diff --git a/src/runtime/asm_386.s b/src/runtime/asm_386.s
index ef82756397..15d9ce9fdf 100644
--- a/src/runtime/asm_386.s
+++ b/src/runtime/asm_386.s
@@ -362,18 +362,6 @@ TEXT runtime·gosave(SB), NOSPLIT, $0-4
 // restore state from Gobuf; longjmp
 TEXT runtime·gogo(SB), NOSPLIT, $8-4
 	MOVL	buf+0(FP), BX		// gobuf
-
-	// If ctxt is not nil, invoke deletion barrier before overwriting.
-	MOVL	gobuf_ctxt(BX), DX
-	TESTL	DX, DX
-	JZ	nilctxt
-	LEAL	gobuf_ctxt(BX), AX
-	MOVL	AX, 0(SP)
-	MOVL	$0, 4(SP)
-	CALL	runtime·writebarrierptr_prewrite(SB)
-	MOVL	buf+0(FP), BX
-
-nilctxt:
 	MOVL	gobuf_g(BX), DX
 	MOVL	0(DX), CX		// make sure g != nil
 	get_tls(CX)
@@ -536,7 +524,7 @@ TEXT runtime·morestack(SB),NOSPLIT,$0-0
 	MOVL	SI, (g_sched+gobuf_g)(SI)
 	LEAL	4(SP), AX	// f's SP
 	MOVL	AX, (g_sched+gobuf_sp)(SI)
-	// newstack will fill gobuf.ctxt.
+	MOVL	DX, (g_sched+gobuf_ctxt)(SI)
 
 	// Call newstack on m->g0's stack.
 	MOVL	m_g0(BX), BP
@@ -544,10 +532,8 @@ TEXT runtime·morestack(SB),NOSPLIT,$0-0
 	MOVL	(g_sched+gobuf_sp)(BP), AX
 	MOVL	-4(AX), BX	// fault if CALL would, before smashing SP
 	MOVL	AX, SP
-	PUSHL	DX	// ctxt argument
 	CALL	runtime·newstack(SB)
 	MOVL	$0, 0x1003	// crash if newstack returns
-	POPL	DX	// keep balance check happy
 	RET
 
 TEXT runtime·morestack_noctxt(SB),NOSPLIT,$0-0
diff --git a/src/runtime/asm_amd64.s b/src/runtime/asm_amd64.s
index 7c5e8e9ada..2ac879c31d 100644
--- a/src/runtime/asm_amd64.s
+++ b/src/runtime/asm_amd64.s
@@ -304,18 +304,6 @@ TEXT runtime·gosave(SB), NOSPLIT, $0-8
 // restore state from Gobuf; longjmp
 TEXT runtime·gogo(SB), NOSPLIT, $16-8
 	MOVQ	buf+0(FP), BX		// gobuf
-
-	// If ctxt is not nil, invoke deletion barrier before overwriting.
-	MOVQ	gobuf_ctxt(BX), AX
-	TESTQ	AX, AX
-	JZ	nilctxt
-	LEAQ	gobuf_ctxt(BX), AX
-	MOVQ	AX, 0(SP)
-	MOVQ	$0, 8(SP)
-	CALL	runtime·writebarrierptr_prewrite(SB)
-	MOVQ	buf+0(FP), BX
-
-nilctxt:
 	MOVQ	gobuf_g(BX), DX
 	MOVQ	0(DX), CX		// make sure g != nil
 	get_tls(CX)
@@ -482,16 +470,14 @@ TEXT runtime·morestack(SB),NOSPLIT,$0-0
 	LEAQ	8(SP), AX // f's SP
 	MOVQ	AX, (g_sched+gobuf_sp)(SI)
 	MOVQ	BP, (g_sched+gobuf_bp)(SI)
-	// newstack will fill gobuf.ctxt.
+	MOVQ	DX, (g_sched+gobuf_ctxt)(SI)
 
