github.com/geraldss/go/src@v0.0.0-20210511222824-ac7d0ebfc235/runtime/sys_darwin_arm64.s

// Copyright 2015 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.

// System calls and other sys.stuff for ARM64, Darwin
// System calls are implemented in libSystem, this file contains
// trampolines that convert from Go to C calling convention.

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

#define CLOCK_REALTIME		0

TEXT notok<>(SB),NOSPLIT,$0
	MOVD	$0, R8
	MOVD	R8, (R8)
	B	0(PC)

TEXT runtime·open_trampoline(SB),NOSPLIT,$0
	SUB	$16, RSP
	MOVW	8(R0), R1	// arg 2 flags
	MOVW	12(R0), R2	// arg 3 mode
	MOVW	R2, (RSP)	// arg 3 is variadic, pass on stack
	MOVD	0(R0), R0	// arg 1 pathname
	BL	libc_open(SB)
	ADD	$16, RSP
	RET

TEXT runtime·close_trampoline(SB),NOSPLIT,$0
	MOVW	0(R0), R0	// arg 1 fd
	BL	libc_close(SB)
	RET

TEXT runtime·write_trampoline(SB),NOSPLIT,$0
	MOVD	8(R0), R1	// arg 2 buf
	MOVW	16(R0), R2	// arg 3 count
	MOVW	0(R0), R0	// arg 1 fd
	BL	libc_write(SB)
	MOVD	$-1, R1
	CMP	R0, R1
	BNE	noerr
	BL	libc_error(SB)
	MOVW	(R0), R0
	NEG	R0, R0		// caller expects negative errno value
noerr:
	RET

TEXT runtime·read_trampoline(SB),NOSPLIT,$0
	MOVD	8(R0), R1	// arg 2 buf
	MOVW	16(R0), R2	// arg 3 count
	MOVW	0(R0), R0	// arg 1 fd
	BL	libc_read(SB)
	MOVD	$-1, R1
	CMP	R0, R1
	BNE	noerr
	BL	libc_error(SB)
	MOVW	(R0), R0
	NEG	R0, R0		// caller expects negative errno value
noerr:
	RET

TEXT runtime·pipe_trampoline(SB),NOSPLIT,$0
	BL	libc_pipe(SB)	// pointer already in R0
	CMP	$0, R0
	BEQ	3(PC)
	BL	libc_error(SB)	// return negative errno value
	NEG	R0, R0
	RET

TEXT runtime·exit_trampoline(SB),NOSPLIT|NOFRAME,$0
	MOVW	0(R0), R0
	BL	libc_exit(SB)
	MOVD	$1234, R0
	MOVD	$1002, R1
	MOVD	R0, (R1)	// fail hard

TEXT runtime·raiseproc_trampoline(SB),NOSPLIT,$0
	MOVD	0(R0), R19	// signal
	BL	libc_getpid(SB)
	// arg 1 pid already in R0 from getpid
	MOVD	R19, R1	// arg 2 signal
	BL	libc_kill(SB)
	RET

TEXT runtime·mmap_trampoline(SB),NOSPLIT,$0
	MOVD	R0, R19
	MOVD	0(R19), R0	// arg 1 addr
	MOVD	8(R19), R1	// arg 2 len
	MOVW	16(R19), R2	// arg 3 prot
	MOVW	20(R19), R3	// arg 4 flags
	MOVW	24(R19), R4	// arg 5 fd
	MOVW	28(R19), R5	// arg 6 off
	BL	libc_mmap(SB)
	MOVD	$0, R1
	MOVD	$-1, R2
	CMP	R0, R2
	BNE	ok
	BL	libc_error(SB)
	MOVW	(R0), R1
	MOVD	$0, R0
ok:
	MOVD	R0, 32(R19) // ret 1 p
	MOVD	R1, 40(R19)	// ret 2 err
	RET

TEXT runtime·munmap_trampoline(SB),NOSPLIT,$0
	MOVD	8(R0), R1	// arg 2 len
	MOVD	0(R0), R0	// arg 1 addr
	BL	libc_munmap(SB)
	CMP	$0, R0
	BEQ	2(PC)
	BL	notok<>(SB)
	RET

