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Factor fsimpl/gofer.host{Preadv,Pwritev} out of fsimpl/gofer.

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Also fix returning EOF when 0 bytes are read.

PiperOrigin-RevId: 308089875
This commit is contained in:
Jamie Liu
2020-04-23 11:08:24 -07:00
committed by gVisor bot
parent 7d1b7daf7e
commit e0c67014cb
8 changed files with 218 additions and 97 deletions
Download Patch File Download Diff File Expand all files Collapse all files
pkg/sentry/fsimpl/gofer/BUILD
+1 -1
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@@ -35,7 +35,6 @@ go_library(
"fstree.go",
"gofer.go",
"handle.go",
"handle_unsafe.go",
"p9file.go",
"pagemath.go",
"regular_file.go",
@@ -53,6 +52,7 @@ go_library(
"//pkg/p9",
"//pkg/safemem",
"//pkg/sentry/fs/fsutil",
"//pkg/sentry/hostfd",
"//pkg/sentry/kernel/auth",
"//pkg/sentry/kernel/time",
"//pkg/sentry/memmap",
pkg/sentry/fsimpl/gofer/handle.go
+3 -2
View File
@@ -20,6 +20,7 @@ import (
"gvisor.dev/gvisor/pkg/context"
"gvisor.dev/gvisor/pkg/p9"
"gvisor.dev/gvisor/pkg/safemem"
"gvisor.dev/gvisor/pkg/sentry/hostfd"
)
// handle represents a remote "open file descriptor", consisting of an opened
@@ -77,7 +78,7 @@ func (h *handle) readToBlocksAt(ctx context.Context, dsts safemem.BlockSeq, offs
}
if h.fd >= 0 {
ctx.UninterruptibleSleepStart(false)
n, err := hostPreadv(h.fd, dsts, int64(offset))
n, err := hostfd.Preadv2(h.fd, dsts, int64(offset), 0 /* flags */)
ctx.UninterruptibleSleepFinish(false)
return n, err
}
@@ -103,7 +104,7 @@ func (h *handle) writeFromBlocksAt(ctx context.Context, srcs safemem.BlockSeq, o
}
if h.fd >= 0 {
ctx.UninterruptibleSleepStart(false)
n, err := hostPwritev(h.fd, srcs, int64(offset))
n, err := hostfd.Pwritev2(h.fd, srcs, int64(offset), 0 /* flags */)
ctx.UninterruptibleSleepFinish(false)
return n, err
}
pkg/sentry/fsimpl/gofer/handle_unsafe.go
-66
View File
@@ -1,66 +0,0 @@
// Copyright 2019 The gVisor Authors.
//
// 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 gofer
import (
"syscall"
"unsafe"
"gvisor.dev/gvisor/pkg/safemem"
)
// Preconditions: !dsts.IsEmpty().
func hostPreadv(fd int32, dsts safemem.BlockSeq, off int64) (uint64, error) {
// No buffering is necessary regardless of safecopy; host syscalls will
// return EFAULT if appropriate, instead of raising SIGBUS.
if dsts.NumBlocks() == 1 {
// Use pread() instead of preadv() to avoid iovec allocation and
// copying.
dst := dsts.Head()
n, _, e := syscall.Syscall6(syscall.SYS_PREAD64, uintptr(fd), dst.Addr(), uintptr(dst.Len()), uintptr(off), 0, 0)
if e != 0 {
return 0, e
}
return uint64(n), nil
}
iovs := safemem.IovecsFromBlockSeq(dsts)
n, _, e := syscall.Syscall6(syscall.SYS_PREADV, uintptr(fd), uintptr((unsafe.Pointer)(&iovs[0])), uintptr(len(iovs)), uintptr(off), 0, 0)
if e != 0 {
return 0, e
}
return uint64(n), nil
}
// Preconditions: !srcs.IsEmpty().
func hostPwritev(fd int32, srcs safemem.BlockSeq, off int64) (uint64, error) {
// No buffering is necessary regardless of safecopy; host syscalls will
// return EFAULT if appropriate, instead of raising SIGBUS.
if srcs.NumBlocks() == 1 {
// Use pwrite() instead of pwritev() to avoid iovec allocation and
// copying.
