Source file src/syscall/syscall_linux.go

     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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