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authorkevin.xu <cming.xu@gmail.com>2020-04-27 21:51:31 +0800
committerGitHub <noreply@github.com>2020-04-27 21:51:31 +0800
commite896ca54db67524afc20b644d43c72185e72dc0e (patch)
tree2a16f3a62a5cafd098f1f028c621f1b655589d69 /pkg/sentry/hostfd
parent1f19624fa127d7d59cabe29593cc80b7fe6c81f8 (diff)
parent3c67754663f424f2ebbc0ff2a4c80e30618d5355 (diff)
Merge pull request #1 from google/master
catch up
Diffstat (limited to 'pkg/sentry/hostfd')
-rw-r--r--pkg/sentry/hostfd/BUILD17
-rw-r--r--pkg/sentry/hostfd/hostfd.go84
-rw-r--r--pkg/sentry/hostfd/hostfd_unsafe.go107
3 files changed, 208 insertions, 0 deletions
diff --git a/pkg/sentry/hostfd/BUILD b/pkg/sentry/hostfd/BUILD
new file mode 100644
index 000000000..364a78306
--- /dev/null
+++ b/pkg/sentry/hostfd/BUILD
@@ -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",
+ ],
+)
diff --git a/pkg/sentry/hostfd/hostfd.go b/pkg/sentry/hostfd/hostfd.go
new file mode 100644
index 000000000..70dd9cafb
--- /dev/null
+++ b/pkg/sentry/hostfd/hostfd.go
@@ -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
+}
diff --git a/pkg/sentry/hostfd/hostfd_unsafe.go b/pkg/sentry/hostfd/hostfd_unsafe.go
new file mode 100644
index 000000000..5e9e60fc4
--- /dev/null
+++ b/pkg/sentry/hostfd/hostfd_unsafe.go
@@ -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
+}