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Source file src/syscall/syscall_linux.go

Documentation: syscall

     1  // Copyright 2009 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  // Linux system calls.
     6  // This file is compiled as ordinary Go code,
     7  // but it is also input to mksyscall,
     8  // which parses the //sys lines and generates system call stubs.
     9  // Note that sometimes we use a lowercase //sys name and
    10  // wrap it in our own nicer implementation.
    11  
    12  package syscall
    13  
    14  import "unsafe"
    15  
    16  func rawSyscallNoError(trap, a1, a2, a3 uintptr) (r1, r2 uintptr)
    17  
    18  /*
    19   * Wrapped
    20   */
    21  
    22  func Access(path string, mode uint32) (err error) {
    23  	return Faccessat(_AT_FDCWD, path, mode, 0)
    24  }
    25  
    26  func Chmod(path string, mode uint32) (err error) {
    27  	return Fchmodat(_AT_FDCWD, path, mode, 0)
    28  }
    29  
    30  func Chown(path string, uid int, gid int) (err error) {
    31  	return Fchownat(_AT_FDCWD, path, uid, gid, 0)
    32  }
    33  
    34  func Creat(path string, mode uint32) (fd int, err error) {
    35  	return Open(path, O_CREAT|O_WRONLY|O_TRUNC, mode)
    36  }
    37  
    38  //sys	faccessat(dirfd int, path string, mode uint32) (err error)
    39  
    40  func Faccessat(dirfd int, path string, mode uint32, flags int) (err error) {
    41  	if flags & ^(_AT_SYMLINK_NOFOLLOW|_AT_EACCESS) != 0 {
    42  		return EINVAL
    43  	}
    44  
    45  	// The Linux kernel faccessat system call does not take any flags.
    46  	// The glibc faccessat implements the flags itself; see
    47  	// https://sourceware.org/git/?p=glibc.git;a=blob;f=sysdeps/unix/sysv/linux/faccessat.c;hb=HEAD
    48  	// Because people naturally expect syscall.Faccessat to act
    49  	// like C faccessat, we do the same.
    50  
    51  	if flags == 0 {
    52  		return faccessat(dirfd, path, mode)
    53  	}
    54  
    55  	var st Stat_t
    56  	if err := fstatat(dirfd, path, &st, flags&_AT_SYMLINK_NOFOLLOW); err != nil {
    57  		return err
    58  	}
    59  
    60  	mode &= 7
    61  	if mode == 0 {
    62  		return nil
    63  	}
    64  
    65  	var uid int
    66  	if flags&_AT_EACCESS != 0 {
    67  		uid = Geteuid()
    68  	} else {
    69  		uid = Getuid()
    70  	}
    71  
    72  	if uid == 0 {
    73  		if mode&1 == 0 {
    74  			// Root can read and write any file.
    75  			return nil
    76  		}
    77  		if st.Mode&0111 != 0 {
    78  			// Root can execute any file that anybody can execute.
    79  			return nil
    80  		}
    81  		return EACCES
    82  	}
    83  
    84  	var fmode uint32
    85  	if uint32(uid) == st.Uid {
    86  		fmode = (st.Mode >> 6) & 7
    87  	} else {
    88  		var gid int
    89  		if flags&_AT_EACCESS != 0 {
    90  			gid = Getegid()
    91  		} else {
    92  			gid = Getgid()
    93  		}
    94  
    95  		if uint32(gid) == st.Gid {
    96  			fmode = (st.Mode >> 3) & 7
    97  		} else {
    98  			fmode = st.Mode & 7
    99  		}
   100  	}
   101  
   102  	if fmode&mode == mode {
   103  		return nil
   104  	}
   105  
   106  	return EACCES
   107  }
   108  
   109  //sys	fchmodat(dirfd int, path string, mode uint32) (err error)
   110  
   111  func Fchmodat(dirfd int, path string, mode uint32, flags int) (err error) {
   112  	// Linux fchmodat doesn't support the flags parameter. Mimick glibc's behavior
   113  	// and check the flags. Otherwise the mode would be applied to the symlink
   114  	// destination which is not what the user expects.
