github.com/mtsmfm/go/src@v0.0.0-20221020090648-44bdcb9f8fde/runtime/sys_linux_ppc64x.s

// Copyright 2014 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

//go:build linux && (ppc64 || ppc64le)

//
// System calls and other sys.stuff for ppc64, Linux
//

#include "go_asm.h"
#include "go_tls.h"
#include "textflag.h"
#include "asm_ppc64x.h"

#define SYS_exit		  1
#define SYS_read		  3
#define SYS_write		  4
#define SYS_open		  5
#define SYS_close		  6
#define SYS_getpid		 20
#define SYS_kill		 37
#define SYS_brk			 45
#define SYS_mmap		 90
#define SYS_munmap		 91
#define SYS_setitimer		104
#define SYS_clone		120
#define SYS_sched_yield		158
#define SYS_nanosleep		162
#define SYS_rt_sigreturn	172
#define SYS_rt_sigaction	173
#define SYS_rt_sigprocmask	174
#define SYS_sigaltstack		185
#define SYS_madvise		205
#define SYS_mincore		206
#define SYS_gettid		207
#define SYS_futex		221
#define SYS_sched_getaffinity	223
#define SYS_exit_group		234
#define SYS_timer_create	240
#define SYS_timer_settime	241
#define SYS_timer_delete	244
#define SYS_clock_gettime	246
#define SYS_tgkill		250
#define SYS_pipe2		317

TEXT runtime·exit(SB),NOSPLIT|NOFRAME,$0-4
	MOVW	code+0(FP), R3
	SYSCALL	$SYS_exit_group
	RET

// func exitThread(wait *atomic.Uint32)
TEXT runtime·exitThread(SB),NOSPLIT|NOFRAME,$0-8
	MOVD	wait+0(FP), R1
	// We're done using the stack.
	MOVW	$0, R2
	SYNC
	MOVW	R2, (R1)
	MOVW	$0, R3	// exit code
	SYSCALL	$SYS_exit
	JMP	0(PC)

TEXT runtime·open(SB),NOSPLIT|NOFRAME,$0-20
	MOVD	name+0(FP), R3
	MOVW	mode+8(FP), R4
	MOVW	perm+12(FP), R5
	SYSCALL	$SYS_open
	BVC	2(PC)
	MOVW	$-1, R3
	MOVW	R3, ret+16(FP)
	RET

TEXT runtime·closefd(SB),NOSPLIT|NOFRAME,$0-12
	MOVW	fd+0(FP), R3
	SYSCALL	$SYS_close
	BVC	2(PC)
	MOVW	$-1, R3
	MOVW	R3, ret+8(FP)
	RET

TEXT runtime·write1(SB),NOSPLIT|NOFRAME,$0-28
	MOVD	fd+0(FP), R3
	MOVD	p+8(FP), R4
	MOVW	n+16(FP), R5
	SYSCALL	$SYS_write
	BVC	2(PC)
	NEG	R3	// caller expects negative errno
	MOVW	R3, ret+24(FP)
	RET

TEXT runtime·read(SB),NOSPLIT|NOFRAME,$0-28
	MOVW	fd+0(FP), R3
	MOVD	p+8(FP), R4
	MOVW	n+16(FP), R5
	SYSCALL	$SYS_read
	BVC	2(PC)
	NEG	R3	// caller expects negative errno
	MOVW	R3, ret+24(FP)
	RET

// func pipe2(flags int32) (r, w int32, errno int32)
TEXT runtime·pipe2(SB),NOSPLIT|NOFRAME,$0-20
	ADD	$FIXED_FRAME+8, R1, R3
	MOVW	flags+0(FP), R4
	SYSCALL	$SYS_pipe2
	MOVW	R3, errno+16(FP)
	RET

TEXT runtime·usleep(SB),NOSPLIT,$16-4
	MOVW	usec+0(FP), R3
	MOVD	R3, R5
	MOVW	$1000000, R4
	DIVD	R4, R3
	MOVD	R3, 8(R1)
	MOVW	$1000, R4
	MULLD	R3, R4
	SUB	R4, R5
	MOVD	R5, 16(R1)

