[gostls13.git] / src / syscall / syscall_linux.go

// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

// Linux system calls.
// This file is compiled as ordinary Go code,
// but it is also input to mksyscall,
// which parses the //sys lines and generates system call stubs.
// Note that sometimes we use a lowercase //sys name and
// wrap it in our own nicer implementation.

package syscall

import (
        "internal/itoa"
        "runtime"
        "unsafe"
)

// N.B. RawSyscall6 is provided via linkname by runtime/internal/syscall.
//
// Errno is uintptr and thus compatible with the runtime/internal/syscall
// definition.

func RawSyscall6(trap, a1, a2, a3, a4, a5, a6 uintptr) (r1, r2 uintptr, err Errno)

// Pull in entersyscall/exitsyscall for Syscall/Syscall6.
//
// Note that this can't be a push linkname because the runtime already has a
// nameless linkname to export to assembly here and in x/sys. Additionally,
// entersyscall fetches the caller PC and SP and thus can't have a wrapper
// inbetween.

//go:linkname runtime_entersyscall runtime.entersyscall
func runtime_entersyscall()

//go:linkname runtime_exitsyscall runtime.exitsyscall
func runtime_exitsyscall()

// N.B. For the Syscall functions below:
//
// //go:uintptrkeepalive because the uintptr argument may be converted pointers
// that need to be kept alive in the caller (this is implied for RawSyscall6
// since it has no body).
//
// //go:nosplit because stack copying does not account for uintptrkeepalive, so
// the stack must not grow. Stack copying cannot blindly assume that all
// uintptr arguments are pointers, because some values may look like pointers,
// but not really be pointers, and adjusting their value would break the call.
//
// //go:norace, on RawSyscall, to avoid race instrumentation if RawSyscall is
// called after fork, or from a signal handler.
//
// //go:linkname to ensure ABI wrappers are generated for external callers
// (notably x/sys/unix assembly).

//go:uintptrkeepalive
//go:nosplit
//go:norace
//go:linkname RawSyscall
func RawSyscall(trap, a1, a2, a3 uintptr) (r1, r2 uintptr, err Errno) {
        return RawSyscall6(trap, a1, a2, a3, 0, 0, 0)
}

//go:uintptrkeepalive
//go:nosplit
//go:linkname Syscall
func Syscall(trap, a1, a2, a3 uintptr) (r1, r2 uintptr, err Errno) {
        runtime_entersyscall()
        // N.B. Calling RawSyscall here is unsafe with atomic coverage
        // instrumentation and race mode.
        //
        // Coverage instrumentation will add a sync/atomic call to RawSyscall.
        // Race mode will add race instrumentation to sync/atomic. Race
        // instrumentation requires a P, which we no longer have.
        //
        // RawSyscall6 is fine because it is implemented in assembly and thus
        // has no coverage instrumentation.
        //
        // This is typically not a problem in the runtime because cmd/go avoids
        // adding coverage instrumentation to the runtime in race mode.
        r1, r2, err = RawSyscall6(trap, a1, a2, a3, 0, 0, 0)
        runtime_exitsyscall()
        return
}

//go:uintptrkeepalive
//go:nosplit
//go:linkname Syscall6
func Syscall6(trap, a1, a2, a3, a4, a5, a6 uintptr) (r1, r2 uintptr, err Errno) {
        runtime_entersyscall()
        r1, r2, err = RawSyscall6(trap, a1, a2, a3, a4, a5, a6)
        runtime_exitsyscall()
        return
}

func rawSyscallNoError(trap, a1, a2, a3 uintptr) (r1, r2 uintptr)
func rawVforkSyscall(trap, a1, a2 uintptr) (r1 uintptr, err Errno)

/*
 * Wrapped
 */

func Access(path string, mode uint32) (err error) {
        return Faccessat(_AT_FDCWD, path, mode, 0)
}

func Chmod(path string, mode uint32) (err error) {
        return Fchmodat(_AT_FDCWD, path, mode, 0)
}

func Chown(path string, uid int, gid int) (err error) {
        return Fchownat(_AT_FDCWD, path, uid, gid, 0)
}

func Creat(path string, mode uint32) (fd int, err error) {
        return Open(path, O_CREAT|O_WRONLY|O_TRUNC, mode)
}

func EpollCreate(size int) (fd int, err error) {
        if size <= 0 {
                return -1, EINVAL
        }
        return EpollCreate1(0)
}

func isGroupMember(gid int) bool {
        groups, err := Getgroups()
        if err != nil {
                return false
        }

        for _, g := range groups {
                if g == gid {
                        return true
                }
        }
        return false
}

func isCapDacOverrideSet() bool {
        const _CAP_DAC_OVERRIDE = 1
        var c caps
        c.hdr.version = _LINUX_CAPABILITY_VERSION_3

        _, _, err := RawSyscall(SYS_CAPGET, uintptr(unsafe.Pointer(&c.hdr)), uintptr(unsafe.Pointer(&c.data[0])), 0)

        return err == 0 && c.data[0].effective&capToMask(_CAP_DAC_OVERRIDE) != 0
}

//sys   faccessat(dirfd int, path string, mode uint32) (err error)
//sys   faccessat2(dirfd int, path string, mode uint32, flags int) (err error) = _SYS_faccessat2

func Faccessat(dirfd int, path string, mode uint32, flags int) (err error) {
        if flags == 0 {
                return faccessat(dirfd, path, mode)
        }