   115  	if flags&^_AT_SYMLINK_NOFOLLOW != 0 {
   116  		return EINVAL
   117  	} else if flags&_AT_SYMLINK_NOFOLLOW != 0 {
   118  		return EOPNOTSUPP
   119  	}
   120  	return fchmodat(dirfd, path, mode)
   121  }
   122  
   123  //sys	linkat(olddirfd int, oldpath string, newdirfd int, newpath string, flags int) (err error)
   124  
   125  func Link(oldpath string, newpath string) (err error) {
   126  	return linkat(_AT_FDCWD, oldpath, _AT_FDCWD, newpath, 0)
   127  }
   128  
   129  func Mkdir(path string, mode uint32) (err error) {
   130  	return Mkdirat(_AT_FDCWD, path, mode)
   131  }
   132  
   133  func Mknod(path string, mode uint32, dev int) (err error) {
   134  	return Mknodat(_AT_FDCWD, path, mode, dev)
   135  }
   136  
   137  func Open(path string, mode int, perm uint32) (fd int, err error) {
   138  	return openat(_AT_FDCWD, path, mode|O_LARGEFILE, perm)
   139  }
   140  
   141  //sys	openat(dirfd int, path string, flags int, mode uint32) (fd int, err error)
   142  
   143  func Openat(dirfd int, path string, flags int, mode uint32) (fd int, err error) {
   144  	return openat(dirfd, path, flags|O_LARGEFILE, mode)
   145  }
   146  
   147  //sys	readlinkat(dirfd int, path string, buf []byte) (n int, err error)
   148  
   149  func Readlink(path string, buf []byte) (n int, err error) {
   150  	return readlinkat(_AT_FDCWD, path, buf)
   151  }
   152  
   153  func Rename(oldpath string, newpath string) (err error) {
   154  	return Renameat(_AT_FDCWD, oldpath, _AT_FDCWD, newpath)
   155  }
   156  
   157  func Rmdir(path string) error {
   158  	return unlinkat(_AT_FDCWD, path, _AT_REMOVEDIR)
   159  }
   160  
   161  //sys	symlinkat(oldpath string, newdirfd int, newpath string) (err error)
   162  
   163  func Symlink(oldpath string, newpath string) (err error) {
   164  	return symlinkat(oldpath, _AT_FDCWD, newpath)
   165  }
   166  
   167  func Unlink(path string) error {
   168  	return unlinkat(_AT_FDCWD, path, 0)
   169  }
   170  
   171  //sys	unlinkat(dirfd int, path string, flags int) (err error)
   172  
   173  func Unlinkat(dirfd int, path string) error {
   174  	return unlinkat(dirfd, path, 0)
   175  }
   176  
   177  //sys	utimes(path string, times *[2]Timeval) (err error)
   178  
   179  func Utimes(path string, tv []Timeval) (err error) {
   180  	if len(tv) != 2 {
   181  		return EINVAL
   182  	}
   183  	return utimes(path, (*[2]Timeval)(unsafe.Pointer(&tv[0])))
   184  }
   185  
   186  //sys	utimensat(dirfd int, path string, times *[2]Timespec, flag int) (err error)
   187  
   188  func UtimesNano(path string, ts []Timespec) (err error) {
   189  	if len(ts) != 2 {
   190  		return EINVAL
   191  	}
   192  	err = utimensat(_AT_FDCWD, path, (*[2]Timespec)(unsafe.Pointer(&ts[0])), 0)
   193  	if err != ENOSYS {
   194  		return err
   195  	}
   196  	// If the utimensat syscall isn't available (utimensat was added to Linux
   197  	// in 2.6.22, Released, 8 July 2007) then fall back to utimes
   198  	var tv [2]Timeval
   199  	for i := 0; i < 2; i++ {
   200  		tv[i].Sec = ts[i].Sec
   201  		tv[i].Usec = ts[i].Nsec / 1000
   202  	}
   203  	return utimes(path, (*[2]Timeval)(unsafe.Pointer(&tv[0])))
   204  }
   205  
   206  //sys	futimesat(dirfd int, path *byte, times *[2]Timeval) (err error)
   207  
   208  func Futimesat(dirfd int, path string, tv []Timeval) (err error) {
   209  	if len(tv) != 2 {
   210  		return EINVAL
   211  	}
   212  	pathp, err := BytePtrFromString(path)
   213  	if err != nil {
   214  		return err
   215  	}
   216  	return futimesat(dirfd, pathp, (*[2]Timeval)(unsafe.Pointer(&tv[0])))
   217  }
   218  
   219  func Futimes(fd int, tv []Timeval) (err error) {
   220  	// Believe it or not, this is the best we can do on Linux
   221  	// (and is what glibc does).
   222  	return Utimes("/proc/self/fd/"+itoa(fd), tv)
   223  }
   224  
   225  const ImplementsGetwd = true
   226  
   227  //sys	Getcwd(buf []byte) (n int, err error)
   228  
   229  func Getwd() (wd string, err error) {
   230  	var buf [PathMax]byte
   231  	n, err := Getcwd(buf[0:])
   232  	if err != nil {
   233  		return "", err
   234  	}
   235  	// Getcwd returns the number of bytes written to buf, including the NUL.
   236  	if n < 1 || n > len(buf) || buf[n-1] != 0 {
   237  		return "", EINVAL
   238  	}
   239  	return string(buf[0 : n-1]), nil
   240  }
   241  
   242  func Getgroups() (gids []int, err error) {
   243  	n, err := getgroups(0, nil)
   244  	if err != nil {
   245  		return nil, err
   246  	}
   247  	if n == 0 {
   248  		return nil, nil
   249  	}
   250  
   251  	// Sanity check group count. Max is 1<<16 on Linux.
   252  	if n < 0 || n > 1<<20 {
   253  		return nil, EINVAL
   254  	}
   255  
   256  	a := make([]_Gid_t, n)
   257  	n, err = getgroups(n, &a[0])
   258  	if err != nil {
   259  		return nil, err
   260  	}
   261  	gids = make([]int, n)
   262  	for i, v := range a[0:n] {
   263  		gids[i] = int(v)
   264  	}
   265  	return
   266  }
   267  
   268  func Setgroups(gids []int) (err error) {
   269  	if len(gids) == 0 {
   270  		return setgroups(0, nil)
   271  	}
   272  
   273  	a := make([]_Gid_t, len(gids))
   274  	for i, v := range gids {
   275  		a[i] = _Gid_t(v)
   276  	}
   277  	return setgroups(len(a), &a[0])
   278  }
   279  
   280  type WaitStatus uint32
   281  
   282  // Wait status is 7 bits at bottom, either 0 (exited),
   283  // 0x7F (stopped), or a signal number that caused an exit.
   284  // The 0x80 bit is whether there was a core dump.