	// nanosleep(&ts, 0)
	ADD	$8, R1, R3
	MOVW	$0, R4
	SYSCALL	$SYS_nanosleep
	RET

TEXT runtime·gettid(SB),NOSPLIT,$0-4
	SYSCALL	$SYS_gettid
	MOVW	R3, ret+0(FP)
	RET

TEXT runtime·raise(SB),NOSPLIT|NOFRAME,$0
	SYSCALL	$SYS_getpid
	MOVW	R3, R14
	SYSCALL	$SYS_gettid
	MOVW	R3, R4	// arg 2 tid
	MOVW	R14, R3	// arg 1 pid
	MOVW	sig+0(FP), R5	// arg 3
	SYSCALL	$SYS_tgkill
	RET

TEXT runtime·raiseproc(SB),NOSPLIT|NOFRAME,$0
	SYSCALL	$SYS_getpid
	MOVW	R3, R3	// arg 1 pid
	MOVW	sig+0(FP), R4	// arg 2
	SYSCALL	$SYS_kill
	RET

TEXT ·getpid(SB),NOSPLIT|NOFRAME,$0-8
	SYSCALL $SYS_getpid
	MOVD	R3, ret+0(FP)
	RET

TEXT ·tgkill(SB),NOSPLIT|NOFRAME,$0-24
	MOVD	tgid+0(FP), R3
	MOVD	tid+8(FP), R4
	MOVD	sig+16(FP), R5
	SYSCALL $SYS_tgkill
	RET

TEXT runtime·setitimer(SB),NOSPLIT|NOFRAME,$0-24
	MOVW	mode+0(FP), R3
	MOVD	new+8(FP), R4
	MOVD	old+16(FP), R5
	SYSCALL	$SYS_setitimer
	RET

TEXT runtime·timer_create(SB),NOSPLIT,$0-28
	MOVW	clockid+0(FP), R3
	MOVD	sevp+8(FP), R4
	MOVD	timerid+16(FP), R5
	SYSCALL	$SYS_timer_create
	MOVW	R3, ret+24(FP)
	RET

TEXT runtime·timer_settime(SB),NOSPLIT,$0-28
	MOVW	timerid+0(FP), R3
	MOVW	flags+4(FP), R4
	MOVD	new+8(FP), R5
	MOVD	old+16(FP), R6
	SYSCALL	$SYS_timer_settime
	MOVW	R3, ret+24(FP)
	RET

TEXT runtime·timer_delete(SB),NOSPLIT,$0-12
	MOVW	timerid+0(FP), R3
	SYSCALL	$SYS_timer_delete
	MOVW	R3, ret+8(FP)
	RET

TEXT runtime·mincore(SB),NOSPLIT|NOFRAME,$0-28
	MOVD	addr+0(FP), R3
	MOVD	n+8(FP), R4
	MOVD	dst+16(FP), R5
	SYSCALL	$SYS_mincore
	NEG	R3		// caller expects negative errno
	MOVW	R3, ret+24(FP)
	RET

// func walltime() (sec int64, nsec int32)
TEXT runtime·walltime(SB),NOSPLIT,$16-12
	MOVD	R1, R15		// R15 is unchanged by C code
	MOVD	g_m(g), R21	// R21 = m

	MOVD	$0, R3		// CLOCK_REALTIME

	MOVD	runtime·vdsoClockgettimeSym(SB), R12	// Check for VDSO availability
	CMP	R12, R0
	BEQ	fallback

	// Set vdsoPC and vdsoSP for SIGPROF traceback.
	// Save the old values on stack and restore them on exit,
	// so this function is reentrant.
	MOVD	m_vdsoPC(R21), R4
	MOVD	m_vdsoSP(R21), R5
	MOVD	R4, 32(R1)
	MOVD	R5, 40(R1)

	MOVD	LR, R14
	MOVD	$ret-FIXED_FRAME(FP), R5 // caller's SP
	MOVD	R14, m_vdsoPC(R21)
	MOVD	R5, m_vdsoSP(R21)

