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Source file src/syscall/syscall_linux.go

Documentation: syscall

  // 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.
  
  // Linux system calls.
  // This file is compiled as ordinary Go code,
  // but it is also input to mksyscall,
  // which parses the //sys lines and generates system call stubs.
  // Note that sometimes we use a lowercase //sys name and
  // wrap it in our own nicer implementation.
  
  package syscall
  
  import "unsafe"
  
  /*
   * Wrapped
   */
  
  func Access(path string, mode uint32) (err error) {
  	return Faccessat(_AT_FDCWD, path, mode, 0)
  }
  
  func Chmod(path string, mode uint32) (err error) {
  	return Fchmodat(_AT_FDCWD, path, mode, 0)
  }
  
  func Chown(path string, uid int, gid int) (err error) {
  	return Fchownat(_AT_FDCWD, path, uid, gid, 0)
  }
  
  func Creat(path string, mode uint32) (fd int, err error) {
  	return Open(path, O_CREAT|O_WRONLY|O_TRUNC, mode)
  }
  
  //sys	linkat(olddirfd int, oldpath string, newdirfd int, newpath string, flags int) (err error)
  
  func Link(oldpath string, newpath string) (err error) {
  	return linkat(_AT_FDCWD, oldpath, _AT_FDCWD, newpath, 0)
  }
  
  func Mkdir(path string, mode uint32) (err error) {
  	return Mkdirat(_AT_FDCWD, path, mode)
  }
  
  func Mknod(path string, mode uint32, dev int) (err error) {
  	return Mknodat(_AT_FDCWD, path, mode, dev)
  }
  
  func Open(path string, mode int, perm uint32) (fd int, err error) {
  	return openat(_AT_FDCWD, path, mode|O_LARGEFILE, perm)
  }
  
  //sys	openat(dirfd int, path string, flags int, mode uint32) (fd int, err error)
  
  func Openat(dirfd int, path string, flags int, mode uint32) (fd int, err error) {
  	return openat(dirfd, path, flags|O_LARGEFILE, mode)
  }
  
  //sys	readlinkat(dirfd int, path string, buf []byte) (n int, err error)
  
  func Readlink(path string, buf []byte) (n int, err error) {
  	return readlinkat(_AT_FDCWD, path, buf)
  }
  
  func Rename(oldpath string, newpath string) (err error) {
  	return Renameat(_AT_FDCWD, oldpath, _AT_FDCWD, newpath)
  }
  
  func Rmdir(path string) error {
  	return unlinkat(_AT_FDCWD, path, _AT_REMOVEDIR)
  }
  
  //sys	symlinkat(oldpath string, newdirfd int, newpath string) (err error)
  
  func Symlink(oldpath string, newpath string) (err error) {
  	return symlinkat(oldpath, _AT_FDCWD, newpath)
  }
  
  func Unlink(path string) error {
  	return unlinkat(_AT_FDCWD, path, 0)
  }
  
  //sys	unlinkat(dirfd int, path string, flags int) (err error)
  
  func Unlinkat(dirfd int, path string) error {
  	return unlinkat(dirfd, path, 0)
  }
  
  //sys	utimes(path string, times *[2]Timeval) (err error)
  
  func Utimes(path string, tv []Timeval) (err error) {
  	if len(tv) != 2 {
  		return EINVAL
  	}
  	return utimes(path, (*[2]Timeval)(unsafe.Pointer(&tv[0])))
  }
  
  //sys	utimensat(dirfd int, path string, times *[2]Timespec) (err error)
  
  func UtimesNano(path string, ts []Timespec) (err error) {
  	if len(ts) != 2 {
  		return EINVAL
  	}
  	err = utimensat(_AT_FDCWD, path, (*[2]Timespec)(unsafe.Pointer(&ts[0])))
  	if err != ENOSYS {
  		return err
  	}
  	// If the utimensat syscall isn't available (utimensat was added to Linux
  	// in 2.6.22, Released, 8 July 2007) then fall back to utimes
  	var tv [2]Timeval
  	for i := 0; i < 2; i++ {
  		tv[i].Sec = ts[i].Sec
  		tv[i].Usec = ts[i].Nsec / 1000
  	}
  	return utimes(path, (*[2]Timeval)(unsafe.Pointer(&tv[0])))
  }
  
