Merge pull request #34 from jcalonso/fix/contact-group-backwards-compatible

[github/fretlink/terraform-provider-statuscake.git] / vendor / golang.org / x / sys / unix / syscall_linux.go

// 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 unix

import (
        "encoding/binary"
        "net"
        "runtime"
        "syscall"
        "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   FanotifyInit(flags uint, event_f_flags uint) (fd int, err error)
//sys   fanotifyMark(fd int, flags uint, mask uint64, dirFd int, pathname *byte) (err error)

func FanotifyMark(fd int, flags uint, mask uint64, dirFd int, pathname string) (err error) {
        if pathname == "" {
                return fanotifyMark(fd, flags, mask, dirFd, nil)
        }
        p, err := BytePtrFromString(pathname)
        if err != nil {
                return err
        }
        return fanotifyMark(fd, flags, mask, dirFd, p)
}

//sys   fchmodat(dirfd int, path string, mode uint32) (err error)

func Fchmodat(dirfd int, path string, mode uint32, flags int) (err error) {
        // Linux fchmodat doesn't support the flags parameter. Mimick glibc's behavior
        // and check the flags. Otherwise the mode would be applied to the symlink
        // destination which is not what the user expects.
        if flags&^AT_SYMLINK_NOFOLLOW != 0 {
                return EINVAL
        } else if flags&AT_SYMLINK_NOFOLLOW != 0 {
                return EOPNOTSUPP
        }
        return fchmodat(dirfd, path, mode)
}

//sys   ioctl(fd int, req uint, arg uintptr) (err error)

// ioctl itself should not be exposed directly, but additional get/set
// functions for specific types are permissible.

// IoctlSetPointerInt performs an ioctl operation which sets an
// integer value on fd, using the specified request number. The ioctl
// argument is called with a pointer to the integer value, rather than
// passing the integer value directly.
func IoctlSetPointerInt(fd int, req uint, value int) error {
        v := int32(value)
        return ioctl(fd, req, uintptr(unsafe.Pointer(&v)))
}

// IoctlSetInt performs an ioctl operation which sets an integer value
// on fd, using the specified request number.
func IoctlSetInt(fd int, req uint, value int) error {
        return ioctl(fd, req, uintptr(value))
}

func ioctlSetWinsize(fd int, req uint, value *Winsize) error {
        return ioctl(fd, req, uintptr(unsafe.Pointer(value)))
}

func ioctlSetTermios(fd int, req uint, value *Termios) error {
        return ioctl(fd, req, uintptr(unsafe.Pointer(value)))
}

func IoctlSetRTCTime(fd int, value *RTCTime) error {
        err := ioctl(fd, RTC_SET_TIME, uintptr(unsafe.Pointer(value)))
        runtime.KeepAlive(value)
        return err
}

// IoctlGetInt performs an ioctl operation which gets an integer value
// from fd, using the specified request number.
func IoctlGetInt(fd int, req uint) (int, error) {
        var value int
        err := ioctl(fd, req, uintptr(unsafe.Pointer(&value)))
        return value, err
}

func IoctlGetWinsize(fd int, req uint) (*Winsize, error) {
        var value Winsize
        err := ioctl(fd, req, uintptr(unsafe.Pointer(&value)))
        return &value, err
}

func IoctlGetTermios(fd int, req uint) (*Termios, error) {
        var value Termios
        err := ioctl(fd, req, uintptr(unsafe.Pointer(&value)))
        return &value, err
}

func IoctlGetRTCTime(fd int) (*RTCTime, error) {
        var value RTCTime
        err := ioctl(fd, RTC_RD_TIME, uintptr(unsafe.Pointer(&value)))
        return &value, err
}

//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   ppoll(fds *PollFd, nfds int, timeout *Timespec, sigmask *Sigset_t) (n int, err error)

func Ppoll(fds []PollFd, timeout *Timespec, sigmask *Sigset_t) (n int, err error) {
        if len(fds) == 0 {
                return ppoll(nil, 0, timeout, sigmask)
        }
        return ppoll(&fds[0], len(fds), timeout, sigmask)
}

//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 Utimes(path string, tv []Timeval) error {
        if tv == nil {
                err := utimensat(AT_FDCWD, path, nil, 0)
                if err != ENOSYS {
                        return err
                }
                return utimes(path, nil)
        }
        if len(tv) != 2 {
                return EINVAL
        }
        var ts [2]Timespec
        ts[0] = NsecToTimespec(TimevalToNsec(tv[0]))
        ts[1] = NsecToTimespec(TimevalToNsec(tv[1]))
        err := utimensat(AT_FDCWD, path, (*[2]Timespec)(unsafe.Pointer(&ts[0])), 0)
        if err != ENOSYS {
                return err
        }
        return utimes(path, (*[2]Timeval)(unsafe.Pointer(&tv[0])))
}