	MOVD	m_curg(R21), R6
	CMP	g, R6
	BNE	noswitch

	MOVD	m_g0(R21), R7
	MOVD	(g_sched+gobuf_sp)(R7), R1	// Set SP to g0 stack

noswitch:
	SUB	$16, R1                 // Space for results
	RLDICR	$0, R1, $59, R1         // Align for C code
	MOVD	R12, CTR
	MOVD	R1, R4

	// Store g on gsignal's stack, so if we receive a signal
	// during VDSO code we can find the g.
	// If we don't have a signal stack, we won't receive signal,
	// so don't bother saving g.
	// When using cgo, we already saved g on TLS, also don't save
	// g here.
	// Also don't save g if we are already on the signal stack.
	// 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

nosaveg:
	BL	(CTR)	// Call from VDSO

finish:
	MOVD	$0, R0		// Restore R0
	MOVD	0(R1), R3	// sec
	MOVD	8(R1), R5	// nsec
	MOVD	R15, R1		// Restore SP

	// Restore vdsoPC, vdsoSP
	// We don't worry about being signaled between the two stores.
	// If we are not in a signal handler, we'll restore vdsoSP to 0,
	// and no one will care about vdsoPC. If we are in a signal handler,
	// we cannot receive another signal.
	MOVD	40(R1), R6
	MOVD	R6, m_vdsoSP(R21)
	MOVD	32(R1), R6
	MOVD	R6, m_vdsoPC(R21)

return:
	MOVD	R3, sec+0(FP)
	MOVW	R5, nsec+8(FP)
	RET

	// Syscall fallback
fallback:
	ADD	$32, R1, R4
	SYSCALL $SYS_clock_gettime
	MOVD	32(R1), R3
	MOVD	40(R1), R5
	JMP	return

TEXT runtime·nanotime1(SB),NOSPLIT,$16-8
	MOVD	$1, R3		// CLOCK_MONOTONIC

	MOVD	R1, R15		// R15 is unchanged by C code
	MOVD	g_m(g), R21	// R21 = m

	MOVD	runtime·vdsoClockgettimeSym(SB), R12	// Check for VDSO availability
	CMP	R12, R0
	BEQ	fallback

	// Set vdsoPC and vdsoSP for SIGPROF traceback.
	// Save the old values on stack and restore them on exit,
	// so this function is reentrant.
	MOVD	m_vdsoPC(R21), R4
	MOVD	m_vdsoSP(R21), R5
	MOVD	R4, 32(R1)
	MOVD	R5, 40(R1)

	MOVD	LR, R14				// R14 is unchanged by C code
	MOVD	$ret-FIXED_FRAME(FP), R5	// caller's SP
	MOVD	R14, m_vdsoPC(R21)
	MOVD	R5, m_vdsoSP(R21)

	MOVD	m_curg(R21), R6
	CMP	g, R6
	BNE	noswitch

	MOVD	m_g0(R21), R7
	MOVD	(g_sched+gobuf_sp)(R7), R1	// Set SP to g0 stack

noswitch:
	SUB	$16, R1			// Space for results
	RLDICR	$0, R1, $59, R1		// Align for C code
	MOVD	R12, CTR
	MOVD	R1, R4

	// Store g on gsignal's stack, so if we receive a signal
	// during VDSO code we can find the g.
	// If we don't have a signal stack, we won't receive signal,
	// so don't bother saving g.
	// When using cgo, we already saved g on TLS, also don't save
	// g here.
	// Also don't save g if we are already on the signal stack.
	// 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

nosaveg:
	BL	(CTR)	// Call from VDSO

finish:
	MOVD	$0, R0			// Restore R0
	MOVD	0(R1), R3		// sec
	MOVD	8(R1), R5		// nsec
	MOVD	R15, R1			// Restore SP

