blob: 1177bc1baa22afa4df03beb4bd750b9267f95f00 [file] [log] [blame] [edit]
// Copyright 2009 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 AMD64, OpenBSD.
// System calls are implemented in libc/libpthread, this file
// contains trampolines that convert from Go to C calling convention.
// Some direct system call implementations currently remain.
//
#include "go_asm.h"
#include "go_tls.h"
#include "textflag.h"
#include "cgo/abi_amd64.h"
#define CLOCK_MONOTONIC $3
TEXT runtime·settls(SB),NOSPLIT,$0
// Nothing to do, pthread already set thread-local storage up.
RET
// 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,$0
// DI points to the m.
// We are already on m's g0 stack.
// Transition from C ABI to Go ABI.
PUSH_REGS_HOST_TO_ABI0()
// Load g and save to TLS entry.
// See cmd/link/internal/ld/sym.go:computeTLSOffset.
MOVQ m_g0(DI), DX // g
MOVQ DX, -8(FS)
CALL runtime·mstart(SB)
POP_REGS_HOST_TO_ABI0()
// 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).
XORL AX, AX
RET
TEXT runtime·sigfwd(SB),NOSPLIT,$0-32
MOVQ fn+0(FP), AX
MOVL sig+8(FP), DI
MOVQ info+16(FP), SI
MOVQ ctx+24(FP), DX
PUSHQ BP
MOVQ SP, BP
ANDQ $~15, SP // alignment for x86_64 ABI
CALL AX
MOVQ BP, SP
POPQ BP
RET
// Called using C ABI.
TEXT runtime·sigtramp(SB),NOSPLIT|TOPFRAME,$0
// Transition from C ABI to Go ABI.
PUSH_REGS_HOST_TO_ABI0()
// Set up ABIInternal environment: g in R14, cleared X15.
get_tls(R12)
MOVQ g(R12), R14
PXOR X15, X15
// Reserve space for spill slots.
NOP SP // disable vet stack checking
ADJSP $24
// Call into the Go signal handler
MOVQ DI, AX // sig
MOVQ SI, BX // info
MOVQ DX, CX // ctx
CALL ·sigtrampgo<ABIInternal>(SB)
ADJSP $-24
POP_REGS_HOST_TO_ABI0()
RET
//
// These trampolines help convert from Go calling convention to C calling convention.
// They should be called with asmcgocall.
// A pointer to the arguments is passed in DI.
// A single int32 result is returned in AX.
// (For more results, make an args/results structure.)
TEXT runtime·pthread_attr_init_trampoline(SB),NOSPLIT,$0
PUSHQ BP
MOVQ SP, BP
MOVQ 0(DI), DI // arg 1 - attr
CALL libc_pthread_attr_init(SB)
POPQ BP
RET
TEXT runtime·pthread_attr_destroy_trampoline(SB),NOSPLIT,$0
PUSHQ BP
MOVQ SP, BP
MOVQ 0(DI), DI // arg 1 - attr
CALL libc_pthread_attr_destroy(SB)
POPQ BP
RET
TEXT runtime·pthread_attr_getstacksize_trampoline(SB),NOSPLIT,$0
PUSHQ BP
MOVQ SP, BP
MOVQ 8(DI), SI // arg 2 - stacksize
MOVQ 0(DI), DI // arg 1 - attr