TEXT runtime·madvise_trampoline(SB),NOSPLIT,$0
	MOVD	8(R0), R1	// arg 2 len
	MOVW	16(R0), R2	// arg 3 advice
	MOVD	0(R0), R0	// arg 1 addr
	BL	libc_madvise(SB)
	RET

TEXT runtime·mlock_trampoline(SB),NOSPLIT,$0
	MOVD	8(R0), R1	// arg 2 len
	MOVD	0(R0), R0	// arg 1 addr
	BL	libc_mlock(SB)
	RET

TEXT runtime·setitimer_trampoline(SB),NOSPLIT,$0
	MOVD	8(R0), R1	// arg 2 new
	MOVD	16(R0), R2	// arg 3 old
	MOVW	0(R0), R0	// arg 1 which
	BL	libc_setitimer(SB)
	RET

TEXT runtime·walltime_trampoline(SB),NOSPLIT,$0
	MOVD	R0, R1			// arg 2 timespec
	MOVW	$CLOCK_REALTIME, R0 	// arg 1 clock_id
	BL	libc_clock_gettime(SB)
	RET

GLOBL timebase<>(SB),NOPTR,$(machTimebaseInfo__size)

TEXT runtime·nanotime_trampoline(SB),NOSPLIT,$40
	MOVD	R0, R19
	BL	libc_mach_absolute_time(SB)
	MOVD	R0, 0(R19)
	MOVW	timebase<>+machTimebaseInfo_numer(SB), R20
	MOVD	$timebase<>+machTimebaseInfo_denom(SB), R21
	LDARW	(R21), R21	// atomic read
	CMP	$0, R21
	BNE	initialized

	SUB	$(machTimebaseInfo__size+15)/16*16, RSP
	MOVD	RSP, R0
	BL	libc_mach_timebase_info(SB)
	MOVW	machTimebaseInfo_numer(RSP), R20
	MOVW	machTimebaseInfo_denom(RSP), R21
	ADD	$(machTimebaseInfo__size+15)/16*16, RSP

	MOVW	R20, timebase<>+machTimebaseInfo_numer(SB)
	MOVD	$timebase<>+machTimebaseInfo_denom(SB), R22
	STLRW	R21, (R22)	// atomic write

initialized:
	MOVW	R20, 8(R19)
	MOVW	R21, 12(R19)
	RET

TEXT runtime·sigfwd(SB),NOSPLIT,$0-32
	MOVW	sig+8(FP), R0
	MOVD	info+16(FP), R1
	MOVD	ctx+24(FP), R2
	MOVD	fn+0(FP), R11
	BL	(R11)
	RET

TEXT runtime·sigtramp(SB),NOSPLIT,$192
	// Save callee-save registers in the case of signal forwarding.
	// Please refer to https://golang.org/issue/31827 .
	MOVD	R19, 8*4(RSP)
	MOVD	R20, 8*5(RSP)
	MOVD	R21, 8*6(RSP)
	MOVD	R22, 8*7(RSP)
	MOVD	R23, 8*8(RSP)
	MOVD	R24, 8*9(RSP)
	MOVD	R25, 8*10(RSP)
	MOVD	R26, 8*11(RSP)
	MOVD	R27, 8*12(RSP)
	MOVD	g, 8*13(RSP)
	MOVD	R29, 8*14(RSP)
	FMOVD	F8, 8*15(RSP)
	FMOVD	F9, 8*16(RSP)
	FMOVD	F10, 8*17(RSP)
	FMOVD	F11, 8*18(RSP)
	FMOVD	F12, 8*19(RSP)
	FMOVD	F13, 8*20(RSP)
	FMOVD	F14, 8*21(RSP)
	FMOVD	F15, 8*22(RSP)

	// Save arguments.
	MOVW	R0, (8*1)(RSP)	// sig
	MOVD	R1, (8*2)(RSP)	// info
	MOVD	R2, (8*3)(RSP)	// ctx

	// this might be called in external code context,
	// where g is not set.
	BL	runtime·load_g(SB)