	// Restore vdsoPC, vdsoSP
	// We don't worry about being signaled between the two stores.
	// If we are not in a signal handler, we'll restore vdsoSP to 0,
	// and no one will care about vdsoPC. If we are in a signal handler,
	// we cannot receive another signal.
	MOVD	40(R1), R6
	MOVD	R6, m_vdsoSP(R21)
	MOVD	32(R1), R6
	MOVD	R6, m_vdsoPC(R21)

return:
	// sec is in R3, nsec in R5
	// return nsec in R3
	MOVD	$1000000000, R4
	MULLD	R4, R3
	ADD	R5, R3
	MOVD	R3, ret+0(FP)
	RET

	// Syscall fallback
fallback:
	ADD	$32, R1, R4
	SYSCALL $SYS_clock_gettime
	MOVD	32(R1), R3
	MOVD	40(R1), R5
	JMP	return

TEXT runtime·rtsigprocmask(SB),NOSPLIT|NOFRAME,$0-28
	MOVW	how+0(FP), R3
	MOVD	new+8(FP), R4
	MOVD	old+16(FP), R5
	MOVW	size+24(FP), R6
	SYSCALL	$SYS_rt_sigprocmask
	BVC	2(PC)
	MOVD	R0, 0xf0(R0)	// crash
	RET

TEXT runtime·rt_sigaction(SB),NOSPLIT|NOFRAME,$0-36
	MOVD	sig+0(FP), R3
	MOVD	new+8(FP), R4
	MOVD	old+16(FP), R5
	MOVD	size+24(FP), R6
	SYSCALL	$SYS_rt_sigaction
	BVC	2(PC)
	NEG	R3	// caller expects negative errno
	MOVW	R3, ret+32(FP)
	RET

#ifdef GOARCH_ppc64le
// Call the function stored in _cgo_sigaction using the GCC calling convention.
TEXT runtime·callCgoSigaction(SB),NOSPLIT,$0
	MOVD    sig+0(FP), R3
	MOVD    new+8(FP), R4
	MOVD    old+16(FP), R5
	MOVD     _cgo_sigaction(SB), R12
	MOVD    R12, CTR                // R12 should contain the function address
	MOVD    R1, R15                 // Save R1
	MOVD    R2, 24(R1)              // Save R2
	SUB     $48, R1                 // reserve 32 (frame) + 16 bytes for sp-8 where fp may be saved.
	RLDICR  $0, R1, $59, R1         // Align to 16 bytes for C code
	BL      (CTR)
	XOR     R0, R0, R0              // Clear R0 as Go expects
	MOVD    R15, R1                 // Restore R1
	MOVD    24(R1), R2              // Restore R2
	MOVW    R3, ret+24(FP)          // Return result
	RET
#endif

TEXT runtime·sigfwd(SB),NOSPLIT,$0-32
	MOVW	sig+8(FP), R3
	MOVD	info+16(FP), R4
	MOVD	ctx+24(FP), R5
	MOVD	fn+0(FP), R12
	MOVD	R12, CTR
	BL	(CTR)
	MOVD	24(R1), R2
	RET

