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 (
    15  	"internal/itoa"
    16  	"runtime"
    17  	"unsafe"
    18  )
    19  
    20  // N.B. RawSyscall6 is provided via linkname by runtime/internal/syscall.
    21  //
    22  // Errno is uintptr and thus compatible with the runtime/internal/syscall
    23  // definition.
    24  
    25  func RawSyscall6(trap, a1, a2, a3, a4, a5, a6 uintptr) (r1, r2 uintptr, err Errno)
    26  
    27  // Pull in entersyscall/exitsyscall for Syscall/Syscall6.
    28  //
    29  // Note that this can't be a push linkname because the runtime already has a
    30  // nameless linkname to export to assembly here and in x/sys. Additionally,
    31  // entersyscall fetches the caller PC and SP and thus can't have a wrapper
    32  // inbetween.
    33  
    34  //go:linkname runtime_entersyscall runtime.entersyscall
    35  func runtime_entersyscall()
    36  
    37  //go:linkname runtime_exitsyscall runtime.exitsyscall
    38  func runtime_exitsyscall()
    39  
    40  // N.B. For the Syscall functions below:
    41  //
    42  // //go:uintptrkeepalive because the uintptr argument may be converted pointers
    43  // that need to be kept alive in the caller (this is implied for RawSyscall6
    44  // since it has no body).
    45  //
    46  // //go:nosplit because stack copying does not account for uintptrkeepalive, so
    47  // the stack must not grow. Stack copying cannot blindly assume that all
    48  // uintptr arguments are pointers, because some values may look like pointers,
    49  // but not really be pointers, and adjusting their value would break the call.
    50  //
    51  // //go:norace, on RawSyscall, to avoid race instrumentation if RawSyscall is
    52  // called after fork, or from a signal handler.
    53  //
    54  // //go:linkname to ensure ABI wrappers are generated for external callers
    55  // (notably x/sys/unix assembly).
    56  
    57  //go:uintptrkeepalive
    58  //go:nosplit
    59  //go:norace
    60  //go:linkname RawSyscall
    61  func RawSyscall(trap, a1, a2, a3 uintptr) (r1, r2 uintptr, err Errno) {
    62  	return RawSyscall6(trap, a1, a2, a3, 0, 0, 0)
    63  }
    64  
    65  //go:uintptrkeepalive
    66  //go:nosplit
    67  //go:linkname Syscall
    68  func Syscall(trap, a1, a2, a3 uintptr) (r1, r2 uintptr, err Errno) {
    69  	runtime_entersyscall()
    70  	// N.B. Calling RawSyscall here is unsafe with atomic coverage
    71  	// instrumentation and race mode.
    72  	//
    73  	// Coverage instrumentation will add a sync/atomic call to RawSyscall.
    74  	// Race mode will add race instrumentation to sync/atomic. Race
    75  	// instrumentation requires a P, which we no longer have.
    76  	//
    77  	// RawSyscall6 is fine because it is implemented in assembly and thus
    78  	// has no coverage instrumentation.
    79  	//
    80  	// This is typically not a problem in the runtime because cmd/go avoids
    81  	// adding coverage instrumentation to the runtime in race mode.
    82  	r1, r2, err = RawSyscall6(trap, a1, a2, a3, 0, 0, 0)
    83  	runtime_exitsyscall()
    84  	return
    85  }
    86  
    87  //go:uintptrkeepalive
    88  //go:nosplit
    89  //go:linkname Syscall6
    90  func Syscall6(trap, a1, a2, a3, a4, a5, a6 uintptr) (r1, r2 uintptr, err Errno) {
    91  	runtime_entersyscall()
    92  	r1, r2, err = RawSyscall6(trap, a1, a2, a3, a4, a5, a6)
    93  	runtime_exitsyscall()
    94  	return
    95  }
    96  
    97  func rawSyscallNoError(trap, a1, a2, a3 uintptr) (r1, r2 uintptr)
    98  func rawVforkSyscall(trap, a1, a2, a3 uintptr) (r1 uintptr, err Errno)
    99  
   100  /*
   101   * Wrapped
   102   */
   103  
   104  func Access(path string, mode uint32) (err error) {
   105  	return Faccessat(_AT_FDCWD, path, mode, 0)
   106  }
   107  
   108  func Chmod(path string, mode uint32) (err error) {
   109  	return Fchmodat(_AT_FDCWD, path, mode, 0)
   110  }
   111  
   112  func Chown(path string, uid int, gid int) (err error) {
   113  	return Fchownat(_AT_FDCWD, path, uid, gid, 0)
   114  }
   115  
   116  func Creat(path string, mode uint32) (fd int, err error) {
   117  	return Open(path, O_CREAT|O_WRONLY|O_TRUNC, mode)
   118  }
   119  
   120  func EpollCreate(size int) (fd int, err error) {
   121  	if size <= 0 {
   122  		return -1, EINVAL
   123  	}
   124  	return EpollCreate1(0)
   125  }
   126  
   127  func isGroupMember(gid int) bool {
   128  	groups, err := Getgroups()
   129  	if err != nil {
   130  		return false
   131  	}
   132  
   133  	for _, g := range groups {
   134  		if g == gid {
   135  			return true
   136  		}
   137  	}
   138  	return false
   139  }
   140  
   141  func isCapDacOverrideSet() bool {
   142  	const _CAP_DAC_OVERRIDE = 1
   143  	var c caps
   144  	c.hdr.version = _LINUX_CAPABILITY_VERSION_3
   145  
   146  	_, _, err := RawSyscall(SYS_CAPGET, uintptr(unsafe.Pointer(&c.hdr)), uintptr(unsafe.Pointer(&c.data[0])), 0)
   147  
   148  	return err == 0 && c.data[0].effective&capToMask(_CAP_DAC_OVERRIDE) != 0
   149  }
   150  
   151  //sys	faccessat(dirfd int, path string, mode uint32) (err error)
   152  //sys	faccessat2(dirfd int, path string, mode uint32, flags int) (err error) = _SYS_faccessat2
   153  
   154  func Faccessat(dirfd int, path string, mode uint32, flags int) (err error) {
   155  	if flags == 0 {
   156  		return faccessat(dirfd, path, mode)
   157  	}
   158  
   159  	// Attempt to use the newer faccessat2, which supports flags directly,
   160  	// falling back if it doesn't exist.
   161  	//
   162  	// Don't attempt on Android, which does not allow faccessat2 through
   163  	// its seccomp policy [1] on any version of Android as of 2022-12-20.
   164  	//
   165  	// [1] https://cs.android.com/android/platform/superproject/+/master:bionic/libc/SECCOMP_BLOCKLIST_APP.TXT;l=4;drc=dbb8670dfdcc677f7e3b9262e93800fa14c4e417
   166  	if runtime.GOOS != "android" {
   167  		if err := faccessat2(dirfd, path, mode, flags); err != ENOSYS && err != EPERM {
   168  			return err
   169  		}
   170  	}
   171  
   172  	// The Linux kernel faccessat system call does not take any flags.
   173  	// The glibc faccessat implements the flags itself; see
   174  	// https://sourceware.org/git/?p=glibc.git;a=blob;f=sysdeps/unix/sysv/linux/faccessat.c;hb=HEAD
   175  	// Because people naturally expect syscall.Faccessat to act
   176  	// like C faccessat, we do the same.