CALL libc_pthread_attr_getstacksize(SB)
POPQ BP
RET
TEXT runtime·pthread_attr_setdetachstate_trampoline(SB),NOSPLIT,$0
PUSHQ BP
MOVQ SP, BP
MOVQ 8(DI), SI // arg 2 - detachstate
MOVQ 0(DI), DI // arg 1 - attr
CALL libc_pthread_attr_setdetachstate(SB)
POPQ BP
RET
TEXT runtime·pthread_create_trampoline(SB),NOSPLIT,$0
PUSHQ BP
MOVQ SP, BP
SUBQ $16, SP
MOVQ 0(DI), SI // arg 2 - attr
MOVQ 8(DI), DX // arg 3 - start
MOVQ 16(DI), CX // arg 4 - arg
MOVQ SP, DI // arg 1 - &thread (discarded)
CALL libc_pthread_create(SB)
MOVQ BP, SP
POPQ BP
RET
TEXT runtime·thrkill_trampoline(SB),NOSPLIT,$0
PUSHQ BP
MOVQ SP, BP
MOVL 8(DI), SI // arg 2 - signal
MOVQ $0, DX // arg 3 - tcb
MOVL 0(DI), DI // arg 1 - tid
CALL libc_thrkill(SB)
POPQ BP
RET
TEXT runtime·thrsleep_trampoline(SB),NOSPLIT,$0
PUSHQ BP
MOVQ SP, BP
MOVL 8(DI), SI // arg 2 - clock_id
MOVQ 16(DI), DX // arg 3 - abstime
MOVQ 24(DI), CX // arg 4 - lock
MOVQ 32(DI), R8 // arg 5 - abort
MOVQ 0(DI), DI // arg 1 - id
CALL libc_thrsleep(SB)
POPQ BP
RET
TEXT runtime·thrwakeup_trampoline(SB),NOSPLIT,$0
PUSHQ BP
MOVQ SP, BP
MOVL 8(DI), SI // arg 2 - count
MOVQ 0(DI), DI // arg 1 - id
CALL libc_thrwakeup(SB)
POPQ BP
RET
TEXT runtime·exit_trampoline(SB),NOSPLIT,$0
PUSHQ BP
MOVQ SP, BP
MOVL 0(DI), DI // arg 1 exit status
CALL libc_exit(SB)
MOVL $0xf1, 0xf1 // crash
POPQ BP
RET
TEXT runtime·getthrid_trampoline(SB),NOSPLIT,$0
PUSHQ BP
MOVQ SP, BP
MOVQ DI, BX // BX is caller-save
CALL libc_getthrid(SB)
MOVL AX, 0(BX) // return value
POPQ BP
RET
TEXT runtime·raiseproc_trampoline(SB),NOSPLIT,$0
PUSHQ BP
MOVQ SP, BP
MOVL 0(DI), BX // signal
CALL libc_getpid(SB)
MOVL AX, DI // arg 1 pid
MOVL BX, SI // arg 2 signal
CALL libc_kill(SB)
POPQ BP
RET
TEXT runtime·sched_yield_trampoline(SB),NOSPLIT,$0
PUSHQ BP
MOVQ SP, BP
CALL libc_sched_yield(SB)
POPQ BP
RET
TEXT runtime·mmap_trampoline(SB),NOSPLIT,$0
PUSHQ BP // make a frame; keep stack aligned
MOVQ SP, BP
MOVQ DI, BX
MOVQ 0(BX), DI // arg 1 addr
MOVQ 8(BX), SI // arg 2 len
MOVL 16(BX), DX // arg 3 prot
MOVL 20(BX), CX // arg 4 flags
MOVL 24(BX), R8 // arg 5 fid
MOVL 28(BX), R9 // arg 6 offset
CALL libc_mmap(SB)
XORL DX, DX
CMPQ AX, $-1
JNE ok
CALL libc_errno(SB)
MOVLQSX (AX), DX // errno
XORQ AX, AX
ok:
MOVQ AX, 32(BX)
MOVQ DX, 40(BX)
POPQ BP
RET
TEXT runtime·munmap_trampoline(SB),NOSPLIT,$0
PUSHQ BP
MOVQ SP, BP
MOVQ 8(DI), SI // arg 2 len
MOVQ 0(DI), DI // arg 1 addr
CALL libc_munmap(SB)
TESTQ AX, AX
JEQ 2(PC)
MOVL $0xf1, 0xf1 // crash