TEXT runtime·sigreturn(SB),NOSPLIT,$0-0
	RET

#ifdef GOARCH_ppc64le
// ppc64le doesn't need function descriptors
// Save callee-save registers in the case of signal forwarding.
// Same as on ARM64 https://golang.org/issue/31827 .
TEXT runtime·sigtramp(SB),NOSPLIT|NOFRAME,$0
#else
// function descriptor for the real sigtramp
TEXT runtime·sigtramp(SB),NOSPLIT|NOFRAME,$0
	DWORD	$sigtramp<>(SB)
	DWORD	$0
	DWORD	$0
TEXT sigtramp<>(SB),NOSPLIT|NOFRAME|TOPFRAME,$0
#endif
	// Start with standard C stack frame layout and linkage.
	MOVD    LR, R0
	MOVD    R0, 16(R1) // Save LR in caller's frame.
	MOVW    CR, R0     // Save CR in caller's frame
	MOVD    R0, 8(R1)
	// The stack must be acquired here and not
	// in the automatic way based on stack size
	// since that sequence clobbers R31 before it
	// gets saved.
	// We are being ultra safe here in saving the
	// Vregs. The case where they might need to
	// be saved is very unlikely.
	MOVDU   R1, -544(R1)
	MOVD    R14, 64(R1)
	MOVD    R15, 72(R1)
	MOVD    R16, 80(R1)
	MOVD    R17, 88(R1)
	MOVD    R18, 96(R1)
	MOVD    R19, 104(R1)
	MOVD    R20, 112(R1)
	MOVD    R21, 120(R1)
	MOVD    R22, 128(R1)
	MOVD    R23, 136(R1)
	MOVD    R24, 144(R1)
	MOVD    R25, 152(R1)
	MOVD    R26, 160(R1)
	MOVD    R27, 168(R1)
	MOVD    R28, 176(R1)
	MOVD    R29, 184(R1)
	MOVD    g, 192(R1) // R30
	MOVD    R31, 200(R1)
	FMOVD   F14, 208(R1)
	FMOVD   F15, 216(R1)
	FMOVD   F16, 224(R1)
	FMOVD   F17, 232(R1)
	FMOVD   F18, 240(R1)
	FMOVD   F19, 248(R1)
	FMOVD   F20, 256(R1)
	FMOVD   F21, 264(R1)
	FMOVD   F22, 272(R1)
	FMOVD   F23, 280(R1)
	FMOVD   F24, 288(R1)
	FMOVD   F25, 296(R1)
	FMOVD   F26, 304(R1)
	FMOVD   F27, 312(R1)
	FMOVD   F28, 320(R1)
	FMOVD   F29, 328(R1)
	FMOVD   F30, 336(R1)
	FMOVD   F31, 344(R1)
	// Save V regs
	// STXVD2X and LXVD2X used since
	// we aren't sure of alignment.
	// Endianness doesn't matter
	// if we are just loading and
	// storing values.
	MOVD	$352, R7 // V20
	STXVD2X VS52, (R7)(R1)
	ADD	$16, R7 // V21 368
	STXVD2X VS53, (R7)(R1)
	ADD	$16, R7 // V22 384
	STXVD2X VS54, (R7)(R1)
	ADD	$16, R7 // V23 400
	STXVD2X VS55, (R7)(R1)
	ADD	$16, R7 // V24 416
	STXVD2X	VS56, (R7)(R1)
	ADD	$16, R7 // V25 432
	STXVD2X	VS57, (R7)(R1)
	ADD	$16, R7 // V26 448
	STXVD2X VS58, (R7)(R1)
	ADD	$16, R7 // V27 464
	STXVD2X VS59, (R7)(R1)
	ADD	$16, R7 // V28 480
	STXVD2X VS60, (R7)(R1)
	ADD	$16, R7 // V29 496
	STXVD2X VS61, (R7)(R1)
	ADD	$16, R7 // V30 512
	STXVD2X VS62, (R7)(R1)
	ADD	$16, R7 // V31 528
	STXVD2X VS63, (R7)(R1)

	// initialize essential registers (just in case)
	BL	runtime·reginit(SB)

	// this might be called in external code context,
	// where g is not set.
	MOVBZ	runtime·iscgo(SB), R6
	CMP	R6, $0
	BEQ	2(PC)
	BL	runtime·load_g(SB)