#ifdef GOOS_ios
	MOVD	RSP, R6
	CMP	$0, g
	BEQ	nog
	// iOS always use the main stack to run the signal handler.
	// We need to switch to gsignal ourselves.
	MOVD	g_m(g), R11
	MOVD	m_gsignal(R11), R5
	MOVD	(g_stack+stack_hi)(R5), R6

nog:
	// Restore arguments.
	MOVW	(8*1)(RSP), R0
	MOVD	(8*2)(RSP), R1
	MOVD	(8*3)(RSP), R2

	// Reserve space for args and the stack pointer on the
	// gsignal stack.
	SUB	$48, R6
	// Save stack pointer.
	MOVD	RSP, R4
	MOVD	R4, (8*4)(R6)
	// Switch to gsignal stack.
	MOVD	R6, RSP

	// Save arguments.
	MOVW	R0, (8*1)(RSP)
	MOVD	R1, (8*2)(RSP)
	MOVD	R2, (8*3)(RSP)
#endif

	// Call sigtrampgo.
	MOVD	$runtime·sigtrampgo(SB), R11
	BL	(R11)

#ifdef GOOS_ios
	// Switch to old stack.
	MOVD	(8*4)(RSP), R5
	MOVD	R5, RSP
#endif

	// Restore callee-save registers.
	MOVD	(8*4)(RSP), R19
	MOVD	(8*5)(RSP), R20
	MOVD	(8*6)(RSP), R21
	MOVD	(8*7)(RSP), R22
	MOVD	(8*8)(RSP), R23
	MOVD	(8*9)(RSP), R24
	MOVD	(8*10)(RSP), R25
	MOVD	(8*11)(RSP), R26
	MOVD	(8*12)(RSP), R27
	MOVD	(8*13)(RSP), g
	MOVD	(8*14)(RSP), R29
	FMOVD	(8*15)(RSP), F8
	FMOVD	(8*16)(RSP), F9
	FMOVD	(8*17)(RSP), F10
	FMOVD	(8*18)(RSP), F11
	FMOVD	(8*19)(RSP), F12
	FMOVD	(8*20)(RSP), F13
	FMOVD	(8*21)(RSP), F14
	FMOVD	(8*22)(RSP), F15

	RET

TEXT runtime·cgoSigtramp(SB),NOSPLIT,$0
	JMP	runtime·sigtramp(SB)

TEXT runtime·sigprocmask_trampoline(SB),NOSPLIT,$0
	MOVD	8(R0), R1	// arg 2 new
	MOVD	16(R0), R2	// arg 3 old
	MOVW	0(R0), R0	// arg 1 how
	BL	libc_pthread_sigmask(SB)
	CMP	$0, R0
	BEQ	2(PC)
	BL	notok<>(SB)
	RET

TEXT runtime·sigaction_trampoline(SB),NOSPLIT,$0
	MOVD	8(R0), R1	// arg 2 new
	MOVD	16(R0), R2	// arg 3 old
	MOVW	0(R0), R0	// arg 1 how
	BL	libc_sigaction(SB)
	CMP	$0, R0
	BEQ	2(PC)
	BL	notok<>(SB)
	RET

TEXT runtime·usleep_trampoline(SB),NOSPLIT,$0
	MOVW	0(R0), R0	// arg 1 usec
	BL	libc_usleep(SB)
	RET

TEXT runtime·sysctl_trampoline(SB),NOSPLIT,$0
	MOVW	8(R0), R1	// arg 2 miblen
	MOVD	16(R0), R2	// arg 3 oldp
	MOVD	24(R0), R3	// arg 4 oldlenp
	MOVD	32(R0), R4	// arg 5 newp
	MOVD	40(R0), R5	// arg 6 newlen
	MOVD	0(R0), R0	// arg 1 mib
	BL	libc_sysctl(SB)
	RET

TEXT runtime·sysctlbyname_trampoline(SB),NOSPLIT,$0
	MOVD	8(R0), R1	// arg 2 oldp
	MOVD	16(R0), R2	// arg 3 oldlenp
	MOVD	24(R0), R3	// arg 4 newp
	MOVD	32(R0), R4	// arg 5 newlen
	MOVD	0(R0), R0	// arg 1 name
	BL	libc_sysctlbyname(SB)
	RET