   285  // An extra number (exit code, signal causing a stop)
   286  // is in the high bits. At least that's the idea.
   287  // There are various irregularities. For example, the
   288  // "continued" status is 0xFFFF, distinguishing itself
   289  // from stopped via the core dump bit.
   290  
   291  const (
   292  	mask    = 0x7F
   293  	core    = 0x80
   294  	exited  = 0x00
   295  	stopped = 0x7F
   296  	shift   = 8
   297  )
   298  
   299  func (w WaitStatus) Exited() bool { return w&mask == exited }
   300  
   301  func (w WaitStatus) Signaled() bool { return w&mask != stopped && w&mask != exited }
   302  
   303  func (w WaitStatus) Stopped() bool { return w&0xFF == stopped }
   304  
   305  func (w WaitStatus) Continued() bool { return w == 0xFFFF }
   306  
   307  func (w WaitStatus) CoreDump() bool { return w.Signaled() && w&core != 0 }
   308  
   309  func (w WaitStatus) ExitStatus() int {
   310  	if !w.Exited() {
   311  		return -1
   312  	}
   313  	return int(w>>shift) & 0xFF
   314  }
   315  
   316  func (w WaitStatus) Signal() Signal {
   317  	if !w.Signaled() {
   318  		return -1
   319  	}
   320  	return Signal(w & mask)
   321  }
   322  
   323  func (w WaitStatus) StopSignal() Signal {
   324  	if !w.Stopped() {
   325  		return -1
   326  	}
   327  	return Signal(w>>shift) & 0xFF
   328  }
   329  
   330  func (w WaitStatus) TrapCause() int {
   331  	if w.StopSignal() != SIGTRAP {
   332  		return -1
   333  	}
   334  	return int(w>>shift) >> 8
   335  }
   336  
   337  //sys	wait4(pid int, wstatus *_C_int, options int, rusage *Rusage) (wpid int, err error)
   338  
   339  func Wait4(pid int, wstatus *WaitStatus, options int, rusage *Rusage) (wpid int, err error) {
   340  	var status _C_int
   341  	wpid, err = wait4(pid, &status, options, rusage)
   342  	if wstatus != nil {
   343  		*wstatus = WaitStatus(status)
   344  	}
   345  	return
   346  }
   347  
   348  func Mkfifo(path string, mode uint32) (err error) {
   349  	return Mknod(path, mode|S_IFIFO, 0)
   350  }
   351  
   352  func (sa *SockaddrInet4) sockaddr() (unsafe.Pointer, _Socklen, error) {
   353  	if sa.Port < 0 || sa.Port > 0xFFFF {
   354  		return nil, 0, EINVAL
   355  	}
   356  	sa.raw.Family = AF_INET
   357  	p := (*[2]byte)(unsafe.Pointer(&sa.raw.Port))
   358  	p[0] = byte(sa.Port >> 8)
   359  	p[1] = byte(sa.Port)
   360  	for i := 0; i < len(sa.Addr); i++ {
   361  		sa.raw.Addr[i] = sa.Addr[i]
   362  	}
   363  	return unsafe.Pointer(&sa.raw), SizeofSockaddrInet4, nil
   364  }
   365  
   366  func (sa *SockaddrInet6) sockaddr() (unsafe.Pointer, _Socklen, error) {
   367  	if sa.Port < 0 || sa.Port > 0xFFFF {
   368  		return nil, 0, EINVAL
   369  	}
   370  	sa.raw.Family = AF_INET6
   371  	p := (*[2]byte)(unsafe.Pointer(&sa.raw.Port))
   372  	p[0] = byte(sa.Port >> 8)
   373  	p[1] = byte(sa.Port)
   374  	sa.raw.Scope_id = sa.ZoneId
   375  	for i := 0; i < len(sa.Addr); i++ {
   376  		sa.raw.Addr[i] = sa.Addr[i]
   377  	}
   378  	return unsafe.Pointer(&sa.raw), SizeofSockaddrInet6, nil
   379  }
   380  
   381  func (sa *SockaddrUnix) sockaddr() (unsafe.Pointer, _Socklen, error) {
   382  	name := sa.Name
   383  	n := len(name)
   384  	if n > len(sa.raw.Path) {
   385  		return nil, 0, EINVAL
   386  	}
   387  	if n == len(sa.raw.Path) && name[0] != '@' {
   388  		return nil, 0, EINVAL
   389  	}
   390  	sa.raw.Family = AF_UNIX
   391  	for i := 0; i < n; i++ {
   392  		sa.raw.Path[i] = int8(name[i])
   393  	}
   394  	// length is family (uint16), name, NUL.
   395  	sl := _Socklen(2)
   396  	if n > 0 {
   397  		sl += _Socklen(n) + 1
   398  	}
   399  	if sa.raw.Path[0] == '@' {
   400  		sa.raw.Path[0] = 0
   401  		// Don't count trailing NUL for abstract address.