//sys   utimensat(dirfd int, path string, times *[2]Timespec, flags int) (err error)

func UtimesNano(path string, ts []Timespec) error {
        if ts == nil {
                err := utimensat(AT_FDCWD, path, nil, 0)
                if err != ENOSYS {
                        return err
                }
                return utimes(path, nil)
        }
        if len(ts) != 2 {
                return EINVAL
        }
        err := utimensat(AT_FDCWD, path, (*[2]Timespec)(unsafe.Pointer(&ts[0])), 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] = NsecToTimeval(TimespecToNsec(ts[i]))
        }
        return utimes(path, (*[2]Timeval)(unsafe.Pointer(&tv[0])))
}

func UtimesNanoAt(dirfd int, path string, ts []Timespec, flags int) error {
        if ts == nil {
                return utimensat(dirfd, path, nil, flags)
        }
        if len(ts) != 2 {
                return EINVAL
        }
        return utimensat(dirfd, path, (*[2]Timespec)(unsafe.Pointer(&ts[0])), flags)
}

func Futimesat(dirfd int, path string, tv []Timeval) error {
        if tv == nil {
                return futimesat(dirfd, path, nil)
        }
        if len(tv) != 2 {
                return EINVAL
        }
        return futimesat(dirfd, path, (*[2]Timeval)(unsafe.Pointer(&tv[0])))
}

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() syscall.Signal {
        if !w.Signaled() {
                return -1
        }
        return syscall.Signal(w & mask)
}

func (w WaitStatus) StopSignal() syscall.Signal {
        if !w.Stopped() {
                return -1
        }
        return syscall.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) error {
        return Mknod(path, mode|S_IFIFO, 0)
}

func Mkfifoat(dirfd int, path string, mode uint32) error {
        return Mknodat(dirfd, 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
}

// SockaddrLinklayer implements the Sockaddr interface for AF_PACKET type sockets.
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
}

// SockaddrNetlink implements the Sockaddr interface for AF_NETLINK type sockets.
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
}

// SockaddrHCI implements the Sockaddr interface for AF_BLUETOOTH type sockets
// using the HCI protocol.
type SockaddrHCI struct {
        Dev     uint16
        Channel uint16
        raw     RawSockaddrHCI
}

func (sa *SockaddrHCI) sockaddr() (unsafe.Pointer, _Socklen, error) {
        sa.raw.Family = AF_BLUETOOTH
        sa.raw.Dev = sa.Dev
        sa.raw.Channel = sa.Channel
        return unsafe.Pointer(&sa.raw), SizeofSockaddrHCI, nil
}

// SockaddrL2 implements the Sockaddr interface for AF_BLUETOOTH type sockets
// using the L2CAP protocol.
type SockaddrL2 struct {
        PSM      uint16
        CID      uint16
        Addr     [6]uint8
        AddrType uint8
        raw      RawSockaddrL2
}

func (sa *SockaddrL2) sockaddr() (unsafe.Pointer, _Socklen, error) {
        sa.raw.Family = AF_BLUETOOTH
        psm := (*[2]byte)(unsafe.Pointer(&sa.raw.Psm))
        psm[0] = byte(sa.PSM)
        psm[1] = byte(sa.PSM >> 8)
        for i := 0; i < len(sa.Addr); i++ {
                sa.raw.Bdaddr[i] = sa.Addr[len(sa.Addr)-1-i]
        }
        cid := (*[2]byte)(unsafe.Pointer(&sa.raw.Cid))
        cid[0] = byte(sa.CID)
        cid[1] = byte(sa.CID >> 8)
        sa.raw.Bdaddr_type = sa.AddrType
        return unsafe.Pointer(&sa.raw), SizeofSockaddrL2, nil
}

// SockaddrRFCOMM implements the Sockaddr interface for AF_BLUETOOTH type sockets
// using the RFCOMM protocol.
//
// Server example:
//
//      fd, _ := Socket(AF_BLUETOOTH, SOCK_STREAM, BTPROTO_RFCOMM)
//      _ = unix.Bind(fd, &unix.SockaddrRFCOMM{
//              Channel: 1,
//              Addr:    [6]uint8{0, 0, 0, 0, 0, 0}, // BDADDR_ANY or 00:00:00:00:00:00
//      })
//      _ = Listen(fd, 1)
//      nfd, sa, _ := Accept(fd)
//      fmt.Printf("conn addr=%v fd=%d", sa.(*unix.SockaddrRFCOMM).Addr, nfd)
//      Read(nfd, buf)
//
// Client example:
//
//      fd, _ := Socket(AF_BLUETOOTH, SOCK_STREAM, BTPROTO_RFCOMM)
//      _ = Connect(fd, &SockaddrRFCOMM{
//              Channel: 1,
//              Addr:    [6]byte{0x11, 0x22, 0x33, 0xaa, 0xbb, 0xcc}, // CC:BB:AA:33:22:11
//      })
//      Write(fd, []byte(`hello`))
type SockaddrRFCOMM struct {
        // Addr represents a bluetooth address, byte ordering is little-endian.
        Addr [6]uint8

        // Channel is a designated bluetooth channel, only 1-30 are available for use.
        // Since Linux 2.6.7 and further zero value is the first available channel.
        Channel uint8

        raw RawSockaddrRFCOMM
}

func (sa *SockaddrRFCOMM) sockaddr() (unsafe.Pointer, _Socklen, error) {
        sa.raw.Family = AF_BLUETOOTH
        sa.raw.Channel = sa.Channel
        sa.raw.Bdaddr = sa.Addr
        return unsafe.Pointer(&sa.raw), SizeofSockaddrRFCOMM, nil
}

