blob: 7be8c4c7242485df682ae19d99e3b4a4d30834b3 [file] [log] [blame]
// 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.
// +build linux
// +build 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_pipe 42
#define SYS_brk 45
#define SYS_fcntl 55
#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_epoll_create 236
#define SYS_epoll_ctl 237
#define SYS_epoll_wait 238
#define SYS_clock_gettime 246
#define SYS_tgkill 250
#define SYS_epoll_create1 315
#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 *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 pipe() (r, w int32, errno int32)
TEXT runtime·pipe(SB),NOSPLIT|NOFRAME,$0-12
ADD $FIXED_FRAME, R1, R3
SYSCALL $SYS_pipe
MOVW R3, errno+8(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·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 walltime1() (sec int64, nsec int32)
TEXT runtime·walltime1(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 R14, m_vdsoPC(R21)
MOVD R15, 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 R14, m_vdsoPC(R21)
MOVD R15, 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
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
TEXT runtime·sigtramp(SB),NOSPLIT,$64
#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,$64
#endif
// 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
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.
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)
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
// int32 runtime·epollcreate(int32 size);
TEXT runtime·epollcreate(SB),NOSPLIT|NOFRAME,$0
MOVW size+0(FP), R3
SYSCALL $SYS_epoll_create
BVC 2(PC)
NEG R3 // caller expects negative errno
MOVW R3, ret+8(FP)
RET
// int32 runtime·epollcreate1(int32 flags);
TEXT runtime·epollcreate1(SB),NOSPLIT|NOFRAME,$0
MOVW flags+0(FP), R3
SYSCALL $SYS_epoll_create1
BVC 2(PC)
NEG R3 // caller expects negative errno
MOVW R3, ret+8(FP)
RET
// func epollctl(epfd, op, fd int32, ev *epollEvent) int
TEXT runtime·epollctl(SB),NOSPLIT|NOFRAME,$0
MOVW epfd+0(FP), R3
MOVW op+4(FP), R4
MOVW fd+8(FP), R5
MOVD ev+16(FP), R6
SYSCALL $SYS_epoll_ctl
NEG R3 // caller expects negative errno
MOVW R3, ret+24(FP)
RET
// int32 runtime·epollwait(int32 epfd, EpollEvent *ev, int32 nev, int32 timeout);
TEXT runtime·epollwait(SB),NOSPLIT|NOFRAME,$0
MOVW epfd+0(FP), R3
MOVD ev+8(FP), R4
MOVW nev+16(FP), R5
MOVW timeout+20(FP), R6
SYSCALL $SYS_epoll_wait
BVC 2(PC)
NEG R3 // caller expects negative errno
MOVW R3, ret+24(FP)
RET
// void runtime·closeonexec(int32 fd);
TEXT runtime·closeonexec(SB),NOSPLIT|NOFRAME,$0
MOVW fd+0(FP), R3 // fd
MOVD $2, R4 // F_SETFD
MOVD $1, R5 // FD_CLOEXEC
SYSCALL $SYS_fcntl
RET
// func runtime·setNonblock(int32 fd)
TEXT runtime·setNonblock(SB),NOSPLIT|NOFRAME,$0-4
MOVW fd+0(FP), R3 // fd
MOVD $3, R4 // F_GETFL
MOVD $0, R5
SYSCALL $SYS_fcntl
OR $0x800, R3, R5 // O_NONBLOCK
MOVW fd+0(FP), R3 // fd
MOVD $4, R4 // F_SETFL
SYSCALL $SYS_fcntl
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