   402  		sl--
   403  	}
   404  
   405  	return unsafe.Pointer(&sa.raw), sl, nil
   406  }
   407  
   408  type SockaddrLinklayer struct {
   409  	Protocol uint16
   410  	Ifindex  int
   411  	Hatype   uint16
   412  	Pkttype  uint8
   413  	Halen    uint8
   414  	Addr     [8]byte
   415  	raw      RawSockaddrLinklayer
   416  }
   417  
   418  func (sa *SockaddrLinklayer) sockaddr() (unsafe.Pointer, _Socklen, error) {
   419  	if sa.Ifindex < 0 || sa.Ifindex > 0x7fffffff {
   420  		return nil, 0, EINVAL
   421  	}
   422  	sa.raw.Family = AF_PACKET
   423  	sa.raw.Protocol = sa.Protocol
   424  	sa.raw.Ifindex = int32(sa.Ifindex)
   425  	sa.raw.Hatype = sa.Hatype
   426  	sa.raw.Pkttype = sa.Pkttype
   427  	sa.raw.Halen = sa.Halen
   428  	for i := 0; i < len(sa.Addr); i++ {
   429  		sa.raw.Addr[i] = sa.Addr[i]
   430  	}
   431  	return unsafe.Pointer(&sa.raw), SizeofSockaddrLinklayer, nil
   432  }
   433  
   434  type SockaddrNetlink struct {
   435  	Family uint16
   436  	Pad    uint16
   437  	Pid    uint32
   438  	Groups uint32
   439  	raw    RawSockaddrNetlink
   440  }
   441  
   442  func (sa *SockaddrNetlink) sockaddr() (unsafe.Pointer, _Socklen, error) {
   443  	sa.raw.Family = AF_NETLINK
   444  	sa.raw.Pad = sa.Pad
   445  	sa.raw.Pid = sa.Pid
   446  	sa.raw.Groups = sa.Groups
   447  	return unsafe.Pointer(&sa.raw), SizeofSockaddrNetlink, nil
   448  }
   449  
   450  func anyToSockaddr(rsa *RawSockaddrAny) (Sockaddr, error) {
   451  	switch rsa.Addr.Family {
   452  	case AF_NETLINK:
   453  		pp := (*RawSockaddrNetlink)(unsafe.Pointer(rsa))
   454  		sa := new(SockaddrNetlink)
   455  		sa.Family = pp.Family
   456  		sa.Pad = pp.Pad
   457  		sa.Pid = pp.Pid
   458  		sa.Groups = pp.Groups
   459  		return sa, nil
   460  
   461  	case AF_PACKET:
   462  		pp := (*RawSockaddrLinklayer)(unsafe.Pointer(rsa))
   463  		sa := new(SockaddrLinklayer)
   464  		sa.Protocol = pp.Protocol
   465  		sa.Ifindex = int(pp.Ifindex)
   466  		sa.Hatype = pp.Hatype
   467  		sa.Pkttype = pp.Pkttype
   468  		sa.Halen = pp.Halen
   469  		for i := 0; i < len(sa.Addr); i++ {
   470  			sa.Addr[i] = pp.Addr[i]
   471  		}
   472  		return sa, nil
   473  
   474  	case AF_UNIX:
   475  		pp := (*RawSockaddrUnix)(unsafe.Pointer(rsa))
   476  		sa := new(SockaddrUnix)
   477  		if pp.Path[0] == 0 {
   478  			// "Abstract" Unix domain socket.
   479  			// Rewrite leading NUL as @ for textual display.
   480  			// (This is the standard convention.)
   481  			// Not friendly to overwrite in place,
   482  			// but the callers below don't care.
   483  			pp.Path[0] = '@'
   484  		}
   485  
   486  		// Assume path ends at NUL.
   487  		// This is not technically the Linux semantics for
   488  		// abstract Unix domain sockets--they are supposed
   489  		// to be uninterpreted fixed-size binary blobs--but
   490  		// everyone uses this convention.
   491  		n := 0
   492  		for n < len(pp.Path) && pp.Path[n] != 0 {
   493  			n++
   494  		}
   495  		bytes := (*[10000]byte)(unsafe.Pointer(&pp.Path[0]))[0:n]
   496  		sa.Name = string(bytes)
   497  		return sa, nil
   498  
   499  	case AF_INET:
   500  		pp := (*RawSockaddrInet4)(unsafe.Pointer(rsa))
   501  		sa := new(SockaddrInet4)
   502  		p := (*[2]byte)(unsafe.Pointer(&pp.Port))
   503  		sa.Port = int(p[0])<<8 + int(p[1])
   504  		for i := 0; i < len(sa.Addr); i++ {
   505  			sa.Addr[i] = pp.Addr[i]
   506  		}
   507  		return sa, nil
   508  
   509  	case AF_INET6:
   510  		pp := (*RawSockaddrInet6)(unsafe.Pointer(rsa))
   511  		sa := new(SockaddrInet6)
   512  		p := (*[2]byte)(unsafe.Pointer(&pp.Port))
   513  		sa.Port = int(p[0])<<8 + int(p[1])
   514  		sa.ZoneId = pp.Scope_id
   515  		for i := 0; i < len(sa.Addr); i++ {
   516  			sa.Addr[i] = pp.Addr[i]
   517  		}
   518  		return sa, nil
   519  	}
   520  	return nil, EAFNOSUPPORT
   521  }
   522  
   523  func Accept(fd int) (nfd int, sa Sockaddr, err error) {
   524  	var rsa RawSockaddrAny
   525  	var len _Socklen = SizeofSockaddrAny
   526  	nfd, err = accept(fd, &rsa, &len)
   527  	if err != nil {
   528  		return
   529  	}
   530  	sa, err = anyToSockaddr(&rsa)
   531  	if err != nil {
   532  		Close(nfd)
   533  		nfd = 0
   534  	}
   535  	return
   536  }
   537  
   538  func Accept4(fd int, flags int) (nfd int, sa Sockaddr, err error) {
   539  	var rsa RawSockaddrAny
   540  	var len _Socklen = SizeofSockaddrAny
   541  	nfd, err = accept4(fd, &rsa, &len, flags)
   542  	if err != nil {
   543  		return
   544  	}
   545  	if len > SizeofSockaddrAny {
   546  		panic("RawSockaddrAny too small")
   547  	}
   548  	sa, err = anyToSockaddr(&rsa)
   549  	if err != nil {
   550  		Close(nfd)
   551  		nfd = 0
   552  	}
   553  	return
   554  }
   555  
   556  func Getsockname(fd int) (sa Sockaddr, err error) {
   557  	var rsa RawSockaddrAny
   558  	var len _Socklen = SizeofSockaddrAny