POPQ BP
RET
TEXT runtime·madvise_trampoline(SB), NOSPLIT, $0
PUSHQ BP
MOVQ SP, BP
MOVQ 8(DI), SI // arg 2 len
MOVL 16(DI), DX // arg 3 advice
MOVQ 0(DI), DI // arg 1 addr
CALL libc_madvise(SB)
// ignore failure - maybe pages are locked
POPQ BP
RET
TEXT runtime·open_trampoline(SB),NOSPLIT,$0
PUSHQ BP
MOVQ SP, BP
MOVL 8(DI), SI // arg 2 - flags
MOVL 12(DI), DX // arg 3 - mode
MOVQ 0(DI), DI // arg 1 - path
XORL AX, AX // vararg: say "no float args"
CALL libc_open(SB)
POPQ BP
RET
TEXT runtime·close_trampoline(SB),NOSPLIT,$0
PUSHQ BP
MOVQ SP, BP
MOVL 0(DI), DI // arg 1 - fd
CALL libc_close(SB)
POPQ BP
RET
TEXT runtime·read_trampoline(SB),NOSPLIT,$0
PUSHQ BP
MOVQ SP, BP
MOVQ 8(DI), SI // arg 2 - buf
MOVL 16(DI), DX // arg 3 - count
MOVL 0(DI), DI // arg 1 - fd
CALL libc_read(SB)
TESTL AX, AX
JGE noerr
CALL libc_errno(SB)
MOVL (AX), AX // errno
NEGL AX // caller expects negative errno value
noerr:
POPQ BP
RET
TEXT runtime·write_trampoline(SB),NOSPLIT,$0
PUSHQ BP
MOVQ SP, BP
MOVQ 8(DI), SI // arg 2 buf
MOVL 16(DI), DX // arg 3 count
MOVL 0(DI), DI // arg 1 fd
CALL libc_write(SB)
TESTL AX, AX
JGE noerr
CALL libc_errno(SB)
MOVL (AX), AX // errno
NEGL AX // caller expects negative errno value
noerr:
POPQ BP
RET
TEXT runtime·pipe2_trampoline(SB),NOSPLIT,$0
PUSHQ BP
MOVQ SP, BP
MOVL 8(DI), SI // arg 2 flags
MOVQ 0(DI), DI // arg 1 filedes
CALL libc_pipe2(SB)
TESTL AX, AX
JEQ 3(PC)
CALL libc_errno(SB)
MOVL (AX), AX // errno
NEGL AX // caller expects negative errno value
POPQ BP
RET
TEXT runtime·setitimer_trampoline(SB),NOSPLIT,$0
PUSHQ BP
MOVQ SP, BP
MOVQ 8(DI), SI // arg 2 new
MOVQ 16(DI), DX // arg 3 old
MOVL 0(DI), DI // arg 1 which
CALL libc_setitimer(SB)
POPQ BP
RET
TEXT runtime·usleep_trampoline(SB),NOSPLIT,$0
PUSHQ BP
MOVQ SP, BP
MOVL 0(DI), DI // arg 1 usec
CALL libc_usleep(SB)
POPQ BP
RET
TEXT runtime·sysctl_trampoline(SB),NOSPLIT,$0
PUSHQ BP
MOVQ SP, BP
MOVL 8(DI), SI // arg 2 miblen
MOVQ 16(DI), DX // arg 3 out
MOVQ 24(DI), CX // arg 4 size
MOVQ 32(DI), R8 // arg 5 dst
MOVQ 40(DI), R9 // arg 6 ndst
MOVQ 0(DI), DI // arg 1 mib
CALL libc_sysctl(SB)
POPQ BP
RET
TEXT runtime·kqueue_trampoline(SB),NOSPLIT,$0
PUSHQ BP
MOVQ SP, BP
CALL libc_kqueue(SB)
POPQ BP
RET
TEXT runtime·kevent_trampoline(SB),NOSPLIT,$0
PUSHQ BP
MOVQ SP, BP
MOVQ 8(DI), SI // arg 2 keventt
MOVL 16(DI), DX // arg 3 nch
MOVQ 24(DI), CX // arg 4 ev
MOVL 32(DI), R8 // arg 5 nev
MOVQ 40(DI), R9 // arg 6 ts
MOVL 0(DI), DI // arg 1 kq