   177  
   178  	if flags & ^(_AT_SYMLINK_NOFOLLOW|_AT_EACCESS) != 0 {
   179  		return EINVAL
   180  	}
   181  
   182  	var st Stat_t
   183  	if err := fstatat(dirfd, path, &st, flags&_AT_SYMLINK_NOFOLLOW); err != nil {
   184  		return err
   185  	}
   186  
   187  	mode &= 7
   188  	if mode == 0 {
   189  		return nil
   190  	}
   191  
   192  	// Fallback to checking permission bits.
   193  	var uid int
   194  	if flags&_AT_EACCESS != 0 {
   195  		uid = Geteuid()
   196  		if uid != 0 && isCapDacOverrideSet() {
   197  			// If CAP_DAC_OVERRIDE is set, file access check is
   198  			// done by the kernel in the same way as for root
   199  			// (see generic_permission() in the Linux sources).
   200  			uid = 0
   201  		}
   202  	} else {
   203  		uid = Getuid()
   204  	}
   205  
   206  	if uid == 0 {
   207  		if mode&1 == 0 {
   208  			// Root can read and write any file.
   209  			return nil
   210  		}
   211  		if st.Mode&0111 != 0 {
   212  			// Root can execute any file that anybody can execute.
   213  			return nil
   214  		}
   215  		return EACCES
   216  	}
   217  
   218  	var fmode uint32
   219  	if uint32(uid) == st.Uid {
   220  		fmode = (st.Mode >> 6) & 7
   221  	} else {
   222  		var gid int
   223  		if flags&_AT_EACCESS != 0 {
   224  			gid = Getegid()
   225  		} else {
   226  			gid = Getgid()
   227  		}
   228  
   229  		if uint32(gid) == st.Gid || isGroupMember(int(st.Gid)) {
   230  			fmode = (st.Mode >> 3) & 7
   231  		} else {
   232  			fmode = st.Mode & 7
   233  		}
   234  	}
   235  
   236  	if fmode&mode == mode {
   237  		return nil
   238  	}
   239  
   240  	return EACCES
   241  }
   242  
   243  //sys	fchmodat(dirfd int, path string, mode uint32) (err error)
   244  //sys	fchmodat2(dirfd int, path string, mode uint32, flags int) (err error) = _SYS_fchmodat2
   245  
   246  func Fchmodat(dirfd int, path string, mode uint32, flags int) error {
   247  	// Linux fchmodat doesn't support the flags parameter, but fchmodat2 does.
   248  	// Try fchmodat2 if flags are specified.
   249  	if flags != 0 {
   250  		err := fchmodat2(dirfd, path, mode, flags)
   251  		if err == ENOSYS {
   252  			// fchmodat2 isn't available. If the flags are known to be valid,
   253  			// return EOPNOTSUPP to indicate that fchmodat doesn't support them.
   254  			if flags&^(_AT_SYMLINK_NOFOLLOW|_AT_EMPTY_PATH) != 0 {
   255  				return EINVAL
   256  			} else if flags&(_AT_SYMLINK_NOFOLLOW|_AT_EMPTY_PATH) != 0 {
   257  				return EOPNOTSUPP
   258  			}
   259  		}
   260  		return err
   261  	}
   262  	return fchmodat(dirfd, path, mode)
   263  }
   264  
   265  //sys	linkat(olddirfd int, oldpath string, newdirfd int, newpath string, flags int) (err error)
   266  
   267  func Link(oldpath string, newpath string) (err error) {
   268  	return linkat(_AT_FDCWD, oldpath, _AT_FDCWD, newpath, 0)
   269  }
   270  
   271  func Mkdir(path string, mode uint32) (err error) {
   272  	return Mkdirat(_AT_FDCWD, path, mode)
   273  }
   274  
   275  func Mknod(path string, mode uint32, dev int) (err error) {
   276  	return Mknodat(_AT_FDCWD, path, mode, dev)
   277  }
   278  
   279  func Open(path string, mode int, perm uint32) (fd int, err error) {
   280  	return openat(_AT_FDCWD, path, mode|O_LARGEFILE, perm)
   281  }
   282  
   283  //sys	openat(dirfd int, path string, flags int, mode uint32) (fd int, err error)
   284  
   285  func Openat(dirfd int, path string, flags int, mode uint32) (fd int, err error) {
   286  	return openat(dirfd, path, flags|O_LARGEFILE, mode)
   287  }
   288  
   289  func Pipe(p []int) error {
   290  	return Pipe2(p, 0)
   291  }
   292  
   293  //sysnb pipe2(p *[2]_C_int, flags int) (err error)
   294  
   295  func Pipe2(p []int, flags int) error {
   296  	if len(p) != 2 {
   297  		return EINVAL
   298  	}
   299  	var pp [2]_C_int
   300  	err := pipe2(&pp, flags)
   301  	if err == nil {
   302  		p[0] = int(pp[0])
   303  		p[1] = int(pp[1])
   304  	}
   305  	return err
   306  }
   307  
   308  //sys	readlinkat(dirfd int, path string, buf []byte) (n int, err error)
   309  
   310  func Readlink(path string, buf []byte) (n int, err error) {
   311  	return readlinkat(_AT_FDCWD, path, buf)
   312  }
   313  
   314  func Rename(oldpath string, newpath string) (err error) {
   315  	return Renameat(_AT_FDCWD, oldpath, _AT_FDCWD, newpath)
   316  }
   317  
   318  func Rmdir(path string) error {
   319  	return unlinkat(_AT_FDCWD, path, _AT_REMOVEDIR)
   320  }
   321  
   322  //sys	symlinkat(oldpath string, newdirfd int, newpath string) (err error)
   323  
   324  func Symlink(oldpath string, newpath string) (err error) {
   325  	return symlinkat(oldpath, _AT_FDCWD, newpath)
   326  }
   327  
   328  func Unlink(path string) error {
   329  	return unlinkat(_AT_FDCWD, path, 0)
   330  }
   331  
   332  //sys	unlinkat(dirfd int, path string, flags int) (err error)
   333  
   334  func Unlinkat(dirfd int, path string) error {
   335  	return unlinkat(dirfd, path, 0)
   336  }
   337  
   338  func Utimes(path string, tv []Timeval) (err error) {
   339  	if len(tv) != 2 {
   340  		return EINVAL
   341  	}
   342  	return utimes(path, (*[2]Timeval)(unsafe.Pointer(&tv[0])))
   343  }
   344  
   345  //sys	utimensat(dirfd int, path string, times *[2]Timespec, flag int) (err error)
   346  
   347  func UtimesNano(path string, ts []Timespec) (err error) {
   348  	if len(ts) != 2 {
   349  		return EINVAL
   350  	}
   351  	return utimensat(_AT_FDCWD, path, (*[2]Timespec)(unsafe.Pointer(&ts[0])), 0)
   352  }
   353  
   354  func Futimesat(dirfd int, path string, tv []Timeval) (err error) {
   355  	if len(tv) != 2 {
   356  		return EINVAL
   357  	}
   358  	return futimesat(dirfd, path, (*[2]Timeval)(unsafe.Pointer(&tv[0])))
   359  }
   360  
   361  func Futimes(fd int, tv []Timeval) (err error) {
   362  	// Believe it or not, this is the best we can do on Linux
   363  	// (and is what glibc does).