 	// Call newstack on m->g0's stack.
 	MOVQ	m_g0(BX), BX
 	MOVQ	BX, g(CX)
 	MOVQ	(g_sched+gobuf_sp)(BX), SP
-	PUSHQ	DX	// ctxt argument
 	CALL	runtime·newstack(SB)
 	MOVQ	$0, 0x1003	// crash if newstack returns
-	POPQ	DX	// keep balance check happy
 	RET
 
 // morestack but not preserving ctxt.
diff --git a/src/runtime/asm_amd64p32.s b/src/runtime/asm_amd64p32.s
index c80a563bda..b7fcf2376e 100644
--- a/src/runtime/asm_amd64p32.s
+++ b/src/runtime/asm_amd64p32.s
@@ -198,18 +198,6 @@ TEXT runtime·gosave(SB), NOSPLIT, $0-4
 // restore state from Gobuf; longjmp
 TEXT runtime·gogo(SB), NOSPLIT, $8-4
 	MOVL	buf+0(FP), BX		// gobuf
-
-	// If ctxt is not nil, invoke deletion barrier before overwriting.
-	MOVL	gobuf_ctxt(BX), DX
-	TESTL	DX, DX
-	JZ	nilctxt
-	LEAL	gobuf_ctxt(BX), AX
-	MOVL	AX, 0(SP)
-	MOVL	$0, 4(SP)
-	CALL	runtime·writebarrierptr_prewrite(SB)
-	MOVL	buf+0(FP), BX
-
-nilctxt:
 	MOVL	gobuf_g(BX), DX
 	MOVL	0(DX), CX		// make sure g != nil
 	get_tls(CX)
@@ -368,16 +356,14 @@ TEXT runtime·morestack(SB),NOSPLIT,$0-0
 	MOVL	SI, (g_sched+gobuf_g)(SI)
 	LEAL	8(SP), AX // f's SP
 	MOVL	AX, (g_sched+gobuf_sp)(SI)
-	// newstack will fill gobuf.ctxt.
+	MOVL	DX, (g_sched+gobuf_ctxt)(SI)
 
 	// Call newstack on m->g0's stack.
 	MOVL	m_g0(BX), BX
 	MOVL	BX, g(CX)
 	MOVL	(g_sched+gobuf_sp)(BX), SP
-	PUSHQ	DX	// ctxt argument
 	CALL	runtime·newstack(SB)
 	MOVL	$0, 0x1003	// crash if newstack returns
-	POPQ	DX	// keep balance check happy
 	RET
 
 // morestack trampolines
diff --git a/src/runtime/asm_arm.s b/src/runtime/asm_arm.s
index 47fa565c52..caa96cc4b3 100644
--- a/src/runtime/asm_arm.s
+++ b/src/runtime/asm_arm.s
@@ -227,19 +227,6 @@ TEXT runtime·gosave(SB),NOSPLIT,$-4-4
 // restore state from Gobuf; longjmp
 TEXT runtime·gogo(SB),NOSPLIT,$8-4
 	MOVW	buf+0(FP), R1
-
-	// If ctxt is not nil, invoke deletion barrier before overwriting.
-	MOVW	gobuf_ctxt(R1), R0
-	CMP	$0, R0
-	B.EQ	nilctxt
-	MOVW	$gobuf_ctxt(R1), R0
-	MOVW	R0, 4(R13)
-	MOVW	$0, R0
-	MOVW	R0, 8(R13)
-	BL	runtime·writebarrierptr_prewrite(SB)
-	MOVW	buf+0(FP), R1
-
-nilctxt:
 	MOVW	gobuf_g(R1), R0
 	BL	setg<>(SB)
 
@@ -412,7 +399,7 @@ TEXT runtime·morestack(SB),NOSPLIT,$-4-0
 	MOVW	R13, (g_sched+gobuf_sp)(g)
 	MOVW	LR, (g_sched+gobuf_pc)(g)
 	MOVW	R3, (g_sched+gobuf_lr)(g)
-	// newstack will fill gobuf.ctxt.
+	MOVW	R7, (g_sched+gobuf_ctxt)(g)
 