	MOVW	R3, FIXED_FRAME+0(R1)
	MOVD	R4, FIXED_FRAME+8(R1)
	MOVD	R5, FIXED_FRAME+16(R1)
	MOVD	$runtime·sigtrampgo(SB), R12
	MOVD	R12, CTR
	BL	(CTR)
	MOVD	24(R1), R2 // Should this be here? Where is it saved?
	// Starts at 64; FIXED_FRAME is 32
	MOVD    64(R1), R14
	MOVD    72(R1), R15
	MOVD    80(R1), R16
	MOVD    88(R1), R17
	MOVD    96(R1), R18
	MOVD    104(R1), R19
	MOVD    112(R1), R20
	MOVD    120(R1), R21
	MOVD    128(R1), R22
	MOVD    136(R1), R23
	MOVD    144(R1), R24
	MOVD    152(R1), R25
	MOVD    160(R1), R26
	MOVD    168(R1), R27
	MOVD    176(R1), R28
	MOVD    184(R1), R29
	MOVD    192(R1), g // R30
	MOVD    200(R1), R31
	FMOVD   208(R1), F14
	FMOVD   216(R1), F15
	FMOVD   224(R1), F16
	FMOVD   232(R1), F17
	FMOVD   240(R1), F18
	FMOVD   248(R1), F19
	FMOVD   256(R1), F20
	FMOVD   264(R1), F21
	FMOVD   272(R1), F22
	FMOVD   280(R1), F23
	FMOVD   288(R1), F24
	FMOVD   292(R1), F25
	FMOVD   300(R1), F26
	FMOVD   308(R1), F27
	FMOVD   316(R1), F28
	FMOVD   328(R1), F29
	FMOVD   336(R1), F30
	FMOVD   344(R1), F31
	MOVD	$352, R7
	LXVD2X	(R7)(R1), VS52
	ADD	$16, R7 // 368 V21
	LXVD2X	(R7)(R1), VS53
	ADD	$16, R7 // 384 V22
	LXVD2X	(R7)(R1), VS54
	ADD	$16, R7 // 400 V23
	LXVD2X	(R7)(R1), VS55
	ADD	$16, R7 // 416 V24
	LXVD2X	(R7)(R1), VS56
	ADD	$16, R7 // 432 V25
	LXVD2X	(R7)(R1), VS57
	ADD	$16, R7 // 448 V26
	LXVD2X	(R7)(R1), VS58
	ADD	$16, R8 // 464 V27
	LXVD2X	(R7)(R1), VS59
	ADD	$16, R7 // 480 V28
	LXVD2X	(R7)(R1), VS60
	ADD	$16, R7 // 496 V29
	LXVD2X	(R7)(R1), VS61
	ADD	$16, R7 // 512 V30
	LXVD2X	(R7)(R1), VS62
	ADD	$16, R7 // 528 V31
	LXVD2X	(R7)(R1), VS63
	ADD	$544, R1
	MOVD	8(R1), R0
	MOVFL	R0, $0xff
	MOVD	16(R1), R0
	MOVD	R0, LR

	RET

#ifdef GOARCH_ppc64le
// ppc64le doesn't need function descriptors
TEXT runtime·cgoSigtramp(SB),NOSPLIT|NOFRAME,$0
	// The stack unwinder, presumably written in C, may not be able to
	// handle Go frame correctly. So, this function is NOFRAME, and we
	// save/restore LR manually.
	MOVD	LR, R10

	// We're coming from C code, initialize essential registers.
	CALL	runtime·reginit(SB)

	// If no traceback function, do usual sigtramp.
	MOVD	runtime·cgoTraceback(SB), R6
	CMP	$0, R6
	BEQ	sigtramp

	// If no traceback support function, which means that
	// runtime/cgo was not linked in, do usual sigtramp.
	MOVD	_cgo_callers(SB), R6
	CMP	$0, R6
	BEQ	sigtramp

	// Set up g register.
	CALL	runtime·load_g(SB)

	// Figure out if we are currently in a cgo call.
	// If not, just do usual sigtramp.
	// compared to ARM64 and others.
	CMP	$0, g
	BEQ	sigtrampnog // g == nil
	MOVD	g_m(g), R6
	CMP	$0, R6
	BEQ	sigtramp    // g.m == nil
	MOVW	m_ncgo(R6), R7
	CMPW	$0, R7
	BEQ	sigtramp    // g.m.ncgo = 0
	MOVD	m_curg(R6), R7
	CMP	$0, R7
	BEQ	sigtramp    // g.m.curg == nil
	MOVD	g_syscallsp(R7), R7
	CMP	$0, R7
	BEQ	sigtramp    // g.m.curg.syscallsp == 0
	MOVD	m_cgoCallers(R6), R7 // R7 is the fifth arg in C calling convention.
	CMP	$0, R7
	BEQ	sigtramp    // g.m.cgoCallers == nil
	MOVW	m_cgoCallersUse(R6), R8
	CMPW	$0, R8
	BNE	sigtramp    // g.m.cgoCallersUse != 0