   364  	return Utimes("/proc/self/fd/"+itoa.Itoa(fd), tv)
   365  }
   366  
   367  const ImplementsGetwd = true
   368  
   369  //sys	Getcwd(buf []byte) (n int, err error)
   370  
   371  func Getwd() (wd string, err error) {
   372  	var buf [PathMax]byte
   373  	n, err := Getcwd(buf[0:])
   374  	if err != nil {
   375  		return "", err
   376  	}
   377  	// Getcwd returns the number of bytes written to buf, including the NUL.
   378  	if n < 1 || n > len(buf) || buf[n-1] != 0 {
   379  		return "", EINVAL
   380  	}
   381  	// In some cases, Linux can return a path that starts with the
   382  	// "(unreachable)" prefix, which can potentially be a valid relative
   383  	// path. To work around that, return ENOENT if path is not absolute.
   384  	if buf[0] != '/' {
   385  		return "", ENOENT
   386  	}
   387  
   388  	return string(buf[0 : n-1]), nil
   389  }
   390  
   391  func Getgroups() (gids []int, err error) {
   392  	n, err := getgroups(0, nil)
   393  	if err != nil {
   394  		return nil, err
   395  	}
   396  	if n == 0 {
   397  		return nil, nil
   398  	}
   399  
   400  	// Sanity check group count. Max is 1<<16 on Linux.
   401  	if n < 0 || n > 1<<20 {
   402  		return nil, EINVAL
   403  	}
   404  
   405  	a := make([]_Gid_t, n)
   406  	n, err = getgroups(n, &a[0])
   407  	if err != nil {
   408  		return nil, err
   409  	}
   410  	gids = make([]int, n)
   411  	for i, v := range a[0:n] {
   412  		gids[i] = int(v)
   413  	}
   414  	return
   415  }
   416  
   417  var cgo_libc_setgroups unsafe.Pointer // non-nil if cgo linked.
   418  
   419  func Setgroups(gids []int) (err error) {
   420  	n := uintptr(len(gids))
   421  	if n == 0 {
   422  		if cgo_libc_setgroups == nil {
   423  			if _, _, e1 := AllThreadsSyscall(_SYS_setgroups, 0, 0, 0); e1 != 0 {
   424  				err = errnoErr(e1)
   425  			}
   426  			return
   427  		}
   428  		if ret := cgocaller(cgo_libc_setgroups, 0, 0); ret != 0 {
   429  			err = errnoErr(Errno(ret))
   430  		}
   431  		return
   432  	}
   433  
   434  	a := make([]_Gid_t, len(gids))
   435  	for i, v := range gids {
   436  		a[i] = _Gid_t(v)
   437  	}
   438  	if cgo_libc_setgroups == nil {
   439  		if _, _, e1 := AllThreadsSyscall(_SYS_setgroups, n, uintptr(unsafe.Pointer(&a[0])), 0); e1 != 0 {
   440  			err = errnoErr(e1)
   441  		}
   442  		return
   443  	}
   444  	if ret := cgocaller(cgo_libc_setgroups, n, uintptr(unsafe.Pointer(&a[0]))); ret != 0 {
   445  		err = errnoErr(Errno(ret))
   446  	}
   447  	return
   448  }
   449  
   450  type WaitStatus uint32
   451  
   452  // Wait status is 7 bits at bottom, either 0 (exited),
   453  // 0x7F (stopped), or a signal number that caused an exit.
   454  // The 0x80 bit is whether there was a core dump.
   455  // An extra number (exit code, signal causing a stop)
   456  // is in the high bits. At least that's the idea.
   457  // There are various irregularities. For example, the
   458  // "continued" status is 0xFFFF, distinguishing itself
   459  // from stopped via the core dump bit.
   460  
   461  const (
   462  	mask    = 0x7F
   463  	core    = 0x80
   464  	exited  = 0x00
   465  	stopped = 0x7F
   466  	shift   = 8
   467  )
   468  
   469  func (w WaitStatus) Exited() bool { return w&mask == exited }
   470  
   471  func (w WaitStatus) Signaled() bool { return w&mask != stopped && w&mask != exited }
   472  
   473  func (w WaitStatus) Stopped() bool { return w&0xFF == stopped }
   474  
   475  func (w WaitStatus) Continued() bool { return w == 0xFFFF }
   476  
   477  func (w WaitStatus) CoreDump() bool { return w.Signaled() && w&core != 0 }
   478  
   479  func (w WaitStatus) ExitStatus() int {
   480  	if !w.Exited() {
   481  		return -1
   482  	}
   483  	return int(w>>shift) & 0xFF
   484  }
   485  
   486  func (w WaitStatus) Signal() Signal {
   487  	if !w.Signaled() {
   488  		return -1
   489  	}
   490  	return Signal(w & mask)
   491  }
   492  
   493  func (w WaitStatus) StopSignal() Signal {
   494  	if !w.Stopped() {
   495  		return -1
   496  	}
   497  	return Signal(w>>shift) & 0xFF
   498  }
   499  
   500  func (w WaitStatus) TrapCause() int {
   501  	if w.StopSignal() != SIGTRAP {
   502  		return -1
   503  	}
   504  	return int(w>>shift) >> 8
   505  }
   506  
   507  //sys	wait4(pid int, wstatus *_C_int, options int, rusage *Rusage) (wpid int, err error)
   508  
   509  func Wait4(pid int, wstatus *WaitStatus, options int, rusage *Rusage) (wpid int, err error) {
   510  	var status _C_int
   511  	wpid, err = wait4(pid, &status, options, rusage)
   512  	if wstatus != nil {
   513  		*wstatus = WaitStatus(status)
   514  	}
   515  	return
   516  }
   517  
   518  func Mkfifo(path string, mode uint32) (err error) {
   519  	return Mknod(path, mode|S_IFIFO, 0)
   520  }
   521  
   522  func (sa *SockaddrInet4) sockaddr() (unsafe.Pointer, _Socklen, error) {
   523  	if sa.Port < 0 || sa.Port > 0xFFFF {
   524  		return nil, 0, EINVAL
   525  	}
   526  	sa.raw.Family = AF_INET
   527  	p := (*[2]byte)(unsafe.Pointer(&sa.raw.Port))
   528  	p[0] = byte(sa.Port >> 8)
   529  	p[1] = byte(sa.Port)
   530  	sa.raw.Addr = sa.Addr
   531  	return unsafe.Pointer(&sa.raw), SizeofSockaddrInet4, nil
   532  }
   533  
   534  func (sa *SockaddrInet6) sockaddr() (unsafe.Pointer, _Socklen, error) {
   535  	if sa.Port < 0 || sa.Port > 0xFFFF {
   536  		return nil, 0, EINVAL
   537  	}
   538  	sa.raw.Family = AF_INET6
   539  	p := (*[2]byte)(unsafe.Pointer(&sa.raw.Port))
   540  	p[0] = byte(sa.Port >> 8)
   541  	p[1] = byte(sa.Port)
   542  	sa.raw.Scope_id = sa.ZoneId
   543  	sa.raw.Addr = sa.Addr
   544  	return unsafe.Pointer(&sa.raw), SizeofSockaddrInet6, nil
   545  }
   546  
   547  func (sa *SockaddrUnix) sockaddr() (unsafe.Pointer, _Socklen, error) {
   548  	name := sa.Name
   549  	n := len(name)
   550  	if n > len(sa.raw.Path) {
   551  		return nil, 0, EINVAL
   552  	}
   553  	if n == len(sa.raw.Path) && name[0] != '@' {
   554  		return nil, 0, EINVAL
   555  	}
   556  	sa.raw.Family = AF_UNIX
   557  	for i := 0; i < n; i++ {
   558  		sa.raw.Path[i] = int8(name[i])
   559  	}
   560  	// length is family (uint16), name, NUL.
