syscall_linux.go

     1  // Copyright 2022 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  // Package syscall provides the syscall primitives required for the runtime.
     6  package syscall
     7  
     8  import (
     9  	"unsafe"
    10  )
    11  
    12  // TODO(https://go.dev/issue/51087): This package is incomplete and currently
    13  // only contains very minimal support for Linux.
    14  
    15  // Syscall6 calls system call number 'num' with arguments a1-6.
    16  func Syscall6(num, a1, a2, a3, a4, a5, a6 uintptr) (r1, r2, errno uintptr)
    17  
    18  // syscall_RawSyscall6 is a push linkname to export Syscall6 as
    19  // syscall.RawSyscall6.
    20  //
    21  // //go:uintptrkeepalive because the uintptr argument may be converted pointers
    22  // that need to be kept alive in the caller (this is implied for Syscall6 since
    23  // it has no body).
    24  //
    25  // //go:nosplit because stack copying does not account for uintptrkeepalive, so
    26  // the stack must not grow. Stack copying cannot blindly assume that all
    27  // uintptr arguments are pointers, because some values may look like pointers,
    28  // but not really be pointers, and adjusting their value would break the call.
    29  //
    30  // This is a separate wrapper because we can't export one function as two
    31  // names. The assembly implementations name themselves Syscall6 would not be
    32  // affected by a linkname.
    33  //
    34  //go:uintptrkeepalive
    35  //go:nosplit
    36  //go:linkname syscall_RawSyscall6 syscall.RawSyscall6
    37  func syscall_RawSyscall6(num, a1, a2, a3, a4, a5, a6 uintptr) (r1, r2, errno uintptr) {
    38  	return Syscall6(num, a1, a2, a3, a4, a5, a6)
    39  }
    40  
    41  func EpollCreate1(flags int32) (fd int32, errno uintptr) {
    42  	r1, _, e := Syscall6(SYS_EPOLL_CREATE1, uintptr(flags), 0, 0, 0, 0, 0)
    43  	return int32(r1), e
    44  }
    45  
    46  var _zero uintptr
    47  
    48  func EpollWait(epfd int32, events []EpollEvent, maxev, waitms int32) (n int32, errno uintptr) {
    49  	var ev unsafe.Pointer
    50  	if len(events) > 0 {
    51  		ev = unsafe.Pointer(&events[0])
    52  	} else {
    53  		ev = unsafe.Pointer(&_zero)
    54  	}
    55  	r1, _, e := Syscall6(SYS_EPOLL_PWAIT, uintptr(epfd), uintptr(ev), uintptr(maxev), uintptr(waitms), 0, 0)
    56  	return int32(r1), e
    57  }
    58  
    59  func EpollCtl(epfd, op, fd int32, event *EpollEvent) (errno uintptr) {
    60  	_, _, e := Syscall6(SYS_EPOLL_CTL, uintptr(epfd), uintptr(op), uintptr(fd), uintptr(unsafe.Pointer(event)), 0, 0)
    61  	return e
    62  }
    63
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