  //sys	futimesat(dirfd int, path *byte, times *[2]Timeval) (err error)
  
  func Futimesat(dirfd int, path string, tv []Timeval) (err error) {
  	if len(tv) != 2 {
  		return EINVAL
  	}
  	pathp, err := BytePtrFromString(path)
  	if err != nil {
  		return err
  	}
  	err = futimesat(dirfd, pathp, (*[2]Timeval)(unsafe.Pointer(&tv[0])))
  	use(unsafe.Pointer(pathp))
  	return err
  }
  
  func Futimes(fd int, tv []Timeval) (err error) {
  	// Believe it or not, this is the best we can do on Linux
  	// (and is what glibc does).
  	return Utimes("/proc/self/fd/"+itoa(fd), tv)
  }
  
  const ImplementsGetwd = true
  
  //sys	Getcwd(buf []byte) (n int, err error)
  
  func Getwd() (wd string, err error) {
  	var buf [PathMax]byte
  	n, err := Getcwd(buf[0:])
  	if err != nil {
  		return "", err
  	}
  	// Getcwd returns the number of bytes written to buf, including the NUL.
  	if n < 1 || n > len(buf) || buf[n-1] != 0 {
  		return "", EINVAL
  	}
  	return string(buf[0 : n-1]), nil
  }
  
  func Getgroups() (gids []int, err error) {
  	n, err := getgroups(0, nil)
  	if err != nil {
  		return nil, err
  	}
  	if n == 0 {
  		return nil, nil
  	}
  
  	// Sanity check group count. Max is 1<<16 on Linux.
  	if n < 0 || n > 1<<20 {
  		return nil, EINVAL
  	}
  
  	a := make([]_Gid_t, n)
  	n, err = getgroups(n, &a[0])
  	if err != nil {
  		return nil, err
  	}
  	gids = make([]int, n)
  	for i, v := range a[0:n] {
  		gids[i] = int(v)
  	}
  	return
  }
  
  func Setgroups(gids []int) (err error) {
  	if len(gids) == 0 {
  		return setgroups(0, nil)
  	}
  
  	a := make([]_Gid_t, len(gids))
  	for i, v := range gids {
  		a[i] = _Gid_t(v)
  	}
  	return setgroups(len(a), &a[0])
  }
  
  type WaitStatus uint32
  
  // Wait status is 7 bits at bottom, either 0 (exited),
  // 0x7F (stopped), or a signal number that caused an exit.
  // The 0x80 bit is whether there was a core dump.
  // An extra number (exit code, signal causing a stop)
  // is in the high bits. At least that's the idea.
  // There are various irregularities. For example, the
  // "continued" status is 0xFFFF, distinguishing itself
  // from stopped via the core dump bit.
  
  const (
  	mask    = 0x7F
  	core    = 0x80
  	exited  = 0x00
  	stopped = 0x7F
  	shift   = 8
  )
  
  func (w WaitStatus) Exited() bool { return w&mask == exited }
  
  func (w WaitStatus) Signaled() bool { return w&mask != stopped && w&mask != exited }
  
  func (w WaitStatus) Stopped() bool { return w&0xFF == stopped }
  
  func (w WaitStatus) Continued() bool { return w == 0xFFFF }
  
  func (w WaitStatus) CoreDump() bool { return w.Signaled() && w&core != 0 }
  
  func (w WaitStatus) ExitStatus() int {
  	if !w.Exited() {
  		return -1
  	}
  	return int(w>>shift) & 0xFF
  }
  
  func (w WaitStatus) Signal() Signal {
  	if !w.Signaled() {
  		return -1
  	}
  	return Signal(w & mask)
  }
  
  func (w WaitStatus) StopSignal() Signal {
  	if !w.Stopped() {
  		return -1
  	}
  	return Signal(w>>shift) & 0xFF
  }
  
  func (w WaitStatus) TrapCause() int {
  	if w.StopSignal() != SIGTRAP {
  		return -1
  	}
  	return int(w>>shift) >> 8
  }
  
  //sys	wait4(pid int, wstatus *_C_int, options int, rusage *Rusage) (wpid int, err error)
  
  func Wait4(pid int, wstatus *WaitStatus, options int, rusage *Rusage) (wpid int, err error) {
  	var status _C_int
  	wpid, err = wait4(pid, &status, options, rusage)
  	if wstatus != nil {
  		*wstatus = WaitStatus(status)
  	}
  	return
  }
  
  func Mkfifo(path string, mode uint32) (err error) {
  	return Mknod(path, mode|S_IFIFO, 0)
  }
  
  func (sa *SockaddrInet4) sockaddr() (unsafe.Pointer, _Socklen, error) {
  	if sa.Port < 0 || sa.Port > 0xFFFF {
  		return nil, 0, EINVAL
  	}
  	sa.raw.Family = AF_INET
  	p := (*[2]byte)(unsafe.Pointer(&sa.raw.Port))
  	p[0] = byte(sa.Port >> 8)
  	p[1] = byte(sa.Port)
  	for i := 0; i < len(sa.Addr); i++ {
  		sa.raw.Addr[i] = sa.Addr[i]
  	}
  	return unsafe.Pointer(&sa.raw), SizeofSockaddrInet4, nil
  }
  