src := srcs.Head()
n, _, e := syscall.Syscall6(syscall.SYS_PWRITE64, uintptr(fd), src.Addr(), uintptr(src.Len()), uintptr(off), 0, 0)
if e != 0 {
return 0, e
}
return uint64(n), nil
}
iovs := safemem.IovecsFromBlockSeq(srcs)
n, _, e := syscall.Syscall6(syscall.SYS_PWRITEV, uintptr(fd), uintptr((unsafe.Pointer)(&iovs[0])), uintptr(len(iovs)), uintptr(off), 0, 0)
if e != 0 {
return 0, e
}
return uint64(n), nil
}
pkg/sentry/fsimpl/host/BUILD
+1 -2
View File
@@ -15,12 +15,11 @@ go_library(
deps = [
"//pkg/abi/linux",
"//pkg/context",
"//pkg/fd",
"//pkg/log",
"//pkg/refs",
"//pkg/safemem",
"//pkg/sentry/arch",
"//pkg/sentry/fsimpl/kernfs",
"//pkg/sentry/hostfd",
"//pkg/sentry/kernel",
"//pkg/sentry/kernel/auth",
"//pkg/sentry/memmap",
pkg/sentry/fsimpl/host/host.go
+5 -26
View File
@@ -25,11 +25,10 @@ import (
"golang.org/x/sys/unix"
"gvisor.dev/gvisor/pkg/abi/linux"
"gvisor.dev/gvisor/pkg/context"
"gvisor.dev/gvisor/pkg/fd"
"gvisor.dev/gvisor/pkg/log"
"gvisor.dev/gvisor/pkg/refs"
"gvisor.dev/gvisor/pkg/safemem"
"gvisor.dev/gvisor/pkg/sentry/fsimpl/kernfs"
"gvisor.dev/gvisor/pkg/sentry/hostfd"
"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
"gvisor.dev/gvisor/pkg/sentry/memmap"
"gvisor.dev/gvisor/pkg/sentry/vfs"
@@ -492,19 +491,9 @@ func readFromHostFD(ctx context.Context, hostFD int, dst usermem.IOSequence, off
if flags != 0 {
return 0, syserror.EOPNOTSUPP
}
var reader safemem.Reader
if offset == -1 {
reader = safemem.FromIOReader{fd.NewReadWriter(hostFD)}
} else {
reader = safemem.FromVecReaderFunc{
func(srcs [][]byte) (int64, error) {
n, err := unix.Preadv(hostFD, srcs, offset)
return int64(n), err
},
}
}
reader := hostfd.GetReadWriterAt(int32(hostFD), offset, flags)
n, err := dst.CopyOutFrom(ctx, reader)
hostfd.PutReadWriterAt(reader)
return int64(n), err
}
@@ -542,19 +531,9 @@ func writeToHostFD(ctx context.Context, hostFD int, src usermem.IOSequence, offs
if flags != 0 {
return 0, syserror.EOPNOTSUPP
}
var writer safemem.Writer
if offset == -1 {
writer = safemem.FromIOWriter{fd.NewReadWriter(hostFD)}
} else {
writer = safemem.FromVecWriterFunc{
func(srcs [][]byte) (int64, error) {
n, err := unix.Pwritev(hostFD, srcs, offset)
return int64(n), err
},
}
}
writer := hostfd.GetReadWriterAt(int32(hostFD), offset, flags)
n, err := src.CopyInTo(ctx, writer)
hostfd.PutReadWriterAt(writer)
return int64(n), err
}
pkg/sentry/hostfd/BUILD
+17
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@@ -0,0 +1,17 @@
load("//tools:defs.bzl", "go_library")
licenses(["notice"])
go_library(
name = "hostfd",
srcs = [
"hostfd.go",
"hostfd_unsafe.go",
],
visibility = ["//pkg/sentry:internal"],
deps = [
"//pkg/safemem",
"//pkg/sync",
"@org_golang_x_sys//unix:go_default_library",
],
)
pkg/sentry/hostfd/hostfd.go
+84
View File
@@ -0,0 +1,84 @@
// Copyright 2020 The gVisor Authors.
//
// 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 hostfd provides efficient I/O with host file descriptors.
package hostfd
import (
"gvisor.dev/gvisor/pkg/safemem"
"gvisor.dev/gvisor/pkg/sync"
)
// ReadWriterAt implements safemem.Reader and safemem.Writer by reading from
// and writing to a host file descriptor respectively. ReadWriterAts should be
// obtained by calling GetReadWriterAt.
//
// Clients should usually prefer to use Preadv2 and Pwritev2 directly.
type ReadWriterAt struct {
fd int32
offset int64
flags uint32
}
var rwpool = sync.Pool{
New: func() interface{} {
return &ReadWriterAt{}
},
}
// GetReadWriterAt returns a ReadWriterAt that reads from / writes to the given
// host file descriptor, starting at the given offset and using the given
// preadv2(2)/pwritev2(2) flags. If offset is -1, the host file descriptor's
// offset is used instead. Users are responsible for ensuring that fd remains
// valid for the lifetime of the returned ReadWriterAt, and must call
// PutReadWriterAt when it is no longer needed.
func GetReadWriterAt(fd int32, offset int64, flags uint32) *ReadWriterAt {
rw := rwpool.Get().(*ReadWriterAt)
*rw = ReadWriterAt{
fd: fd,
offset: offset,
flags: flags,
}
return rw
}
// PutReadWriterAt releases a ReadWriterAt returned by a previous call to
// GetReadWriterAt that is no longer in use.
func PutReadWriterAt(rw *ReadWriterAt) {
rwpool.Put(rw)
}
// ReadToBlocks implements safemem.Reader.ReadToBlocks.
func (rw *ReadWriterAt) ReadToBlocks(dsts safemem.BlockSeq) (uint64, error) {
if dsts.IsEmpty() {
return 0, nil
}
n, err := Preadv2(rw.fd, dsts, rw.offset, rw.flags)
if rw.offset >= 0 {
rw.offset += int64(n)
}
return n, err
}
// WriteFromBlocks implements safemem.Writer.WriteFromBlocks.
func (rw *ReadWriterAt) WriteFromBlocks(srcs safemem.BlockSeq) (uint64, error) {
if srcs.IsEmpty() {
return 0, nil
}
n, err := Pwritev2(rw.fd, srcs, rw.offset, rw.flags)
if rw.offset >= 0 {
rw.offset += int64(n)
}
return n, err
}
pkg/sentry/hostfd/hostfd_unsafe.go
+107
View File
@@ -0,0 +1,107 @@
// Copyright 2020 The gVisor Authors.
