. (See issue 54332)
+	MOVW	R29, R29
+
 	MOVW	R0, REGCTXT
 	JMP	runtime·morestack(SB)
 
diff --git a/src/runtime/asm_ppc64x.s b/src/runtime/asm_ppc64x.s
index ae14213999..10ae161a13 100644
--- a/src/runtime/asm_ppc64x.s
+++ b/src/runtime/asm_ppc64x.s
@@ -338,6 +338,13 @@ TEXT runtime·morestack(SB),NOSPLIT|NOFRAME,$0-0
 	UNDEF
 
 TEXT runtime·morestack_noctxt(SB),NOSPLIT|NOFRAME,$0-0
+	// Force SPWRITE. This function doesn't actually write SP,
+	// but it is called with a special calling convention where
+	// the caller doesn't save LR on stack but passes it as a
+	// register (R5), and the unwinder currently doesn't understand.
+	// Make it SPWRITE to stop unwinding. (See issue 54332)
+	MOVD	R1, R1
+
 	MOVD	R0, R11
 	BR	runtime·morestack(SB)
 
diff --git a/src/runtime/asm_riscv64.s b/src/runtime/asm_riscv64.s
index 2a4837b399..c88bef6ed8 100644
--- a/src/runtime/asm_riscv64.s
+++ b/src/runtime/asm_riscv64.s
@@ -158,8 +158,8 @@ TEXT runtime·getcallerpc(SB),NOSPLIT|NOFRAME,$0-8
  */
 
 // Called during function prolog when more stack is needed.
-// Caller has already loaded:
-// R1: framesize, R2: argsize, R3: LR
+// Called with return address (i.e. caller's PC) in X5 (aka T0),
+// and the LR register contains the caller's LR.
 //
 // The traceback routines see morestack on a g0 as being
 // the top of a stack (for example, morestack calling newstack
@@ -209,6 +209,13 @@ TEXT runtime·morestack(SB),NOSPLIT|NOFRAME,$0-0
 
 // func morestack_noctxt()
 TEXT runtime·morestack_noctxt(SB),NOSPLIT|NOFRAME,$0-0
+	// Force SPWRITE. This function doesn't actually write SP,
+	// but it is called with a special calling convention where
+	// the caller doesn't save LR on stack but passes it as a
+	// register, and the unwinder currently doesn't understand.
+	// Make it SPWRITE to stop unwinding. (See issue 54332)
+	MOV	X2, X2
+
 	MOV	ZERO, CTXT
 	JMP	runtime·morestack(SB)
 
diff --git a/src/runtime/asm_s390x.s b/src/runtime/asm_s390x.s
index 9159a67372..334e1aa909 100644
--- a/src/runtime/asm_s390x.s
+++ b/src/runtime/asm_s390x.s
@@ -346,6 +346,13 @@ TEXT runtime·morestack(SB),NOSPLIT|NOFRAME,$0-0
 	UNDEF
 
 TEXT runtime·morestack_noctxt(SB),NOSPLIT|NOFRAME,$0-0
+	// Force SPWRITE. This function doesn't actually write SP,
+	// but it is called with a special calling convention where
+	// the caller doesn't save LR on stack but passes it as a
+	// register (R5), and the unwinder currently doesn't understand.
+	// Make it SPWRITE to stop unwinding. (See issue 54332)
+	MOVD	R15, R15
+
 	MOVD	$0, R12
 	BR	runtime·morestack(SB)