  func (sa *SockaddrInet6) sockaddr() (unsafe.Pointer, _Socklen, error) {
  	if sa.Port < 0 || sa.Port > 0xFFFF {
  		return nil, 0, EINVAL
  	}
  	sa.raw.Family = AF_INET6
  	p := (*[2]byte)(unsafe.Pointer(&sa.raw.Port))
  	p[0] = byte(sa.Port >> 8)
  	p[1] = byte(sa.Port)
  	sa.raw.Scope_id = sa.ZoneId
  	for i := 0; i < len(sa.Addr); i++ {
  		sa.raw.Addr[i] = sa.Addr[i]
  	}
  	return unsafe.Pointer(&sa.raw), SizeofSockaddrInet6, nil
  }
  
  func (sa *SockaddrUnix) sockaddr() (unsafe.Pointer, _Socklen, error) {
  	name := sa.Name
  	n := len(name)
  	if n >= len(sa.raw.Path) {
  		return nil, 0, EINVAL
  	}
  	sa.raw.Family = AF_UNIX
  	for i := 0; i < n; i++ {
  		sa.raw.Path[i] = int8(name[i])
  	}
  	// length is family (uint16), name, NUL.
  	sl := _Socklen(2)
  	if n > 0 {
  		sl += _Socklen(n) + 1
  	}
  	if sa.raw.Path[0] == '@' {
  		sa.raw.Path[0] = 0
  		// Don't count trailing NUL for abstract address.
  		sl--
  	}
  
  	return unsafe.Pointer(&sa.raw), sl, nil
  }
  
  type SockaddrLinklayer struct {
  	Protocol uint16
  	Ifindex  int
  	Hatype   uint16
  	Pkttype  uint8
  	Halen    uint8
  	Addr     [8]byte
  	raw      RawSockaddrLinklayer
  }
  
  func (sa *SockaddrLinklayer) sockaddr() (unsafe.Pointer, _Socklen, error) {
  	if sa.Ifindex < 0 || sa.Ifindex > 0x7fffffff {
  		return nil, 0, EINVAL
  	}
  	sa.raw.Family = AF_PACKET
  	sa.raw.Protocol = sa.Protocol
  	sa.raw.Ifindex = int32(sa.Ifindex)
  	sa.raw.Hatype = sa.Hatype
  	sa.raw.Pkttype = sa.Pkttype
  	sa.raw.Halen = sa.Halen
  	for i := 0; i < len(sa.Addr); i++ {
  		sa.raw.Addr[i] = sa.Addr[i]
  	}
  	return unsafe.Pointer(&sa.raw), SizeofSockaddrLinklayer, nil
  }
  
  type SockaddrNetlink struct {
  	Family uint16
  	Pad    uint16
  	Pid    uint32
  	Groups uint32
  	raw    RawSockaddrNetlink
  }
  
  func (sa *SockaddrNetlink) sockaddr() (unsafe.Pointer, _Socklen, error) {
  	sa.raw.Family = AF_NETLINK
  	sa.raw.Pad = sa.Pad
  	sa.raw.Pid = sa.Pid
  	sa.raw.Groups = sa.Groups
  	return unsafe.Pointer(&sa.raw), SizeofSockaddrNetlink, nil
  }
  
  func anyToSockaddr(rsa *RawSockaddrAny) (Sockaddr, error) {
  	switch rsa.Addr.Family {
  	case AF_NETLINK:
  		pp := (*RawSockaddrNetlink)(unsafe.Pointer(rsa))
  		sa := new(SockaddrNetlink)
  		sa.Family = pp.Family
  		sa.Pad = pp.Pad
  		sa.Pid = pp.Pid
  		sa.Groups = pp.Groups
  		return sa, nil
  
  	case AF_PACKET:
  		pp := (*RawSockaddrLinklayer)(unsafe.Pointer(rsa))
  		sa := new(SockaddrLinklayer)
  		sa.Protocol = pp.Protocol
  		sa.Ifindex = int(pp.Ifindex)
  		sa.Hatype = pp.Hatype
  		sa.Pkttype = pp.Pkttype
  		sa.Halen = pp.Halen
  		for i := 0; i < len(sa.Addr); i++ {
  			sa.Addr[i] = pp.Addr[i]
  		}
  		return sa, nil
  
  	case AF_UNIX:
  		pp := (*RawSockaddrUnix)(unsafe.Pointer(rsa))
  		sa := new(SockaddrUnix)
  		if pp.Path[0] == 0 {
  			// "Abstract" Unix domain socket.
  			// Rewrite leading NUL as @ for textual display.
  			// (This is the standard convention.)
  			// Not friendly to overwrite in place,
  			// but the callers below don't care.
  			pp.Path[0] = '@'
  		}
  
