MOV	$8(X2), A1

	// Store g on gsignal's stack, see sys_linux_arm64.s for detail
	MOVBU	runtime·iscgo(SB), S4
	BNEZ	S4, nosaveg
	MOV	m_gsignal(S3), S4 // g.m.gsignal
	BEQZ	S4, nosaveg
	BEQ	g, S4, nosaveg
	MOV	(g_stack+stack_lo)(S4), S4 // g.m.gsignal.stack.lo
	MOV	g, (S4)

	JALR	RA, A7

	MOV	ZERO, (S4)
	JMP	finish

nosaveg:
	JALR	RA, A7

finish:
	MOV	8(X2), T0	// sec

	MOVV	fn+0(FP), R1	// R1 = fn
	MOVV	R1, REGCTXT		// context
	MOVV	g_m(g), R2	// R2 = m

	MOVV	m_gsignal(R2), R3	// R3 = gsignal
	BEQ	g, R3, noswitch

	MOVV	m_g0(R2), R3	// R3 = g0
	BEQ	g, R3, noswitch

	MOVV	m_curg(R2), R4
	BEQ	g, R4, switch

	// Bad: g is not gsignal, not g0, not curg. What is it?
	// Hide call from linker nosplit analysis.
	MOVV	$runtime·badsystemstack(SB), R4
	JAL	(R4)

	BEQ	R20, fallback

	// Store g on gsignal's stack, see sys_linux_arm64.s for detail
	MOVBU	runtime·iscgo(SB), R25
	BNE	R25, nosaveg

	MOVV	m_gsignal(R24), R25	// g.m.gsignal
	BEQ	R25, nosaveg
	BEQ	g, R25, nosaveg

	MOVV	(g_stack+stack_lo)(R25), R25	// g.m.gsignal.stack.lo
	MOVV	g, (R25)

	JAL	(R20)

	MOVV	R0, (R25)
	JMP	finish

nosaveg:
	JAL	(R20)

finish:

TEXT runtime·systemstack(SB), NOSPLIT, $0-8
	MOV	fn+0(FP), CTXT	// CTXT = fn
	MOV	g_m(g), T0	// T0 = m

	MOV	m_gsignal(T0), T1	// T1 = gsignal
	BEQ	g, T1, noswitch

	MOV	m_g0(T0), T1	// T1 = g0
	BEQ	g, T1, noswitch

	MOV	m_curg(T0), T2
	BEQ	g, T2, switch

	// Bad: g is not gsignal, not g0, not curg. What is it?
	// Hide call from linker nosplit analysis.
	MOV	$runtime·badsystemstack(SB), T1
	JALR	RA, T1

	MOVD	fn+0(FP), R3	// R3 = fn
	MOVD	R3, R12		// context
	MOVD	g_m(g), R4	// R4 = m

	MOVD	m_gsignal(R4), R5	// R5 = gsignal
	CMPBEQ	g, R5, noswitch

	MOVD	m_g0(R4), R5	// R5 = g0
	CMPBEQ	g, R5, noswitch

	MOVD	m_curg(R4), R6
	CMPBEQ	g, R6, switch

	// Bad: g is not gsignal, not g0, not curg. What is it?
	// Hide call from linker nosplit analysis.
	MOVD	$runtime·badsystemstack(SB), R3

	MOVW	fn+0(FP), R1	// R1 = fn
	MOVW	R1, REGCTXT	// context
	MOVW	g_m(g), R2	// R2 = m

	MOVW	m_gsignal(R2), R3	// R3 = gsignal
	BEQ	g, R3, noswitch

	MOVW	m_g0(R2), R3	// R3 = g0
	BEQ	g, R3, noswitch

	MOVW	m_curg(R2), R4
	BEQ	g, R4, switch

	// Bad: g is not gsignal, not g0, not curg. What is it?
	// Hide call from linker nosplit analysis.
	MOVW	$runtime·badsystemstack(SB), R4
	JAL	(R4)

	// We won't get a nested signal.
	MOVBZ	runtime·iscgo(SB), R22
	CMP	R22, $0
	BNE	nosaveg
	MOVD	m_gsignal(R21), R22	// g.m.gsignal
	CMP	R22, $0
	BEQ	nosaveg

	CMP	g, R22
	BEQ	nosaveg
	MOVD	(g_stack+stack_lo)(R22), R22 // g.m.gsignal.stack.lo
	MOVD	g, (R22)

	BL	(CTR)	// Call from VDSO

	MOVD	$0, (R22)	// clear g slot, R22 is unchanged by C code

	JMP	finish

	MOVV	fn+0(FP), R19	// R19 = fn
	MOVV	R19, REGCTXT		// context
	MOVV	g_m(g), R4	// R4 = m

	MOVV	m_gsignal(R4), R5	// R5 = gsignal
	BEQ	g, R5, noswitch

	MOVV	m_g0(R4), R5	// R5 = g0
	BEQ	g, R5, noswitch

	MOVV	m_curg(R4), R6
	BEQ	g, R6, switch

	// Bad: g is not gsignal, not g0, not curg. What is it?
	// Hide call from linker nosplit analysis.
	MOVV	$runtime·badsystemstack(SB), R7
	JAL	(R7)

TEXT runtime·systemstack(SB),NOSPLIT,$0-4
	MOVW	fn+0(FP), R0	// R0 = fn
	MOVW	g_m(g), R1	// R1 = m

	MOVW	m_gsignal(R1), R2	// R2 = gsignal
	CMP	g, R2
	B.EQ	noswitch

	MOVW	m_g0(R1), R2	// R2 = g0
	CMP	g, R2
	B.EQ	noswitch

	MOVW	m_curg(R1), R3
	CMP	g, R3
	B.EQ	switch

	// Bad: g is not gsignal, not g0, not curg. What is it?
	// Hide call from linker nosplit analysis.
	MOVW	$runtime·badsystemstack(SB), R0

	// Cannot grow scheduler stack (m->g0).
	Get g
	Get R2
	I64Eq
	If
		CALLNORESUME runtime·badmorestackg0(SB)
		CALLNORESUME runtime·abort(SB)
	End

	// Cannot grow signal stack (m->gsignal).
	Get g
	I64Load m_gsignal(R1)
	I64Eq
	If
		CALLNORESUME runtime·badmorestackgsignal(SB)
		CALLNORESUME runtime·abort(SB)
	End

	// Called from f.
	// Set m->morebuf to f's caller.