        // Attempt to use the newer faccessat2, which supports flags directly,
        // falling back if it doesn't exist.
        //
        // Don't attempt on Android, which does not allow faccessat2 through
        // its seccomp policy [1] on any version of Android as of 2022-12-20.
        //
        // [1] https://cs.android.com/android/platform/superproject/+/master:bionic/libc/SECCOMP_BLOCKLIST_APP.TXT;l=4;drc=dbb8670dfdcc677f7e3b9262e93800fa14c4e417
        if runtime.GOOS != "android" {
                if err := faccessat2(dirfd, path, mode, flags); err != ENOSYS && err != EPERM {
                        return err
                }
        }

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

        if flags & ^(_AT_SYMLINK_NOFOLLOW|_AT_EACCESS) != 0 {
                return EINVAL
        }

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

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

        // Fallback to checking permission bits.
        var uid int
        if flags&_AT_EACCESS != 0 {
                uid = Geteuid()
                if uid != 0 && isCapDacOverrideSet() {
                        // If CAP_DAC_OVERRIDE is set, file access check is
                        // done by the kernel in the same way as for root
                        // (see generic_permission() in the Linux sources).
                        uid = 0
                }
        } else {
                uid = Getuid()
        }

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

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

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

        if fmode&mode == mode {
                return nil
        }

        return EACCES
}

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

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

//sys   linkat(olddirfd int, oldpath string, newdirfd int, newpath string, flags int) (err error)

func Link(oldpath string, newpath string) (err error) {
        return linkat(_AT_FDCWD, oldpath, _AT_FDCWD, newpath, 0)
}

func Mkdir(path string, mode uint32) (err error) {
        return Mkdirat(_AT_FDCWD, path, mode)
}

func Mknod(path string, mode uint32, dev int) (err error) {
        return Mknodat(_AT_FDCWD, path, mode, dev)
}

func Open(path string, mode int, perm uint32) (fd int, err error) {
        return openat(_AT_FDCWD, path, mode|O_LARGEFILE, perm)
}

//sys   openat(dirfd int, path string, flags int, mode uint32) (fd int, err error)

func Openat(dirfd int, path string, flags int, mode uint32) (fd int, err error) {
        return openat(dirfd, path, flags|O_LARGEFILE, mode)
}

func Pipe(p []int) error {
        return Pipe2(p, 0)
}

//sysnb pipe2(p *[2]_C_int, flags int) (err error)

func Pipe2(p []int, flags int) error {
        if len(p) != 2 {
                return EINVAL
        }
        var pp [2]_C_int
        err := pipe2(&pp, flags)
        if err == nil {
                p[0] = int(pp[0])
                p[1] = int(pp[1])
        }
        return err
}

//sys   readlinkat(dirfd int, path string, buf []byte) (n int, err error)

func Readlink(path string, buf []byte) (n int, err error) {
        return readlinkat(_AT_FDCWD, path, buf)
}

func Rename(oldpath string, newpath string) (err error) {
        return Renameat(_AT_FDCWD, oldpath, _AT_FDCWD, newpath)
}

func Rmdir(path string) error {
        return unlinkat(_AT_FDCWD, path, _AT_REMOVEDIR)
}

//sys   symlinkat(oldpath string, newdirfd int, newpath string) (err error)

func Symlink(oldpath string, newpath string) (err error) {
        return symlinkat(oldpath, _AT_FDCWD, newpath)
}

func Unlink(path string) error {
        return unlinkat(_AT_FDCWD, path, 0)
}

//sys   unlinkat(dirfd int, path string, flags int) (err error)

func Unlinkat(dirfd int, path string) error {
        return unlinkat(dirfd, path, 0)
}

func Utimes(path string, tv []Timeval) (err error) {
        if len(tv) != 2 {
                return EINVAL
        }
        return utimes(path, (*[2]Timeval)(unsafe.Pointer(&tv[0])))
}

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

func UtimesNano(path string, ts []Timespec) (err error) {
        if len(ts) != 2 {
                return EINVAL
        }
        return utimensat(_AT_FDCWD, path, (*[2]Timespec)(unsafe.Pointer(&ts[0])), 0)
}

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

func Futimes(fd int, tv []Timeval) (err error) {
        // Believe it or not, this is the best we can do on Linux
        // (and is what glibc does).
        return Utimes("/proc/self/fd/"+itoa.Itoa(fd), tv)
}

const ImplementsGetwd = true

//sys   Getcwd(buf []byte) (n int, err error)

func Getwd() (wd string, err error) {
        var buf [PathMax]byte
        n, err := Getcwd(buf[0:])
        if err != nil {
                return "", err
        }
        // Getcwd returns the number of bytes written to buf, including the NUL.
        if n < 1 || n > len(buf) || buf[n-1] != 0 {
                return "", EINVAL
        }
        // In some cases, Linux can return a path that starts with the
        // "(unreachable)" prefix, which can potentially be a valid relative
        // path. To work around that, return ENOENT if path is not absolute.
        if buf[0] != '/' {
                return "", ENOENT
        }

        return string(buf[0 : n-1]), nil
}

func Getgroups() (gids []int, err error) {
        n, err := getgroups(0, nil)
        if err != nil {
                return nil, err
        }
        if n == 0 {
                return nil, nil
        }

        // Sanity check group count. Max is 1<<16 on Linux.
        if n < 0 || n > 1<<20 {
                return nil, EINVAL
        }

        a := make([]_Gid_t, n)
        n, err = getgroups(n, &a[0])
        if err != nil {
                return nil, err
        }
        gids = make([]int, n)
        for i, v := range a[0:n] {
                gids[i] = int(v)
        }
        return
}

var cgo_libc_setgroups unsafe.Pointer // non-nil if cgo linked.