  		// Assume path ends at NUL.
  		// This is not technically the Linux semantics for
  		// abstract Unix domain sockets--they are supposed
  		// to be uninterpreted fixed-size binary blobs--but
  		// everyone uses this convention.
  		n := 0
  		for n < len(pp.Path) && pp.Path[n] != 0 {
  			n++
  		}
  		bytes := (*[10000]byte)(unsafe.Pointer(&pp.Path[0]))[0:n]
  		sa.Name = string(bytes)
  		return sa, nil
  
  	case AF_INET:
  		pp := (*RawSockaddrInet4)(unsafe.Pointer(rsa))
  		sa := new(SockaddrInet4)
  		p := (*[2]byte)(unsafe.Pointer(&pp.Port))
  		sa.Port = int(p[0])<<8 + int(p[1])
  		for i := 0; i < len(sa.Addr); i++ {
  			sa.Addr[i] = pp.Addr[i]
  		}
  		return sa, nil
  
  	case AF_INET6:
  		pp := (*RawSockaddrInet6)(unsafe.Pointer(rsa))
  		sa := new(SockaddrInet6)
  		p := (*[2]byte)(unsafe.Pointer(&pp.Port))
  		sa.Port = int(p[0])<<8 + int(p[1])
  		sa.ZoneId = pp.Scope_id
  		for i := 0; i < len(sa.Addr); i++ {
  			sa.Addr[i] = pp.Addr[i]
  		}
  		return sa, nil
  	}
  	return nil, EAFNOSUPPORT
  }
  
  func Accept(fd int) (nfd int, sa Sockaddr, err error) {
  	var rsa RawSockaddrAny
  	var len _Socklen = SizeofSockaddrAny
  	nfd, err = accept(fd, &rsa, &len)
  	if err != nil {
  		return
  	}
  	sa, err = anyToSockaddr(&rsa)
  	if err != nil {
  		Close(nfd)
  		nfd = 0
  	}
  	return
  }
  
  func Accept4(fd int, flags int) (nfd int, sa Sockaddr, err error) {
  	var rsa RawSockaddrAny
  	var len _Socklen = SizeofSockaddrAny
  	nfd, err = accept4(fd, &rsa, &len, flags)
  	if err != nil {
  		return
  	}
  	if len > SizeofSockaddrAny {
  		panic("RawSockaddrAny too small")
  	}
  	sa, err = anyToSockaddr(&rsa)
  	if err != nil {
  		Close(nfd)
  		nfd = 0
  	}
  	return
  }
  
  func Getsockname(fd int) (sa Sockaddr, err error) {
  	var rsa RawSockaddrAny
  	var len _Socklen = SizeofSockaddrAny
  	if err = getsockname(fd, &rsa, &len); err != nil {
  		return
  	}
  	return anyToSockaddr(&rsa)
  }
  
  func GetsockoptInet4Addr(fd, level, opt int) (value [4]byte, err error) {
  	vallen := _Socklen(4)
  	err = getsockopt(fd, level, opt, unsafe.Pointer(&value[0]), &vallen)
  	return value, err
  }
  
  func GetsockoptIPMreq(fd, level, opt int) (*IPMreq, error) {
  	var value IPMreq
  	vallen := _Socklen(SizeofIPMreq)
  	err := getsockopt(fd, level, opt, unsafe.Pointer(&value), &vallen)
  	return &value, err
  }
  
  func GetsockoptIPMreqn(fd, level, opt int) (*IPMreqn, error) {
  	var value IPMreqn
  	vallen := _Socklen(SizeofIPMreqn)
  	err := getsockopt(fd, level, opt, unsafe.Pointer(&value), &vallen)
  	return &value, err
  }
  
  func GetsockoptIPv6Mreq(fd, level, opt int) (*IPv6Mreq, error) {
  	var value IPv6Mreq
  	vallen := _Socklen(SizeofIPv6Mreq)
  	err := getsockopt(fd, level, opt, unsafe.Pointer(&value), &vallen)
  	return &value, err
  }
  
  func GetsockoptIPv6MTUInfo(fd, level, opt int) (*IPv6MTUInfo, error) {
  	var value IPv6MTUInfo
  	vallen := _Socklen(SizeofIPv6MTUInfo)
  	err := getsockopt(fd, level, opt, unsafe.Pointer(&value), &vallen)
  	return &value, err
  }
  
  func GetsockoptICMPv6Filter(fd, level, opt int) (*ICMPv6Filter, error) {
  	var value ICMPv6Filter
  	vallen := _Socklen(SizeofICMPv6Filter)
  	err := getsockopt(fd, level, opt, unsafe.Pointer(&value), &vallen)
  	return &value, err
  }
  
  func GetsockoptUcred(fd, level, opt int) (*Ucred, error) {
  	var value Ucred
  	vallen := _Socklen(SizeofUcred)
  	err := getsockopt(fd, level, opt, unsafe.Pointer(&value), &vallen)
  	return &value, err
  }
  
  func SetsockoptIPMreqn(fd, level, opt int, mreq *IPMreqn) (err error) {
  	return setsockopt(fd, level, opt, unsafe.Pointer(mreq), unsafe.Sizeof(*mreq))
  }
  