 	// Called from f.
 	// Set m->morebuf to f's caller.
@@ -426,8 +413,7 @@ TEXT runtime·morestack(SB),NOSPLIT,$-4-0
 	BL	setg<>(SB)
 	MOVW	(g_sched+gobuf_sp)(g), R13
 	MOVW	$0, R0
-	MOVW.W	R0, -8(R13)	// create a call frame on g0
-	MOVW	R7, 4(R13)	// ctxt argument
+	MOVW.W  R0, -4(R13)	// create a call frame on g0 (saved LR)
 	BL	runtime·newstack(SB)
 
 	// Not reached, but make sure the return PC from the call to newstack
diff --git a/src/runtime/asm_arm64.s b/src/runtime/asm_arm64.s
index e4b2c37038..b2aff1aab7 100644
--- a/src/runtime/asm_arm64.s
+++ b/src/runtime/asm_arm64.s
@@ -122,18 +122,6 @@ TEXT runtime·gosave(SB), NOSPLIT, $-8-8
 // restore state from Gobuf; longjmp
 TEXT runtime·gogo(SB), NOSPLIT, $24-8
 	MOVD	buf+0(FP), R5
-
-	// If ctxt is not nil, invoke deletion barrier before overwriting.
-	MOVD	gobuf_ctxt(R5), R0
-	CMP	$0, R0
-	BEQ	nilctxt
-	MOVD	$gobuf_ctxt(R5), R0
-	MOVD	R0, 8(RSP)
-	MOVD	ZR, 16(RSP)
-	BL	runtime·writebarrierptr_prewrite(SB)
-	MOVD	buf+0(FP), R5
-
-nilctxt:
 	MOVD	gobuf_g(R5), g
 	BL	runtime·save_g(SB)
 
@@ -289,7 +277,7 @@ TEXT runtime·morestack(SB),NOSPLIT,$-8-0
 	MOVD	R0, (g_sched+gobuf_sp)(g)
 	MOVD	LR, (g_sched+gobuf_pc)(g)
 	MOVD	R3, (g_sched+gobuf_lr)(g)
-	// newstack will fill gobuf.ctxt.
+	MOVD	R26, (g_sched+gobuf_ctxt)(g)
 
 	// Called from f.
 	// Set m->morebuf to f's callers.
@@ -303,8 +291,7 @@ TEXT runtime·morestack(SB),NOSPLIT,$-8-0
 	BL	runtime·save_g(SB)
 	MOVD	(g_sched+gobuf_sp)(g), R0
 	MOVD	R0, RSP
-	MOVD.W	$0, -16(RSP)	// create a call frame on g0
-	MOVD	R26, 8(RSP)	// ctxt argument
+	MOVD.W	$0, -16(RSP)	// create a call frame on g0 (saved LR; keep 16-aligned)
 	BL	runtime·newstack(SB)
 
 	// Not reached, but make sure the return PC from the call to newstack
diff --git a/src/runtime/asm_mips64x.s b/src/runtime/asm_mips64x.s
index 4902d04640..3510853804 100644
--- a/src/runtime/asm_mips64x.s
+++ b/src/runtime/asm_mips64x.s
@@ -108,17 +108,6 @@ TEXT runtime·gosave(SB), NOSPLIT, $-8-8
 // restore state from Gobuf; longjmp
 TEXT runtime·gogo(SB), NOSPLIT, $16-8
 	MOVV	buf+0(FP), R3
-
-	// If ctxt is not nil, invoke deletion barrier before overwriting.
-	MOVV	gobuf_ctxt(R3), R1
-	BEQ	R1, nilctxt
-	MOVV	$gobuf_ctxt(R3), R1
-	MOVV	R1, 8(R29)
-	MOVV	R0, 16(R29)
-	JAL	runtime·writebarrierptr_prewrite(SB)
-	MOVV	buf+0(FP), R3
-
-nilctxt:
 	MOVV	gobuf_g(R3), g	// make sure g is not nil
 	JAL	runtime·save_g(SB)
 