   561  	sl := _Socklen(2)
   562  	if n > 0 {
   563  		sl += _Socklen(n) + 1
   564  	}
   565  	if sa.raw.Path[0] == '@' || (sa.raw.Path[0] == 0 && sl > 3) {
   566  		// Check sl > 3 so we don't change unnamed socket behavior.
   567  		sa.raw.Path[0] = 0
   568  		// Don't count trailing NUL for abstract address.
   569  		sl--
   570  	}
   571  
   572  	return unsafe.Pointer(&sa.raw), sl, nil
   573  }
   574  
   575  type SockaddrLinklayer struct {
   576  	Protocol uint16
   577  	Ifindex  int
   578  	Hatype   uint16
   579  	Pkttype  uint8
   580  	Halen    uint8
   581  	Addr     [8]byte
   582  	raw      RawSockaddrLinklayer
   583  }
   584  
   585  func (sa *SockaddrLinklayer) sockaddr() (unsafe.Pointer, _Socklen, error) {
   586  	if sa.Ifindex < 0 || sa.Ifindex > 0x7fffffff {
   587  		return nil, 0, EINVAL
   588  	}
   589  	sa.raw.Family = AF_PACKET
   590  	sa.raw.Protocol = sa.Protocol
   591  	sa.raw.Ifindex = int32(sa.Ifindex)
   592  	sa.raw.Hatype = sa.Hatype
   593  	sa.raw.Pkttype = sa.Pkttype
   594  	sa.raw.Halen = sa.Halen
   595  	sa.raw.Addr = sa.Addr
   596  	return unsafe.Pointer(&sa.raw), SizeofSockaddrLinklayer, nil
   597  }
   598  
   599  type SockaddrNetlink struct {
   600  	Family uint16
   601  	Pad    uint16
   602  	Pid    uint32
   603  	Groups uint32
   604  	raw    RawSockaddrNetlink
   605  }
   606  
   607  func (sa *SockaddrNetlink) sockaddr() (unsafe.Pointer, _Socklen, error) {
   608  	sa.raw.Family = AF_NETLINK
   609  	sa.raw.Pad = sa.Pad
   610  	sa.raw.Pid = sa.Pid
   611  	sa.raw.Groups = sa.Groups
   612  	return unsafe.Pointer(&sa.raw), SizeofSockaddrNetlink, nil
   613  }
   614  
   615  func anyToSockaddr(rsa *RawSockaddrAny) (Sockaddr, error) {
   616  	switch rsa.Addr.Family {
   617  	case AF_NETLINK:
   618  		pp := (*RawSockaddrNetlink)(unsafe.Pointer(rsa))
   619  		sa := new(SockaddrNetlink)
   620  		sa.Family = pp.Family
   621  		sa.Pad = pp.Pad
   622  		sa.Pid = pp.Pid
   623  		sa.Groups = pp.Groups
   624  		return sa, nil
   625  
   626  	case AF_PACKET:
   627  		pp := (*RawSockaddrLinklayer)(unsafe.Pointer(rsa))
   628  		sa := new(SockaddrLinklayer)
   629  		sa.Protocol = pp.Protocol
   630  		sa.Ifindex = int(pp.Ifindex)
   631  		sa.Hatype = pp.Hatype
   632  		sa.Pkttype = pp.Pkttype
   633  		sa.Halen = pp.Halen
   634  		sa.Addr = pp.Addr
   635  		return sa, nil
   636  
   637  	case AF_UNIX:
   638  		pp := (*RawSockaddrUnix)(unsafe.Pointer(rsa))
   639  		sa := new(SockaddrUnix)
   640  		if pp.Path[0] == 0 {
   641  			// "Abstract" Unix domain socket.
   642  			// Rewrite leading NUL as @ for textual display.
   643  			// (This is the standard convention.)
   644  			// Not friendly to overwrite in place,
   645  			// but the callers below don't care.
   646  			pp.Path[0] = '@'
   647  		}
   648  
   649  		// Assume path ends at NUL.
   650  		// This is not technically the Linux semantics for
   651  		// abstract Unix domain sockets--they are supposed
   652  		// to be uninterpreted fixed-size binary blobs--but
   653  		// everyone uses this convention.
   654  		n := 0
   655  		for n < len(pp.Path) && pp.Path[n] != 0 {
   656  			n++
   657  		}
   658  		sa.Name = string(unsafe.Slice((*byte)(unsafe.Pointer(&pp.Path[0])), n))
   659  		return sa, nil
   660  
   661  	case AF_INET:
   662  		pp := (*RawSockaddrInet4)(unsafe.Pointer(rsa))
   663  		sa := new(SockaddrInet4)
   664  		p := (*[2]byte)(unsafe.Pointer(&pp.Port))
   665  		sa.Port = int(p[0])<<8 + int(p[1])
   666  		sa.Addr = pp.Addr
   667  		return sa, nil
   668  
   669  	case AF_INET6:
   670  		pp := (*RawSockaddrInet6)(unsafe.Pointer(rsa))
   671  		sa := new(SockaddrInet6)
   672  		p := (*[2]byte)(unsafe.Pointer(&pp.Port))
   673  		sa.Port = int(p[0])<<8 + int(p[1])
   674  		sa.ZoneId = pp.Scope_id
   675  		sa.Addr = pp.Addr
   676  		return sa, nil
   677  	}
   678  	return nil, EAFNOSUPPORT
   679  }
   680  
   681  func Accept4(fd int, flags int) (nfd int, sa Sockaddr, err error) {
   682  	var rsa RawSockaddrAny
   683  	var len _Socklen = SizeofSockaddrAny
   684  	nfd, err = accept4(fd, &rsa, &len, flags)
   685  	if err != nil {
   686  		return
   687  	}
   688  	if len > SizeofSockaddrAny {
   689  		panic("RawSockaddrAny too small")
   690  	}
   691  	sa, err = anyToSockaddr(&rsa)
   692  	if err != nil {
   693  		Close(nfd)
   694  		nfd = 0
   695  	}
   696  	return
   697  }
   698  
   699  func Getsockname(fd int) (sa Sockaddr, err error) {
   700  	var rsa RawSockaddrAny
   701  	var len _Socklen = SizeofSockaddrAny
   702  	if err = getsockname(fd, &rsa, &len); err != nil {
   703  		return
   704  	}
   705  	return anyToSockaddr(&rsa)
   706  }
   707  
   708  func GetsockoptInet4Addr(fd, level, opt int) (value [4]byte, err error) {
   709  	vallen := _Socklen(4)
   710  	err = getsockopt(fd, level, opt, unsafe.Pointer(&value[0]), &vallen)
   711  	return value, err
   712  }
   713  
   714  func GetsockoptIPMreq(fd, level, opt int) (*IPMreq, error) {
   715  	var value IPMreq
   716  	vallen := _Socklen(SizeofIPMreq)
   717  	err := getsockopt(fd, level, opt, unsafe.Pointer(&value), &vallen)
   718  	return &value, err
   719  }
   720  