  func Recvmsg(fd int, p, oob []byte, flags int) (n, oobn int, recvflags int, from Sockaddr, err error) {
  	var msg Msghdr
  	var rsa RawSockaddrAny
  	msg.Name = (*byte)(unsafe.Pointer(&rsa))
  	msg.Namelen = uint32(SizeofSockaddrAny)
  	var iov Iovec
  	if len(p) > 0 {
  		iov.Base = (*byte)(unsafe.Pointer(&p[0]))
  		iov.SetLen(len(p))
  	}
  	var dummy byte
  	if len(oob) > 0 {
  		// receive at least one normal byte
  		if len(p) == 0 {
  			iov.Base = &dummy
  			iov.SetLen(1)
  		}
  		msg.Control = (*byte)(unsafe.Pointer(&oob[0]))
  		msg.SetControllen(len(oob))
  	}
  	msg.Iov = &iov
  	msg.Iovlen = 1
  	if n, err = recvmsg(fd, &msg, flags); err != nil {
  		return
  	}
  	oobn = int(msg.Controllen)
  	recvflags = int(msg.Flags)
  	// source address is only specified if the socket is unconnected
  	if rsa.Addr.Family != AF_UNSPEC {
  		from, err = anyToSockaddr(&rsa)
  	}
  	return
  }
  
  func Sendmsg(fd int, p, oob []byte, to Sockaddr, flags int) (err error) {
  	_, err = SendmsgN(fd, p, oob, to, flags)
  	return
  }
  
  func SendmsgN(fd int, p, oob []byte, to Sockaddr, flags int) (n int, err error) {
  	var ptr unsafe.Pointer
  	var salen _Socklen
  	if to != nil {
  		var err error
  		ptr, salen, err = to.sockaddr()
  		if err != nil {
  			return 0, err
  		}
  	}
  	var msg Msghdr
  	msg.Name = (*byte)(unsafe.Pointer(ptr))
  	msg.Namelen = uint32(salen)
  	var iov Iovec
  	if len(p) > 0 {
  		iov.Base = (*byte)(unsafe.Pointer(&p[0]))
  		iov.SetLen(len(p))
  	}
  	var dummy byte
  	if len(oob) > 0 {
  		// send at least one normal byte
  		if len(p) == 0 {
  			iov.Base = &dummy
  			iov.SetLen(1)
  		}
  		msg.Control = (*byte)(unsafe.Pointer(&oob[0]))
  		msg.SetControllen(len(oob))
  	}
  	msg.Iov = &iov
  	msg.Iovlen = 1
  	if n, err = sendmsg(fd, &msg, flags); err != nil {
  		return 0, err
  	}
  	if len(oob) > 0 && len(p) == 0 {
  		n = 0
  	}
  	return n, nil
  }
  
  // BindToDevice binds the socket associated with fd to device.
  func BindToDevice(fd int, device string) (err error) {
  	return SetsockoptString(fd, SOL_SOCKET, SO_BINDTODEVICE, device)
  }
  
  //sys	ptrace(request int, pid int, addr uintptr, data uintptr) (err error)
  
  func ptracePeek(req int, pid int, addr uintptr, out []byte) (count int, err error) {
  	// The peek requests are machine-size oriented, so we wrap it
  	// to retrieve arbitrary-length data.
  
  	// The ptrace syscall differs from glibc's ptrace.
  	// Peeks returns the word in *data, not as the return value.
  
  	var buf [sizeofPtr]byte
  
  	// Leading edge. PEEKTEXT/PEEKDATA don't require aligned
  	// access (PEEKUSER warns that it might), but if we don't
  	// align our reads, we might straddle an unmapped page
  	// boundary and not get the bytes leading up to the page
  	// boundary.
  	n := 0
  	if addr%sizeofPtr != 0 {
  		err = ptrace(req, pid, addr-addr%sizeofPtr, uintptr(unsafe.Pointer(&buf[0])))
  		if err != nil {
  			return 0, err
  		}
  		n += copy(out, buf[addr%sizeofPtr:])
  		out = out[n:]
  	}
  
  	// Remainder.
  	for len(out) > 0 {
  		// We use an internal buffer to guarantee alignment.
  		// It's not documented if this is necessary, but we're paranoid.
  		err = ptrace(req, pid, addr+uintptr(n), uintptr(unsafe.Pointer(&buf[0])))
  		if err != nil {
  			return n, err
  		}
  		copied := copy(out, buf[0:])
  		n += copied
  		out = out[copied:]
  	}
  
  	return n, nil
  }
  
  func PtracePeekText(pid int, addr uintptr, out []byte) (count int, err error) {
  	return ptracePeek(PTRACE_PEEKTEXT, pid, addr, out)
  }
  
  func PtracePeekData(pid int, addr uintptr, out []byte) (count int, err error) {
  	return ptracePeek(PTRACE_PEEKDATA, pid, addr, out)
  }
  
  func ptracePoke(pokeReq int, peekReq int, pid int, addr uintptr, data []byte) (count int, err error) {
  	// As for ptracePeek, we need to align our accesses to deal
  	// with the possibility of straddling an invalid page.
  