   559  	if err = getsockname(fd, &rsa, &len); err != nil {
   560  		return
   561  	}
   562  	return anyToSockaddr(&rsa)
   563  }
   564  
   565  func GetsockoptInet4Addr(fd, level, opt int) (value [4]byte, err error) {
   566  	vallen := _Socklen(4)
   567  	err = getsockopt(fd, level, opt, unsafe.Pointer(&value[0]), &vallen)
   568  	return value, err
   569  }
   570  
   571  func GetsockoptIPMreq(fd, level, opt int) (*IPMreq, error) {
   572  	var value IPMreq
   573  	vallen := _Socklen(SizeofIPMreq)
   574  	err := getsockopt(fd, level, opt, unsafe.Pointer(&value), &vallen)
   575  	return &value, err
   576  }
   577  
   578  func GetsockoptIPMreqn(fd, level, opt int) (*IPMreqn, error) {
   579  	var value IPMreqn
   580  	vallen := _Socklen(SizeofIPMreqn)
   581  	err := getsockopt(fd, level, opt, unsafe.Pointer(&value), &vallen)
   582  	return &value, err
   583  }
   584  
   585  func GetsockoptIPv6Mreq(fd, level, opt int) (*IPv6Mreq, error) {
   586  	var value IPv6Mreq
   587  	vallen := _Socklen(SizeofIPv6Mreq)
   588  	err := getsockopt(fd, level, opt, unsafe.Pointer(&value), &vallen)
   589  	return &value, err
   590  }
   591  
   592  func GetsockoptIPv6MTUInfo(fd, level, opt int) (*IPv6MTUInfo, error) {
   593  	var value IPv6MTUInfo
   594  	vallen := _Socklen(SizeofIPv6MTUInfo)
   595  	err := getsockopt(fd, level, opt, unsafe.Pointer(&value), &vallen)
   596  	return &value, err
   597  }
   598  
   599  func GetsockoptICMPv6Filter(fd, level, opt int) (*ICMPv6Filter, error) {
   600  	var value ICMPv6Filter
   601  	vallen := _Socklen(SizeofICMPv6Filter)
   602  	err := getsockopt(fd, level, opt, unsafe.Pointer(&value), &vallen)
   603  	return &value, err
   604  }
   605  
   606  func GetsockoptUcred(fd, level, opt int) (*Ucred, error) {
   607  	var value Ucred
   608  	vallen := _Socklen(SizeofUcred)
   609  	err := getsockopt(fd, level, opt, unsafe.Pointer(&value), &vallen)
   610  	return &value, err
   611  }
   612  
   613  func SetsockoptIPMreqn(fd, level, opt int, mreq *IPMreqn) (err error) {
   614  	return setsockopt(fd, level, opt, unsafe.Pointer(mreq), unsafe.Sizeof(*mreq))
   615  }
   616  
   617  func Recvmsg(fd int, p, oob []byte, flags int) (n, oobn int, recvflags int, from Sockaddr, err error) {
   618  	var msg Msghdr
   619  	var rsa RawSockaddrAny
   620  	msg.Name = (*byte)(unsafe.Pointer(&rsa))
   621  	msg.Namelen = uint32(SizeofSockaddrAny)
   622  	var iov Iovec
   623  	if len(p) > 0 {
   624  		iov.Base = &p[0]
   625  		iov.SetLen(len(p))
   626  	}
   627  	var dummy byte
   628  	if len(oob) > 0 {
   629  		if len(p) == 0 {
   630  			var sockType int
   631  			sockType, err = GetsockoptInt(fd, SOL_SOCKET, SO_TYPE)
   632  			if err != nil {
   633  				return
   634  			}
   635  			// receive at least one normal byte
   636  			if sockType != SOCK_DGRAM {
   637  				iov.Base = &dummy
   638  				iov.SetLen(1)
   639  			}
   640  		}
   641  		msg.Control = &oob[0]
   642  		msg.SetControllen(len(oob))
   643  	}
   644  	msg.Iov = &iov
   645  	msg.Iovlen = 1
   646  	if n, err = recvmsg(fd, &msg, flags); err != nil {
   647  		return
   648  	}
   649  	oobn = int(msg.Controllen)
   650  	recvflags = int(msg.Flags)
   651  	// source address is only specified if the socket is unconnected
   652  	if rsa.Addr.Family != AF_UNSPEC {
   653  		from, err = anyToSockaddr(&rsa)
   654  	}
   655  	return
   656  }
   657  
   658  func Sendmsg(fd int, p, oob []byte, to Sockaddr, flags int) (err error) {
   659  	_, err = SendmsgN(fd, p, oob, to, flags)
   660  	return
   661  }
   662  
   663  func SendmsgN(fd int, p, oob []byte, to Sockaddr, flags int) (n int, err error) {
   664  	var ptr unsafe.Pointer
   665  	var salen _Socklen
   666  	if to != nil {
   667  		var err error
   668  		ptr, salen, err = to.sockaddr()
   669  		if err != nil {
   670  			return 0, err
   671  		}
   672  	}
   673  	var msg Msghdr
   674  	msg.Name = (*byte)(ptr)
   675  	msg.Namelen = uint32(salen)
   676  	var iov Iovec
   677  	if len(p) > 0 {
   678  		iov.Base = &p[0]
   679  		iov.SetLen(len(p))
   680  	}
   681  	var dummy byte
   682  	if len(oob) > 0 {
   683  		if len(p) == 0 {
   684  			var sockType int
   685  			sockType, err = GetsockoptInt(fd, SOL_SOCKET, SO_TYPE)
   686  			if err != nil {
   687  				return 0, err
   688  			}
   689  			// send at least one normal byte
   690  			if sockType != SOCK_DGRAM {
   691  				iov.Base = &dummy
   692  				iov.SetLen(1)
   693  			}
   694  		}
   695  		msg.Control = &oob[0]
   696  		msg.SetControllen(len(oob))
   697  	}
   698  	msg.Iov = &iov
   699  	msg.Iovlen = 1
   700  	if n, err = sendmsg(fd, &msg, flags); err != nil {
   701  		return 0, err
   702  	}
   703  	if len(oob) > 0 && len(p) == 0 {
   704  		n = 0
   705  	}
   706  	return n, nil
   707  }
   708  
   709  // BindToDevice binds the socket associated with fd to device.
