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// Copyright 2018 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package linux
import (
"gvisor.googlesource.com/gvisor/pkg/abi/linux"
"gvisor.googlesource.com/gvisor/pkg/sentry/arch"
"gvisor.googlesource.com/gvisor/pkg/sentry/fs"
"gvisor.googlesource.com/gvisor/pkg/sentry/kernel"
"gvisor.googlesource.com/gvisor/pkg/sentry/kernel/kdefs"
"gvisor.googlesource.com/gvisor/pkg/sentry/usermem"
"gvisor.googlesource.com/gvisor/pkg/syserror"
"gvisor.googlesource.com/gvisor/pkg/waiter"
)
const (
// EventMaskRead contains events that can be triggerd on reads.
EventMaskRead = waiter.EventIn | waiter.EventHUp | waiter.EventErr
)
// Read implements linux syscall read(2). Note that we try to get a buffer that
// is exactly the size requested because some applications like qemu expect
// they can do large reads all at once. Bug for bug. Same for other read
// calls below.
func Read(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
fd := kdefs.FD(args[0].Int())
addr := args[1].Pointer()
size := args[2].SizeT()
file := t.FDMap().GetFile(fd)
if file == nil {
return 0, nil, syserror.EBADF
}
defer file.DecRef()
// Check that the file is readable.
if !file.Flags().Read {
return 0, nil, syserror.EBADF
}
// Check that the size is legitimate.
si := int(size)
if si < 0 {
return 0, nil, syserror.EINVAL
}
// Get the destination of the read.
dst, err := t.SingleIOSequence(addr, si, usermem.IOOpts{
AddressSpaceActive: true,
})
if err != nil {
return 0, nil, err
}
n, err := readv(t, file, dst)
t.IOUsage().AccountReadSyscall(n)
return uintptr(n), nil, handleIOError(t, n != 0, err, kernel.ERESTARTSYS, "read", file)
}
// Pread64 implements linux syscall pread64(2).
func Pread64(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
fd := kdefs.FD(args[0].Int())
addr := args[1].Pointer()
size := args[2].SizeT()
offset := args[3].Int64()
file := t.FDMap().GetFile(fd)
if file == nil {
return 0, nil, syserror.EBADF
}
defer file.DecRef()
// Check that the offset is legitimate.
if offset < 0 {
return 0, nil, syserror.EINVAL
}
// Is reading at an offset supported?
if !file.Flags().Pread {
return 0, nil, syserror.ESPIPE
}
// Check that the file is readable.
if !file.Flags().Read {
return 0, nil, syserror.EBADF
}
// Check that the size is legitimate.
si := int(size)
if si < 0 {
return 0, nil, syserror.EINVAL
}
// Get the destination of the read.
dst, err := t.SingleIOSequence(addr, si, usermem.IOOpts{
AddressSpaceActive: true,
})
if err != nil {
return 0, nil, err
}
n, err := preadv(t, file, dst, offset)
t.IOUsage().AccountReadSyscall(n)
return uintptr(n), nil, handleIOError(t, n != 0, err, kernel.ERESTARTSYS, "pread64", file)
}
// Readv implements linux syscall readv(2).
func Readv(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
fd := kdefs.FD(args[0].Int())
addr := args[1].Pointer()
iovcnt := int(args[2].Int())
file := t.FDMap().GetFile(fd)
if file == nil {
return 0, nil, syserror.EBADF
}
defer file.DecRef()
// Check that the file is readable.
if !file.Flags().Read {
return 0, nil, syserror.EBADF
}
// Read the iovecs that specify the destination of the read.
dst, err := t.IovecsIOSequence(addr, iovcnt, usermem.IOOpts{
AddressSpaceActive: true,
})
if err != nil {
return 0, nil, err
}
n, err := readv(t, file, dst)
t.IOUsage().AccountReadSyscall(n)
return uintptr(n), nil, handleIOError(t, n != 0, err, kernel.ERESTARTSYS, "readv", file)
}
// Preadv implements linux syscall preadv(2).
func Preadv(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
fd := kdefs.FD(args[0].Int())
addr := args[1].Pointer()
iovcnt := int(args[2].Int())
offset := args[3].Int64()
file := t.FDMap().GetFile(fd)
if file == nil {
return 0, nil, syserror.EBADF
}
defer file.DecRef()
// Check that the offset is legitimate.
if offset < 0 {
return 0, nil, syserror.EINVAL
}
// Is reading at an offset supported?
if !file.Flags().Pread {
return 0, nil, syserror.ESPIPE
}
// Check that the file is readable.