  	// Leading edge.
  	n := 0
  	if addr%sizeofPtr != 0 {
  		var buf [sizeofPtr]byte
  		err = ptrace(peekReq, pid, addr-addr%sizeofPtr, uintptr(unsafe.Pointer(&buf[0])))
  		if err != nil {
  			return 0, err
  		}
  		n += copy(buf[addr%sizeofPtr:], data)
  		word := *((*uintptr)(unsafe.Pointer(&buf[0])))
  		err = ptrace(pokeReq, pid, addr-addr%sizeofPtr, word)
  		if err != nil {
  			return 0, err
  		}
  		data = data[n:]
  	}
  
  	// Interior.
  	for len(data) > sizeofPtr {
  		word := *((*uintptr)(unsafe.Pointer(&data[0])))
  		err = ptrace(pokeReq, pid, addr+uintptr(n), word)
  		if err != nil {
  			return n, err
  		}
  		n += sizeofPtr
  		data = data[sizeofPtr:]
  	}
  
  	// Trailing edge.
  	if len(data) > 0 {
  		var buf [sizeofPtr]byte
  		err = ptrace(peekReq, pid, addr+uintptr(n), uintptr(unsafe.Pointer(&buf[0])))
  		if err != nil {
  			return n, err
  		}
  		copy(buf[0:], data)
  		word := *((*uintptr)(unsafe.Pointer(&buf[0])))
  		err = ptrace(pokeReq, pid, addr+uintptr(n), word)
  		if err != nil {
  			return n, err
  		}
  		n += len(data)
  	}
  
  	return n, nil
  }
  
  func PtracePokeText(pid int, addr uintptr, data []byte) (count int, err error) {
  	return ptracePoke(PTRACE_POKETEXT, PTRACE_PEEKTEXT, pid, addr, data)
  }
  
  func PtracePokeData(pid int, addr uintptr, data []byte) (count int, err error) {
  	return ptracePoke(PTRACE_POKEDATA, PTRACE_PEEKDATA, pid, addr, data)
  }
  
  func PtraceGetRegs(pid int, regsout *PtraceRegs) (err error) {
  	return ptrace(PTRACE_GETREGS, pid, 0, uintptr(unsafe.Pointer(regsout)))
  }
  
  func PtraceSetRegs(pid int, regs *PtraceRegs) (err error) {
  	return ptrace(PTRACE_SETREGS, pid, 0, uintptr(unsafe.Pointer(regs)))
  }
  
  func PtraceSetOptions(pid int, options int) (err error) {
  	return ptrace(PTRACE_SETOPTIONS, pid, 0, uintptr(options))
  }
  
  func PtraceGetEventMsg(pid int) (msg uint, err error) {
  	var data _C_long
  	err = ptrace(PTRACE_GETEVENTMSG, pid, 0, uintptr(unsafe.Pointer(&data)))
  	msg = uint(data)
  	return
  }
  
  func PtraceCont(pid int, signal int) (err error) {
  	return ptrace(PTRACE_CONT, pid, 0, uintptr(signal))
  }
  
  func PtraceSyscall(pid int, signal int) (err error) {
  	return ptrace(PTRACE_SYSCALL, pid, 0, uintptr(signal))
  }
  
  func PtraceSingleStep(pid int) (err error) { return ptrace(PTRACE_SINGLESTEP, pid, 0, 0) }
  
  func PtraceAttach(pid int) (err error) { return ptrace(PTRACE_ATTACH, pid, 0, 0) }
  
  func PtraceDetach(pid int) (err error) { return ptrace(PTRACE_DETACH, pid, 0, 0) }
  
  //sys	reboot(magic1 uint, magic2 uint, cmd int, arg string) (err error)
  
  func Reboot(cmd int) (err error) {
  	return reboot(LINUX_REBOOT_MAGIC1, LINUX_REBOOT_MAGIC2, cmd, "")
  }
  
  func ReadDirent(fd int, buf []byte) (n int, err error) {
  	return Getdents(fd, buf)
  }
  
  func direntIno(buf []byte) (uint64, bool) {
  	return readInt(buf, unsafe.Offsetof(Dirent{}.Ino), unsafe.Sizeof(Dirent{}.Ino))
  }
  
  func direntReclen(buf []byte) (uint64, bool) {
  	return readInt(buf, unsafe.Offsetof(Dirent{}.Reclen), unsafe.Sizeof(Dirent{}.Reclen))
  }
  
  func direntNamlen(buf []byte) (uint64, bool) {
  	reclen, ok := direntReclen(buf)
  	if !ok {
  		return 0, false
  	}
  	return reclen - uint64(unsafe.Offsetof(Dirent{}.Name)), true
  }
  