// SockaddrCAN implements the Sockaddr interface for AF_CAN type sockets.
// The RxID and TxID fields are used for transport protocol addressing in
// (CAN_TP16, CAN_TP20, CAN_MCNET, and CAN_ISOTP), they can be left with
// zero values for CAN_RAW and CAN_BCM sockets as they have no meaning.
//
// The SockaddrCAN struct must be bound to the socket file descriptor
// using Bind before the CAN socket can be used.
//
//      // Read one raw CAN frame
//      fd, _ := Socket(AF_CAN, SOCK_RAW, CAN_RAW)
//      addr := &SockaddrCAN{Ifindex: index}
//      Bind(fd, addr)
//      frame := make([]byte, 16)
//      Read(fd, frame)
//
// The full SocketCAN documentation can be found in the linux kernel
// archives at: https://www.kernel.org/doc/Documentation/networking/can.txt
type SockaddrCAN struct {
        Ifindex int
        RxID    uint32
        TxID    uint32
        raw     RawSockaddrCAN
}

func (sa *SockaddrCAN) sockaddr() (unsafe.Pointer, _Socklen, error) {
        if sa.Ifindex < 0 || sa.Ifindex > 0x7fffffff {
                return nil, 0, EINVAL
        }
        sa.raw.Family = AF_CAN
        sa.raw.Ifindex = int32(sa.Ifindex)
        rx := (*[4]byte)(unsafe.Pointer(&sa.RxID))
        for i := 0; i < 4; i++ {
                sa.raw.Addr[i] = rx[i]
        }
        tx := (*[4]byte)(unsafe.Pointer(&sa.TxID))
        for i := 0; i < 4; i++ {
                sa.raw.Addr[i+4] = tx[i]
        }
        return unsafe.Pointer(&sa.raw), SizeofSockaddrCAN, nil
}

// SockaddrALG implements the Sockaddr interface for AF_ALG type sockets.
// SockaddrALG enables userspace access to the Linux kernel's cryptography
// subsystem. The Type and Name fields specify which type of hash or cipher
// should be used with a given socket.
//
// To create a file descriptor that provides access to a hash or cipher, both
// Bind and Accept must be used. Once the setup process is complete, input
// data can be written to the socket, processed by the kernel, and then read
// back as hash output or ciphertext.
//
// Here is an example of using an AF_ALG socket with SHA1 hashing.
// The initial socket setup process is as follows:
//
//      // Open a socket to perform SHA1 hashing.
//      fd, _ := unix.Socket(unix.AF_ALG, unix.SOCK_SEQPACKET, 0)
//      addr := &unix.SockaddrALG{Type: "hash", Name: "sha1"}
//      unix.Bind(fd, addr)
//      // Note: unix.Accept does not work at this time; must invoke accept()
//      // manually using unix.Syscall.
//      hashfd, _, _ := unix.Syscall(unix.SYS_ACCEPT, uintptr(fd), 0, 0)
//
// Once a file descriptor has been returned from Accept, it may be used to
// perform SHA1 hashing. The descriptor is not safe for concurrent use, but
// may be re-used repeatedly with subsequent Write and Read operations.
//
// When hashing a small byte slice or string, a single Write and Read may
// be used:
//
//      // Assume hashfd is already configured using the setup process.
//      hash := os.NewFile(hashfd, "sha1")
//      // Hash an input string and read the results. Each Write discards
//      // previous hash state. Read always reads the current state.
//      b := make([]byte, 20)
//      for i := 0; i < 2; i++ {
//          io.WriteString(hash, "Hello, world.")
//          hash.Read(b)
//          fmt.Println(hex.EncodeToString(b))
//      }
//      // Output:
//      // 2ae01472317d1935a84797ec1983ae243fc6aa28
//      // 2ae01472317d1935a84797ec1983ae243fc6aa28
//
// For hashing larger byte slices, or byte streams such as those read from
// a file or socket, use Sendto with MSG_MORE to instruct the kernel to update
// the hash digest instead of creating a new one for a given chunk and finalizing it.
//
//      // Assume hashfd and addr are already configured using the setup process.
//      hash := os.NewFile(hashfd, "sha1")
//      // Hash the contents of a file.
//      f, _ := os.Open("/tmp/linux-4.10-rc7.tar.xz")
//      b := make([]byte, 4096)
//      for {
//          n, err := f.Read(b)
//          if err == io.EOF {
//              break
//          }
//          unix.Sendto(hashfd, b[:n], unix.MSG_MORE, addr)
//      }
//      hash.Read(b)
//      fmt.Println(hex.EncodeToString(b))
//      // Output: 85cdcad0c06eef66f805ecce353bec9accbeecc5
//
// For more information, see: http://www.chronox.de/crypto-API/crypto/userspace-if.html.
type SockaddrALG struct {
        Type    string
        Name    string
        Feature uint32
        Mask    uint32
        raw     RawSockaddrALG
}

func (sa *SockaddrALG) sockaddr() (unsafe.Pointer, _Socklen, error) {
        // Leave room for NUL byte terminator.
        if len(sa.Type) > 13 {
                return nil, 0, EINVAL
        }
        if len(sa.Name) > 63 {
                return nil, 0, EINVAL
        }

        sa.raw.Family = AF_ALG
        sa.raw.Feat = sa.Feature
        sa.raw.Mask = sa.Mask

        typ, err := ByteSliceFromString(sa.Type)
        if err != nil {
                return nil, 0, err
        }
        name, err := ByteSliceFromString(sa.Name)
        if err != nil {
                return nil, 0, err
        }

        copy(sa.raw.Type[:], typ)
        copy(sa.raw.Name[:], name)

        return unsafe.Pointer(&sa.raw), SizeofSockaddrALG, nil
}

// SockaddrVM implements the Sockaddr interface for AF_VSOCK type sockets.
// SockaddrVM provides access to Linux VM sockets: a mechanism that enables
// bidirectional communication between a hypervisor and its guest virtual
// machines.
type SockaddrVM struct {
        // CID and Port specify a context ID and port address for a VM socket.
        // Guests have a unique CID, and hosts may have a well-known CID of:
        //  - VMADDR_CID_HYPERVISOR: refers to the hypervisor process.
        //  - VMADDR_CID_HOST: refers to other processes on the host.
        CID  uint32
        Port uint32
        raw  RawSockaddrVM
}

