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// 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.
//
// System calls and other sys.stuff for arm64, Linux
//
#include "go_asm.h"
#include "go_tls.h"
#include "textflag.h"
#include "cgo/abi_arm64.h"
#define AT_FDCWD -100
#define CLOCK_REALTIME 0
#define CLOCK_MONOTONIC 1
#define SYS_exit 93
#define SYS_read 63
#define SYS_write 64
#define SYS_openat 56
#define SYS_close 57
#define SYS_pipe2 59
#define SYS_nanosleep 101
#define SYS_mmap 222
#define SYS_munmap 215
#define SYS_setitimer 103
#define SYS_clone 220
#define SYS_sched_yield 124
#define SYS_rt_sigreturn 139
#define SYS_rt_sigaction 134
#define SYS_rt_sigprocmask 135
#define SYS_sigaltstack 132
#define SYS_madvise 233
#define SYS_mincore 232
#define SYS_getpid 172
#define SYS_gettid 178
#define SYS_kill 129
#define SYS_tgkill 131
#define SYS_futex 98
#define SYS_sched_getaffinity 123
#define SYS_exit_group 94
#define SYS_clock_gettime 113
#define SYS_faccessat 48
#define SYS_socket 198
#define SYS_connect 203
#define SYS_brk 214
#define SYS_timer_create 107
#define SYS_timer_settime 110
#define SYS_timer_delete 111
TEXT runtime·exit(SB),NOSPLIT|NOFRAME,$0-4
MOVW code+0(FP), R0
MOVD $SYS_exit_group, R8
SVC
RET
// func exitThread(wait *atomic.Uint32)
TEXT runtime·exitThread(SB),NOSPLIT|NOFRAME,$0-8
MOVD wait+0(FP), R0
// We're done using the stack.
MOVW $0, R1
STLRW R1, (R0)
MOVW $0, R0 // exit code
MOVD $SYS_exit, R8
SVC
JMP 0(PC)
TEXT runtime·open(SB),NOSPLIT|NOFRAME,$0-20
MOVD $AT_FDCWD, R0
MOVD name+0(FP), R1
MOVW mode+8(FP), R2
MOVW perm+12(FP), R3
MOVD $SYS_openat, R8
SVC
CMN $4095, R0
BCC done
MOVW $-1, R0
done:
MOVW R0, ret+16(FP)
RET
TEXT runtime·closefd(SB),NOSPLIT|NOFRAME,$0-12
MOVW fd+0(FP), R0
MOVD $SYS_close, R8
SVC
CMN $4095, R0
BCC done
MOVW $-1, R0
done:
MOVW R0, ret+8(FP)
RET
TEXT runtime·write1(SB),NOSPLIT|NOFRAME,$0-28
MOVD fd+0(FP), R0
MOVD p+8(FP), R1
MOVW n+16(FP), R2
MOVD $SYS_write, R8
SVC
MOVW R0, ret+24(FP)
RET
TEXT runtime·read(SB),NOSPLIT|NOFRAME,$0-28
MOVW fd+0(FP), R0
MOVD p+8(FP), R1
MOVW n+16(FP), R2
MOVD $SYS_read, R8
SVC
MOVW R0, ret+24(FP)
RET
// func pipe2(flags int32) (r, w int32, errno int32)
TEXT runtime·pipe2(SB),NOSPLIT|NOFRAME,$0-20
MOVD $r+8(FP), R0
MOVW flags+0(FP), R1
MOVW $SYS_pipe2, R8
SVC
MOVW R0, errno+16(FP)
RET
TEXT runtime·usleep(SB),NOSPLIT,$24-4
MOVWU usec+0(FP), R3
MOVD R3, R5
MOVW $1000000, R4
UDIV R4, R3
MOVD R3, 8(RSP)
MUL R3, R4
SUB R4, R5
MOVW $1000, R4
MUL R4, R5
MOVD R5, 16(RSP)
// nanosleep(&ts, 0)
ADD $8, RSP, R0
MOVD $0, R1
MOVD $SYS_nanosleep, R8
SVC
RET
TEXT runtime·gettid(SB),NOSPLIT,$0-4
MOVD $SYS_gettid, R8
SVC
MOVW R0, ret+0(FP)
RET
TEXT runtime·raise(SB),NOSPLIT|NOFRAME,$0
MOVD $SYS_getpid, R8
SVC
MOVW R0, R19
MOVD $SYS_gettid, R8
SVC
MOVW R0, R1 // arg 2 tid
MOVW R19, R0 // arg 1 pid
MOVW sig+0(FP), R2 // arg 3
MOVD $SYS_tgkill, R8
SVC
RET
TEXT runtime·raiseproc(SB),NOSPLIT|NOFRAME,$0
MOVD $SYS_getpid, R8
SVC