//
// 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 hostfd
import (
"io"
"syscall"
"unsafe"
"golang.org/x/sys/unix"
"gvisor.dev/gvisor/pkg/safemem"
)
// Preadv2 reads up to dsts.NumBytes() bytes from host file descriptor fd into
// dsts. offset and flags are interpreted as for preadv2(2).
//
// Preconditions: !dsts.IsEmpty().
func Preadv2(fd int32, dsts safemem.BlockSeq, offset int64, flags uint32) (uint64, error) {
// No buffering is necessary regardless of safecopy; host syscalls will
// return EFAULT if appropriate, instead of raising SIGBUS.
var (
n uintptr
e syscall.Errno
)
// Avoid preadv2(2) if possible, since it's relatively new and thus least
// likely to be supported by the host kernel.
if flags == 0 {
if dsts.NumBlocks() == 1 {
// Use read() or pread() to avoid iovec allocation and copying.
dst := dsts.Head()
if offset == -1 {
n, _, e = syscall.Syscall(unix.SYS_READ, uintptr(fd), dst.Addr(), uintptr(dst.Len()))
} else {
n, _, e = syscall.Syscall6(unix.SYS_PREAD64, uintptr(fd), dst.Addr(), uintptr(dst.Len()), uintptr(offset), 0 /* pos_h */, 0 /* unused */)
}
} else {
iovs := safemem.IovecsFromBlockSeq(dsts)
if offset == -1 {
n, _, e = syscall.Syscall(unix.SYS_READV, uintptr(fd), uintptr((unsafe.Pointer)(&iovs[0])), uintptr(len(iovs)))
} else {
n, _, e = syscall.Syscall6(unix.SYS_PREADV, uintptr(fd), uintptr((unsafe.Pointer)(&iovs[0])), uintptr(len(iovs)), uintptr(offset), 0 /* pos_h */, 0 /* unused */)
}
}
} else {
iovs := safemem.IovecsFromBlockSeq(dsts)
n, _, e = syscall.Syscall6(unix.SYS_PREADV2, uintptr(fd), uintptr((unsafe.Pointer)(&iovs[0])), uintptr(len(iovs)), uintptr(offset), 0 /* pos_h */, uintptr(flags))
}
if e != 0 {
return 0, e
}
if n == 0 {
return 0, io.EOF
}
return uint64(n), nil
}
// Pwritev2 writes up to srcs.NumBytes() from srcs into host file descriptor
// fd. offset and flags are interpreted as for pwritev2(2).
//
// Preconditions: !srcs.IsEmpty().
func Pwritev2(fd int32, srcs safemem.BlockSeq, offset int64, flags uint32) (uint64, error) {
// No buffering is necessary regardless of safecopy; host syscalls will
// return EFAULT if appropriate, instead of raising SIGBUS.
var (
n uintptr
e syscall.Errno
)
// Avoid pwritev2(2) if possible, since it's relatively new and thus least
// likely to be supported by the host kernel.
if flags == 0 {
if srcs.NumBlocks() == 1 {
// Use write() or pwrite() to avoid iovec allocation and copying.
src := srcs.Head()
if offset == -1 {
n, _, e = syscall.Syscall(unix.SYS_WRITE, uintptr(fd), src.Addr(), uintptr(src.Len()))
} else {
n, _, e = syscall.Syscall6(unix.SYS_PWRITE64, uintptr(fd), src.Addr(), uintptr(src.Len()), uintptr(offset), 0 /* pos_h */, 0 /* unused */)
}
} else {
iovs := safemem.IovecsFromBlockSeq(srcs)
if offset == -1 {
n, _, e = syscall.Syscall(unix.SYS_WRITEV, uintptr(fd), uintptr((unsafe.Pointer)(&iovs[0])), uintptr(len(iovs)))
} else {
n, _, e = syscall.Syscall6(unix.SYS_PWRITEV, uintptr(fd), uintptr((unsafe.Pointer)(&iovs[0])), uintptr(len(iovs)), uintptr(offset), 0 /* pos_h */, 0 /* unused */)
}
}
} else {
iovs := safemem.IovecsFromBlockSeq(srcs)
n, _, e = syscall.Syscall6(unix.SYS_PWRITEV2, uintptr(fd), uintptr((unsafe.Pointer)(&iovs[0])), uintptr(len(iovs)), uintptr(offset), 0 /* pos_h */, uintptr(flags))
}
if e != 0 {
return 0, e
}
return uint64(n), nil
}