func Setgroups(gids []int) (err error) {
        n := uintptr(len(gids))
        if n == 0 {
                if cgo_libc_setgroups == nil {
                        if _, _, e1 := AllThreadsSyscall(_SYS_setgroups, 0, 0, 0); e1 != 0 {
                                err = errnoErr(e1)
                        }
                        return
                }
                if ret := cgocaller(cgo_libc_setgroups, 0, 0); ret != 0 {
                        err = errnoErr(Errno(ret))
                }
                return
        }

        a := make([]_Gid_t, len(gids))
        for i, v := range gids {
                a[i] = _Gid_t(v)
        }
        if cgo_libc_setgroups == nil {
                if _, _, e1 := AllThreadsSyscall(_SYS_setgroups, n, uintptr(unsafe.Pointer(&a[0])), 0); e1 != 0 {
                        err = errnoErr(e1)
                }
                return
        }
        if ret := cgocaller(cgo_libc_setgroups, n, uintptr(unsafe.Pointer(&a[0]))); ret != 0 {
                err = errnoErr(Errno(ret))
        }
        return
}

type WaitStatus uint32

// Wait status is 7 bits at bottom, either 0 (exited),
// 0x7F (stopped), or a signal number that caused an exit.
// The 0x80 bit is whether there was a core dump.
// An extra number (exit code, signal causing a stop)
// is in the high bits. At least that's the idea.
// There are various irregularities. For example, the
// "continued" status is 0xFFFF, distinguishing itself
// from stopped via the core dump bit.

const (
        mask    = 0x7F
        core    = 0x80
        exited  = 0x00
        stopped = 0x7F
        shift   = 8
)

func (w WaitStatus) Exited() bool { return w&mask == exited }

func (w WaitStatus) Signaled() bool { return w&mask != stopped && w&mask != exited }

func (w WaitStatus) Stopped() bool { return w&0xFF == stopped }

func (w WaitStatus) Continued() bool { return w == 0xFFFF }

func (w WaitStatus) CoreDump() bool { return w.Signaled() && w&core != 0 }

func (w WaitStatus) ExitStatus() int {
        if !w.Exited() {
                return -1
        }
        return int(w>>shift) & 0xFF
}

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

func (w WaitStatus) StopSignal() Signal {
        if !w.Stopped() {
                return -1
        }
        return Signal(w>>shift) & 0xFF
}

func (w WaitStatus) TrapCause() int {
        if w.StopSignal() != SIGTRAP {
                return -1
        }
        return int(w>>shift) >> 8
}

//sys   wait4(pid int, wstatus *_C_int, options int, rusage *Rusage) (wpid int, err error)

func Wait4(pid int, wstatus *WaitStatus, options int, rusage *Rusage) (wpid int, err error) {
        var status _C_int
        wpid, err = wait4(pid, &status, options, rusage)
        if wstatus != nil {
                *wstatus = WaitStatus(status)
        }
        return
}

func Mkfifo(path string, mode uint32) (err error) {
        return Mknod(path, mode|S_IFIFO, 0)
}

func (sa *SockaddrInet4) sockaddr() (unsafe.Pointer, _Socklen, error) {
        if sa.Port < 0 || sa.Port > 0xFFFF {
                return nil, 0, EINVAL
        }
        sa.raw.Family = AF_INET
        p := (*[2]byte)(unsafe.Pointer(&sa.raw.Port))
        p[0] = byte(sa.Port >> 8)
        p[1] = byte(sa.Port)
        sa.raw.Addr = sa.Addr
        return unsafe.Pointer(&sa.raw), SizeofSockaddrInet4, nil
}

func (sa *SockaddrInet6) sockaddr() (unsafe.Pointer, _Socklen, error) {
        if sa.Port < 0 || sa.Port > 0xFFFF {
                return nil, 0, EINVAL
        }
        sa.raw.Family = AF_INET6
        p := (*[2]byte)(unsafe.Pointer(&sa.raw.Port))
        p[0] = byte(sa.Port >> 8)
        p[1] = byte(sa.Port)
        sa.raw.Scope_id = sa.ZoneId
        sa.raw.Addr = sa.Addr
        return unsafe.Pointer(&sa.raw), SizeofSockaddrInet6, nil
}

func (sa *SockaddrUnix) sockaddr() (unsafe.Pointer, _Socklen, error) {
        name := sa.Name
        n := len(name)
        if n > len(sa.raw.Path) {
                return nil, 0, EINVAL
        }
        if n == len(sa.raw.Path) && name[0] != '@' {
                return nil, 0, EINVAL
        }
        sa.raw.Family = AF_UNIX
        for i := 0; i < n; i++ {
                sa.raw.Path[i] = int8(name[i])
        }
        // length is family (uint16), name, NUL.
        sl := _Socklen(2)
        if n > 0 {
                sl += _Socklen(n) + 1
        }
        if sa.raw.Path[0] == '@' {
                sa.raw.Path[0] = 0
                // Don't count trailing NUL for abstract address.
                sl--
        }