@@ -260,7 +249,7 @@ TEXT runtime·morestack(SB),NOSPLIT,$-8-0
 	MOVV	R29, (g_sched+gobuf_sp)(g)
 	MOVV	R31, (g_sched+gobuf_pc)(g)
 	MOVV	R3, (g_sched+gobuf_lr)(g)
-	// newstack will fill gobuf.ctxt.
+	MOVV	REGCTXT, (g_sched+gobuf_ctxt)(g)
 
 	// Called from f.
 	// Set m->morebuf to f's caller.
@@ -273,9 +262,8 @@ TEXT runtime·morestack(SB),NOSPLIT,$-8-0
 	JAL	runtime·save_g(SB)
 	MOVV	(g_sched+gobuf_sp)(g), R29
 	// Create a stack frame on g0 to call newstack.
-	MOVV	R0, -16(R29)	// Zero saved LR in frame
-	ADDV	$-16, R29
-	MOVV	REGCTXT, 8(R29)	// ctxt argument
+	MOVV	R0, -8(R29)	// Zero saved LR in frame
+	ADDV	$-8, R29
 	JAL	runtime·newstack(SB)
 
 	// Not reached, but make sure the return PC from the call to newstack
diff --git a/src/runtime/asm_mipsx.s b/src/runtime/asm_mipsx.s
index 82e01b0bac..334f259186 100644
--- a/src/runtime/asm_mipsx.s
+++ b/src/runtime/asm_mipsx.s
@@ -109,17 +109,6 @@ TEXT runtime·gosave(SB),NOSPLIT,$-4-4
 // restore state from Gobuf; longjmp
 TEXT runtime·gogo(SB),NOSPLIT,$8-4
 	MOVW	buf+0(FP), R3
-
-	// If ctxt is not nil, invoke deletion barrier before overwriting.
-	MOVW	gobuf_ctxt(R3), R1
-	BEQ	R1, nilctxt
-	MOVW	$gobuf_ctxt(R3), R1
-	MOVW	R1, 4(R29)
-	MOVW	R0, 8(R29)
-	JAL	runtime·writebarrierptr_prewrite(SB)
-	MOVW	buf+0(FP), R3
-
-nilctxt:
 	MOVW	gobuf_g(R3), g	// make sure g is not nil
 	JAL	runtime·save_g(SB)
 
@@ -261,7 +250,7 @@ TEXT runtime·morestack(SB),NOSPLIT,$-4-0
 	MOVW	R29, (g_sched+gobuf_sp)(g)
 	MOVW	R31, (g_sched+gobuf_pc)(g)
 	MOVW	R3, (g_sched+gobuf_lr)(g)
-	// newstack will fill gobuf.ctxt.
+	MOVW	REGCTXT, (g_sched+gobuf_ctxt)(g)
 
 	// Called from f.
 	// Set m->morebuf to f's caller.
@@ -274,9 +263,8 @@ TEXT runtime·morestack(SB),NOSPLIT,$-4-0
 	JAL	runtime·save_g(SB)
 	MOVW	(g_sched+gobuf_sp)(g), R29
 	// Create a stack frame on g0 to call newstack.
-	MOVW	R0, -8(R29)	// Zero saved LR in frame
-	ADDU	$-8, R29
-	MOVW	REGCTXT, 4(R29)	// ctxt argument
+	MOVW	R0, -4(R29)	// Zero saved LR in frame
+	ADDU	$-4, R29
 	JAL	runtime·newstack(SB)
 