TEXT runtime·kqueue_trampoline(SB),NOSPLIT,$0
	BL	libc_kqueue(SB)
	RET

TEXT runtime·kevent_trampoline(SB),NOSPLIT,$0
	MOVD	8(R0), R1	// arg 2 keventt
	MOVW	16(R0), R2	// arg 3 nch
	MOVD	24(R0), R3	// arg 4 ev
	MOVW	32(R0), R4	// arg 5 nev
	MOVD	40(R0), R5	// arg 6 ts
	MOVW	0(R0), R0	// arg 1 kq
	BL	libc_kevent(SB)
	MOVD	$-1, R2
	CMP	R0, R2
	BNE	ok
	BL	libc_error(SB)
	MOVW	(R0), R0	// errno
	NEG	R0, R0	// caller wants it as a negative error code
ok:
	RET

TEXT runtime·fcntl_trampoline(SB),NOSPLIT,$0
	SUB	$16, RSP
	MOVW	4(R0), R1	// arg 2 cmd
	MOVW	8(R0), R2	// arg 3 arg
	MOVW	R2, (RSP)	// arg 3 is variadic, pass on stack
	MOVW	0(R0), R0	// arg 1 fd
	BL	libc_fcntl(SB)
	ADD	$16, RSP
	RET

TEXT runtime·sigaltstack_trampoline(SB),NOSPLIT,$0
#ifdef GOOS_ios
	// sigaltstack on iOS is not supported and will always
	// run the signal handler on the main stack, so our sigtramp has
	// to do the stack switch ourselves.
	MOVW	$43, R0
	BL	libc_exit(SB)
#else
	MOVD	8(R0), R1		// arg 2 old
	MOVD	0(R0), R0		// arg 1 new
	CALL	libc_sigaltstack(SB)
	CBZ	R0, 2(PC)
	BL	notok<>(SB)
#endif
	RET

// Thread related functions

// mstart_stub is the first function executed on a new thread started by pthread_create.
// It just does some low-level setup and then calls mstart.
// Note: called with the C calling convention.
TEXT runtime·mstart_stub(SB),NOSPLIT,$160
	// R0 points to the m.
	// We are already on m's g0 stack.

	// Save callee-save registers.
	MOVD	R19, 8(RSP)
	MOVD	R20, 16(RSP)
	MOVD	R21, 24(RSP)
	MOVD	R22, 32(RSP)
	MOVD	R23, 40(RSP)
	MOVD	R24, 48(RSP)
	MOVD	R25, 56(RSP)
	MOVD	R26, 64(RSP)
	MOVD	R27, 72(RSP)
	MOVD	g, 80(RSP)
	MOVD	R29, 88(RSP)
	FMOVD	F8, 96(RSP)
	FMOVD	F9, 104(RSP)
	FMOVD	F10, 112(RSP)
	FMOVD	F11, 120(RSP)
	FMOVD	F12, 128(RSP)
	FMOVD	F13, 136(RSP)
	FMOVD	F14, 144(RSP)
	FMOVD	F15, 152(RSP)

	MOVD	m_g0(R0), g
	BL	·save_g(SB)

	BL	runtime·mstart(SB)

	// Restore callee-save registers.
	MOVD	8(RSP), R19
	MOVD	16(RSP), R20
	MOVD	24(RSP), R21
	MOVD	32(RSP), R22
	MOVD	40(RSP), R23
	MOVD	48(RSP), R24
	MOVD	56(RSP), R25
	MOVD	64(RSP), R26
	MOVD	72(RSP), R27
	MOVD	80(RSP), g
	MOVD	88(RSP), R29
	FMOVD	96(RSP), F8
	FMOVD	104(RSP), F9
	FMOVD	112(RSP), F10
	FMOVD	120(RSP), F11
	FMOVD	128(RSP), F12
	FMOVD	136(RSP), F13
	FMOVD	144(RSP), F14
	FMOVD	152(RSP), F15

	// Go is all done with this OS thread.
	// Tell pthread everything is ok (we never join with this thread, so
	// the value here doesn't really matter).
	MOVD	$0, R0