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

type SockaddrLinklayer struct {
        Protocol uint16
        Ifindex  int
        Hatype   uint16
        Pkttype  uint8
        Halen    uint8
        Addr     [8]byte
        raw      RawSockaddrLinklayer
}

func (sa *SockaddrLinklayer) sockaddr() (unsafe.Pointer, _Socklen, error) {
        if sa.Ifindex < 0 || sa.Ifindex > 0x7fffffff {
                return nil, 0, EINVAL
        }
        sa.raw.Family = AF_PACKET
        sa.raw.Protocol = sa.Protocol
        sa.raw.Ifindex = int32(sa.Ifindex)
        sa.raw.Hatype = sa.Hatype
        sa.raw.Pkttype = sa.Pkttype
        sa.raw.Halen = sa.Halen
        sa.raw.Addr = sa.Addr
        return unsafe.Pointer(&sa.raw), SizeofSockaddrLinklayer, nil
}

type SockaddrNetlink struct {
        Family uint16
        Pad    uint16
        Pid    uint32
        Groups uint32
        raw    RawSockaddrNetlink
}

func (sa *SockaddrNetlink) sockaddr() (unsafe.Pointer, _Socklen, error) {
        sa.raw.Family = AF_NETLINK
        sa.raw.Pad = sa.Pad
        sa.raw.Pid = sa.Pid
        sa.raw.Groups = sa.Groups
        return unsafe.Pointer(&sa.raw), SizeofSockaddrNetlink, nil
}

func anyToSockaddr(rsa *RawSockaddrAny) (Sockaddr, error) {
        switch rsa.Addr.Family {
        case AF_NETLINK:
                pp := (*RawSockaddrNetlink)(unsafe.Pointer(rsa))
                sa := new(SockaddrNetlink)
                sa.Family = pp.Family
                sa.Pad = pp.Pad
                sa.Pid = pp.Pid
                sa.Groups = pp.Groups
                return sa, nil

        case AF_PACKET:
                pp := (*RawSockaddrLinklayer)(unsafe.Pointer(rsa))
                sa := new(SockaddrLinklayer)
                sa.Protocol = pp.Protocol
                sa.Ifindex = int(pp.Ifindex)
                sa.Hatype = pp.Hatype
                sa.Pkttype = pp.Pkttype
                sa.Halen = pp.Halen
                sa.Addr = pp.Addr
                return sa, nil

        case AF_UNIX:
                pp := (*RawSockaddrUnix)(unsafe.Pointer(rsa))
                sa := new(SockaddrUnix)
                if pp.Path[0] == 0 {
                        // "Abstract" Unix domain socket.
                        // Rewrite leading NUL as @ for textual display.
                        // (This is the standard convention.)
                        // Not friendly to overwrite in place,
                        // but the callers below don't care.
                        pp.Path[0] = '@'
                }

                // Assume path ends at NUL.
                // This is not technically the Linux semantics for
                // abstract Unix domain sockets--they are supposed
                // to be uninterpreted fixed-size binary blobs--but
                // everyone uses this convention.
                n := 0
                for n < len(pp.Path) && pp.Path[n] != 0 {
                        n++
                }
                sa.Name = string(unsafe.Slice((*byte)(unsafe.Pointer(&pp.Path[0])), n))
                return sa, nil

        case AF_INET:
                pp := (*RawSockaddrInet4)(unsafe.Pointer(rsa))
                sa := new(SockaddrInet4)
                p := (*[2]byte)(unsafe.Pointer(&pp.Port))
                sa.Port = int(p[0])<<8 + int(p[1])
                sa.Addr = pp.Addr
                return sa, nil

        case AF_INET6:
                pp := (*RawSockaddrInet6)(unsafe.Pointer(rsa))
                sa := new(SockaddrInet6)
                p := (*[2]byte)(unsafe.Pointer(&pp.Port))
                sa.Port = int(p[0])<<8 + int(p[1])
                sa.ZoneId = pp.Scope_id
                sa.Addr = pp.Addr
                return sa, nil
        }
        return nil, EAFNOSUPPORT
}

func Accept4(fd int, flags int) (nfd int, sa Sockaddr, err error) {
        var rsa RawSockaddrAny
        var len _Socklen = SizeofSockaddrAny
        nfd, err = accept4(fd, &rsa, &len, flags)
        if err != nil {
                return
        }
        if len > SizeofSockaddrAny {
                panic("RawSockaddrAny too small")
        }
        sa, err = anyToSockaddr(&rsa)
        if err != nil {
                Close(nfd)
                nfd = 0
        }
        return
}

func Getsockname(fd int) (sa Sockaddr, err error) {
        var rsa RawSockaddrAny
        var len _Socklen = SizeofSockaddrAny
        if err = getsockname(fd, &rsa, &len); err != nil {
                return
        }
        return anyToSockaddr(&rsa)
}

func GetsockoptInet4Addr(fd, level, opt int) (value [4]byte, err error) {
        vallen := _Socklen(4)
        err = getsockopt(fd, level, opt, unsafe.Pointer(&value[0]), &vallen)
        return value, err
}

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

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

func GetsockoptIPv6Mreq(fd, level, opt int) (*IPv6Mreq, error) {
        var value IPv6Mreq
        vallen := _Socklen(SizeofIPv6Mreq)
        err := getsockopt(fd, level, opt, unsafe.Pointer(&value), &vallen)
        return &value, err
}

func GetsockoptIPv6MTUInfo(fd, level, opt int) (*IPv6MTUInfo, error) {
        var value IPv6MTUInfo
        vallen := _Socklen(SizeofIPv6MTUInfo)
        err := getsockopt(fd, level, opt, unsafe.Pointer(&value), &vallen)
        return &value, err
}

func GetsockoptICMPv6Filter(fd, level, opt int) (*ICMPv6Filter, error) {
        var value ICMPv6Filter
        vallen := _Socklen(SizeofICMPv6Filter)
        err := getsockopt(fd, level, opt, unsafe.Pointer(&value), &vallen)
        return &value, err
}