 	// Not reached, but make sure the return PC from the call to newstack
diff --git a/src/runtime/asm_ppc64x.s b/src/runtime/asm_ppc64x.s
index 40ad1010a9..2f2a4a7b04 100644
--- a/src/runtime/asm_ppc64x.s
+++ b/src/runtime/asm_ppc64x.s
@@ -133,18 +133,6 @@ TEXT runtime·gosave(SB), NOSPLIT|NOFRAME, $0-8
 // restore state from Gobuf; longjmp
 TEXT runtime·gogo(SB), NOSPLIT, $16-8
 	MOVD	buf+0(FP), R5
-
-	// If ctxt is not nil, invoke deletion barrier before overwriting.
-	MOVD	gobuf_ctxt(R5), R3
-	CMP	R0, R3
-	BEQ	nilctxt
-	MOVD	$gobuf_ctxt(R5), R3
-	MOVD	R3, FIXED_FRAME+0(R1)
-	MOVD	R0, FIXED_FRAME+8(R1)
-	BL	runtime·writebarrierptr_prewrite(SB)
-	MOVD	buf+0(FP), R5
-
-nilctxt:
 	MOVD	gobuf_g(R5), g	// make sure g is not nil
 	BL	runtime·save_g(SB)
 
@@ -317,7 +305,7 @@ TEXT runtime·morestack(SB),NOSPLIT|NOFRAME,$0-0
 	MOVD	LR, R8
 	MOVD	R8, (g_sched+gobuf_pc)(g)
 	MOVD	R5, (g_sched+gobuf_lr)(g)
-	// newstack will fill gobuf.ctxt.
+	MOVD	R11, (g_sched+gobuf_ctxt)(g)
 
 	// Called from f.
 	// Set m->morebuf to f's caller.
@@ -329,8 +317,7 @@ TEXT runtime·morestack(SB),NOSPLIT|NOFRAME,$0-0
 	MOVD	m_g0(R7), g
 	BL	runtime·save_g(SB)
 	MOVD	(g_sched+gobuf_sp)(g), R1
-	MOVDU   R0, -(FIXED_FRAME+8)(R1)	// create a call frame on g0
-	MOVD	R11, FIXED_FRAME+0(R1)	// ctxt argument
+	MOVDU   R0, -(FIXED_FRAME+0)(R1)	// create a call frame on g0
 	BL	runtime·newstack(SB)
 
 	// Not reached, but make sure the return PC from the call to newstack
diff --git a/src/runtime/asm_s390x.s b/src/runtime/asm_s390x.s
index 241be17842..524b866b21 100644
--- a/src/runtime/asm_s390x.s
+++ b/src/runtime/asm_s390x.s
@@ -116,17 +116,6 @@ TEXT runtime·gosave(SB), NOSPLIT, $-8-8
 // restore state from Gobuf; longjmp
 TEXT runtime·gogo(SB), NOSPLIT, $16-8
 	MOVD	buf+0(FP), R5
-
-	// If ctxt is not nil, invoke deletion barrier before overwriting.
-	MOVD	gobuf_ctxt(R5), R1
-	CMPBEQ	R1, $0, nilctxt
-	MOVD	$gobuf_ctxt(R5), R1
-	MOVD	R1, 8(R15)
-	MOVD	R0, 16(R15)
-	BL	runtime·writebarrierptr_prewrite(SB)
-	MOVD	buf+0(FP), R5
-
-nilctxt:
 	MOVD	gobuf_g(R5), g	// make sure g is not nil
 	BL	runtime·save_g(SB)
 
@@ -272,7 +261,7 @@ TEXT runtime·morestack(SB),NOSPLIT|NOFRAME,$0-0
 	MOVD	LR, R8
 	MOVD	R8, (g_sched+gobuf_pc)(g)
 	MOVD	R5, (g_sched+gobuf_lr)(g)
-	// newstack will fill gobuf.ctxt.
+	MOVD	R12, (g_sched+gobuf_ctxt)(g)
 
 	// Called from f.
 	// Set m->morebuf to f's caller.
@@ -285,9 +274,8 @@ TEXT runtime·morestack(SB),NOSPLIT|NOFRAME,$0-0
 	BL	runtime·save_g(SB)
 	MOVD	(g_sched+gobuf_sp)(g), R15
 	// Create a stack frame on g0 to call newstack.
-	MOVD	$0, -16(R15)	// Zero saved LR in frame
-	SUB	$16, R15
-	MOVD	R12, 8(R15)	// ctxt argument
+	MOVD	$0, -8(R15)	// Zero saved LR in frame
+	SUB	$8, R15
 	BL	runtime·newstack(SB)
 