	// Jump to a function in runtime/cgo.
	// That function, written in C, will call the user's traceback
	// function with proper unwind info, and will then call back here.
	// The first three arguments, and the fifth, are already in registers.
	// Set the two remaining arguments now.
	MOVD	runtime·cgoTraceback(SB), R6
	MOVD	$runtime·sigtramp(SB), R8
	MOVD	_cgo_callers(SB), R12
	MOVD	R12, CTR
	MOVD	R10, LR // restore LR
	JMP	(CTR)

sigtramp:
	MOVD	R10, LR // restore LR
	JMP	runtime·sigtramp(SB)

sigtrampnog:
	// Signal arrived on a non-Go thread. If this is SIGPROF, get a
	// stack trace.
	CMPW	R3, $27 // 27 == SIGPROF
	BNE	sigtramp

	// Lock sigprofCallersUse (cas from 0 to 1).
	MOVW	$1, R7
	MOVD	$runtime·sigprofCallersUse(SB), R8
	SYNC
	LWAR    (R8), R6
	CMPW    $0, R6
	BNE     sigtramp
	STWCCC  R7, (R8)
	BNE     -4(PC)
	ISYNC

	// Jump to the traceback function in runtime/cgo.
	// It will call back to sigprofNonGo, which will ignore the
	// arguments passed in registers.
	// First three arguments to traceback function are in registers already.
	MOVD	runtime·cgoTraceback(SB), R6
	MOVD	$runtime·sigprofCallers(SB), R7
	MOVD	$runtime·sigprofNonGoWrapper<>(SB), R8
	MOVD	_cgo_callers(SB), R12
	MOVD	R12, CTR
	MOVD	R10, LR // restore LR
	JMP	(CTR)
#else
// function descriptor for the real sigtramp
TEXT runtime·cgoSigtramp(SB),NOSPLIT|NOFRAME,$0
	DWORD	$cgoSigtramp<>(SB)
	DWORD	$0
	DWORD	$0
TEXT cgoSigtramp<>(SB),NOSPLIT,$0
	JMP	sigtramp<>(SB)
#endif

TEXT runtime·sigprofNonGoWrapper<>(SB),NOSPLIT,$0
	// We're coming from C code, set up essential register, then call sigprofNonGo.
	CALL	runtime·reginit(SB)
	MOVW	R3, FIXED_FRAME+0(R1)	// sig
	MOVD	R4, FIXED_FRAME+8(R1)	// info
	MOVD	R5, FIXED_FRAME+16(R1)	// ctx
	CALL	runtime·sigprofNonGo(SB)
	RET

TEXT runtime·mmap(SB),NOSPLIT|NOFRAME,$0
	MOVD	addr+0(FP), R3
	MOVD	n+8(FP), R4
	MOVW	prot+16(FP), R5
	MOVW	flags+20(FP), R6
	MOVW	fd+24(FP), R7
	MOVW	off+28(FP), R8

	SYSCALL	$SYS_mmap
	BVC	ok
	MOVD	$0, p+32(FP)
	MOVD	R3, err+40(FP)
	RET
ok:
	MOVD	R3, p+32(FP)
	MOVD	$0, err+40(FP)
	RET

TEXT runtime·munmap(SB),NOSPLIT|NOFRAME,$0
	MOVD	addr+0(FP), R3
	MOVD	n+8(FP), R4
	SYSCALL	$SYS_munmap
	BVC	2(PC)
	MOVD	R0, 0xf0(R0)
	RET

TEXT runtime·madvise(SB),NOSPLIT|NOFRAME,$0
	MOVD	addr+0(FP), R3
	MOVD	n+8(FP), R4
	MOVW	flags+16(FP), R5
	SYSCALL	$SYS_madvise
	MOVW	R3, ret+24(FP)
	RET

// int64 futex(int32 *uaddr, int32 op, int32 val,
//	struct timespec *timeout, int32 *uaddr2, int32 val2);
TEXT runtime·futex(SB),NOSPLIT|NOFRAME,$0
	MOVD	addr+0(FP), R3
	MOVW	op+8(FP), R4
	MOVW	val+12(FP), R5
	MOVD	ts+16(FP), R6
	MOVD	addr2+24(FP), R7
	MOVW	val3+32(FP), R8
	SYSCALL	$SYS_futex
	BVC	2(PC)
	NEG	R3	// caller expects negative errno
	MOVW	R3, ret+40(FP)
	RET