   710  func BindToDevice(fd int, device string) (err error) {
   711  	return SetsockoptString(fd, SOL_SOCKET, SO_BINDTODEVICE, device)
   712  }
   713  
   714  //sys	ptrace(request int, pid int, addr uintptr, data uintptr) (err error)
   715  
   716  func ptracePeek(req int, pid int, addr uintptr, out []byte) (count int, err error) {
   717  	// The peek requests are machine-size oriented, so we wrap it
   718  	// to retrieve arbitrary-length data.
   719  
   720  	// The ptrace syscall differs from glibc's ptrace.
   721  	// Peeks returns the word in *data, not as the return value.
   722  
   723  	var buf [sizeofPtr]byte
   724  
   725  	// Leading edge. PEEKTEXT/PEEKDATA don't require aligned
   726  	// access (PEEKUSER warns that it might), but if we don't
   727  	// align our reads, we might straddle an unmapped page
   728  	// boundary and not get the bytes leading up to the page
   729  	// boundary.
   730  	n := 0
   731  	if addr%sizeofPtr != 0 {
   732  		err = ptrace(req, pid, addr-addr%sizeofPtr, uintptr(unsafe.Pointer(&buf[0])))
   733  		if err != nil {
   734  			return 0, err
   735  		}
   736  		n += copy(out, buf[addr%sizeofPtr:])
   737  		out = out[n:]
   738  	}
   739  
   740  	// Remainder.
   741  	for len(out) > 0 {
   742  		// We use an internal buffer to guarantee alignment.
   743  		// It's not documented if this is necessary, but we're paranoid.
   744  		err = ptrace(req, pid, addr+uintptr(n), uintptr(unsafe.Pointer(&buf[0])))
   745  		if err != nil {
   746  			return n, err
   747  		}
   748  		copied := copy(out, buf[0:])
   749  		n += copied
   750  		out = out[copied:]
   751  	}
   752  
   753  	return n, nil
   754  }
   755  
   756  func PtracePeekText(pid int, addr uintptr, out []byte) (count int, err error) {
   757  	return ptracePeek(PTRACE_PEEKTEXT, pid, addr, out)
   758  }
   759  
   760  func PtracePeekData(pid int, addr uintptr, out []byte) (count int, err error) {
   761  	return ptracePeek(PTRACE_PEEKDATA, pid, addr, out)
   762  }
   763  
   764  func ptracePoke(pokeReq int, peekReq int, pid int, addr uintptr, data []byte) (count int, err error) {
   765  	// As for ptracePeek, we need to align our accesses to deal
   766  	// with the possibility of straddling an invalid page.
   767  
   768  	// Leading edge.
   769  	n := 0
   770  	if addr%sizeofPtr != 0 {
   771  		var buf [sizeofPtr]byte
   772  		err = ptrace(peekReq, pid, addr-addr%sizeofPtr, uintptr(unsafe.Pointer(&buf[0])))
   773  		if err != nil {
   774  			return 0, err
   775  		}
   776  		n += copy(buf[addr%sizeofPtr:], data)
   777  		word := *((*uintptr)(unsafe.Pointer(&buf[0])))
   778  		err = ptrace(pokeReq, pid, addr-addr%sizeofPtr, word)
   779  		if err != nil {
   780  			return 0, err
   781  		}
   782  		data = data[n:]
   783  	}
   784  
   785  	// Interior.
   786  	for len(data) > sizeofPtr {
   787  		word := *((*uintptr)(unsafe.Pointer(&data[0])))
   788  		err = ptrace(pokeReq, pid, addr+uintptr(n), word)
   789  		if err != nil {
   790  			return n, err
   791  		}
   792  		n += sizeofPtr
   793  		data = data[sizeofPtr:]
   794  	}
   795  
   796  	// Trailing edge.