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

func SetsockoptIPMreqn(fd, level, opt int, mreq *IPMreqn) (err error) {
        return setsockopt(fd, level, opt, unsafe.Pointer(mreq), unsafe.Sizeof(*mreq))
}

func recvmsgRaw(fd int, p, oob []byte, flags int, rsa *RawSockaddrAny) (n, oobn int, recvflags int, err error) {
        var msg Msghdr
        msg.Name = (*byte)(unsafe.Pointer(rsa))
        msg.Namelen = uint32(SizeofSockaddrAny)
        var iov Iovec
        if len(p) > 0 {
                iov.Base = &p[0]
                iov.SetLen(len(p))
        }
        var dummy byte
        if len(oob) > 0 {
                if len(p) == 0 {
                        var sockType int
                        sockType, err = GetsockoptInt(fd, SOL_SOCKET, SO_TYPE)
                        if err != nil {
                                return
                        }
                        // receive at least one normal byte
                        if sockType != SOCK_DGRAM {
                                iov.Base = &dummy
                                iov.SetLen(1)
                        }
                }
                msg.Control = &oob[0]
                msg.SetControllen(len(oob))
        }
        msg.Iov = &iov
        msg.Iovlen = 1
        if n, err = recvmsg(fd, &msg, flags); err != nil {
                return
        }
        oobn = int(msg.Controllen)
        recvflags = int(msg.Flags)
        return
}

func sendmsgN(fd int, p, oob []byte, ptr unsafe.Pointer, salen _Socklen, flags int) (n int, err error) {
        var msg Msghdr
        msg.Name = (*byte)(ptr)
        msg.Namelen = uint32(salen)
        var iov Iovec
        if len(p) > 0 {
                iov.Base = &p[0]
                iov.SetLen(len(p))
        }
        var dummy byte
        if len(oob) > 0 {
                if len(p) == 0 {
                        var sockType int
                        sockType, err = GetsockoptInt(fd, SOL_SOCKET, SO_TYPE)
                        if err != nil {
                                return 0, err
                        }
                        // send at least one normal byte
                        if sockType != SOCK_DGRAM {
                                iov.Base = &dummy
                                iov.SetLen(1)
                        }
                }
                msg.Control = &oob[0]
                msg.SetControllen(len(oob))
        }
        msg.Iov = &iov
        msg.Iovlen = 1
        if n, err = sendmsg(fd, &msg, flags); err != nil {
                return 0, err
        }
        if len(oob) > 0 && len(p) == 0 {
                n = 0
        }
        return n, nil
}

// BindToDevice binds the socket associated with fd to device.
func BindToDevice(fd int, device string) (err error) {
        return SetsockoptString(fd, SOL_SOCKET, SO_BINDTODEVICE, device)
}

//sys   ptrace(request int, pid int, addr uintptr, data uintptr) (err error)
//sys   ptracePtr(request int, pid int, addr uintptr, data unsafe.Pointer) (err error) = SYS_PTRACE

func ptracePeek(req int, pid int, addr uintptr, out []byte) (count int, err error) {
        // The peek requests are machine-size oriented, so we wrap it
        // to retrieve arbitrary-length data.

        // The ptrace syscall differs from glibc's ptrace.
        // Peeks returns the word in *data, not as the return value.

        var buf [sizeofPtr]byte

        // Leading edge. PEEKTEXT/PEEKDATA don't require aligned
        // access (PEEKUSER warns that it might), but if we don't
        // align our reads, we might straddle an unmapped page
        // boundary and not get the bytes leading up to the page
        // boundary.
        n := 0
        if addr%sizeofPtr != 0 {
                err = ptracePtr(req, pid, addr-addr%sizeofPtr, unsafe.Pointer(&buf[0]))
                if err != nil {
                        return 0, err
                }
                n += copy(out, buf[addr%sizeofPtr:])
                out = out[n:]
        }

        // Remainder.
        for len(out) > 0 {
                // We use an internal buffer to guarantee alignment.
                // It's not documented if this is necessary, but we're paranoid.
                err = ptracePtr(req, pid, addr+uintptr(n), unsafe.Pointer(&buf[0]))
                if err != nil {
                        return n, err
                }
                copied := copy(out, buf[0:])
                n += copied
                out = out[copied:]
        }

        return n, nil
}

func PtracePeekText(pid int, addr uintptr, out []byte) (count int, err error) {
        return ptracePeek(PTRACE_PEEKTEXT, pid, addr, out)
}

func PtracePeekData(pid int, addr uintptr, out []byte) (count int, err error) {
        return ptracePeek(PTRACE_PEEKDATA, pid, addr, out)
}

func ptracePoke(pokeReq int, peekReq int, pid int, addr uintptr, data []byte) (count int, err error) {
        // As for ptracePeek, we need to align our accesses to deal
        // with the possibility of straddling an invalid page.