	RET

TEXT runtime·pthread_attr_init_trampoline(SB),NOSPLIT,$0
	MOVD	0(R0), R0	// arg 1 attr
	BL	libc_pthread_attr_init(SB)
	RET

TEXT runtime·pthread_attr_getstacksize_trampoline(SB),NOSPLIT,$0
	MOVD	8(R0), R1	// arg 2 size
	MOVD	0(R0), R0	// arg 1 attr
	BL	libc_pthread_attr_getstacksize(SB)
	RET

TEXT runtime·pthread_attr_setdetachstate_trampoline(SB),NOSPLIT,$0
	MOVD	8(R0), R1	// arg 2 state
	MOVD	0(R0), R0	// arg 1 attr
	BL	libc_pthread_attr_setdetachstate(SB)
	RET

TEXT runtime·pthread_create_trampoline(SB),NOSPLIT,$0
	SUB	$16, RSP
	MOVD	0(R0), R1	// arg 2 state
	MOVD	8(R0), R2	// arg 3 start
	MOVD	16(R0), R3	// arg 4 arg
	MOVD	RSP, R0 	// arg 1 &threadid (which we throw away)
	BL	libc_pthread_create(SB)
	ADD	$16, RSP
	RET

TEXT runtime·raise_trampoline(SB),NOSPLIT,$0
	MOVW	0(R0), R0	// arg 1 sig
	BL	libc_raise(SB)
	RET

TEXT runtime·pthread_mutex_init_trampoline(SB),NOSPLIT,$0
	MOVD	8(R0), R1	// arg 2 attr
	MOVD	0(R0), R0	// arg 1 mutex
	BL	libc_pthread_mutex_init(SB)
	RET

TEXT runtime·pthread_mutex_lock_trampoline(SB),NOSPLIT,$0
	MOVD	0(R0), R0	// arg 1 mutex
	BL	libc_pthread_mutex_lock(SB)
	RET

TEXT runtime·pthread_mutex_unlock_trampoline(SB),NOSPLIT,$0
	MOVD	0(R0), R0	// arg 1 mutex
	BL	libc_pthread_mutex_unlock(SB)
	RET

TEXT runtime·pthread_cond_init_trampoline(SB),NOSPLIT,$0
	MOVD	8(R0), R1	// arg 2 attr
	MOVD	0(R0), R0	// arg 1 cond
	BL	libc_pthread_cond_init(SB)
	RET

TEXT runtime·pthread_cond_wait_trampoline(SB),NOSPLIT,$0
	MOVD	8(R0), R1	// arg 2 mutex
	MOVD	0(R0), R0	// arg 1 cond
	BL	libc_pthread_cond_wait(SB)
	RET

TEXT runtime·pthread_cond_timedwait_relative_np_trampoline(SB),NOSPLIT,$0
	MOVD	8(R0), R1	// arg 2 mutex
	MOVD	16(R0), R2	// arg 3 timeout
	MOVD	0(R0), R0	// arg 1 cond
	BL	libc_pthread_cond_timedwait_relative_np(SB)
	RET

TEXT runtime·pthread_cond_signal_trampoline(SB),NOSPLIT,$0
	MOVD	0(R0), R0	// arg 1 cond
	BL	libc_pthread_cond_signal(SB)
	RET

TEXT runtime·pthread_self_trampoline(SB),NOSPLIT,$0
	MOVD	R0, R19		// R19 is callee-save
	BL	libc_pthread_self(SB)
	MOVD	R0, 0(R19)	// return value
	RET

TEXT runtime·pthread_kill_trampoline(SB),NOSPLIT,$0
	MOVD	8(R0), R1	// arg 2 sig
	MOVD	0(R0), R0	// arg 1 thread
	BL	libc_pthread_kill(SB)
	RET

TEXT runtime·pthread_key_create_trampoline(SB),NOSPLIT,$0
	MOVD	8(R0), R1	// arg 2 destructor
	MOVD	0(R0), R0	// arg 1 *key
	BL	libc_pthread_key_create(SB)
	RET