   797  	if len(data) > 0 {
   798  		var buf [sizeofPtr]byte
   799  		err = ptrace(peekReq, pid, addr+uintptr(n), uintptr(unsafe.Pointer(&buf[0])))
   800  		if err != nil {
   801  			return n, err
   802  		}
   803  		copy(buf[0:], data)
   804  		word := *((*uintptr)(unsafe.Pointer(&buf[0])))
   805  		err = ptrace(pokeReq, pid, addr+uintptr(n), word)
   806  		if err != nil {
   807  			return n, err
   808  		}
   809  		n += len(data)
   810  	}
   811  
   812  	return n, nil
   813  }
   814  
   815  func PtracePokeText(pid int, addr uintptr, data []byte) (count int, err error) {
   816  	return ptracePoke(PTRACE_POKETEXT, PTRACE_PEEKTEXT, pid, addr, data)
   817  }
   818  
   819  func PtracePokeData(pid int, addr uintptr, data []byte) (count int, err error) {
   820  	return ptracePoke(PTRACE_POKEDATA, PTRACE_PEEKDATA, pid, addr, data)
   821  }
   822  
   823  func PtraceGetRegs(pid int, regsout *PtraceRegs) (err error) {
   824  	return ptrace(PTRACE_GETREGS, pid, 0, uintptr(unsafe.Pointer(regsout)))
   825  }
   826  
   827  func PtraceSetRegs(pid int, regs *PtraceRegs) (err error) {
   828  	return ptrace(PTRACE_SETREGS, pid, 0, uintptr(unsafe.Pointer(regs)))
   829  }
   830  
   831  func PtraceSetOptions(pid int, options int) (err error) {
   832  	return ptrace(PTRACE_SETOPTIONS, pid, 0, uintptr(options))
   833  }
   834  
   835  func PtraceGetEventMsg(pid int) (msg uint, err error) {
   836  	var data _C_long
   837  	err = ptrace(PTRACE_GETEVENTMSG, pid, 0, uintptr(unsafe.Pointer(&data)))
   838  	msg = uint(data)
   839  	return
   840  }
   841  
   842  func PtraceCont(pid int, signal int) (err error) {
   843  	return ptrace(PTRACE_CONT, pid, 0, uintptr(signal))
   844  }
   845  
   846  func PtraceSyscall(pid int, signal int) (err error) {
   847  	return ptrace(PTRACE_SYSCALL, pid, 0, uintptr(signal))
   848  }
   849  
   850  func PtraceSingleStep(pid int) (err error) { return ptrace(PTRACE_SINGLESTEP, pid, 0, 0) }
   851  
   852  func PtraceAttach(pid int) (err error) { return ptrace(PTRACE_ATTACH, pid, 0, 0) }
   853  
   854  func PtraceDetach(pid int) (err error) { return ptrace(PTRACE_DETACH, pid, 0, 0) }
   855  
   856  //sys	reboot(magic1 uint, magic2 uint, cmd int, arg string) (err error)
   857  
   858  func Reboot(cmd int) (err error) {
   859  	return reboot(LINUX_REBOOT_MAGIC1, LINUX_REBOOT_MAGIC2, cmd, "")
   860  }
   861  
   862  func ReadDirent(fd int, buf []byte) (n int, err error) {
   863  	return Getdents(fd, buf)
   864  }
   865  
   866  func direntIno(buf []byte) (uint64, bool) {
   867  	return readInt(buf, unsafe.Offsetof(Dirent{}.Ino), unsafe.Sizeof(Dirent{}.Ino))
   868  }
   869  
   870  func direntReclen(buf []byte) (uint64, bool) {
   871  	return readInt(buf, unsafe.Offsetof(Dirent{}.Reclen), unsafe.Sizeof(Dirent{}.Reclen))
   872  }
   873  
   874  func direntNamlen(buf []byte) (uint64, bool) {
   875  	reclen, ok := direntReclen(buf)
   876  	if !ok {
   877  		return 0, false
   878  	}
   879  	return reclen - uint64(unsafe.Offsetof(Dirent{}.Name)), true
   880  }
   881  
   882  //sys	mount(source string, target string, fstype string, flags uintptr, data *byte) (err error)
   883  
   884  func Mount(source string, target string, fstype string, flags uintptr, data string) (err error) {
   885  	// Certain file systems get rather angry and EINVAL if you give
   886  	// them an empty string of data, rather than NULL.