        // Leading edge.
        n := 0
        if addr%sizeofPtr != 0 {
                var buf [sizeofPtr]byte
                err = ptracePtr(peekReq, pid, addr-addr%sizeofPtr, unsafe.Pointer(&buf[0]))
                if err != nil {
                        return 0, err
                }
                n += copy(buf[addr%sizeofPtr:], data)
                word := *((*uintptr)(unsafe.Pointer(&buf[0])))
                err = ptrace(pokeReq, pid, addr-addr%sizeofPtr, word)
                if err != nil {
                        return 0, err
                }
                data = data[n:]
        }

        // Interior.
        for len(data) > sizeofPtr {
                word := *((*uintptr)(unsafe.Pointer(&data[0])))
                err = ptrace(pokeReq, pid, addr+uintptr(n), word)
                if err != nil {
                        return n, err
                }
                n += sizeofPtr
                data = data[sizeofPtr:]
        }

        // Trailing edge.
        if len(data) > 0 {
                var buf [sizeofPtr]byte
                err = ptracePtr(peekReq, pid, addr+uintptr(n), unsafe.Pointer(&buf[0]))
                if err != nil {
                        return n, err
                }
                copy(buf[0:], data)
                word := *((*uintptr)(unsafe.Pointer(&buf[0])))
                err = ptrace(pokeReq, pid, addr+uintptr(n), word)
                if err != nil {
                        return n, err
                }
                n += len(data)
        }

        return n, nil
}

func PtracePokeText(pid int, addr uintptr, data []byte) (count int, err error) {
        return ptracePoke(PTRACE_POKETEXT, PTRACE_PEEKTEXT, pid, addr, data)
}

func PtracePokeData(pid int, addr uintptr, data []byte) (count int, err error) {
        return ptracePoke(PTRACE_POKEDATA, PTRACE_PEEKDATA, pid, addr, data)
}

const (
        _NT_PRSTATUS = 1
)

func PtraceGetRegs(pid int, regsout *PtraceRegs) (err error) {
        var iov Iovec
        iov.Base = (*byte)(unsafe.Pointer(regsout))
        iov.SetLen(int(unsafe.Sizeof(*regsout)))
        return ptracePtr(PTRACE_GETREGSET, pid, uintptr(_NT_PRSTATUS), unsafe.Pointer(&iov))
}

func PtraceSetRegs(pid int, regs *PtraceRegs) (err error) {
        var iov Iovec
        iov.Base = (*byte)(unsafe.Pointer(regs))
        iov.SetLen(int(unsafe.Sizeof(*regs)))
        return ptracePtr(PTRACE_SETREGSET, pid, uintptr(_NT_PRSTATUS), unsafe.Pointer(&iov))
}

func PtraceSetOptions(pid int, options int) (err error) {
        return ptrace(PTRACE_SETOPTIONS, pid, 0, uintptr(options))
}

func PtraceGetEventMsg(pid int) (msg uint, err error) {
        var data _C_long
        err = ptracePtr(PTRACE_GETEVENTMSG, pid, 0, unsafe.Pointer(&data))
        msg = uint(data)
        return
}

func PtraceCont(pid int, signal int) (err error) {
        return ptrace(PTRACE_CONT, pid, 0, uintptr(signal))
}

func PtraceSyscall(pid int, signal int) (err error) {
        return ptrace(PTRACE_SYSCALL, pid, 0, uintptr(signal))
}

func PtraceSingleStep(pid int) (err error) { return ptrace(PTRACE_SINGLESTEP, pid, 0, 0) }

func PtraceAttach(pid int) (err error) { return ptrace(PTRACE_ATTACH, pid, 0, 0) }

func PtraceDetach(pid int) (err error) { return ptrace(PTRACE_DETACH, pid, 0, 0) }

//sys   reboot(magic1 uint, magic2 uint, cmd int, arg string) (err error)

func Reboot(cmd int) (err error) {
        return reboot(LINUX_REBOOT_MAGIC1, LINUX_REBOOT_MAGIC2, cmd, "")
}

func ReadDirent(fd int, buf []byte) (n int, err error) {
        return Getdents(fd, buf)
}

func direntIno(buf []byte) (uint64, bool) {
        return readInt(buf, unsafe.Offsetof(Dirent{}.Ino), unsafe.Sizeof(Dirent{}.Ino))
}

func direntReclen(buf []byte) (uint64, bool) {
        return readInt(buf, unsafe.Offsetof(Dirent{}.Reclen), unsafe.Sizeof(Dirent{}.Reclen))
}

func direntNamlen(buf []byte) (uint64, bool) {
        reclen, ok := direntReclen(buf)
        if !ok {
                return 0, false
        }
        return reclen - uint64(unsafe.Offsetof(Dirent{}.Name)), true
}

//sys   mount(source string, target string, fstype string, flags uintptr, data *byte) (err error)

func Mount(source string, target string, fstype string, flags uintptr, data string) (err error) {
        // Certain file systems get rather angry and EINVAL if you give
        // them an empty string of data, rather than NULL.
        if data == "" {
                return mount(source, target, fstype, flags, nil)
        }
        datap, err := BytePtrFromString(data)
        if err != nil {
                return err
        }
        return mount(source, target, fstype, flags, datap)
}

// Sendto
// Recvfrom
// Socketpair

/*
 * Direct access
 */
//sys   Acct(path string) (err error)
//sys   Adjtimex(buf *Timex) (state int, err error)
//sys   Chdir(path string) (err error)
//sys   Chroot(path string) (err error)
//sys   Close(fd int) (err error)
//sys   Dup(oldfd int) (fd int, err error)
//sys   Dup3(oldfd int, newfd int, flags int) (err error)
//sysnb EpollCreate1(flag int) (fd int, err error)
//sysnb EpollCtl(epfd int, op int, fd int, event *EpollEvent) (err error)
//sys   Fallocate(fd int, mode uint32, off int64, len int64) (err error)
//sys   Fchdir(fd int) (err error)
//sys   Fchmod(fd int, mode uint32) (err error)
//sys   Fchownat(dirfd int, path string, uid int, gid int, flags int) (err error)
//sys   fcntl(fd int, cmd int, arg int) (val int, err error)
//sys   Fdatasync(fd int) (err error)
//sys   Flock(fd int, how int) (err error)
//sys   Fsync(fd int) (err error)
//sys   Getdents(fd int, buf []byte) (n int, err error) = SYS_GETDENTS64
//sysnb Getpgid(pid int) (pgid int, err error)