TEXT runtime·pthread_setspecific_trampoline(SB),NOSPLIT,$0
	MOVD	8(R0), R1	// arg 2 value
	MOVD	0(R0), R0	// arg 1 key
	BL	libc_pthread_setspecific(SB)
	RET

// syscall calls a function in libc on behalf of the syscall package.
// syscall takes a pointer to a struct like:
// struct {
//	fn    uintptr
//	a1    uintptr
//	a2    uintptr
//	a3    uintptr
//	r1    uintptr
//	r2    uintptr
//	err   uintptr
// }
// syscall must be called on the g0 stack with the
// C calling convention (use libcCall).
TEXT runtime·syscall(SB),NOSPLIT,$0
	SUB	$16, RSP	// push structure pointer
	MOVD	R0, 8(RSP)

	MOVD	0(R0), R12	// fn
	MOVD	16(R0), R1	// a2
	MOVD	24(R0), R2	// a3
	MOVD	8(R0), R0	// a1

	// If fn is declared as vararg, we have to pass the vararg arguments on the stack.
	// (Because ios decided not to adhere to the standard arm64 calling convention, sigh...)
	// The only libSystem calls we support that are vararg are open, fcntl, and ioctl,
	// which are all of the form fn(x, y, ...). So we just need to put the 3rd arg
	// on the stack as well.
	// If we ever have other vararg libSystem calls, we might need to handle more cases.
	MOVD	R2, (RSP)

	BL	(R12)

	MOVD	8(RSP), R2	// pop structure pointer
	ADD	$16, RSP
	MOVD	R0, 32(R2)	// save r1
	MOVD	R1, 40(R2)	// save r2
	CMPW	$-1, R0
	BNE	ok
	SUB	$16, RSP	// push structure pointer
	MOVD	R2, 8(RSP)
	BL	libc_error(SB)
	MOVW	(R0), R0
	MOVD	8(RSP), R2	// pop structure pointer
	ADD	$16, RSP
	MOVD	R0, 48(R2)	// save err
ok:
	RET

// syscallX calls a function in libc on behalf of the syscall package.
// syscallX takes a pointer to a struct like:
// struct {
//	fn    uintptr
//	a1    uintptr
//	a2    uintptr
//	a3    uintptr
//	r1    uintptr
//	r2    uintptr
//	err   uintptr
// }
// syscallX must be called on the g0 stack with the
// C calling convention (use libcCall).
TEXT runtime·syscallX(SB),NOSPLIT,$0
	SUB	$16, RSP	// push structure pointer
	MOVD	R0, (RSP)

	MOVD	0(R0), R12	// fn
	MOVD	16(R0), R1	// a2
	MOVD	24(R0), R2	// a3
	MOVD	8(R0), R0	// a1
	BL	(R12)

	MOVD	(RSP), R2	// pop structure pointer
	ADD	$16, RSP
	MOVD	R0, 32(R2)	// save r1
	MOVD	R1, 40(R2)	// save r2
	CMP	$-1, R0
	BNE	ok
	SUB	$16, RSP	// push structure pointer
	MOVD	R2, (RSP)
	BL	libc_error(SB)
	MOVW	(R0), R0
	MOVD	(RSP), R2	// pop structure pointer
	ADD	$16, RSP
	MOVD	R0, 48(R2)	// save err
ok:
	RET

// syscallPtr is like syscallX except that the libc function reports an
// error by returning NULL and setting errno.
TEXT runtime·syscallPtr(SB),NOSPLIT,$0
	SUB	$16, RSP	// push structure pointer
	MOVD	R0, (RSP)

	MOVD	0(R0), R12	// fn
	MOVD	16(R0), R1	// a2
	MOVD	24(R0), R2	// a3
	MOVD	8(R0), R0	// a1
	BL	(R12)

	MOVD	(RSP), R2	// pop structure pointer
	ADD	$16, RSP
	MOVD	R0, 32(R2)	// save r1
	MOVD	R1, 40(R2)	// save r2
	CMP	$0, R0
	BNE	ok
	SUB	$16, RSP	// push structure pointer
	MOVD	R2, (RSP)
	BL	libc_error(SB)
	MOVW	(R0), R0
	MOVD	(RSP), R2	// pop structure pointer
	ADD	$16, RSP
	MOVD	R0, 48(R2)	// save err
ok:
	RET