MOVW R0, R0 // arg 1 pid
MOVW sig+0(FP), R1 // arg 2
MOVD $SYS_kill, R8
SVC
RET
TEXT ·getpid(SB),NOSPLIT|NOFRAME,$0-8
MOVD $SYS_getpid, R8
SVC
MOVD R0, ret+0(FP)
RET
TEXT ·tgkill(SB),NOSPLIT,$0-24
MOVD tgid+0(FP), R0
MOVD tid+8(FP), R1
MOVD sig+16(FP), R2
MOVD $SYS_tgkill, R8
SVC
RET
TEXT runtime·setitimer(SB),NOSPLIT|NOFRAME,$0-24
MOVW mode+0(FP), R0
MOVD new+8(FP), R1
MOVD old+16(FP), R2
MOVD $SYS_setitimer, R8
SVC
RET
TEXT runtime·timer_create(SB),NOSPLIT,$0-28
MOVW clockid+0(FP), R0
MOVD sevp+8(FP), R1
MOVD timerid+16(FP), R2
MOVD $SYS_timer_create, R8
SVC
MOVW R0, ret+24(FP)
RET
TEXT runtime·timer_settime(SB),NOSPLIT,$0-28
MOVW timerid+0(FP), R0
MOVW flags+4(FP), R1
MOVD new+8(FP), R2
MOVD old+16(FP), R3
MOVD $SYS_timer_settime, R8
SVC
MOVW R0, ret+24(FP)
RET
TEXT runtime·timer_delete(SB),NOSPLIT,$0-12
MOVW timerid+0(FP), R0
MOVD $SYS_timer_delete, R8
SVC
MOVW R0, ret+8(FP)
RET
TEXT runtime·mincore(SB),NOSPLIT|NOFRAME,$0-28
MOVD addr+0(FP), R0
MOVD n+8(FP), R1
MOVD dst+16(FP), R2
MOVD $SYS_mincore, R8
SVC
MOVW R0, ret+24(FP)
RET
// func walltime() (sec int64, nsec int32)
TEXT runtime·walltime(SB),NOSPLIT,$24-12
MOVD RSP, R20 // R20 is unchanged by C code
MOVD RSP, R1
MOVD g_m(g), R21 // R21 = m
// 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), R2
MOVD m_vdsoSP(R21), R3
MOVD R2, 8(RSP)
MOVD R3, 16(RSP)
MOVD $ret-8(FP), R2 // caller's SP
MOVD LR, m_vdsoPC(R21)
MOVD R2, m_vdsoSP(R21)
MOVD m_curg(R21), R0
CMP g, R0
BNE noswitch
MOVD m_g0(R21), R3
MOVD (g_sched+gobuf_sp)(R3), R1 // Set RSP to g0 stack
noswitch:
SUB $16, R1
BIC $15, R1 // Align for C code
MOVD R1, RSP
MOVW $CLOCK_REALTIME, R0
MOVD runtime·vdsoClockgettimeSym(SB), R2
CBZ R2, fallback
// 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.
MOVBU runtime·iscgo(SB), R22
CBNZ R22, nosaveg
MOVD m_gsignal(R21), R22 // g.m.gsignal
CBZ R22, nosaveg
CMP g, R22
BEQ nosaveg
MOVD (g_stack+stack_lo)(R22), R22 // g.m.gsignal.stack.lo
MOVD g, (R22)
BL (R2)
MOVD ZR, (R22) // clear g slot, R22 is unchanged by C code
B finish
nosaveg:
BL (R2)
B finish
fallback:
MOVD $SYS_clock_gettime, R8
SVC
finish:
MOVD 0(RSP), R3 // sec
MOVD 8(RSP), R5 // nsec
MOVD R20, RSP // 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 16(RSP), R1
MOVD R1, m_vdsoSP(R21)
MOVD 8(RSP), R1
MOVD R1, m_vdsoPC(R21)
MOVD R3, sec+0(FP)
MOVW R5, nsec+8(FP)
RET
TEXT runtime·nanotime1(SB),NOSPLIT,$24-8
MOVD RSP, R20 // R20 is unchanged by C code
MOVD RSP, R1
MOVD g_m(g), R21 // R21 = m
// 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), R2
MOVD m_vdsoSP(R21), R3
MOVD R2, 8(RSP)
MOVD R3, 16(RSP)
MOVD $ret-8(FP), R2 // caller's SP
MOVD LR, m_vdsoPC(R21)
MOVD R2, m_vdsoSP(R21)
MOVD m_curg(R21), R0
CMP g, R0
BNE noswitch
MOVD m_g0(R21), R3
MOVD (g_sched+gobuf_sp)(R3), R1 // Set RSP to g0 stack
noswitch:
SUB $32, R1
BIC $15, R1
MOVD R1, RSP
MOVW $CLOCK_MONOTONIC, R0
MOVD runtime·vdsoClockgettimeSym(SB), R2
CBZ R2, fallback
// 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.