func (sa *SockaddrVM) sockaddr() (unsafe.Pointer, _Socklen, error) {
        sa.raw.Family = AF_VSOCK
        sa.raw.Port = sa.Port
        sa.raw.Cid = sa.CID

        return unsafe.Pointer(&sa.raw), SizeofSockaddrVM, nil
}

type SockaddrXDP struct {
        Flags        uint16
        Ifindex      uint32
        QueueID      uint32
        SharedUmemFD uint32
        raw          RawSockaddrXDP
}

func (sa *SockaddrXDP) sockaddr() (unsafe.Pointer, _Socklen, error) {
        sa.raw.Family = AF_XDP
        sa.raw.Flags = sa.Flags
        sa.raw.Ifindex = sa.Ifindex
        sa.raw.Queue_id = sa.QueueID
        sa.raw.Shared_umem_fd = sa.SharedUmemFD

        return unsafe.Pointer(&sa.raw), SizeofSockaddrXDP, nil
}

// This constant mirrors the #define of PX_PROTO_OE in
// linux/if_pppox.h. We're defining this by hand here instead of
// autogenerating through mkerrors.sh because including
// linux/if_pppox.h causes some declaration conflicts with other
// includes (linux/if_pppox.h includes linux/in.h, which conflicts
// with netinet/in.h). Given that we only need a single zero constant
// out of that file, it's cleaner to just define it by hand here.
const px_proto_oe = 0

type SockaddrPPPoE struct {
        SID    uint16
        Remote net.HardwareAddr
        Dev    string
        raw    RawSockaddrPPPoX
}

func (sa *SockaddrPPPoE) sockaddr() (unsafe.Pointer, _Socklen, error) {
        if len(sa.Remote) != 6 {
                return nil, 0, EINVAL
        }
        if len(sa.Dev) > IFNAMSIZ-1 {
                return nil, 0, EINVAL
        }

        *(*uint16)(unsafe.Pointer(&sa.raw[0])) = AF_PPPOX
        // This next field is in host-endian byte order. We can't use the
        // same unsafe pointer cast as above, because this value is not
        // 32-bit aligned and some architectures don't allow unaligned
        // access.
        //
        // However, the value of px_proto_oe is 0, so we can use
        // encoding/binary helpers to write the bytes without worrying
        // about the ordering.
        binary.BigEndian.PutUint32(sa.raw[2:6], px_proto_oe)
        // This field is deliberately big-endian, unlike the previous
        // one. The kernel expects SID to be in network byte order.
        binary.BigEndian.PutUint16(sa.raw[6:8], sa.SID)
        copy(sa.raw[8:14], sa.Remote)
        for i := 14; i < 14+IFNAMSIZ; i++ {
                sa.raw[i] = 0
        }
        copy(sa.raw[14:], sa.Dev)
        return unsafe.Pointer(&sa.raw), SizeofSockaddrPPPoX, nil
}

func anyToSockaddr(fd int, 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

        case AF_VSOCK:
                pp := (*RawSockaddrVM)(unsafe.Pointer(rsa))
                sa := &SockaddrVM{
                        CID:  pp.Cid,
                        Port: pp.Port,
                }
                return sa, nil
        case AF_BLUETOOTH:
                proto, err := GetsockoptInt(fd, SOL_SOCKET, SO_PROTOCOL)
                if err != nil {
                        return nil, err
                }
                // only BTPROTO_L2CAP and BTPROTO_RFCOMM can accept connections
                switch proto {
                case BTPROTO_L2CAP:
                        pp := (*RawSockaddrL2)(unsafe.Pointer(rsa))
                        sa := &SockaddrL2{
                                PSM:      pp.Psm,
                                CID:      pp.Cid,
                                Addr:     pp.Bdaddr,
                                AddrType: pp.Bdaddr_type,
                        }
                        return sa, nil
                case BTPROTO_RFCOMM:
                        pp := (*RawSockaddrRFCOMM)(unsafe.Pointer(rsa))
                        sa := &SockaddrRFCOMM{
                                Channel: pp.Channel,
                                Addr:    pp.Bdaddr,
                        }
                        return sa, nil
                }
        case AF_XDP:
                pp := (*RawSockaddrXDP)(unsafe.Pointer(rsa))
                sa := &SockaddrXDP{
                        Flags:        pp.Flags,
                        Ifindex:      pp.Ifindex,
                        QueueID:      pp.Queue_id,
                        SharedUmemFD: pp.Shared_umem_fd,
                }
                return sa, nil
        case AF_PPPOX:
                pp := (*RawSockaddrPPPoX)(unsafe.Pointer(rsa))
                if binary.BigEndian.Uint32(pp[2:6]) != px_proto_oe {
                        return nil, EINVAL
                }
                sa := &SockaddrPPPoE{
                        SID:    binary.BigEndian.Uint16(pp[6:8]),
                        Remote: net.HardwareAddr(pp[8:14]),
                }
                for i := 14; i < 14+IFNAMSIZ; i++ {
                        if pp[i] == 0 {
                                sa.Dev = string(pp[14:i])
                                break
                        }
                }
                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(fd, &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(fd, &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(fd, &rsa)
}