// syscall6 calls a function in libc on behalf of the syscall package.
// syscall6 takes a pointer to a struct like:
// struct {
//	fn    uintptr
//	a1    uintptr
//	a2    uintptr
//	a3    uintptr
//	a4    uintptr
//	a5    uintptr
//	a6    uintptr
//	r1    uintptr
//	r2    uintptr
//	err   uintptr
// }
// syscall6 must be called on the g0 stack with the
// C calling convention (use libcCall).
TEXT runtime·syscall6(SB),NOSPLIT,$0
	SUB	$16, RSP	// push structure pointer
	MOVD	R0, 8(RSP)

	MOVD	0(R0), R12	// fn
	MOVD	16(R0), R1	// a2
	MOVD	24(R0), R2	// a3
	MOVD	32(R0), R3	// a4
	MOVD	40(R0), R4	// a5
	MOVD	48(R0), R5	// a6
	MOVD	8(R0), R0	// a1

	// If fn is declared as vararg, we have to pass the vararg arguments on the stack.
	// See syscall above. The only function this applies to is openat, for which the 4th
	// arg must be on the stack.
	MOVD	R3, (RSP)

	BL	(R12)

	MOVD	8(RSP), R2	// pop structure pointer
	ADD	$16, RSP
	MOVD	R0, 56(R2)	// save r1
	MOVD	R1, 64(R2)	// save r2
	CMPW	$-1, R0
	BNE	ok
	SUB	$16, RSP	// push structure pointer
	MOVD	R2, 8(RSP)
	BL	libc_error(SB)
	MOVW	(R0), R0
	MOVD	8(RSP), R2	// pop structure pointer
	ADD	$16, RSP
	MOVD	R0, 72(R2)	// save err
ok:
	RET

// syscall6X calls a function in libc on behalf of the syscall package.
// syscall6X takes a pointer to a struct like:
// struct {
//	fn    uintptr
//	a1    uintptr
//	a2    uintptr
//	a3    uintptr
//	a4    uintptr
//	a5    uintptr
//	a6    uintptr
//	r1    uintptr
//	r2    uintptr
//	err   uintptr
// }
// syscall6X must be called on the g0 stack with the
// C calling convention (use libcCall).
TEXT runtime·syscall6X(SB),NOSPLIT,$0
	SUB	$16, RSP	// push structure pointer
	MOVD	R0, (RSP)

	MOVD	0(R0), R12	// fn
	MOVD	16(R0), R1	// a2
	MOVD	24(R0), R2	// a3
	MOVD	32(R0), R3	// a4
	MOVD	40(R0), R4	// a5
	MOVD	48(R0), R5	// a6
	MOVD	8(R0), R0	// a1
	BL	(R12)

	MOVD	(RSP), R2	// pop structure pointer
	ADD	$16, RSP
	MOVD	R0, 56(R2)	// save r1
	MOVD	R1, 64(R2)	// save r2
	CMP	$-1, R0
	BNE	ok
	SUB	$16, RSP	// push structure pointer
	MOVD	R2, (RSP)
	BL	libc_error(SB)
	MOVW	(R0), R0
	MOVD	(RSP), R2	// pop structure pointer
	ADD	$16, RSP
	MOVD	R0, 72(R2)	// save err
ok:
	RET

// syscallNoErr is like syscall6 but does not check for errors, and
// only returns one value, for use with standard C ABI library functions.
TEXT runtime·syscallNoErr(SB),NOSPLIT,$0
	SUB	$16, RSP	// push structure pointer
	MOVD	R0, (RSP)

	MOVD	0(R0), R12	// fn
	MOVD	16(R0), R1	// a2
	MOVD	24(R0), R2	// a3
	MOVD	32(R0), R3	// a4
	MOVD	40(R0), R4	// a5
	MOVD	48(R0), R5	// a6
	MOVD	8(R0), R0	// a1
	BL	(R12)

	MOVD	(RSP), R2	// pop structure pointer
	ADD	$16, RSP
	MOVD	R0, 56(R2)	// save r1
	RET