   721  func GetsockoptIPMreqn(fd, level, opt int) (*IPMreqn, error) {
   722  	var value IPMreqn
   723  	vallen := _Socklen(SizeofIPMreqn)
   724  	err := getsockopt(fd, level, opt, unsafe.Pointer(&value), &vallen)
   725  	return &value, err
   726  }
   727  
   728  func GetsockoptIPv6Mreq(fd, level, opt int) (*IPv6Mreq, error) {
   729  	var value IPv6Mreq
   730  	vallen := _Socklen(SizeofIPv6Mreq)
   731  	err := getsockopt(fd, level, opt, unsafe.Pointer(&value), &vallen)
   732  	return &value, err
   733  }
   734  
   735  func GetsockoptIPv6MTUInfo(fd, level, opt int) (*IPv6MTUInfo, error) {
   736  	var value IPv6MTUInfo
   737  	vallen := _Socklen(SizeofIPv6MTUInfo)
   738  	err := getsockopt(fd, level, opt, unsafe.Pointer(&value), &vallen)
   739  	return &value, err
   740  }
   741  
   742  func GetsockoptICMPv6Filter(fd, level, opt int) (*ICMPv6Filter, error) {
   743  	var value ICMPv6Filter
   744  	vallen := _Socklen(SizeofICMPv6Filter)
   745  	err := getsockopt(fd, level, opt, unsafe.Pointer(&value), &vallen)
   746  	return &value, err
   747  }
   748  
   749  func GetsockoptUcred(fd, level, opt int) (*Ucred, error) {
   750  	var value Ucred
   751  	vallen := _Socklen(SizeofUcred)
   752  	err := getsockopt(fd, level, opt, unsafe.Pointer(&value), &vallen)
   753  	return &value, err
   754  }
   755  
   756  func SetsockoptIPMreqn(fd, level, opt int, mreq *IPMreqn) (err error) {
   757  	return setsockopt(fd, level, opt, unsafe.Pointer(mreq), unsafe.Sizeof(*mreq))
   758  }
   759  
   760  func recvmsgRaw(fd int, p, oob []byte, flags int, rsa *RawSockaddrAny) (n, oobn int, recvflags int, err error) {
   761  	var msg Msghdr
   762  	msg.Name = (*byte)(unsafe.Pointer(rsa))
   763  	msg.Namelen = uint32(SizeofSockaddrAny)
   764  	var iov Iovec
   765  	if len(p) > 0 {
   766  		iov.Base = &p[0]
   767  		iov.SetLen(len(p))
   768  	}
   769  	var dummy byte
   770  	if len(oob) > 0 {
   771  		if len(p) == 0 {
   772  			var sockType int
   773  			sockType, err = GetsockoptInt(fd, SOL_SOCKET, SO_TYPE)
   774  			if err != nil {
   775  				return
   776  			}
   777  			// receive at least one normal byte
   778  			if sockType != SOCK_DGRAM {
   779  				iov.Base = &dummy
   780  				iov.SetLen(1)
   781  			}
   782  		}
   783  		msg.Control = &oob[0]
   784  		msg.SetControllen(len(oob))
   785  	}
   786  	msg.Iov = &iov
   787  	msg.Iovlen = 1
   788  	if n, err = recvmsg(fd, &msg, flags); err != nil {
   789  		return
   790  	}
   791  	oobn = int(msg.Controllen)
   792  	recvflags = int(msg.Flags)
   793  	return
   794  }
   795  
   796  func sendmsgN(fd int, p, oob []byte, ptr unsafe.Pointer, salen _Socklen, flags int) (n int, err error) {
   797  	var msg Msghdr
   798  	msg.Name = (*byte)(ptr)
   799  	msg.Namelen = uint32(salen)
   800  	var iov Iovec
   801  	if len(p) > 0 {
   802  		iov.Base = &p[0]
   803  		iov.SetLen(len(p))
   804  	}
   805  	var dummy byte
   806  	if len(oob) > 0 {
   807  		if len(p) == 0 {
   808  			var sockType int
   809  			sockType, err = GetsockoptInt(fd, SOL_SOCKET, SO_TYPE)
   810  			if err != nil {
   811  				return 0, err
   812  			}
   813  			// send at least one normal byte
   814  			if sockType != SOCK_DGRAM {
   815  				iov.Base = &dummy
   816  				iov.SetLen(1)
   817  			}
   818  		}
   819  		msg.Control = &oob[0]
   820  		msg.SetControllen(len(oob))
   821  	}
   822  	msg.Iov = &iov
   823  	msg.Iovlen = 1
   824  	if n, err = sendmsg(fd, &msg, flags); err != nil {
   825  		return 0, err
   826  	}
   827  	if len(oob) > 0 && len(p) == 0 {
   828  		n = 0
   829  	}
   830  	return n, nil
   831  }
   832  
   833  // BindToDevice binds the socket associated with fd to device.
   834  func BindToDevice(fd int, device string) (err error) {
   835  	return SetsockoptString(fd, SOL_SOCKET, SO_BINDTODEVICE, device)
   836  }
   837  
   838  //sys	ptrace(request int, pid int, addr uintptr, data uintptr) (err error)
   839  //sys	ptracePtr(request int, pid int, addr uintptr, data unsafe.Pointer) (err error) = SYS_PTRACE
   840  
   841  func ptracePeek(req int, pid int, addr uintptr, out []byte) (count int, err error) {
   842  	// The peek requests are machine-size oriented, so we wrap it
   843  	// to retrieve arbitrary-length data.
   844  
   845  	// The ptrace syscall differs from glibc's ptrace.
   846  	// Peeks returns the word in *data, not as the return value.
   847  
   848  	var buf [sizeofPtr]byte
   849  
   850  	// Leading edge. PEEKTEXT/PEEKDATA don't require aligned
   851  	// access (PEEKUSER warns that it might), but if we don't
   852  	// align our reads, we might straddle an unmapped page
   853  	// boundary and not get the bytes leading up to the page
   854  	// boundary.
   855  	n := 0
   856  	if addr%sizeofPtr != 0 {
   857  		err = ptracePtr(req, pid, addr-addr%sizeofPtr, unsafe.Pointer(&buf[0]))
   858  		if err != nil {
   859  			return 0, err
   860  		}
   861  		n += copy(out, buf[addr%sizeofPtr:])
   862  		out = out[n:]
   863  	}
   864  
   865  	// Remainder.
   866  	for len(out) > 0 {
   867  		// We use an internal buffer to guarantee alignment.
   868  		// It's not documented if this is necessary, but we're paranoid.