 	// Not reached, but make sure the return PC from the call to newstack
diff --git a/src/runtime/mgcmark.go b/src/runtime/mgcmark.go
index ed256efc80..ce697e5809 100644
--- a/src/runtime/mgcmark.go
+++ b/src/runtime/mgcmark.go
@@ -770,6 +770,13 @@ func scanstack(gp *g, gcw *gcWork) {
 		shrinkstack(gp)
 	}
 
+	// Scan the saved context register. This is effectively a live
+	// register that gets moved back and forth between the
+	// register and sched.ctxt without a write barrier.
+	if gp.sched.ctxt != nil {
+		scanblock(uintptr(unsafe.Pointer(&gp.sched.ctxt)), sys.PtrSize, &oneptrmask[0], gcw)
+	}
+
 	// Scan the stack.
 	var cache pcvalueCache
 	scanframe := func(frame *stkframe, unused unsafe.Pointer) bool {
diff --git a/src/runtime/runtime2.go b/src/runtime/runtime2.go
index ca796169fe..a79faba8ce 100644
--- a/src/runtime/runtime2.go
+++ b/src/runtime/runtime2.go
@@ -254,17 +254,19 @@ type gobuf struct {
 	// The offsets of sp, pc, and g are known to (hard-coded in) libmach.
 	//
 	// ctxt is unusual with respect to GC: it may be a
-	// heap-allocated funcval so write require a write barrier,
-	// but gobuf needs to be cleared from assembly. We take
-	// advantage of the fact that the only path that uses a
-	// non-nil ctxt is morestack. As a result, gogo is the only
-	// place where it may not already be nil, so gogo uses an
-	// explicit write barrier. Everywhere else that resets the
-	// gobuf asserts that ctxt is already nil.
+	// heap-allocated funcval, so GC needs to track it, but it
+	// needs to be set and cleared from assembly, where it's
+	// difficult to have write barriers. However, ctxt is really a
+	// saved, live register, and we only ever exchange it between
+	// the real register and the gobuf. Hence, we treat it as a
+	// root during stack scanning, which means assembly that saves
+	// and restores it doesn't need write barriers. It's still
+	// typed as a pointer so that any other writes from Go get
+	// write barriers.
 	sp   uintptr
 	pc   uintptr
 	g    guintptr
-	ctxt unsafe.Pointer // this has to be a pointer so that gc scans it
+	ctxt unsafe.Pointer
 	ret  sys.Uintreg
 	lr   uintptr
 	bp   uintptr // for GOEXPERIMENT=framepointer
diff --git a/src/runtime/stack.go b/src/runtime/stack.go
index 4e60e80863..89458b7ff6 100644
--- a/src/runtime/stack.go
+++ b/src/runtime/stack.go
@@ -913,9 +913,12 @@ func round2(x int32) int32 {
 // g->atomicstatus will be Grunning or Gscanrunning upon entry.
 // If the GC is trying to stop this g then it will set preemptscan to true.
 //
-// ctxt is the value of the context register on morestack. newstack
-// will write it to g.sched.ctxt.
-func newstack(ctxt unsafe.Pointer) {
+// This must be nowritebarrierrec because it can be called as part of
+// stack growth from other nowritebarrierrec functions, but the
+// compiler doesn't check this.
+//
+//go:nowritebarrierrec
+func newstack() {
 	thisg := getg()
 	// TODO: double check all gp. shouldn't be getg().
 	if thisg.m.morebuf.g.ptr().stackguard0 == stackFork {
@@ -929,9 +932,6 @@ func newstack(ctxt unsafe.Pointer) {
 	}
 
 	gp := thisg.m.curg
-	// Write ctxt to gp.sched. We do this here instead of in
-	// morestack so it has the necessary write barrier.
-	gp.sched.ctxt = ctxt
 
 	if thisg.m.curg.throwsplit {
 		// Update syscallsp, syscallpc in case traceback uses them.