  //sys	mount(source string, target string, fstype string, flags uintptr, data *byte) (err error)
  
  func Mount(source string, target string, fstype string, flags uintptr, data string) (err error) {
  	// Certain file systems get rather angry and EINVAL if you give
  	// them an empty string of data, rather than NULL.
  	if data == "" {
  		return mount(source, target, fstype, flags, nil)
  	}
  	datap, err := BytePtrFromString(data)
  	if err != nil {
  		return err
  	}
  	err = mount(source, target, fstype, flags, datap)
  	use(unsafe.Pointer(datap))
  	return err
  }
  
  // Sendto
  // Recvfrom
  // Socketpair
  
  /*
   * Direct access
   */
  //sys	Acct(path string) (err error)
  //sys	Adjtimex(buf *Timex) (state int, err error)
  //sys	Chdir(path string) (err error)
  //sys	Chroot(path string) (err error)
  //sys	Close(fd int) (err error)
  //sys	Dup(oldfd int) (fd int, err error)
  //sys	Dup3(oldfd int, newfd int, flags int) (err error)
  //sysnb	EpollCreate(size int) (fd int, err error)
  //sysnb	EpollCreate1(flag int) (fd int, err error)
  //sysnb	EpollCtl(epfd int, op int, fd int, event *EpollEvent) (err error)
  //sys	EpollWait(epfd int, events []EpollEvent, msec int) (n int, err error)
  //sys	Exit(code int) = SYS_EXIT_GROUP
  //sys	Faccessat(dirfd int, path string, mode uint32, flags int) (err error)
  //sys	Fallocate(fd int, mode uint32, off int64, len int64) (err error)
  //sys	Fchdir(fd int) (err error)
  //sys	Fchmod(fd int, mode uint32) (err error)
  //sys	Fchmodat(dirfd int, path string, mode uint32, flags int) (err error)
  //sys	Fchownat(dirfd int, path string, uid int, gid int, flags int) (err error)
  //sys	fcntl(fd int, cmd int, arg int) (val int, err error)
  //sys	Fdatasync(fd int) (err error)
  //sys	Flock(fd int, how int) (err error)
  //sys	Fsync(fd int) (err error)
  //sys	Getdents(fd int, buf []byte) (n int, err error) = _SYS_getdents
  //sysnb	Getpgid(pid int) (pgid int, err error)
  
  func Getpgrp() (pid int) {
  	pid, _ = Getpgid(0)
  	return
  }
  
  //sysnb	Getpid() (pid int)
  //sysnb	Getppid() (ppid int)
  //sys	Getpriority(which int, who int) (prio int, err error)
  //sysnb	Getrusage(who int, rusage *Rusage) (err error)
  //sysnb	Gettid() (tid int)
  //sys	Getxattr(path string, attr string, dest []byte) (sz int, err error)
  //sys	InotifyAddWatch(fd int, pathname string, mask uint32) (watchdesc int, err error)
  //sysnb	InotifyInit1(flags int) (fd int, err error)
  //sysnb	InotifyRmWatch(fd int, watchdesc uint32) (success int, err error)
  //sysnb	Kill(pid int, sig Signal) (err error)
  //sys	Klogctl(typ int, buf []byte) (n int, err error) = SYS_SYSLOG
  //sys	Listxattr(path string, dest []byte) (sz int, err error)
  //sys	Mkdirat(dirfd int, path string, mode uint32) (err error)
  //sys	Mknodat(dirfd int, path string, mode uint32, dev int) (err error)
  //sys	Nanosleep(time *Timespec, leftover *Timespec) (err error)
  //sys	Pause() (err error)
  //sys	PivotRoot(newroot string, putold string) (err error) = SYS_PIVOT_ROOT
  //sysnb prlimit(pid int, resource int, newlimit *Rlimit, old *Rlimit) (err error) = SYS_PRLIMIT64
  //sys	read(fd int, p []byte) (n int, err error)
  //sys	Removexattr(path string, attr string) (err error)
  //sys	Renameat(olddirfd int, oldpath string, newdirfd int, newpath string) (err error)
  //sys	Setdomainname(p []byte) (err error)
  //sys	Sethostname(p []byte) (err error)
  //sysnb	Setpgid(pid int, pgid int) (err error)
  //sysnb	Setsid() (pid int, err error)
  //sysnb	Settimeofday(tv *Timeval) (err error)
  
  // issue 1435.
  // On linux Setuid and Setgid only affects the current thread, not the process.
  // This does not match what most callers expect so we must return an error
  // here rather than letting the caller think that the call succeeded.
  