   869  		err = ptracePtr(req, pid, addr+uintptr(n), unsafe.Pointer(&buf[0]))
   870  		if err != nil {
   871  			return n, err
   872  		}
   873  		copied := copy(out, buf[0:])
   874  		n += copied
   875  		out = out[copied:]
   876  	}
   877  
   878  	return n, nil
   879  }
   880  
   881  func PtracePeekText(pid int, addr uintptr, out []byte) (count int, err error) {
   882  	return ptracePeek(PTRACE_PEEKTEXT, pid, addr, out)
   883  }
   884  
   885  func PtracePeekData(pid int, addr uintptr, out []byte) (count int, err error) {
   886  	return ptracePeek(PTRACE_PEEKDATA, pid, addr, out)
   887  }
   888  
   889  func ptracePoke(pokeReq int, peekReq int, pid int, addr uintptr, data []byte) (count int, err error) {
   890  	// As for ptracePeek, we need to align our accesses to deal
   891  	// with the possibility of straddling an invalid page.
   892  
   893  	// Leading edge.
   894  	n := 0
   895  	if addr%sizeofPtr != 0 {
   896  		var buf [sizeofPtr]byte
   897  		err = ptracePtr(peekReq, pid, addr-addr%sizeofPtr, unsafe.Pointer(&buf[0]))
   898  		if err != nil {
   899  			return 0, err
   900  		}
   901  		n += copy(buf[addr%sizeofPtr:], data)
   902  		word := *((*uintptr)(unsafe.Pointer(&buf[0])))
   903  		err = ptrace(pokeReq, pid, addr-addr%sizeofPtr, word)
   904  		if err != nil {
   905  			return 0, err
   906  		}
   907  		data = data[n:]
   908  	}
   909  
   910  	// Interior.
   911  	for len(data) > sizeofPtr {
   912  		word := *((*uintptr)(unsafe.Pointer(&data[0])))
   913  		err = ptrace(pokeReq, pid, addr+uintptr(n), word)
   914  		if err != nil {
   915  			return n, err
   916  		}
   917  		n += sizeofPtr
   918  		data = data[sizeofPtr:]
   919  	}
   920  
   921  	// Trailing edge.
   922  	if len(data) > 0 {
   923  		var buf [sizeofPtr]byte
   924  		err = ptracePtr(peekReq, pid, addr+uintptr(n), unsafe.Pointer(&buf[0]))
   925  		if err != nil {
   926  			return n, err
   927  		}
   928  		copy(buf[0:], data)
   929  		word := *((*uintptr)(unsafe.Pointer(&buf[0])))
   930  		err = ptrace(pokeReq, pid, addr+uintptr(n), word)
   931  		if err != nil {
   932  			return n, err
   933  		}
   934  		n += len(data)
   935  	}
   936  
   937  	return n, nil
   938  }
   939  
   940  func PtracePokeText(pid int, addr uintptr, data []byte) (count int, err error) {
   941  	return ptracePoke(PTRACE_POKETEXT, PTRACE_PEEKTEXT, pid, addr, data)
   942  }
   943  
   944  func PtracePokeData(pid int, addr uintptr, data []byte) (count int, err error) {
   945  	return ptracePoke(PTRACE_POKEDATA, PTRACE_PEEKDATA, pid, addr, data)
   946  }
   947  
   948  const (
   949  	_NT_PRSTATUS = 1
   950  )
   951  
   952  func PtraceGetRegs(pid int, regsout *PtraceRegs) (err error) {
   953  	var iov Iovec
   954  	iov.Base = (*byte)(unsafe.Pointer(regsout))
   955  	iov.SetLen(int(unsafe.Sizeof(*regsout)))
   956  	return ptracePtr(PTRACE_GETREGSET, pid, uintptr(_NT_PRSTATUS), unsafe.Pointer(&iov))
   957  }
   958  
   959  func PtraceSetRegs(pid int, regs *PtraceRegs) (err error) {
   960  	var iov Iovec
   961  	iov.Base = (*byte)(unsafe.Pointer(regs))
   962  	iov.SetLen(int(unsafe.Sizeof(*regs)))
   963  	return ptracePtr(PTRACE_SETREGSET, pid, uintptr(_NT_PRSTATUS), unsafe.Pointer(&iov))
   964  }
   965  
   966  func PtraceSetOptions(pid int, options int) (err error) {
   967  	return ptrace(PTRACE_SETOPTIONS, pid, 0, uintptr(options))
   968  }
   969  
   970  func PtraceGetEventMsg(pid int) (msg uint, err error) {
   971  	var data _C_long
   972  	err = ptracePtr(PTRACE_GETEVENTMSG, pid, 0, unsafe.Pointer(&data))
   973  	msg = uint(data)
   974  	return
   975  }
   976  
   977  func PtraceCont(pid int, signal int) (err error) {
   978  	return ptrace(PTRACE_CONT, pid, 0, uintptr(signal))
   979  }
   980  
   981  func PtraceSyscall(pid int, signal int) (err error) {
   982  	return ptrace(PTRACE_SYSCALL, pid, 0, uintptr(signal))
   983  }
   984  
   985  func PtraceSingleStep(pid int) (err error) { return ptrace(PTRACE_SINGLESTEP, pid, 0, 0) }
   986  
   987  func PtraceAttach(pid int) (err error) { return ptrace(PTRACE_ATTACH, pid, 0, 0) }
   988  
   989  func PtraceDetach(pid int) (err error) { return ptrace(PTRACE_DETACH, pid, 0, 0) }
   990  
   991  //sys	reboot(magic1 uint, magic2 uint, cmd int, arg string) (err error)
   992  
   993  func Reboot(cmd int) (err error) {
   994  	return reboot(LINUX_REBOOT_MAGIC1, LINUX_REBOOT_MAGIC2, cmd, "")
   995  }
   996  
   997  func ReadDirent(fd int, buf []byte) (n int, err error) {
   998  	return Getdents(fd, buf)
   999  }
  1000  
  1001  func direntIno(buf []byte) (uint64, bool) {
  1002  	return readInt(buf, unsafe.Offsetof(Dirent{}.Ino), unsafe.Sizeof(Dirent{}.Ino))
  1003  }
  1004  
  1005  func direntReclen(buf []byte) (uint64, bool) {
  1006  	return readInt(buf, unsafe.Offsetof(Dirent{}.Reclen), unsafe.Sizeof(Dirent{}.Reclen))
  1007  }
  1008  
  1009  func direntNamlen(buf []byte) (uint64, bool) {
  1010  	reclen, ok := direntReclen(buf)
  1011  	if !ok {
  1012  		return 0, false
  1013  	}
  1014  	return reclen - uint64(unsafe.Offsetof(Dirent{}.Name)), true
  1015  }
  1016  
  1017  //sys	mount(source string, target string, fstype string, flags uintptr, data *byte) (err error)
  1018  
  1019  func Mount(source string, target string, fstype string, flags uintptr, data string) (err error) {
  1020  	// Certain file systems get rather angry and EINVAL if you give
  1021  	// them an empty string of data, rather than NULL.
