275 lines
6.9 KiB
Go
275 lines
6.9 KiB
Go
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// Copyright 2018 Google Inc.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package linux
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import (
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"gvisor.googlesource.com/gvisor/pkg/abi/linux"
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"gvisor.googlesource.com/gvisor/pkg/sentry/arch"
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"gvisor.googlesource.com/gvisor/pkg/sentry/fs"
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"gvisor.googlesource.com/gvisor/pkg/sentry/kernel"
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"gvisor.googlesource.com/gvisor/pkg/sentry/kernel/kdefs"
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"gvisor.googlesource.com/gvisor/pkg/sentry/usermem"
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"gvisor.googlesource.com/gvisor/pkg/syserror"
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"gvisor.googlesource.com/gvisor/pkg/waiter"
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)
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const (
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// EventMaskRead contains events that can be triggerd on reads.
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EventMaskRead = waiter.EventIn | waiter.EventHUp | waiter.EventErr
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)
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// Read implements linux syscall read(2). Note that we try to get a buffer that
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// is exactly the size requested because some applications like qemu expect
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// they can do large reads all at once. Bug for bug. Same for other read
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// calls below.
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func Read(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
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fd := kdefs.FD(args[0].Int())
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addr := args[1].Pointer()
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size := args[2].SizeT()
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file := t.FDMap().GetFile(fd)
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if file == nil {
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return 0, nil, syserror.EBADF
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}
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defer file.DecRef()
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// Check that the file is readable.
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if !file.Flags().Read {
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return 0, nil, syserror.EBADF
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}
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// Check that the size is legitimate.
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si := int(size)
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if si < 0 {
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return 0, nil, syserror.EINVAL
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}
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// Get the destination of the read.
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dst, err := t.SingleIOSequence(addr, si, usermem.IOOpts{
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AddressSpaceActive: true,
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})
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if err != nil {
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return 0, nil, err
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}
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n, err := readv(t, file, dst)
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t.IOUsage().AccountReadSyscall(n)
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return uintptr(n), nil, handleIOError(t, n != 0, err, kernel.ERESTARTSYS, "read", file)
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}
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// Pread64 implements linux syscall pread64(2).
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func Pread64(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
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fd := kdefs.FD(args[0].Int())
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addr := args[1].Pointer()
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size := args[2].SizeT()
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offset := args[3].Int64()
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file := t.FDMap().GetFile(fd)
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if file == nil {
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return 0, nil, syserror.EBADF
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}
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defer file.DecRef()
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// Check that the offset is legitimate.
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if offset < 0 {
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return 0, nil, syserror.EINVAL
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}
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// Is reading at an offset supported?
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if !file.Flags().Pread {
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return 0, nil, syserror.ESPIPE
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}
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// Check that the file is readable.
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if !file.Flags().Read {
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return 0, nil, syserror.EBADF
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}
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// Check that the size is legitimate.
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si := int(size)
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if si < 0 {
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return 0, nil, syserror.EINVAL
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}
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// Get the destination of the read.
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dst, err := t.SingleIOSequence(addr, si, usermem.IOOpts{
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AddressSpaceActive: true,
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})
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if err != nil {
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return 0, nil, err
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}
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n, err := preadv(t, file, dst, offset)
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t.IOUsage().AccountReadSyscall(n)
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return uintptr(n), nil, handleIOError(t, n != 0, err, kernel.ERESTARTSYS, "pread64", file)
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}
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// Readv implements linux syscall readv(2).
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func Readv(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
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fd := kdefs.FD(args[0].Int())
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addr := args[1].Pointer()
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iovcnt := int(args[2].Int())
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file := t.FDMap().GetFile(fd)
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if file == nil {
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return 0, nil, syserror.EBADF
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}
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defer file.DecRef()
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// Check that the file is readable.
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if !file.Flags().Read {
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return 0, nil, syserror.EBADF
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}
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// Read the iovecs that specify the destination of the read.