MOVBU runtime·iscgo(SB), R22
CBNZ R22, nosaveg
MOVD m_gsignal(R21), R22 // g.m.gsignal
CBZ R22, nosaveg
CMP g, R22
BEQ nosaveg
MOVD (g_stack+stack_lo)(R22), R22 // g.m.gsignal.stack.lo
MOVD g, (R22)
BL (R2)
MOVD ZR, (R22) // clear g slot, R22 is unchanged by C code
B finish
nosaveg:
BL (R2)
B finish
fallback:
MOVD $SYS_clock_gettime, R8
SVC
finish:
MOVD 0(RSP), R3 // sec
MOVD 8(RSP), R5 // nsec
MOVD R20, RSP // 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 16(RSP), R1
MOVD R1, m_vdsoSP(R21)
MOVD 8(RSP), R1
MOVD R1, m_vdsoPC(R21)
// sec is in R3, nsec in R5
// return nsec in R3
MOVD $1000000000, R4
MUL R4, R3
ADD R5, R3
MOVD R3, ret+0(FP)
RET
TEXT runtime·rtsigprocmask(SB),NOSPLIT|NOFRAME,$0-28
MOVW how+0(FP), R0
MOVD new+8(FP), R1
MOVD old+16(FP), R2
MOVW size+24(FP), R3
MOVD $SYS_rt_sigprocmask, R8
SVC
CMN $4095, R0
BCC done
MOVD $0, R0
MOVD R0, (R0) // crash
done:
RET
TEXT runtime·rt_sigaction(SB),NOSPLIT|NOFRAME,$0-36
MOVD sig+0(FP), R0
MOVD new+8(FP), R1
MOVD old+16(FP), R2
MOVD size+24(FP), R3
MOVD $SYS_rt_sigaction, R8
SVC
MOVW R0, ret+32(FP)
RET
// Call the function stored in _cgo_sigaction using the GCC calling convention.
TEXT runtime·callCgoSigaction(SB),NOSPLIT,$0
MOVD sig+0(FP), R0
MOVD new+8(FP), R1
MOVD old+16(FP), R2
MOVD _cgo_sigaction(SB), R3
SUB $16, RSP // reserve 16 bytes for sp-8 where fp may be saved.
BL R3
ADD $16, RSP
MOVW R0, ret+24(FP)
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
// Called from c-abi, R0: sig, R1: info, R2: cxt
TEXT runtime·sigtramp(SB),NOSPLIT|TOPFRAME,$176
// Save callee-save registers in the case of signal forwarding.
// Please refer to https://golang.org/issue/31827 .
SAVE_R19_TO_R28(8*4)
SAVE_F8_TO_F15(8*14)
// this might be called in external code context,
// where g is not set.
// first save R0, because runtime·load_g will clobber it
MOVW R0, 8(RSP)
MOVBU runtime·iscgo(SB), R0
CBZ R0, 2(PC)
BL runtime·load_g(SB)
#ifdef GOEXPERIMENT_regabiargs
// Restore signum to R0.
MOVW 8(RSP), R0
// R1 and R2 already contain info and ctx, respectively.
#else
MOVD R1, 16(RSP)
MOVD R2, 24(RSP)
#endif
MOVD $runtime·sigtrampgo<ABIInternal>(SB), R3
BL (R3)
// Restore callee-save registers.
RESTORE_R19_TO_R28(8*4)
RESTORE_F8_TO_F15(8*14)
RET
// Called from c-abi, R0: sig, R1: info, R2: cxt
TEXT runtime·sigprofNonGoWrapper<>(SB),NOSPLIT,$176
// Save callee-save registers because it's a callback from c code.
SAVE_R19_TO_R28(8*4)
SAVE_F8_TO_F15(8*14)
#ifdef GOEXPERIMENT_regabiargs
// R0, R1 and R2 already contain sig, info and ctx, respectively.