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 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 GetsockoptTCPInfo(fd, level, opt int) (*TCPInfo, error) {
        var value TCPInfo
        vallen := _Socklen(SizeofTCPInfo)
        err := getsockopt(fd, level, opt, unsafe.Pointer(&value), &vallen)
        return &value, err
}

// GetsockoptString returns the string value of the socket option opt for the
// socket associated with fd at the given socket level.
func GetsockoptString(fd, level, opt int) (string, error) {
        buf := make([]byte, 256)
        vallen := _Socklen(len(buf))
        err := getsockopt(fd, level, opt, unsafe.Pointer(&buf[0]), &vallen)
        if err != nil {
                if err == ERANGE {
                        buf = make([]byte, vallen)
                        err = getsockopt(fd, level, opt, unsafe.Pointer(&buf[0]), &vallen)
                }
                if err != nil {
                        return "", err
                }
        }
        return string(buf[:vallen-1]), nil
}

func GetsockoptTpacketStats(fd, level, opt int) (*TpacketStats, error) {
        var value TpacketStats
        vallen := _Socklen(SizeofTpacketStats)
        err := getsockopt(fd, level, opt, unsafe.Pointer(&value), &vallen)
        return &value, err
}

func GetsockoptTpacketStatsV3(fd, level, opt int) (*TpacketStatsV3, error) {
        var value TpacketStatsV3
        vallen := _Socklen(SizeofTpacketStatsV3)
        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 SetsockoptPacketMreq(fd, level, opt int, mreq *PacketMreq) error {
        return setsockopt(fd, level, opt, unsafe.Pointer(mreq), unsafe.Sizeof(*mreq))
}

// SetsockoptSockFprog attaches a classic BPF or an extended BPF program to a
// socket to filter incoming packets.  See 'man 7 socket' for usage information.
func SetsockoptSockFprog(fd, level, opt int, fprog *SockFprog) error {
        return setsockopt(fd, level, opt, unsafe.Pointer(fprog), unsafe.Sizeof(*fprog))
}

func SetsockoptCanRawFilter(fd, level, opt int, filter []CanFilter) error {
        var p unsafe.Pointer
        if len(filter) > 0 {
                p = unsafe.Pointer(&filter[0])
        }
        return setsockopt(fd, level, opt, p, uintptr(len(filter)*SizeofCanFilter))
}

func SetsockoptTpacketReq(fd, level, opt int, tp *TpacketReq) error {
        return setsockopt(fd, level, opt, unsafe.Pointer(tp), unsafe.Sizeof(*tp))
}

func SetsockoptTpacketReq3(fd, level, opt int, tp *TpacketReq3) error {
        return setsockopt(fd, level, opt, unsafe.Pointer(tp), unsafe.Sizeof(*tp))
}

// Keyctl Commands (http://man7.org/linux/man-pages/man2/keyctl.2.html)

// KeyctlInt calls keyctl commands in which each argument is an int.
// These commands are KEYCTL_REVOKE, KEYCTL_CHOWN, KEYCTL_CLEAR, KEYCTL_LINK,
// KEYCTL_UNLINK, KEYCTL_NEGATE, KEYCTL_SET_REQKEY_KEYRING, KEYCTL_SET_TIMEOUT,
// KEYCTL_ASSUME_AUTHORITY, KEYCTL_SESSION_TO_PARENT, KEYCTL_REJECT,
// KEYCTL_INVALIDATE, and KEYCTL_GET_PERSISTENT.
//sys   KeyctlInt(cmd int, arg2 int, arg3 int, arg4 int, arg5 int) (ret int, err error) = SYS_KEYCTL

// KeyctlBuffer calls keyctl commands in which the third and fourth
// arguments are a buffer and its length, respectively.
// These commands are KEYCTL_UPDATE, KEYCTL_READ, and KEYCTL_INSTANTIATE.
//sys   KeyctlBuffer(cmd int, arg2 int, buf []byte, arg5 int) (ret int, err error) = SYS_KEYCTL

// KeyctlString calls keyctl commands which return a string.
// These commands are KEYCTL_DESCRIBE and KEYCTL_GET_SECURITY.
func KeyctlString(cmd int, id int) (string, error) {
        // We must loop as the string data may change in between the syscalls.
        // We could allocate a large buffer here to reduce the chance that the
        // syscall needs to be called twice; however, this is unnecessary as
        // the performance loss is negligible.
        var buffer []byte
        for {
                // Try to fill the buffer with data
                length, err := KeyctlBuffer(cmd, id, buffer, 0)
                if err != nil {
                        return "", err
                }

                // Check if the data was written
                if length <= len(buffer) {
                        // Exclude the null terminator
                        return string(buffer[:length-1]), nil
                }

                // Make a bigger buffer if needed
                buffer = make([]byte, length)
        }
}

// Keyctl commands with special signatures.