   887  	if data == "" {
   888  		return mount(source, target, fstype, flags, nil)
   889  	}
   890  	datap, err := BytePtrFromString(data)
   891  	if err != nil {
   892  		return err
   893  	}
   894  	return mount(source, target, fstype, flags, datap)
   895  }
   896  
   897  // Sendto
   898  // Recvfrom
   899  // Socketpair
   900  
   901  /*
   902   * Direct access
   903   */
   904  //sys	Acct(path string) (err error)
   905  //sys	Adjtimex(buf *Timex) (state int, err error)
   906  //sys	Chdir(path string) (err error)
   907  //sys	Chroot(path string) (err error)
   908  //sys	Close(fd int) (err error)
   909  //sys	Dup(oldfd int) (fd int, err error)
   910  //sys	Dup3(oldfd int, newfd int, flags int) (err error)
   911  //sysnb	EpollCreate(size int) (fd int, err error)
   912  //sysnb	EpollCreate1(flag int) (fd int, err error)
   913  //sysnb	EpollCtl(epfd int, op int, fd int, event *EpollEvent) (err error)
   914  //sys	Fallocate(fd int, mode uint32, off int64, len int64) (err error)
   915  //sys	Fchdir(fd int) (err error)
   916  //sys	Fchmod(fd int, mode uint32) (err error)
   917  //sys	Fchownat(dirfd int, path string, uid int, gid int, flags int) (err error)
   918  //sys	fcntl(fd int, cmd int, arg int) (val int, err error)
   919  //sys	Fdatasync(fd int) (err error)
   920  //sys	Flock(fd int, how int) (err error)
   921  //sys	Fsync(fd int) (err error)
   922  //sys	Getdents(fd int, buf []byte) (n int, err error) = SYS_GETDENTS64
   923  //sysnb	Getpgid(pid int) (pgid int, err error)
   924  
   925  func Getpgrp() (pid int) {
   926  	pid, _ = Getpgid(0)
   927  	return
   928  }
   929  
   930  //sysnb	Getpid() (pid int)
   931  //sysnb	Getppid() (ppid int)
   932  //sys	Getpriority(which int, who int) (prio int, err error)
   933  //sysnb	Getrusage(who int, rusage *Rusage) (err error)
   934  //sysnb	Gettid() (tid int)
   935  //sys	Getxattr(path string, attr string, dest []byte) (sz int, err error)
   936  //sys	InotifyAddWatch(fd int, pathname string, mask uint32) (watchdesc int, err error)
   937  //sysnb	InotifyInit1(flags int) (fd int, err error)
   938  //sysnb	InotifyRmWatch(fd int, watchdesc uint32) (success int, err error)
   939  //sysnb	Kill(pid int, sig Signal) (err error)
   940  //sys	Klogctl(typ int, buf []byte) (n int, err error) = SYS_SYSLOG
   941  //sys	Listxattr(path string, dest []byte) (sz int, err error)
   942  //sys	Mkdirat(dirfd int, path string, mode uint32) (err error)
   943  //sys	Mknodat(dirfd int, path string, mode uint32, dev int) (err error)
   944  //sys	Nanosleep(time *Timespec, leftover *Timespec) (err error)
   945  //sys	Pause() (err error)
   946  //sys	PivotRoot(newroot string, putold string) (err error) = SYS_PIVOT_ROOT
   947  //sysnb prlimit(pid int, resource int, newlimit *Rlimit, old *Rlimit) (err error) = SYS_PRLIMIT64
   948  //sys	read(fd int, p []byte) (n int, err error)
   949  //sys	Removexattr(path string, attr string) (err error)
   950  //sys	Renameat(olddirfd int, oldpath string, newdirfd int, newpath string) (err error)
   951  //sys	Setdomainname(p []byte) (err error)
   952  //sys	Sethostname(p []byte) (err error)
   953  //sysnb	Setpgid(pid int, pgid int) (err error)
   954  //sysnb	Setsid() (pid int, err error)
   955  //sysnb	Settimeofday(tv *Timeval) (err error)
   956  
   957  // issue 1435.
   958  // On linux Setuid and Setgid only affects the current thread, not the process.
   959  // This does not match what most callers expect so we must return an error
   960  // here rather than letting the caller think that the call succeeded.
   961  
   962  func Setuid(uid int) (err error) {
   963  	return EOPNOTSUPP
   964  }
   965  
   966  func Setgid(gid int) (err error) {
   967  	return EOPNOTSUPP
   968  }
   969  
   970  //sys	Setpriority(which int, who int, prio int) (err error)
   971  //sys	Setxattr(path string, attr string, data []byte, flags int) (err error)
   972  //sys	Sync()
   973  //sysnb	Sysinfo(info *Sysinfo_t) (err error)
   974  //sys	Tee(rfd int, wfd int, len int, flags int) (n int64, err error)
   975  //sysnb	Tgkill(tgid int, tid int, sig Signal) (err error)
   976  //sysnb	Times(tms *Tms) (ticks uintptr, err error)
   977  //sysnb	Umask(mask int) (oldmask int)
   978  //sysnb	Uname(buf *Utsname) (err error)
   979  //sys	Unmount(target string, flags int) (err error) = SYS_UMOUNT2
   980  //sys	Unshare(flags int) (err error)
   981  //sys	Ustat(dev int, ubuf *Ustat_t) (err error)
   982  //sys	Utime(path string, buf *Utimbuf) (err error)
   983  //sys	write(fd int, p []byte) (n int, err error)
   984  //sys	exitThread(code int) (err error) = SYS_EXIT
   985  //sys	readlen(fd int, p *byte, np int) (n int, err error) = SYS_READ
   986  //sys	writelen(fd int, p *byte, np int) (n int, err error) = SYS_WRITE
   987  
   988  // mmap varies by architecture; see syscall_linux_*.go.
   989  //sys	munmap(addr uintptr, length uintptr) (err error)
   990  
   991  var mapper = &mmapper{
   992  	active: make(map[*byte][]byte),
   993  	mmap:   mmap,
   994  	munmap: munmap,
   995  }
   996  
   997  func Mmap(fd int, offset int64, length int, prot int, flags int) (data []byte, err error) {
   998  	return mapper.Mmap(fd, offset, length, prot, flags)
   999  }
  1000  
  1001  func Munmap(b []byte) (err error) {
  1002  	return mapper.Munmap(b)
  1003  }
  1004  
  1005  //sys	Madvise(b []byte, advice int) (err error)
  1006  //sys	Mprotect(b []byte, prot int) (err error)
  1007  //sys	Mlock(b []byte) (err error)
  1008  //sys	Munlock(b []byte) (err error)
  1009  //sys	Mlockall(flags int) (err error)
  1010  //sys	Munlockall() (err error)
  1011  

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