#else
MOVW R0, 8(RSP) // sig
MOVD R1, 16(RSP) // info
MOVD R2, 24(RSP) // ctx
#endif
CALL runtime·sigprofNonGo<ABIInternal>(SB)
// Restore callee-save registers.
RESTORE_R19_TO_R28(8*4)
RESTORE_F8_TO_F15(8*14)
RET
// Called from c-abi, R0: sig, R1: info, R2: cxt
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
// Save R27, g because they will be clobbered,
// we need to restore them before jump to sigtramp.
MOVD R27, R11
MOVD g, R12
// If no traceback function, do usual sigtramp.
MOVD runtime·cgoTraceback(SB), R6
CBZ R6, sigtramp
// If no traceback support function, which means that
// runtime/cgo was not linked in, do usual sigtramp.
MOVD _cgo_callers(SB), R7
CBZ R7, sigtramp
// Figure out if we are currently in a cgo call.
// If not, just do usual sigtramp.
// first save R0, because runtime·load_g will clobber it.
MOVD R0, R8
// Set up g register.
CALL runtime·load_g(SB)
MOVD R8, R0
CBZ g, sigtrampnog // g == nil
MOVD g_m(g), R6
CBZ R6, sigtramp // g.m == nil
MOVW m_ncgo(R6), R7
CBZW R7, sigtramp // g.m.ncgo = 0
MOVD m_curg(R6), R8
CBZ R8, sigtramp // g.m.curg == nil
MOVD g_syscallsp(R8), R7
CBZ R7, sigtramp // g.m.curg.syscallsp == 0
MOVD m_cgoCallers(R6), R4 // R4 is the fifth arg in C calling convention.
CBZ R4, sigtramp // g.m.cgoCallers == nil
MOVW m_cgoCallersUse(R6), R8
CBNZW R8, 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), R3
MOVD $runtime·sigtramp(SB), R5
MOVD _cgo_callers(SB), R13
MOVD R10, LR // restore
MOVD R11, R27
MOVD R12, g
B (R13)
sigtramp:
MOVD R10, LR // restore
MOVD R11, R27
MOVD R12, g
B runtime·sigtramp(SB)
sigtrampnog:
// Signal arrived on a non-Go thread. If this is SIGPROF, get a
// stack trace.
CMPW $27, R0 // 27 == SIGPROF
BNE sigtramp
// Lock sigprofCallersUse (cas from 0 to 1).
MOVW $1, R7
MOVD $runtime·sigprofCallersUse(SB), R8
load_store_loop:
LDAXRW (R8), R9
CBNZW R9, sigtramp // Skip stack trace if already locked.
STLXRW R7, (R8), R9
CBNZ R9, load_store_loop
// 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), R3
MOVD $runtime·sigprofCallers(SB), R4
MOVD $runtime·sigprofNonGoWrapper<>(SB), R5
MOVD _cgo_callers(SB), R13
MOVD R10, LR // restore
MOVD R11, R27
MOVD R12, g
B (R13)
TEXT runtime·sysMmap(SB),NOSPLIT|NOFRAME,$0
MOVD addr+0(FP), R0
MOVD n+8(FP), R1
MOVW prot+16(FP), R2
MOVW flags+20(FP), R3
MOVW fd+24(FP), R4
MOVW off+28(FP), R5
MOVD $SYS_mmap, R8
SVC
CMN $4095, R0
BCC ok
NEG R0,R0
MOVD $0, p+32(FP)
MOVD R0, err+40(FP)
RET
ok:
MOVD R0, p+32(FP)
MOVD $0, err+40(FP)
RET
// Call the function stored in _cgo_mmap using the GCC calling convention.
// This must be called on the system stack.
TEXT runtime·callCgoMmap(SB),NOSPLIT,$0
MOVD addr+0(FP), R0
MOVD n+8(FP), R1
MOVW prot+16(FP), R2
MOVW flags+20(FP), R3
MOVW fd+24(FP), R4
MOVW off+28(FP), R5
MOVD _cgo_mmap(SB), R9
SUB $16, RSP // reserve 16 bytes for sp-8 where fp may be saved.
BL R9
ADD $16, RSP
MOVD R0, ret+32(FP)
RET
TEXT runtime·sysMunmap(SB),NOSPLIT|NOFRAME,$0
MOVD addr+0(FP), R0
MOVD n+8(FP), R1
MOVD $SYS_munmap, R8
SVC
CMN $4095, R0
BCC cool
MOVD R0, 0xf0(R0)
cool:
RET
// Call the function stored in _cgo_munmap using the GCC calling convention.