// KeyctlGetKeyringID implements the KEYCTL_GET_KEYRING_ID command.
// See the full documentation at:
// http://man7.org/linux/man-pages/man3/keyctl_get_keyring_ID.3.html
func KeyctlGetKeyringID(id int, create bool) (ringid int, err error) {
        createInt := 0
        if create {
                createInt = 1
        }
        return KeyctlInt(KEYCTL_GET_KEYRING_ID, id, createInt, 0, 0)
}

// KeyctlSetperm implements the KEYCTL_SETPERM command. The perm value is the
// key handle permission mask as described in the "keyctl setperm" section of
// http://man7.org/linux/man-pages/man1/keyctl.1.html.
// See the full documentation at:
// http://man7.org/linux/man-pages/man3/keyctl_setperm.3.html
func KeyctlSetperm(id int, perm uint32) error {
        _, err := KeyctlInt(KEYCTL_SETPERM, id, int(perm), 0, 0)
        return err
}

//sys   keyctlJoin(cmd int, arg2 string) (ret int, err error) = SYS_KEYCTL

// KeyctlJoinSessionKeyring implements the KEYCTL_JOIN_SESSION_KEYRING command.
// See the full documentation at:
// http://man7.org/linux/man-pages/man3/keyctl_join_session_keyring.3.html
func KeyctlJoinSessionKeyring(name string) (ringid int, err error) {
        return keyctlJoin(KEYCTL_JOIN_SESSION_KEYRING, name)
}

//sys   keyctlSearch(cmd int, arg2 int, arg3 string, arg4 string, arg5 int) (ret int, err error) = SYS_KEYCTL

// KeyctlSearch implements the KEYCTL_SEARCH command.
// See the full documentation at:
// http://man7.org/linux/man-pages/man3/keyctl_search.3.html
func KeyctlSearch(ringid int, keyType, description string, destRingid int) (id int, err error) {
        return keyctlSearch(KEYCTL_SEARCH, ringid, keyType, description, destRingid)
}

//sys   keyctlIOV(cmd int, arg2 int, payload []Iovec, arg5 int) (err error) = SYS_KEYCTL

// KeyctlInstantiateIOV implements the KEYCTL_INSTANTIATE_IOV command. This
// command is similar to KEYCTL_INSTANTIATE, except that the payload is a slice
// of Iovec (each of which represents a buffer) instead of a single buffer.
// See the full documentation at:
// http://man7.org/linux/man-pages/man3/keyctl_instantiate_iov.3.html
func KeyctlInstantiateIOV(id int, payload []Iovec, ringid int) error {
        return keyctlIOV(KEYCTL_INSTANTIATE_IOV, id, payload, ringid)
}

//sys   keyctlDH(cmd int, arg2 *KeyctlDHParams, buf []byte) (ret int, err error) = SYS_KEYCTL

// KeyctlDHCompute implements the KEYCTL_DH_COMPUTE command. This command
// computes a Diffie-Hellman shared secret based on the provide params. The
// secret is written to the provided buffer and the returned size is the number
// of bytes written (returning an error if there is insufficient space in the
// buffer). If a nil buffer is passed in, this function returns the minimum
// buffer length needed to store the appropriate data. Note that this differs
// from KEYCTL_READ's behavior which always returns the requested payload size.
// See the full documentation at:
// http://man7.org/linux/man-pages/man3/keyctl_dh_compute.3.html
func KeyctlDHCompute(params *KeyctlDHParams, buffer []byte) (size int, err error) {
        return keyctlDH(KEYCTL_DH_COMPUTE, params, buffer)
}

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 = &p[0]
                iov.SetLen(len(p))
        }
        var dummy byte
        if len(oob) > 0 {
                if len(p) == 0 {
                        var sockType int
                        sockType, err = GetsockoptInt(fd, SOL_SOCKET, SO_TYPE)
                        if err != nil {
                                return
                        }
                        // receive at least one normal byte
                        if sockType != SOCK_DGRAM {
                                iov.Base = &dummy
                                iov.SetLen(1)
                        }
                }
                msg.Control = &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(fd, &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)(ptr)
        msg.Namelen = uint32(salen)
        var iov Iovec
        if len(p) > 0 {
                iov.Base = &p[0]
                iov.SetLen(len(p))
        }
        var dummy byte
        if len(oob) > 0 {
                if len(p) == 0 {
                        var sockType int
                        sockType, err = GetsockoptInt(fd, SOL_SOCKET, SO_TYPE)
                        if err != nil {
                                return 0, err
                        }
                        // send at least one normal byte
                        if sockType != SOCK_DGRAM {
                                iov.Base = &dummy
                                iov.SetLen(1)
                        }
                }
                msg.Control = &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 PtracePeekUser(pid int, addr uintptr, out []byte) (count int, err error) {
        return ptracePeek(PTRACE_PEEKUSR, 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 PtracePokeUser(pid int, addr uintptr, data []byte) (count int, err error) {
        return ptracePoke(PTRACE_POKEUSR, PTRACE_PEEKUSR, 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)
}

//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
        }
        return mount(source, target, fstype, flags, datap)
}

func Sendfile(outfd int, infd int, offset *int64, count int) (written int, err error) {
        if raceenabled {
                raceReleaseMerge(unsafe.Pointer(&ioSync))
        }
        return sendfile(outfd, infd, offset, count)
}