func Getpgrp() (pid int) {
        pid, _ = Getpgid(0)
        return
}

//sysnb Getpid() (pid int)
//sysnb Getppid() (ppid int)
//sys   Getpriority(which int, who int) (prio int, err error)
//sysnb Getrusage(who int, rusage *Rusage) (err error)
//sysnb Gettid() (tid int)
//sys   Getxattr(path string, attr string, dest []byte) (sz int, err error)
//sys   InotifyAddWatch(fd int, pathname string, mask uint32) (watchdesc int, err error)
//sysnb InotifyInit1(flags int) (fd int, err error)
//sysnb InotifyRmWatch(fd int, watchdesc uint32) (success int, err error)
//sysnb Kill(pid int, sig Signal) (err error)
//sys   Klogctl(typ int, buf []byte) (n int, err error) = SYS_SYSLOG
//sys   Listxattr(path string, dest []byte) (sz int, err error)
//sys   Mkdirat(dirfd int, path string, mode uint32) (err error)
//sys   Mknodat(dirfd int, path string, mode uint32, dev int) (err error)
//sys   Nanosleep(time *Timespec, leftover *Timespec) (err error)
//sys   PivotRoot(newroot string, putold string) (err error) = SYS_PIVOT_ROOT
//sysnb prlimit1(pid int, resource int, newlimit *Rlimit, old *Rlimit) (err error) = SYS_PRLIMIT64
//sys   read(fd int, p []byte) (n int, err error)
//sys   Removexattr(path string, attr string) (err error)
//sys   Setdomainname(p []byte) (err error)
//sys   Sethostname(p []byte) (err error)
//sysnb Setpgid(pid int, pgid int) (err error)
//sysnb Setsid() (pid int, err error)
//sysnb Settimeofday(tv *Timeval) (err error)

// Provided by runtime.syscall_runtime_doAllThreadsSyscall which stops the
// world and invokes the syscall on each OS thread. Once this function returns,
// all threads are in sync.
//
//go:uintptrescapes
func runtime_doAllThreadsSyscall(trap, a1, a2, a3, a4, a5, a6 uintptr) (r1, r2, err uintptr)

// AllThreadsSyscall performs a syscall on each OS thread of the Go
// runtime. It first invokes the syscall on one thread. Should that
// invocation fail, it returns immediately with the error status.
// Otherwise, it invokes the syscall on all of the remaining threads
// in parallel. It will terminate the program if it observes any
// invoked syscall's return value differs from that of the first
// invocation.
//
// AllThreadsSyscall is intended for emulating simultaneous
// process-wide state changes that require consistently modifying
// per-thread state of the Go runtime.
//
// AllThreadsSyscall is unaware of any threads that are launched
// explicitly by cgo linked code, so the function always returns
// ENOTSUP in binaries that use cgo.
//
//go:uintptrescapes
func AllThreadsSyscall(trap, a1, a2, a3 uintptr) (r1, r2 uintptr, err Errno) {
        if cgo_libc_setegid != nil {
                return minus1, minus1, ENOTSUP
        }
        r1, r2, errno := runtime_doAllThreadsSyscall(trap, a1, a2, a3, 0, 0, 0)
        return r1, r2, Errno(errno)
}

// AllThreadsSyscall6 is like AllThreadsSyscall, but extended to six
// arguments.
//
//go:uintptrescapes
func AllThreadsSyscall6(trap, a1, a2, a3, a4, a5, a6 uintptr) (r1, r2 uintptr, err Errno) {
        if cgo_libc_setegid != nil {
                return minus1, minus1, ENOTSUP
        }
        r1, r2, errno := runtime_doAllThreadsSyscall(trap, a1, a2, a3, a4, a5, a6)
        return r1, r2, Errno(errno)
}

// linked by runtime.cgocall.go
//
//go:uintptrescapes
func cgocaller(unsafe.Pointer, ...uintptr) uintptr

var cgo_libc_setegid unsafe.Pointer // non-nil if cgo linked.

const minus1 = ^uintptr(0)

func Setegid(egid int) (err error) {
        if cgo_libc_setegid == nil {
                if _, _, e1 := AllThreadsSyscall(SYS_SETRESGID, minus1, uintptr(egid), minus1); e1 != 0 {
                        err = errnoErr(e1)
                }
        } else if ret := cgocaller(cgo_libc_setegid, uintptr(egid)); ret != 0 {
                err = errnoErr(Errno(ret))
        }
        return
}

var cgo_libc_seteuid unsafe.Pointer // non-nil if cgo linked.

func Seteuid(euid int) (err error) {
        if cgo_libc_seteuid == nil {
                if _, _, e1 := AllThreadsSyscall(SYS_SETRESUID, minus1, uintptr(euid), minus1); e1 != 0 {
                        err = errnoErr(e1)
                }
        } else if ret := cgocaller(cgo_libc_seteuid, uintptr(euid)); ret != 0 {
                err = errnoErr(Errno(ret))
        }
        return
}

var cgo_libc_setgid unsafe.Pointer // non-nil if cgo linked.

