Clean up pipe internals and add fcntl support

Pipe internals are made more efficient by avoiding garbage collection.
A pool is now used that can be shared by all pipes, and buffers are
chained via an intrusive list. The documentation for pipe structures
and methods is also simplified and clarified.

The pipe tests are now parameterized, so that they are run on all
different variants (named pipes, small buffers, default buffers).

The pipe buffer sizes are exposed by fcntl, which is now supported
by this change. A size change test has been added to the suite.

These new tests uncovered a bug regarding the semantics of open
named pipes with O_NONBLOCK, which is also fixed by this CL. This
fix also addresses the lack of the O_LARGEFILE flag for named pipes.

PiperOrigin-RevId: 249375888
Change-Id: I48e61e9c868aedb0cadda2dff33f09a560dee773

1 files changed, 32 insertions, 0 deletions

diff --git a/pkg/sentry/kernel/pipe/buffer_test.go b/pkg/sentry/kernel/pipe/buffer_test.go
new file mode 100644
index 000000000..4b7dbc43f
--- /dev/null
+++ b/pkg/sentry/kernel/pipe/buffer_test.go
@@ -0,0 +1,32 @@
+// 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 pipe
+
+import (
+	"testing"
+	"unsafe"
+
+	"gvisor.googlesource.com/gvisor/pkg/sentry/usermem"
+)
+
+func TestBufferSize(t *testing.T) {
+	bufferSize := unsafe.Sizeof(buffer{})
+	if bufferSize < usermem.PageSize {
+		t.Errorf("buffer is less than a page")
+	}
+	if bufferSize > (2 * usermem.PageSize) {
+		t.Errorf("buffer is greater than two pages")
+	}
+}