  1022  	if data == "" {
  1023  		return mount(source, target, fstype, flags, nil)
  1024  	}
  1025  	datap, err := BytePtrFromString(data)
  1026  	if err != nil {
  1027  		return err
  1028  	}
  1029  	return mount(source, target, fstype, flags, datap)
  1030  }
  1031  
  1032  // Sendto
  1033  // Recvfrom
  1034  // Socketpair
  1035  
  1036  /*
  1037   * Direct access
  1038   */
  1039  //sys	Acct(path string) (err error)
  1040  //sys	Adjtimex(buf *Timex) (state int, err error)
  1041  //sys	Chdir(path string) (err error)
  1042  //sys	Chroot(path string) (err error)
  1043  //sys	Close(fd int) (err error)
  1044  //sys	Dup(oldfd int) (fd int, err error)
  1045  //sys	Dup3(oldfd int, newfd int, flags int) (err error)
  1046  //sysnb	EpollCreate1(flag int) (fd int, err error)
  1047  //sysnb	EpollCtl(epfd int, op int, fd int, event *EpollEvent) (err error)
  1048  //sys	Fallocate(fd int, mode uint32, off int64, len int64) (err error)
  1049  //sys	Fchdir(fd int) (err error)
  1050  //sys	Fchmod(fd int, mode uint32) (err error)
  1051  //sys	Fchownat(dirfd int, path string, uid int, gid int, flags int) (err error)
  1052  //sys	fcntl(fd int, cmd int, arg int) (val int, err error)
  1053  //sys	Fdatasync(fd int) (err error)
  1054  //sys	Flock(fd int, how int) (err error)
  1055  //sys	Fsync(fd int) (err error)
  1056  //sys	Getdents(fd int, buf []byte) (n int, err error) = SYS_GETDENTS64
  1057  //sysnb	Getpgid(pid int) (pgid int, err error)
  1058  
  1059  func Getpgrp() (pid int) {
  1060  	pid, _ = Getpgid(0)
  1061  	return
  1062  }
  1063  
  1064  //sysnb	Getpid() (pid int)
  1065  //sysnb	Getppid() (ppid int)
  1066  //sys	Getpriority(which int, who int) (prio int, err error)
  1067  //sysnb	Getrusage(who int, rusage *Rusage) (err error)
  1068  //sysnb	Gettid() (tid int)
  1069  //sys	Getxattr(path string, attr string, dest []byte) (sz int, err error)
  1070  //sys	InotifyAddWatch(fd int, pathname string, mask uint32) (watchdesc int, err error)
  1071  //sysnb	InotifyInit1(flags int) (fd int, err error)
  1072  //sysnb	InotifyRmWatch(fd int, watchdesc uint32) (success int, err error)
  1073  //sysnb	Kill(pid int, sig Signal) (err error)
  1074  //sys	Klogctl(typ int, buf []byte) (n int, err error) = SYS_SYSLOG
  1075  //sys	Listxattr(path string, dest []byte) (sz int, err error)
  1076  //sys	Mkdirat(dirfd int, path string, mode uint32) (err error)
  1077  //sys	Mknodat(dirfd int, path string, mode uint32, dev int) (err error)
  1078  //sys	Nanosleep(time *Timespec, leftover *Timespec) (err error)
  1079  //sys	PivotRoot(newroot string, putold string) (err error) = SYS_PIVOT_ROOT
  1080  //sysnb prlimit1(pid int, resource int, newlimit *Rlimit, old *Rlimit) (err error) = SYS_PRLIMIT64
  1081  //sys	read(fd int, p []byte) (n int, err error)
  1082  //sys	Removexattr(path string, attr string) (err error)
  1083  //sys	Setdomainname(p []byte) (err error)
  1084  //sys	Sethostname(p []byte) (err error)
  1085  //sysnb	Setpgid(pid int, pgid int) (err error)
  1086  //sysnb	Setsid() (pid int, err error)
  1087  //sysnb	Settimeofday(tv *Timeval) (err error)
  1088  
  1089  // Provided by runtime.syscall_runtime_doAllThreadsSyscall which stops the
  1090  // world and invokes the syscall on each OS thread. Once this function returns,
  1091  // all threads are in sync.
  1092  //
  1093  //go:uintptrescapes
  1094  func runtime_doAllThreadsSyscall(trap, a1, a2, a3, a4, a5, a6 uintptr) (r1, r2, err uintptr)
  1095  
  1096  // AllThreadsSyscall performs a syscall on each OS thread of the Go
  1097  // runtime. It first invokes the syscall on one thread. Should that
  1098  // invocation fail, it returns immediately with the error status.
  1099  // Otherwise, it invokes the syscall on all of the remaining threads
  1100  // in parallel. It will terminate the program if it observes any
  1101  // invoked syscall's return value differs from that of the first
  1102  // invocation.
  1103  //
  1104  // AllThreadsSyscall is intended for emulating simultaneous
  1105  // process-wide state changes that require consistently modifying
  1106  // per-thread state of the Go runtime.
  1107  //
  1108  // AllThreadsSyscall is unaware of any threads that are launched
  1109  // explicitly by cgo linked code, so the function always returns
  1110  // ENOTSUP in binaries that use cgo.
  1111  //
  1112  //go:uintptrescapes
  1113  func AllThreadsSyscall(trap, a1, a2, a3 uintptr) (r1, r2 uintptr, err Errno) {
  1114  	if cgo_libc_setegid != nil {
  1115  		return minus1, minus1, ENOTSUP
  1116  	}
  1117  	r1, r2, errno := runtime_doAllThreadsSyscall(trap, a1, a2, a3, 0, 0, 0)
  1118  	return r1, r2, Errno(errno)
  1119  }
  1120  
  1121  // AllThreadsSyscall6 is like AllThreadsSyscall, but extended to six
  1122  // arguments.
  1123  //
  1124  //go:uintptrescapes
  1125  func AllThreadsSyscall6(trap, a1, a2, a3, a4, a5, a6 uintptr) (r1, r2 uintptr, err Errno) {
  1126  	if cgo_libc_setegid != nil {
  1127  		return minus1, minus1, ENOTSUP
  1128  	}
  1129  	r1, r2, errno := runtime_doAllThreadsSyscall(trap, a1, a2, a3, a4, a5, a6)
  1130  	return r1, r2, Errno(errno)
  1131  }
  1132  
  1133  // linked by runtime.cgocall.go
  1134  //
  1135  //go:uintptrescapes
  1136  func cgocaller(unsafe.Pointer, ...uintptr) uintptr
  1137  
  1138  var cgo_libc_setegid unsafe.Pointer // non-nil if cgo linked.
  1139  
  1140  const minus1 = ^uintptr(0)
  1141  
  1142  func Setegid(egid int) (err error) {
  1143  	if cgo_libc_setegid == nil {
  1144  		if _, _, e1 := AllThreadsSyscall(SYS_SETRESGID, minus1, uintptr(egid), minus1); e1 != 0 {
  1145  			err = errnoErr(e1)
  1146  		}
  1147  	} else if ret := cgocaller(cgo_libc_setegid, uintptr(egid)); ret != 0 {
  1148  		err = errnoErr(Errno(ret))
  1149  	}
  1150  	return
  1151  }
  1152  
  1153  var cgo_libc_seteuid unsafe.Pointer // non-nil if cgo linked.