if !file.Flags().Read {
return 0, nil, syserror.EBADF
}
// Read the iovecs that specify the destination of the read.
dst, err := t.IovecsIOSequence(addr, iovcnt, usermem.IOOpts{
AddressSpaceActive: true,
})
if err != nil {
return 0, nil, err
}
n, err := preadv(t, file, dst, offset)
t.IOUsage().AccountReadSyscall(n)
return uintptr(n), nil, handleIOError(t, n != 0, err, kernel.ERESTARTSYS, "preadv", file)
}
// Preadv2 implements linux syscall preadv2(2).
func Preadv2(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
fd := kdefs.FD(args[0].Int())
addr := args[1].Pointer()
iovcnt := int(args[2].Int())
offset := args[3].Int64()
flags := int(args[4].Int())
validFlags := linux.RWF_HIPRI
file := t.FDMap().GetFile(fd)
if file == nil {
return 0, nil, syserror.EBADF
}
defer file.DecRef()
// Check that the offset is legitimate.
if offset < -1 {
return 0, nil, syserror.EINVAL
}
// Is reading at an offset supported?
if offset > -1 && !file.Flags().Pread {
return 0, nil, syserror.ESPIPE
}
// Check that the file is readable.
if !file.Flags().Read {
return 0, nil, syserror.EBADF
}
// Check flags field.
if flags != 0 {
if flags&^validFlags != 0 {
return 0, nil, syserror.EINVAL
}
// RWF_HIPRI must be called on a file with O_DIRECT flag set.
if flags&linux.RWF_HIPRI != 0 && !file.Flags().Direct {
return 0, nil, syserror.EINVAL
}
}
// Read the iovecs that specify the destination of the read.
dst, err := t.IovecsIOSequence(addr, iovcnt, usermem.IOOpts{
AddressSpaceActive: true,
})
if err != nil {
return 0, nil, err
}
// If preadv2 is called with an offset of -1, readv is called.
if offset == -1 {
n, err := readv(t, file, dst)
t.IOUsage().AccountReadSyscall(n)
return uintptr(n), nil, handleIOError(t, n != 0, err, kernel.ERESTARTSYS, "preadv2", file)
}
n, err := preadv(t, file, dst, offset)
t.IOUsage().AccountReadSyscall(n)
return uintptr(n), nil, handleIOError(t, n != 0, err, kernel.ERESTARTSYS, "preadv2", file)
}
func readv(t *kernel.Task, f *fs.File, dst usermem.IOSequence) (int64, error) {
n, err := f.Readv(t, dst)
if err != syserror.ErrWouldBlock || f.Flags().NonBlocking {
if n > 0 {
// Queue notification if we read anything.
f.Dirent.InotifyEvent(linux.IN_ACCESS, 0)
}
return n, err
}
// Register for notifications.
w, ch := waiter.NewChannelEntry(nil)
f.EventRegister(&w, EventMaskRead)
total := n
for {
// Shorten dst to reflect bytes previously read.
dst = dst.DropFirst64(n)
// Issue the request and break out if it completes with anything
// other than "would block".
n, err = f.Readv(t, dst)
total += n
if err != syserror.ErrWouldBlock {
break
}
// Wait for a notification that we should retry.
if err = t.Block(ch); err != nil {
break
}
}
f.EventUnregister(&w)
if total > 0 {
// Queue notification if we read anything.
f.Dirent.InotifyEvent(linux.IN_ACCESS, 0)
}
return total, err
}
func preadv(t *kernel.Task, f *fs.File, dst usermem.IOSequence, offset int64) (int64, error) {
n, err := f.Preadv(t, dst, offset)
if err != syserror.ErrWouldBlock || f.Flags().NonBlocking {
if n > 0 {
// Queue notification if we read anything.
f.Dirent.InotifyEvent(linux.IN_ACCESS, 0)
}
return n, err
}
// Register for notifications.
w, ch := waiter.NewChannelEntry(nil)
f.EventRegister(&w, EventMaskRead)
total := n
for {
// Shorten dst to reflect bytes previously read.
dst = dst.DropFirst64(n)
// Issue the request and break out if it completes with anything
// other than "would block".
n, err = f.Preadv(t, dst, offset+total)
total += n
if err != syserror.ErrWouldBlock {
break
}
// Wait for a notification that we should retry.
if err = t.Block(ch); err != nil {
break
}
}
f.EventUnregister(&w)
if total > 0 {
// Queue notification if we read anything.
f.Dirent.InotifyEvent(linux.IN_ACCESS, 0)
}
return total, err
}
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