CALL libc_kevent(SB)
CMPL AX, $-1
JNE ok
CALL libc_errno(SB)
MOVL (AX), AX // errno
NEGL AX // caller expects negative errno value
ok:
POPQ BP
RET
TEXT runtime·clock_gettime_trampoline(SB),NOSPLIT,$0
PUSHQ BP // make a frame; keep stack aligned
MOVQ SP, BP
MOVQ 8(DI), SI // arg 2 tp
MOVL 0(DI), DI // arg 1 clock_id
CALL libc_clock_gettime(SB)
TESTL AX, AX
JEQ noerr
CALL libc_errno(SB)
MOVL (AX), AX // errno
NEGL AX // caller expects negative errno value
noerr:
POPQ BP
RET
TEXT runtime·fcntl_trampoline(SB),NOSPLIT,$0
PUSHQ BP
MOVQ SP, BP
MOVQ DI, BX
MOVL 0(BX), DI // arg 1 fd
MOVL 4(BX), SI // arg 2 cmd
MOVL 8(BX), DX // arg 3 arg
XORL AX, AX // vararg: say "no float args"
CALL libc_fcntl(SB)
XORL DX, DX
CMPL AX, $-1
JNE noerr
CALL libc_errno(SB)
MOVL (AX), DX
MOVL $-1, AX
noerr:
MOVL AX, 12(BX)
MOVL DX, 16(BX)
POPQ BP
RET
TEXT runtime·sigaction_trampoline(SB),NOSPLIT,$0
PUSHQ BP
MOVQ SP, BP
MOVQ 8(DI), SI // arg 2 new
MOVQ 16(DI), DX // arg 3 old
MOVL 0(DI), DI // arg 1 sig
CALL libc_sigaction(SB)
TESTL AX, AX
JEQ 2(PC)
MOVL $0xf1, 0xf1 // crash
POPQ BP
RET
TEXT runtime·sigprocmask_trampoline(SB),NOSPLIT,$0
PUSHQ BP
MOVQ SP, BP
MOVQ 8(DI), SI // arg 2 new
MOVQ 16(DI), DX // arg 3 old
MOVL 0(DI), DI // arg 1 how
CALL libc_pthread_sigmask(SB)
TESTL AX, AX
JEQ 2(PC)
MOVL $0xf1, 0xf1 // crash
POPQ BP
RET
TEXT runtime·sigaltstack_trampoline(SB),NOSPLIT,$0
PUSHQ BP
MOVQ SP, BP
MOVQ 8(DI), SI // arg 2 old
MOVQ 0(DI), DI // arg 1 new
CALL libc_sigaltstack(SB)
TESTQ AX, AX
JEQ 2(PC)
MOVL $0xf1, 0xf1 // crash
POPQ BP
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).
//
// syscall expects a 32-bit result and tests for 32-bit -1
// to decide there was an error.
TEXT runtime·syscall(SB),NOSPLIT,$0
PUSHQ BP
MOVQ SP, BP
SUBQ $16, SP
MOVQ (0*8)(DI), CX // fn
MOVQ (2*8)(DI), SI // a2
MOVQ (3*8)(DI), DX // a3
MOVQ DI, (SP)
MOVQ (1*8)(DI), DI // a1
XORL AX, AX // vararg: say "no float args"
CALL CX
MOVQ (SP), DI
MOVQ AX, (4*8)(DI) // r1
MOVQ DX, (5*8)(DI) // r2
// Standard libc functions return -1 on error
// and set errno.
CMPL AX, $-1 // Note: high 32 bits are junk
JNE ok
// Get error code from libc.
CALL libc_errno(SB)
MOVLQSX (AX), AX
MOVQ (SP), DI
MOVQ AX, (6*8)(DI) // err
ok:
XORL AX, AX // no error (it's ignored anyway)
MOVQ BP, SP
POPQ BP
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).
//
// syscallX is like syscall but expects a 64-bit result
// and tests for 64-bit -1 to decide there was an error.