  1154  
  1155  func Seteuid(euid int) (err error) {
  1156  	if cgo_libc_seteuid == nil {
  1157  		if _, _, e1 := AllThreadsSyscall(SYS_SETRESUID, minus1, uintptr(euid), minus1); e1 != 0 {
  1158  			err = errnoErr(e1)
  1159  		}
  1160  	} else if ret := cgocaller(cgo_libc_seteuid, uintptr(euid)); ret != 0 {
  1161  		err = errnoErr(Errno(ret))
  1162  	}
  1163  	return
  1164  }
  1165  
  1166  var cgo_libc_setgid unsafe.Pointer // non-nil if cgo linked.
  1167  
  1168  func Setgid(gid int) (err error) {
  1169  	if cgo_libc_setgid == nil {
  1170  		if _, _, e1 := AllThreadsSyscall(sys_SETGID, uintptr(gid), 0, 0); e1 != 0 {
  1171  			err = errnoErr(e1)
  1172  		}
  1173  	} else if ret := cgocaller(cgo_libc_setgid, uintptr(gid)); ret != 0 {
  1174  		err = errnoErr(Errno(ret))
  1175  	}
  1176  	return
  1177  }
  1178  
  1179  var cgo_libc_setregid unsafe.Pointer // non-nil if cgo linked.
  1180  
  1181  func Setregid(rgid, egid int) (err error) {
  1182  	if cgo_libc_setregid == nil {
  1183  		if _, _, e1 := AllThreadsSyscall(sys_SETREGID, uintptr(rgid), uintptr(egid), 0); e1 != 0 {
  1184  			err = errnoErr(e1)
  1185  		}
  1186  	} else if ret := cgocaller(cgo_libc_setregid, uintptr(rgid), uintptr(egid)); ret != 0 {
  1187  		err = errnoErr(Errno(ret))
  1188  	}
  1189  	return
  1190  }
  1191  
  1192  var cgo_libc_setresgid unsafe.Pointer // non-nil if cgo linked.
  1193  
  1194  func Setresgid(rgid, egid, sgid int) (err error) {
  1195  	if cgo_libc_setresgid == nil {
  1196  		if _, _, e1 := AllThreadsSyscall(sys_SETRESGID, uintptr(rgid), uintptr(egid), uintptr(sgid)); e1 != 0 {
  1197  			err = errnoErr(e1)
  1198  		}
  1199  	} else if ret := cgocaller(cgo_libc_setresgid, uintptr(rgid), uintptr(egid), uintptr(sgid)); ret != 0 {
  1200  		err = errnoErr(Errno(ret))
  1201  	}
  1202  	return
  1203  }
  1204  
  1205  var cgo_libc_setresuid unsafe.Pointer // non-nil if cgo linked.
  1206  
  1207  func Setresuid(ruid, euid, suid int) (err error) {
  1208  	if cgo_libc_setresuid == nil {
  1209  		if _, _, e1 := AllThreadsSyscall(sys_SETRESUID, uintptr(ruid), uintptr(euid), uintptr(suid)); e1 != 0 {
  1210  			err = errnoErr(e1)
  1211  		}
  1212  	} else if ret := cgocaller(cgo_libc_setresuid, uintptr(ruid), uintptr(euid), uintptr(suid)); ret != 0 {
  1213  		err = errnoErr(Errno(ret))
  1214  	}
  1215  	return
  1216  }
  1217  
  1218  var cgo_libc_setreuid unsafe.Pointer // non-nil if cgo linked.
  1219  
  1220  func Setreuid(ruid, euid int) (err error) {
  1221  	if cgo_libc_setreuid == nil {
  1222  		if _, _, e1 := AllThreadsSyscall(sys_SETREUID, uintptr(ruid), uintptr(euid), 0); e1 != 0 {
  1223  			err = errnoErr(e1)
  1224  		}
  1225  	} else if ret := cgocaller(cgo_libc_setreuid, uintptr(ruid), uintptr(euid)); ret != 0 {
  1226  		err = errnoErr(Errno(ret))
  1227  	}
  1228  	return
  1229  }
  1230  
  1231  var cgo_libc_setuid unsafe.Pointer // non-nil if cgo linked.
  1232  
  1233  func Setuid(uid int) (err error) {
  1234  	if cgo_libc_setuid == nil {
  1235  		if _, _, e1 := AllThreadsSyscall(sys_SETUID, uintptr(uid), 0, 0); e1 != 0 {
  1236  			err = errnoErr(e1)
  1237  		}
  1238  	} else if ret := cgocaller(cgo_libc_setuid, uintptr(uid)); ret != 0 {
  1239  		err = errnoErr(Errno(ret))
  1240  	}
  1241  	return
  1242  }
  1243  
  1244  //sys	Setpriority(which int, who int, prio int) (err error)
  1245  //sys	Setxattr(path string, attr string, data []byte, flags int) (err error)
  1246  //sys	Sync()
  1247  //sysnb	Sysinfo(info *Sysinfo_t) (err error)
  1248  //sys	Tee(rfd int, wfd int, len int, flags int) (n int64, err error)
  1249  //sysnb	Tgkill(tgid int, tid int, sig Signal) (err error)
  1250  //sysnb	Times(tms *Tms) (ticks uintptr, err error)
  1251  //sysnb	Umask(mask int) (oldmask int)
  1252  //sysnb	Uname(buf *Utsname) (err error)
  1253  //sys	Unmount(target string, flags int) (err error) = SYS_UMOUNT2
  1254  //sys	Unshare(flags int) (err error)
  1255  //sys	write(fd int, p []byte) (n int, err error)
  1256  //sys	exitThread(code int) (err error) = SYS_EXIT
  1257  //sys	readlen(fd int, p *byte, np int) (n int, err error) = SYS_READ
  1258  
  1259  // mmap varies by architecture; see syscall_linux_*.go.
  1260  //sys	munmap(addr uintptr, length uintptr) (err error)
  1261  
  1262  var mapper = &mmapper{
  1263  	active: make(map[*byte][]byte),
  1264  	mmap:   mmap,
  1265  	munmap: munmap,
  1266  }
  1267  
  1268  func Mmap(fd int, offset int64, length int, prot int, flags int) (data []byte, err error) {
  1269  	return mapper.Mmap(fd, offset, length, prot, flags)
  1270  }
  1271  
  1272  func Munmap(b []byte) (err error) {
  1273  	return mapper.Munmap(b)
  1274  }
  1275  
  1276  //sys	Madvise(b []byte, advice int) (err error)
  1277  //sys	Mprotect(b []byte, prot int) (err error)
  1278  //sys	Mlock(b []byte) (err error)
  1279  //sys	Munlock(b []byte) (err error)
  1280  //sys	Mlockall(flags int) (err error)
  1281  //sys	Munlockall() (err error)
  1282  
  1283  // prlimit changes a resource limit. We use a single definition so that
  1284  // we can tell StartProcess to not restore the original NOFILE limit.
  1285  // This is unexported but can be called from x/sys/unix.
  1286  func prlimit(pid int, resource int, newlimit *Rlimit, old *Rlimit) (err error) {
  1287  	err = prlimit1(pid, resource, newlimit, old)
  1288  	if err == nil && newlimit != nil && resource == RLIMIT_NOFILE {
  1289  		origRlimitNofile.Store(nil)
  1290  	}
  1291  	return err
  1292  }
  1293  

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