  func Setuid(uid int) (err error) {
  	return EOPNOTSUPP
  }
  
  func Setgid(gid int) (err error) {
  	return EOPNOTSUPP
  }
  
  //sys	Setpriority(which int, who int, prio int) (err error)
  //sys	Setxattr(path string, attr string, data []byte, flags int) (err error)
  //sys	Sync()
  //sysnb	Sysinfo(info *Sysinfo_t) (err error)
  //sys	Tee(rfd int, wfd int, len int, flags int) (n int64, err error)
  //sysnb	Tgkill(tgid int, tid int, sig Signal) (err error)
  //sysnb	Times(tms *Tms) (ticks uintptr, err error)
  //sysnb	Umask(mask int) (oldmask int)
  //sysnb	Uname(buf *Utsname) (err error)
  //sys	Unmount(target string, flags int) (err error) = SYS_UMOUNT2
  //sys	Unshare(flags int) (err error)
  //sys	Ustat(dev int, ubuf *Ustat_t) (err error)
  //sys	Utime(path string, buf *Utimbuf) (err error)
  //sys	write(fd int, p []byte) (n int, err error)
  //sys	exitThread(code int) (err error) = SYS_EXIT
  //sys	readlen(fd int, p *byte, np int) (n int, err error) = SYS_READ
  //sys	writelen(fd int, p *byte, np int) (n int, err error) = SYS_WRITE
  
  // mmap varies by architecture; see syscall_linux_*.go.
  //sys	munmap(addr uintptr, length uintptr) (err error)
  
  var mapper = &mmapper{
  	active: make(map[*byte][]byte),
  	mmap:   mmap,
  	munmap: munmap,
  }
  
  func Mmap(fd int, offset int64, length int, prot int, flags int) (data []byte, err error) {
  	return mapper.Mmap(fd, offset, length, prot, flags)
  }
  
  func Munmap(b []byte) (err error) {
  	return mapper.Munmap(b)
  }
  
  //sys	Madvise(b []byte, advice int) (err error)
  //sys	Mprotect(b []byte, prot int) (err error)
  //sys	Mlock(b []byte) (err error)
  //sys	Munlock(b []byte) (err error)
  //sys	Mlockall(flags int) (err error)
  //sys	Munlockall() (err error)
  
  /*
   * Unimplemented
   */
  // AddKey
  // AfsSyscall
  // Alarm
  // ArchPrctl
  // Brk
  // Capget
  // Capset
  // ClockGetres
  // ClockGettime
  // ClockNanosleep
  // ClockSettime
  // Clone
  // CreateModule
  // DeleteModule
  // EpollCtlOld
  // EpollPwait
  // EpollWaitOld
  // Eventfd
  // Execve
  // Fadvise64
  // Fgetxattr
  // Flistxattr
  // Fork
  // Fremovexattr
  // Fsetxattr
  // Futex
  // GetKernelSyms
  // GetMempolicy
  // GetRobustList
  // GetThreadArea
  // Getitimer
  // Getpmsg
  // IoCancel
  // IoDestroy
  // IoGetevents
  // IoSetup
  // IoSubmit
  // Ioctl
  // IoprioGet
  // IoprioSet
  // KexecLoad
  // Keyctl
  // Lgetxattr
  // Llistxattr
  // LookupDcookie
  // Lremovexattr
  // Lsetxattr
  // Mbind
  // MigratePages
  // Mincore
  // ModifyLdt
  // Mount
  // MovePages
  // Mprotect
  // MqGetsetattr
  // MqNotify
  // MqOpen
  // MqTimedreceive
  // MqTimedsend
  // MqUnlink
  // Mremap
  // Msgctl
  // Msgget
  // Msgrcv
  // Msgsnd
  // Msync
  // Newfstatat
  // Nfsservctl
  // Personality
  // Poll
  // Ppoll
  // Prctl
  // Pselect6
  // Ptrace
  // Putpmsg
  // QueryModule
  // Quotactl
  // Readahead
  // Readv
  // RemapFilePages
  // RequestKey
  // RestartSyscall
  // RtSigaction
  // RtSigpending
  // RtSigprocmask
  // RtSigqueueinfo
  // RtSigreturn
  // RtSigsuspend
  // RtSigtimedwait
  // SchedGetPriorityMax
  // SchedGetPriorityMin
  // SchedGetaffinity
  // SchedGetparam
  // SchedGetscheduler
  // SchedRrGetInterval
  // SchedSetaffinity
  // SchedSetparam
  // SchedYield
  // Security
  // Semctl
  // Semget
  // Semop
  // Semtimedop
  // SetMempolicy
  // SetRobustList
  // SetThreadArea
  // SetTidAddress
  // Shmat
  // Shmctl
  // Shmdt
  // Shmget
  // Sigaltstack
  // Signalfd
  // Swapoff
  // Swapon
  // Sysfs
  // TimerCreate
  // TimerDelete
  // TimerGetoverrun
  // TimerGettime
  // TimerSettime
  // Timerfd
  // Tkill (obsolete)
  // Tuxcall
  // Umount2
  // Uselib
  // Utimensat
  // Vfork
  // Vhangup
  // Vmsplice
  // Vserver
  // Waitid
  // _Sysctl
  

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