TEXT runtime·syscallX(SB),NOSPLIT,$0
PUSHQ BP
MOVQ SP, BP
SUBQ $16, SP
MOVQ (0*8)(DI), CX // fn
MOVQ (2*8)(DI), SI // a2
MOVQ (3*8)(DI), DX // a3
MOVQ DI, (SP)
MOVQ (1*8)(DI), DI // a1
XORL AX, AX // vararg: say "no float args"
CALL CX
MOVQ (SP), DI
MOVQ AX, (4*8)(DI) // r1
MOVQ DX, (5*8)(DI) // r2
// Standard libc functions return -1 on error
// and set errno.
CMPQ AX, $-1
JNE ok
// Get error code from libc.
CALL libc_errno(SB)
MOVLQSX (AX), AX
MOVQ (SP), DI
MOVQ AX, (6*8)(DI) // err
ok:
XORL AX, AX // no error (it's ignored anyway)
MOVQ BP, SP
POPQ BP
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).
//
// syscall6 expects a 32-bit result and tests for 32-bit -1
// to decide there was an error.
TEXT runtime·syscall6(SB),NOSPLIT,$0
PUSHQ BP
MOVQ SP, BP
SUBQ $16, SP
MOVQ (0*8)(DI), R11// fn
MOVQ (2*8)(DI), SI // a2
MOVQ (3*8)(DI), DX // a3
MOVQ (4*8)(DI), CX // a4
MOVQ (5*8)(DI), R8 // a5
MOVQ (6*8)(DI), R9 // a6
MOVQ DI, (SP)
MOVQ (1*8)(DI), DI // a1
XORL AX, AX // vararg: say "no float args"
CALL R11
MOVQ (SP), DI
MOVQ AX, (7*8)(DI) // r1
MOVQ DX, (8*8)(DI) // r2
CMPL AX, $-1
JNE ok
CALL libc_errno(SB)
MOVLQSX (AX), AX
MOVQ (SP), DI
MOVQ AX, (9*8)(DI) // err
ok:
XORL AX, AX // no error (it's ignored anyway)
MOVQ BP, SP
POPQ BP
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).
//
// syscall6X is like syscall6 but expects a 64-bit result
// and tests for 64-bit -1 to decide there was an error.
TEXT runtime·syscall6X(SB),NOSPLIT,$0
PUSHQ BP
MOVQ SP, BP
SUBQ $16, SP
MOVQ (0*8)(DI), R11// fn
MOVQ (2*8)(DI), SI // a2
MOVQ (3*8)(DI), DX // a3
MOVQ (4*8)(DI), CX // a4
MOVQ (5*8)(DI), R8 // a5
MOVQ (6*8)(DI), R9 // a6
MOVQ DI, (SP)
MOVQ (1*8)(DI), DI // a1
XORL AX, AX // vararg: say "no float args"
CALL R11
MOVQ (SP), DI
MOVQ AX, (7*8)(DI) // r1
MOVQ DX, (8*8)(DI) // r2
CMPQ AX, $-1
JNE ok
CALL libc_errno(SB)
MOVLQSX (AX), AX
MOVQ (SP), DI
MOVQ AX, (9*8)(DI) // err
ok:
XORL AX, AX // no error (it's ignored anyway)
MOVQ BP, SP
POPQ BP
RET
// syscall10 calls a function in libc on behalf of the syscall package.
// syscall10 takes a pointer to a struct like:
// struct {
// fn uintptr
// a1 uintptr
// a2 uintptr
// a3 uintptr
// a4 uintptr
// a5 uintptr
// a6 uintptr
// a7 uintptr
// a8 uintptr
// a9 uintptr
// a10 uintptr
// r1 uintptr
// r2 uintptr
// err uintptr
// }
// syscall10 must be called on the g0 stack with the
// C calling convention (use libcCall).
TEXT runtime·syscall10(SB),NOSPLIT,$0
PUSHQ BP
MOVQ SP, BP
SUBQ $48, SP
// Arguments a1 to a6 get passed in registers, with a7 onwards being
// passed via the stack per the x86-64 System V ABI
// (https://github.com/hjl-tools/x86-psABI/wiki/x86-64-psABI-1.0.pdf).