// Sendto
// Recvfrom
// Socketpair

/*
 * Direct access
 */
//sys   Acct(path string) (err error)
//sys   AddKey(keyType string, description string, payload []byte, ringid int) (id int, err error)
//sys   Adjtimex(buf *Timex) (state int, err error)
//sys   Chdir(path string) (err error)
//sys   Chroot(path string) (err error)
//sys   ClockGetres(clockid int32, res *Timespec) (err error)
//sys   ClockGettime(clockid int32, time *Timespec) (err error)
//sys   ClockNanosleep(clockid int32, flags int, request *Timespec, remain *Timespec) (err error)
//sys   Close(fd int) (err error)
//sys   CopyFileRange(rfd int, roff *int64, wfd int, woff *int64, len int, flags int) (n int, err error)
//sys   DeleteModule(name string, flags int) (err error)
//sys   Dup(oldfd int) (fd int, err error)
//sys   Dup3(oldfd int, newfd int, flags int) (err error)
//sysnb EpollCreate1(flag int) (fd int, err error)
//sysnb EpollCtl(epfd int, op int, fd int, event *EpollEvent) (err error)
//sys   Eventfd(initval uint, flags int) (fd int, err error) = SYS_EVENTFD2
//sys   Exit(code int) = SYS_EXIT_GROUP
//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   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   Fgetxattr(fd int, attr string, dest []byte) (sz int, err error)
//sys   FinitModule(fd int, params string, flags int) (err error)
//sys   Flistxattr(fd int, dest []byte) (sz int, err error)
//sys   Flock(fd int, how int) (err error)
//sys   Fremovexattr(fd int, attr string) (err error)
//sys   Fsetxattr(fd int, attr string, dest []byte, flags int) (err error)
//sys   Fsync(fd int) (err error)
//sys   Getdents(fd int, buf []byte) (n int, err error) = SYS_GETDENTS64
//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)
//sys   Getrandom(buf []byte, flags int) (n int, err error)
//sysnb Getrusage(who int, rusage *Rusage) (err error)
//sysnb Getsid(pid int) (sid int, err error)
//sysnb Gettid() (tid int)
//sys   Getxattr(path string, attr string, dest []byte) (sz int, err error)
//sys   InitModule(moduleImage []byte, params string) (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 syscall.Signal) (err error)
//sys   Klogctl(typ int, buf []byte) (n int, err error) = SYS_SYSLOG
//sys   Lgetxattr(path string, attr string, dest []byte) (sz int, err error)
//sys   Listxattr(path string, dest []byte) (sz int, err error)
//sys   Llistxattr(path string, dest []byte) (sz int, err error)
//sys   Lremovexattr(path string, attr string) (err error)
//sys   Lsetxattr(path string, attr string, data []byte, flags int) (err error)
//sys   MemfdCreate(name string, flags int) (fd 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   PerfEventOpen(attr *PerfEventAttr, pid int, cpu int, groupFd int, flags int) (fd int, 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   Prctl(option int, arg2 uintptr, arg3 uintptr, arg4 uintptr, arg5 uintptr) (err error)
//sys   Pselect(nfd int, r *FdSet, w *FdSet, e *FdSet, timeout *Timespec, sigmask *Sigset_t) (n int, err error) = SYS_PSELECT6
//sys   read(fd int, p []byte) (n int, err error)
//sys   Removexattr(path string, attr string) (err error)
//sys   Renameat2(olddirfd int, oldpath string, newdirfd int, newpath string, flags uint) (err error)
//sys   RequestKey(keyType string, description string, callback string, destRingid int) (id int, 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)
//sys   Setns(fd int, nstype int) (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(uid 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   Signalfd(fd int, mask *Sigset_t, flags int) = SYS_SIGNALFD4
//sys   Statx(dirfd int, path string, flags int, mask int, stat *Statx_t) (err error)
//sys   Sync()
//sys   Syncfs(fd int) (err error)
//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 syscall.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   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   Mlockall(flags int) (err error)
//sys   Msync(b []byte, flags int) (err error)
//sys   Munlock(b []byte) (err error)
//sys   Munlockall() (err error)

// Vmsplice splices user pages from a slice of Iovecs into a pipe specified by fd,
// using the specified flags.
func Vmsplice(fd int, iovs []Iovec, flags int) (int, error) {
        var p unsafe.Pointer
        if len(iovs) > 0 {
                p = unsafe.Pointer(&iovs[0])
        }

        n, _, errno := Syscall6(SYS_VMSPLICE, uintptr(fd), uintptr(p), uintptr(len(iovs)), uintptr(flags), 0, 0)
        if errno != 0 {
                return 0, syscall.Errno(errno)
        }

        return int(n), nil
}

//sys   faccessat(dirfd int, path string, mode uint32) (err error)

func Faccessat(dirfd int, path string, mode uint32, flags int) (err error) {
        if flags & ^(AT_SYMLINK_NOFOLLOW|AT_EACCESS) != 0 {
                return EINVAL
        }

        // The Linux kernel faccessat system call does not take any flags.
        // The glibc faccessat implements the flags itself; see
        // https://sourceware.org/git/?p=glibc.git;a=blob;f=sysdeps/unix/sysv/linux/faccessat.c;hb=HEAD
        // Because people naturally expect syscall.Faccessat to act
        // like C faccessat, we do the same.

        if flags == 0 {
                return faccessat(dirfd, path, mode)
        }

        var st Stat_t
        if err := Fstatat(dirfd, path, &st, flags&AT_SYMLINK_NOFOLLOW); err != nil {
                return err
        }

        mode &= 7
        if mode == 0 {
                return nil
        }

        var uid int
        if flags&AT_EACCESS != 0 {
                uid = Geteuid()
        } else {
                uid = Getuid()
        }

        if uid == 0 {
                if mode&1 == 0 {
                        // Root can read and write any file.
                        return nil
                }
                if st.Mode&0111 != 0 {
                        // Root can execute any file that anybody can execute.
                        return nil
                }
                return EACCES
        }

        var fmode uint32
        if uint32(uid) == st.Uid {
                fmode = (st.Mode >> 6) & 7
        } else {
                var gid int
                if flags&AT_EACCESS != 0 {
                        gid = Getegid()
                } else {
                        gid = Getgid()
                }

                if uint32(gid) == st.Gid {
                        fmode = (st.Mode >> 3) & 7
                } else {
                        fmode = st.Mode & 7
                }
        }

        if fmode&mode == mode {
                return nil
        }

        return EACCES
}

//sys nameToHandleAt(dirFD int, pathname string, fh *fileHandle, mountID *_C_int, flags int) (err error) = SYS_NAME_TO_HANDLE_AT
//sys openByHandleAt(mountFD int, fh *fileHandle, flags int) (fd int, err error) = SYS_OPEN_BY_HANDLE_AT