// int64 clone(int32 flags, void *stk, M *mp, G *gp, void (*fn)(void));
TEXT runtime·clone(SB),NOSPLIT|NOFRAME,$0
	MOVW	flags+0(FP), R3
	MOVD	stk+8(FP), R4

	// Copy mp, gp, fn off parent stack for use by child.
	// Careful: Linux system call clobbers ???.
	MOVD	mp+16(FP), R7
	MOVD	gp+24(FP), R8
	MOVD	fn+32(FP), R12

	MOVD	R7, -8(R4)
	MOVD	R8, -16(R4)
	MOVD	R12, -24(R4)
	MOVD	$1234, R7
	MOVD	R7, -32(R4)

	SYSCALL $SYS_clone
	BVC	2(PC)
	NEG	R3	// caller expects negative errno

	// In parent, return.
	CMP	R3, $0
	BEQ	3(PC)
	MOVW	R3, ret+40(FP)
	RET

	// In child, on new stack.
	// initialize essential registers
	BL	runtime·reginit(SB)
	MOVD	-32(R1), R7
	CMP	R7, $1234
	BEQ	2(PC)
	MOVD	R0, 0(R0)

	// Initialize m->procid to Linux tid
	SYSCALL $SYS_gettid

	MOVD	-24(R1), R12       // fn
	MOVD	-16(R1), R8        // g
	MOVD	-8(R1), R7         // m

	CMP	R7, $0
	BEQ	nog
	CMP	R8, $0
	BEQ	nog

	MOVD	R3, m_procid(R7)

	// TODO: setup TLS.

	// In child, set up new stack
	MOVD	R7, g_m(R8)
	MOVD	R8, g
	//CALL	runtime·stackcheck(SB)

nog:
	// Call fn
	MOVD	R12, CTR
	BL	(CTR)

	// It shouldn't return.	 If it does, exit that thread.
	MOVW	$111, R3
	SYSCALL	$SYS_exit
	BR	-2(PC)	// keep exiting

TEXT runtime·sigaltstack(SB),NOSPLIT|NOFRAME,$0
	MOVD	new+0(FP), R3
	MOVD	old+8(FP), R4
	SYSCALL	$SYS_sigaltstack
	BVC	2(PC)
	MOVD	R0, 0xf0(R0)  // crash
	RET

TEXT runtime·osyield(SB),NOSPLIT|NOFRAME,$0
	SYSCALL	$SYS_sched_yield
	RET

TEXT runtime·sched_getaffinity(SB),NOSPLIT|NOFRAME,$0
	MOVD	pid+0(FP), R3
	MOVD	len+8(FP), R4
	MOVD	buf+16(FP), R5
	SYSCALL	$SYS_sched_getaffinity
	BVC	2(PC)
	NEG	R3	// caller expects negative errno
	MOVW	R3, ret+24(FP)
	RET

// func sbrk0() uintptr
TEXT runtime·sbrk0(SB),NOSPLIT|NOFRAME,$0
	// Implemented as brk(NULL).
	MOVD	$0, R3
	SYSCALL	$SYS_brk
	MOVD	R3, ret+0(FP)
	RET

TEXT runtime·access(SB),$0-20
	MOVD	R0, 0(R0) // unimplemented, only needed for android; declared in stubs_linux.go
	MOVW	R0, ret+16(FP) // for vet
	RET

TEXT runtime·connect(SB),$0-28
	MOVD	R0, 0(R0) // unimplemented, only needed for android; declared in stubs_linux.go
	MOVW	R0, ret+24(FP) // for vet
	RET

TEXT runtime·socket(SB),$0-20
	MOVD	R0, 0(R0) // unimplemented, only needed for android; declared in stubs_linux.go
	MOVW	R0, ret+16(FP) // for vet
	RET