MOVQ (7*8)(DI), R10 // a7
MOVQ (8*8)(DI), R11 // a8
MOVQ (9*8)(DI), R12 // a9
MOVQ (10*8)(DI), R13 // a10
MOVQ R10, (0*8)(SP) // a7
MOVQ R11, (1*8)(SP) // a8
MOVQ R12, (2*8)(SP) // a9
MOVQ R13, (3*8)(SP) // a10
MOVQ (0*8)(DI), R11 // fn
MOVQ (2*8)(DI), SI // a2
MOVQ (3*8)(DI), DX // a3
MOVQ (4*8)(DI), CX // a4
MOVQ (5*8)(DI), R8 // a5
MOVQ (6*8)(DI), R9 // a6
MOVQ DI, (4*8)(SP)
MOVQ (1*8)(DI), DI // a1
XORL AX, AX // vararg: say "no float args"
CALL R11
MOVQ (4*8)(SP), DI
MOVQ AX, (11*8)(DI) // r1
MOVQ DX, (12*8)(DI) // r2
CMPL AX, $-1
JNE ok
CALL libc_errno(SB)
MOVLQSX (AX), AX
MOVQ (4*8)(SP), DI
MOVQ AX, (13*8)(DI) // err
ok:
XORL AX, AX // no error (it's ignored anyway)
MOVQ BP, SP
POPQ BP
RET
// syscall10X calls a function in libc on behalf of the syscall package.
// syscall10X takes a pointer to a struct like:
// struct {
// fn uintptr
// a1 uintptr
// a2 uintptr
// a3 uintptr
// a4 uintptr
// a5 uintptr
// a6 uintptr
// a7 uintptr
// a8 uintptr
// a9 uintptr
// a10 uintptr
// r1 uintptr
// r2 uintptr
// err uintptr
// }
// syscall10X must be called on the g0 stack with the
// C calling convention (use libcCall).
//
// syscall10X is like syscall10 but expects a 64-bit result
// and tests for 64-bit -1 to decide there was an error.
TEXT runtime·syscall10X(SB),NOSPLIT,$0
PUSHQ BP
MOVQ SP, BP
SUBQ $48, SP
// Arguments a1 to a6 get passed in registers, with a7 onwards being
// passed via the stack per the x86-64 System V ABI
// (https://github.com/hjl-tools/x86-psABI/wiki/x86-64-psABI-1.0.pdf).
MOVQ (7*8)(DI), R10 // a7
MOVQ (8*8)(DI), R11 // a8
MOVQ (9*8)(DI), R12 // a9
MOVQ (10*8)(DI), R13 // a10
MOVQ R10, (0*8)(SP) // a7
MOVQ R11, (1*8)(SP) // a8
MOVQ R12, (2*8)(SP) // a9
MOVQ R13, (3*8)(SP) // a10
MOVQ (0*8)(DI), R11 // fn
MOVQ (2*8)(DI), SI // a2
MOVQ (3*8)(DI), DX // a3
MOVQ (4*8)(DI), CX // a4
MOVQ (5*8)(DI), R8 // a5
MOVQ (6*8)(DI), R9 // a6
MOVQ DI, (4*8)(SP)
MOVQ (1*8)(DI), DI // a1
XORL AX, AX // vararg: say "no float args"
CALL R11
MOVQ (4*8)(SP), DI
MOVQ AX, (11*8)(DI) // r1
MOVQ DX, (12*8)(DI) // r2
CMPQ AX, $-1
JNE ok
CALL libc_errno(SB)
MOVLQSX (AX), AX
MOVQ (4*8)(SP), DI
MOVQ AX, (13*8)(DI) // err
ok:
XORL AX, AX // no error (it's ignored anyway)
MOVQ BP, SP
POPQ BP
RET
TEXT runtime·issetugid_trampoline(SB),NOSPLIT,$0
MOVQ DI, BX // BX is caller-save
CALL libc_issetugid(SB)
MOVL AX, 0(BX) // return value
RET