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dst, err := t.IovecsIOSequence(addr, iovcnt, usermem.IOOpts{
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AddressSpaceActive: true,
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})
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if err != nil {
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return 0, nil, err
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}
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n, err := readv(t, file, dst)
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t.IOUsage().AccountReadSyscall(n)
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return uintptr(n), nil, handleIOError(t, n != 0, err, kernel.ERESTARTSYS, "readv", file)
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}
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// Preadv implements linux syscall preadv(2).
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func Preadv(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
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fd := kdefs.FD(args[0].Int())
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addr := args[1].Pointer()
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iovcnt := int(args[2].Int())
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offset := args[3].Int64()
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file := t.FDMap().GetFile(fd)
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if file == nil {
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return 0, nil, syserror.EBADF
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}
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defer file.DecRef()
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// Check that the offset is legitimate.
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if offset < 0 {
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return 0, nil, syserror.EINVAL
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}
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// Is reading at an offset supported?
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if !file.Flags().Pread {
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return 0, nil, syserror.ESPIPE
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}
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// Check that the file is readable.
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if !file.Flags().Read {
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return 0, nil, syserror.EBADF
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}
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// Read the iovecs that specify the destination of the read.
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dst, err := t.IovecsIOSequence(addr, iovcnt, usermem.IOOpts{
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AddressSpaceActive: true,
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})
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if err != nil {
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return 0, nil, err
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}
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n, err := preadv(t, file, dst, offset)
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t.IOUsage().AccountReadSyscall(n)
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return uintptr(n), nil, handleIOError(t, n != 0, err, kernel.ERESTARTSYS, "preadv", file)
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}
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func readv(t *kernel.Task, f *fs.File, dst usermem.IOSequence) (int64, error) {
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n, err := f.Readv(t, dst)
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if err != syserror.ErrWouldBlock || f.Flags().NonBlocking {
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if n > 0 {
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// Queue notification if we read anything.
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f.Dirent.InotifyEvent(linux.IN_ACCESS, 0)
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}
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return n, err
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}
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// Register for notifications.
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w, ch := waiter.NewChannelEntry(nil)
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f.EventRegister(&w, EventMaskRead)
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total := n
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for {
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// Shorten dst to reflect bytes previously read.
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dst = dst.DropFirst64(n)
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// Issue the request and break out if it completes with anything
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// other than "would block".
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n, err = f.Readv(t, dst)
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total += n
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if err != syserror.ErrWouldBlock {
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break
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}
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// Wait for a notification that we should retry.
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if err = t.Block(ch); err != nil {
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break
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}
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}
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f.EventUnregister(&w)
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if total > 0 {
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// Queue notification if we read anything.
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f.Dirent.InotifyEvent(linux.IN_ACCESS, 0)
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}
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return total, err
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}
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func preadv(t *kernel.Task, f *fs.File, dst usermem.IOSequence, offset int64) (int64, error) {
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n, err := f.Preadv(t, dst, offset)
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if err != syserror.ErrWouldBlock || f.Flags().NonBlocking {
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if n > 0 {
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// Queue notification if we read anything.
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f.Dirent.InotifyEvent(linux.IN_ACCESS, 0)
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}
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return n, err
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}
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// Register for notifications.
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w, ch := waiter.NewChannelEntry(nil)
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f.EventRegister(&w, EventMaskRead)
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total := n
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for {
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// Shorten dst to reflect bytes previously read.
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dst = dst.DropFirst64(n)
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// Issue the request and break out if it completes with anything
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// other than "would block".
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n, err = f.Preadv(t, dst, offset+total)
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total += n
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if err != syserror.ErrWouldBlock {
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break
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}
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// Wait for a notification that we should retry.
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if err = t.Block(ch); err != nil {
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break
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}
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}
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f.EventUnregister(&w)
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if total > 0 {
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// Queue notification if we read anything.
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f.Dirent.InotifyEvent(linux.IN_ACCESS, 0)
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}
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return total, err
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}
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