Check in gVisor.

PiperOrigin-RevId: 194583126
Change-Id: Ica1d8821a90f74e7e745962d71801c598c652463

1 files changed, 274 insertions, 0 deletions

diff --git a/pkg/sentry/syscalls/linux/sys_write.go b/pkg/sentry/syscalls/linux/sys_write.go
new file mode 100644
index 000000000..caa7b01ea
--- /dev/null
+++ b/pkg/sentry/syscalls/linux/sys_write.go
@@ -0,0 +1,274 @@
+// Copyright 2018 Google Inc.
+//
+// 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 (
+	// EventMaskWrite contains events that can be triggered on writes.
+	//
+	// Note that EventHUp is not going to happen for pipes but may for
+	// implementations of poll on some sockets, see net/core/datagram.c.
+	EventMaskWrite = waiter.EventOut | waiter.EventHUp | waiter.EventErr
+)
+
+// Write implements linux syscall write(2).
+func Write(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 writable.
+	if !file.Flags().Write {
+		return 0, nil, syserror.EBADF
+	}
+
+	// Check that the size is legitimate.
+	si := int(size)
+	if si < 0 {
+		return 0, nil, syserror.EINVAL
+	}
+
+	// Get the source of the write.
+	src, err := t.SingleIOSequence(addr, si, usermem.IOOpts{
+		AddressSpaceActive: true,
+	})
+	if err != nil {
+		return 0, nil, err
+	}
+
+	n, err := writev(t, file, src)
+	t.IOUsage().AccountWriteSyscall(n)
+	return uintptr(n), nil, handleIOError(t, n != 0, err, kernel.ERESTARTSYS, "write", file)
+}
+
+// Pwrite64 implements linux syscall pwrite64(2).
+func Pwrite64(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 writing at an offset supported?
+	if !file.Flags().Pwrite {
+		return 0, nil, syserror.ESPIPE
+	}
+
+	// Check that the file is writable.
+	if !file.Flags().Write {
+		return 0, nil, syserror.EBADF
+	}
+
+	// Check that the size is legitimate.
+	si := int(size)
+	if si < 0 {
+		return 0, nil, syserror.EINVAL
+	}
+
+	// Get the source of the write.
+	src, err := t.SingleIOSequence(addr, si, usermem.IOOpts{
+		AddressSpaceActive: true,
+	})
+	if err != nil {
+		return 0, nil, err
+	}
+
+	n, err := pwritev(t, file, src, offset)
+	t.IOUsage().AccountWriteSyscall(n)
+	return uintptr(n), nil, handleIOError(t, n != 0, err, kernel.ERESTARTSYS, "pwrite64", file)
+}
+
+// Writev implements linux syscall writev(2).
+func Writev(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 writable.
+	if !file.Flags().Write {
+		return 0, nil, syserror.EBADF
+	}
+
+	// Read the iovecs that specify the source of the write.
+	src, err := t.IovecsIOSequence(addr, iovcnt, usermem.IOOpts{
+		AddressSpaceActive: true,
+	})
+	if err != nil {
+		return 0, nil, err
+	}
+
+	n, err := writev(t, file, src)
+	t.IOUsage().AccountWriteSyscall(n)
+	return uintptr(n), nil, handleIOError(t, n != 0, err, kernel.ERESTARTSYS, "writev", file)
+}
+
+// Pwritev implements linux syscall pwritev(2).
+func Pwritev(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 writing at an offset supported?
+	if !file.Flags().Pwrite {
+		return 0, nil, syserror.ESPIPE
+	}
+
+	// Check that the file is writable.
+	if !file.Flags().Write {
+		return 0, nil, syserror.EBADF
+	}
+
+	// Read the iovecs that specify the source of the write.
+	src, err := t.IovecsIOSequence(addr, iovcnt, usermem.IOOpts{
+		AddressSpaceActive: true,
+	})
+	if err != nil {
+		return 0, nil, err
+	}
+
+	n, err := pwritev(t, file, src, offset)
+	t.IOUsage().AccountWriteSyscall(n)
+	return uintptr(n), nil, handleIOError(t, n != 0, err, kernel.ERESTARTSYS, "pwritev", file)
+}
+
+func writev(t *kernel.Task, f *fs.File, src usermem.IOSequence) (int64, error) {
+	n, err := f.Writev(t, src)
+	if err != syserror.ErrWouldBlock || f.Flags().NonBlocking {
+		if n > 0 {
+			// Queue notification if we wrote anything.
+			f.Dirent.InotifyEvent(linux.IN_MODIFY, 0)
+		}
+		return n, err
+	}
+
+	// Register for notifications.
+	w, ch := waiter.NewChannelEntry(nil)
+	f.EventRegister(&w, EventMaskWrite)
+
+	total := n
+	for {
+		// Shorten src to reflect bytes previously written.
+		src = src.DropFirst64(n)
+
+		// Issue the request and break out if it completes with
+		// anything other than "would block".
+		n, err = f.Writev(t, src)
+		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 wrote anything.
+		f.Dirent.InotifyEvent(linux.IN_MODIFY, 0)
+	}
+
+	return total, err
+}
+
+func pwritev(t *kernel.Task, f *fs.File, src usermem.IOSequence, offset int64) (int64, error) {
+	n, err := f.Pwritev(t, src, offset)
+	if err != syserror.ErrWouldBlock || f.Flags().NonBlocking {
+		if n > 0 {
+			// Queue notification if we wrote anything.
+			f.Dirent.InotifyEvent(linux.IN_MODIFY, 0)
+		}
+		return n, err
+	}
+
+	// Register for notifications.
+	w, ch := waiter.NewChannelEntry(nil)
+	f.EventRegister(&w, EventMaskWrite)
+
+	total := n
+	for {
+		// Shorten src to reflect bytes previously written.
+		src = src.DropFirst64(n)
+
+		// Issue the request and break out if it completes with
+		// anything other than "would block".
+		n, err = f.Pwritev(t, src, 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 wrote anything.
+		f.Dirent.InotifyEvent(linux.IN_MODIFY, 0)
+	}
+
+	return total, err
+}