// This must be called on the system stack.
TEXT runtime·callCgoMunmap(SB),NOSPLIT,$0
MOVD addr+0(FP), R0
MOVD n+8(FP), R1
MOVD _cgo_munmap(SB), R9
SUB $16, RSP // reserve 16 bytes for sp-8 where fp may be saved.
BL R9
ADD $16, RSP
RET
TEXT runtime·madvise(SB),NOSPLIT|NOFRAME,$0
MOVD addr+0(FP), R0
MOVD n+8(FP), R1
MOVW flags+16(FP), R2
MOVD $SYS_madvise, R8
SVC
MOVW R0, 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), R0
MOVW op+8(FP), R1
MOVW val+12(FP), R2
MOVD ts+16(FP), R3
MOVD addr2+24(FP), R4
MOVW val3+32(FP), R5
MOVD $SYS_futex, R8
SVC
MOVW R0, 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), R0
MOVD stk+8(FP), R1
// Copy mp, gp, fn off parent stack for use by child.
MOVD mp+16(FP), R10
MOVD gp+24(FP), R11
MOVD fn+32(FP), R12
MOVD R10, -8(R1)
MOVD R11, -16(R1)
MOVD R12, -24(R1)
MOVD $1234, R10
MOVD R10, -32(R1)
MOVD $SYS_clone, R8
SVC
// In parent, return.
CMP ZR, R0
BEQ child
MOVW R0, ret+40(FP)
RET
child:
// In child, on new stack.
MOVD -32(RSP), R10
MOVD $1234, R0
CMP R0, R10
BEQ good
MOVD $0, R0
MOVD R0, (R0) // crash
good:
// Initialize m->procid to Linux tid
MOVD $SYS_gettid, R8
SVC
MOVD -24(RSP), R12 // fn
MOVD -16(RSP), R11 // g
MOVD -8(RSP), R10 // m
CMP $0, R10
BEQ nog
CMP $0, R11
BEQ nog
MOVD R0, m_procid(R10)
// TODO: setup TLS.
// In child, set up new stack
MOVD R10, g_m(R11)
MOVD R11, g
//CALL runtime·stackcheck(SB)
nog:
// Call fn
MOVD R12, R0
BL (R0)
// It shouldn't return. If it does, exit that thread.
MOVW $111, R0
again:
MOVD $SYS_exit, R8
SVC
B again // keep exiting
TEXT runtime·sigaltstack(SB),NOSPLIT|NOFRAME,$0
MOVD new+0(FP), R0
MOVD old+8(FP), R1
MOVD $SYS_sigaltstack, R8
SVC
CMN $4095, R0
BCC ok
MOVD $0, R0
MOVD R0, (R0) // crash
ok:
RET
TEXT runtime·osyield(SB),NOSPLIT|NOFRAME,$0
MOVD $SYS_sched_yield, R8
SVC
RET
TEXT runtime·sched_getaffinity(SB),NOSPLIT|NOFRAME,$0
MOVD pid+0(FP), R0
MOVD len+8(FP), R1
MOVD buf+16(FP), R2
MOVD $SYS_sched_getaffinity, R8
SVC
MOVW R0, ret+24(FP)
RET
// int access(const char *name, int mode)
TEXT runtime·access(SB),NOSPLIT,$0-20
MOVD $AT_FDCWD, R0
MOVD name+0(FP), R1
MOVW mode+8(FP), R2
MOVD $SYS_faccessat, R8
SVC
MOVW R0, ret+16(FP)
RET
// int connect(int fd, const struct sockaddr *addr, socklen_t len)
TEXT runtime·connect(SB),NOSPLIT,$0-28
MOVW fd+0(FP), R0
MOVD addr+8(FP), R1
MOVW len+16(FP), R2
MOVD $SYS_connect, R8
SVC
MOVW R0, ret+24(FP)
RET
// int socket(int domain, int typ, int prot)
TEXT runtime·socket(SB),NOSPLIT,$0-20
MOVW domain+0(FP), R0
MOVW typ+4(FP), R1
MOVW prot+8(FP), R2
MOVD $SYS_socket, R8
SVC
MOVW R0, ret+16(FP)
RET
// func sbrk0() uintptr
TEXT runtime·sbrk0(SB),NOSPLIT,$0-8
// Implemented as brk(NULL).
MOVD $0, R0
MOVD $SYS_brk, R8
SVC
MOVD R0, ret+0(FP)
RET
TEXT runtime·sigreturn(SB),NOSPLIT,$0-0
RET