func Setgid(gid int) (err error) {
        if cgo_libc_setgid == nil {
                if _, _, e1 := AllThreadsSyscall(sys_SETGID, uintptr(gid), 0, 0); e1 != 0 {
                        err = errnoErr(e1)
                }
        } else if ret := cgocaller(cgo_libc_setgid, uintptr(gid)); ret != 0 {
                err = errnoErr(Errno(ret))
        }
        return
}

var cgo_libc_setregid unsafe.Pointer // non-nil if cgo linked.

func Setregid(rgid, egid int) (err error) {
        if cgo_libc_setregid == nil {
                if _, _, e1 := AllThreadsSyscall(sys_SETREGID, uintptr(rgid), uintptr(egid), 0); e1 != 0 {
                        err = errnoErr(e1)
                }
        } else if ret := cgocaller(cgo_libc_setregid, uintptr(rgid), uintptr(egid)); ret != 0 {
                err = errnoErr(Errno(ret))
        }
        return
}

var cgo_libc_setresgid unsafe.Pointer // non-nil if cgo linked.

func Setresgid(rgid, egid, sgid int) (err error) {
        if cgo_libc_setresgid == nil {
                if _, _, e1 := AllThreadsSyscall(sys_SETRESGID, uintptr(rgid), uintptr(egid), uintptr(sgid)); e1 != 0 {
                        err = errnoErr(e1)
                }
        } else if ret := cgocaller(cgo_libc_setresgid, uintptr(rgid), uintptr(egid), uintptr(sgid)); ret != 0 {
                err = errnoErr(Errno(ret))
        }
        return
}

var cgo_libc_setresuid unsafe.Pointer // non-nil if cgo linked.

func Setresuid(ruid, euid, suid int) (err error) {
        if cgo_libc_setresuid == nil {
                if _, _, e1 := AllThreadsSyscall(sys_SETRESUID, uintptr(ruid), uintptr(euid), uintptr(suid)); e1 != 0 {
                        err = errnoErr(e1)
                }
        } else if ret := cgocaller(cgo_libc_setresuid, uintptr(ruid), uintptr(euid), uintptr(suid)); ret != 0 {
                err = errnoErr(Errno(ret))
        }
        return
}

var cgo_libc_setreuid unsafe.Pointer // non-nil if cgo linked.

func Setreuid(ruid, euid int) (err error) {
        if cgo_libc_setreuid == nil {
                if _, _, e1 := AllThreadsSyscall(sys_SETREUID, uintptr(ruid), uintptr(euid), 0); e1 != 0 {
                        err = errnoErr(e1)
                }
        } else if ret := cgocaller(cgo_libc_setreuid, uintptr(ruid), uintptr(euid)); ret != 0 {
                err = errnoErr(Errno(ret))
        }
        return
}

var cgo_libc_setuid unsafe.Pointer // non-nil if cgo linked.

func Setuid(uid int) (err error) {
        if cgo_libc_setuid == nil {
                if _, _, e1 := AllThreadsSyscall(sys_SETUID, uintptr(uid), 0, 0); e1 != 0 {
                        err = errnoErr(e1)
                }
        } else if ret := cgocaller(cgo_libc_setuid, uintptr(uid)); ret != 0 {
                err = errnoErr(Errno(ret))
        }
        return
}

//sys   Setpriority(which int, who int, prio int) (err error)
//sys   Setxattr(path string, attr string, data []byte, flags int) (err error)
//sys   Sync()
//sysnb Sysinfo(info *Sysinfo_t) (err error)
//sys   Tee(rfd int, wfd int, len int, flags int) (n int64, err error)
//sysnb Tgkill(tgid int, tid int, sig Signal) (err error)
//sysnb Times(tms *Tms) (ticks uintptr, err error)
//sysnb Umask(mask int) (oldmask int)
//sysnb Uname(buf *Utsname) (err error)
//sys   Unmount(target string, flags int) (err error) = SYS_UMOUNT2
//sys   Unshare(flags int) (err error)
//sys   write(fd int, p []byte) (n int, err error)
//sys   exitThread(code int) (err error) = SYS_EXIT
//sys   readlen(fd int, p *byte, np int) (n int, err error) = SYS_READ
//sys   writelen(fd int, p *byte, np int) (n int, err error) = SYS_WRITE

// mmap varies by architecture; see syscall_linux_*.go.
//sys   munmap(addr uintptr, length uintptr) (err error)

var mapper = &mmapper{
        active: make(map[*byte][]byte),
        mmap:   mmap,
        munmap: munmap,
}

func Mmap(fd int, offset int64, length int, prot int, flags int) (data []byte, err error) {
        return mapper.Mmap(fd, offset, length, prot, flags)
}

func Munmap(b []byte) (err error) {
        return mapper.Munmap(b)
}

//sys   Madvise(b []byte, advice int) (err error)
//sys   Mprotect(b []byte, prot int) (err error)
//sys   Mlock(b []byte) (err error)
//sys   Munlock(b []byte) (err error)
//sys   Mlockall(flags int) (err error)
//sys   Munlockall() (err error)

// prlimit changes a resource limit. We use a single definition so that
// we can tell StartProcess to not restore the original NOFILE limit.
// This is unexported but can be called from x/sys/unix.
func prlimit(pid int, resource int, newlimit *Rlimit, old *Rlimit) (err error) {
        err = prlimit1(pid, resource, newlimit, old)
        if err == nil && newlimit != nil && resource == RLIMIT_NOFILE {
                origRlimitNofile.Store(Rlimit{0, 0})
        }
        return err
}