// fileHandle is the argument to nameToHandleAt and openByHandleAt. We
// originally tried to generate it via unix/linux/types.go with "type
// fileHandle C.struct_file_handle" but that generated empty structs
// for mips64 and mips64le. Instead, hard code it for now (it's the
// same everywhere else) until the mips64 generator issue is fixed.
type fileHandle struct {
        Bytes uint32
        Type  int32
}

// FileHandle represents the C struct file_handle used by
// name_to_handle_at (see NameToHandleAt) and open_by_handle_at (see
// OpenByHandleAt).
type FileHandle struct {
        *fileHandle
}

// NewFileHandle constructs a FileHandle.
func NewFileHandle(handleType int32, handle []byte) FileHandle {
        const hdrSize = unsafe.Sizeof(fileHandle{})
        buf := make([]byte, hdrSize+uintptr(len(handle)))
        copy(buf[hdrSize:], handle)
        fh := (*fileHandle)(unsafe.Pointer(&buf[0]))
        fh.Type = handleType
        fh.Bytes = uint32(len(handle))
        return FileHandle{fh}
}

func (fh *FileHandle) Size() int   { return int(fh.fileHandle.Bytes) }
func (fh *FileHandle) Type() int32 { return fh.fileHandle.Type }
func (fh *FileHandle) Bytes() []byte {
        n := fh.Size()
        if n == 0 {
                return nil
        }
        return (*[1 << 30]byte)(unsafe.Pointer(uintptr(unsafe.Pointer(&fh.fileHandle.Type)) + 4))[:n:n]
}

// NameToHandleAt wraps the name_to_handle_at system call; it obtains
// a handle for a path name.
func NameToHandleAt(dirfd int, path string, flags int) (handle FileHandle, mountID int, err error) {
        var mid _C_int
        // Try first with a small buffer, assuming the handle will
        // only be 32 bytes.
        size := uint32(32 + unsafe.Sizeof(fileHandle{}))
        didResize := false
        for {
                buf := make([]byte, size)
                fh := (*fileHandle)(unsafe.Pointer(&buf[0]))
                fh.Bytes = size - uint32(unsafe.Sizeof(fileHandle{}))
                err = nameToHandleAt(dirfd, path, fh, &mid, flags)
                if err == EOVERFLOW {
                        if didResize {
                                // We shouldn't need to resize more than once
                                return
                        }
                        didResize = true
                        size = fh.Bytes + uint32(unsafe.Sizeof(fileHandle{}))
                        continue
                }
                if err != nil {
                        return
                }
                return FileHandle{fh}, int(mid), nil
        }
}

// OpenByHandleAt wraps the open_by_handle_at system call; it opens a
// file via a handle as previously returned by NameToHandleAt.
func OpenByHandleAt(mountFD int, handle FileHandle, flags int) (fd int, err error) {
        return openByHandleAt(mountFD, handle.fileHandle, flags)
}

/*
 * Unimplemented
 */
// AfsSyscall
// Alarm
// ArchPrctl
// Brk
// Capget
// Capset
// ClockNanosleep
// ClockSettime
// Clone
// EpollCtlOld
// EpollPwait
// EpollWaitOld
// Execve
// Fork
// Futex
// GetKernelSyms
// GetMempolicy
// GetRobustList
// GetThreadArea
// Getitimer
// Getpmsg
// IoCancel
// IoDestroy
// IoGetevents
// IoSetup
// IoSubmit
// IoprioGet
// IoprioSet
// KexecLoad
// LookupDcookie
// Mbind
// MigratePages
// Mincore
// ModifyLdt
// Mount
// MovePages
// MqGetsetattr
// MqNotify
// MqOpen
// MqTimedreceive
// MqTimedsend
// MqUnlink
// Mremap
// Msgctl
// Msgget
// Msgrcv
// Msgsnd
// Nfsservctl
// Personality
// Pselect6
// Ptrace
// Putpmsg
// Quotactl
// Readahead
// Readv
// RemapFilePages
// RestartSyscall
// RtSigaction
// RtSigpending
// RtSigprocmask
// RtSigqueueinfo
// RtSigreturn
// RtSigsuspend
// RtSigtimedwait
// SchedGetPriorityMax
// SchedGetPriorityMin
// SchedGetparam
// SchedGetscheduler
// SchedRrGetInterval
// SchedSetparam
// SchedYield
// Security
// Semctl
// Semget
// Semop
// Semtimedop
// SetMempolicy
// SetRobustList
// SetThreadArea
// SetTidAddress
// Shmat
// Shmctl
// Shmdt
// Shmget
// Sigaltstack
// Swapoff
// Swapon
// Sysfs
// TimerCreate
// TimerDelete
// TimerGetoverrun
// TimerGettime
// TimerSettime
// Timerfd
// Tkill (obsolete)
// Tuxcall
// Umount2
// Uselib
// Utimensat
// Vfork
// Vhangup
// Vserver
// Waitid
// _Sysctl