Implement sysfs.

PiperOrigin-RevId: 290822487

3 files changed, 249 insertions, 0 deletions

diff --git a/pkg/sentry/fsimpl/sys/BUILD b/pkg/sentry/fsimpl/sys/BUILD
new file mode 100644
index 000000000..ee3c842bd
--- /dev/null
+++ b/pkg/sentry/fsimpl/sys/BUILD
@@ -0,0 +1,35 @@
+load("//tools/go_stateify:defs.bzl", "go_library")
+load("@io_bazel_rules_go//go:def.bzl", "go_test")
+
+package(licenses = ["notice"])
+
+go_library(
+    name = "sys",
+    srcs = [
+        "sys.go",
+    ],
+    importpath = "gvisor.dev/gvisor/pkg/sentry/fsimpl/sys",
+    deps = [
+        "//pkg/abi/linux",
+        "//pkg/sentry/context",
+        "//pkg/sentry/fsimpl/kernfs",
+        "//pkg/sentry/kernel",
+        "//pkg/sentry/kernel/auth",
+        "//pkg/sentry/vfs",
+        "//pkg/syserror",
+    ],
+)
+
+go_test(
+    name = "sys_test",
+    srcs = ["sys_test.go"],
+    deps = [
+        ":sys",
+        "//pkg/abi/linux",
+        "//pkg/sentry/fsimpl/testutil",
+        "//pkg/sentry/kernel",
+        "//pkg/sentry/kernel/auth",
+        "//pkg/sentry/vfs",
+        "@com_github_google_go-cmp//cmp:go_default_library",
+    ],
+)
diff --git a/pkg/sentry/fsimpl/sys/sys.go b/pkg/sentry/fsimpl/sys/sys.go
new file mode 100644
index 000000000..1305ad01d
--- /dev/null
+++ b/pkg/sentry/fsimpl/sys/sys.go
@@ -0,0 +1,124 @@
+// 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 sys implements sysfs.
+package sys
+
+import (
+	"bytes"
+	"fmt"
+
+	"gvisor.dev/gvisor/pkg/abi/linux"
+	"gvisor.dev/gvisor/pkg/sentry/context"
+	"gvisor.dev/gvisor/pkg/sentry/fsimpl/kernfs"
+	"gvisor.dev/gvisor/pkg/sentry/kernel"
+	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
+	"gvisor.dev/gvisor/pkg/sentry/vfs"
+	"gvisor.dev/gvisor/pkg/syserror"
+)
+
+// FilesystemType implements vfs.FilesystemType.
+type FilesystemType struct{}
+
+// filesystem implements vfs.FilesystemImpl.
+type filesystem struct {
+	kernfs.Filesystem
+}
+
+// GetFilesystem implements vfs.FilesystemType.GetFilesystem.
+func (FilesystemType) GetFilesystem(ctx context.Context, vfsObj *vfs.VirtualFilesystem, creds *auth.Credentials, source string, opts vfs.GetFilesystemOptions) (*vfs.Filesystem, *vfs.Dentry, error) {
+	fs := &filesystem{}
+	fs.Filesystem.Init(vfsObj)
+	k := kernel.KernelFromContext(ctx)
+	maxCPUCores := k.ApplicationCores()
+	defaultSysDirMode := linux.FileMode(0755)
+
+	root := fs.newDir(creds, defaultSysDirMode, map[string]*kernfs.Dentry{
+		"block": fs.newDir(creds, defaultSysDirMode, nil),
+		"bus":   fs.newDir(creds, defaultSysDirMode, nil),
+		"class": fs.newDir(creds, defaultSysDirMode, map[string]*kernfs.Dentry{
+			"power_supply": fs.newDir(creds, defaultSysDirMode, nil),
+		}),
+		"dev": fs.newDir(creds, defaultSysDirMode, nil),
+		"devices": fs.newDir(creds, defaultSysDirMode, map[string]*kernfs.Dentry{
+			"system": fs.newDir(creds, defaultSysDirMode, map[string]*kernfs.Dentry{
+				"cpu": fs.newDir(creds, defaultSysDirMode, map[string]*kernfs.Dentry{
+					"online":   fs.newCPUFile(creds, maxCPUCores, linux.FileMode(0444)),
+					"possible": fs.newCPUFile(creds, maxCPUCores, linux.FileMode(0444)),
+					"present":  fs.newCPUFile(creds, maxCPUCores, linux.FileMode(0444)),
+				}),
+			}),
+		}),
+		"firmware": fs.newDir(creds, defaultSysDirMode, nil),
+		"fs":       fs.newDir(creds, defaultSysDirMode, nil),
+		"kernel":   fs.newDir(creds, defaultSysDirMode, nil),
+		"module":   fs.newDir(creds, defaultSysDirMode, nil),
+		"power":    fs.newDir(creds, defaultSysDirMode, nil),
+	})
+	return fs.VFSFilesystem(), root.VFSDentry(), nil
+}
+
+// dir implements kernfs.Inode.
+type dir struct {
+	kernfs.InodeAttrs
+	kernfs.InodeNoDynamicLookup
+	kernfs.InodeNotSymlink
+	kernfs.InodeDirectoryNoNewChildren
+
+	kernfs.OrderedChildren
+	dentry kernfs.Dentry
+}
+
+func (fs *filesystem) newDir(creds *auth.Credentials, mode linux.FileMode, contents map[string]*kernfs.Dentry) *kernfs.Dentry {
+	d := &dir{}
+	d.InodeAttrs.Init(creds, fs.NextIno(), linux.ModeDirectory|0755)
+	d.OrderedChildren.Init(kernfs.OrderedChildrenOptions{})
+	d.dentry.Init(d)
+
+	d.IncLinks(d.OrderedChildren.Populate(&d.dentry, contents))
+
+	return &d.dentry
+}
+
+// SetStat implements kernfs.Inode.SetStat.
+func (d *dir) SetStat(fs *vfs.Filesystem, opts vfs.SetStatOptions) error {
+	return syserror.EPERM
+}
+
+// Open implements kernfs.Inode.Open.
+func (d *dir) Open(rp *vfs.ResolvingPath, vfsd *vfs.Dentry, flags uint32) (*vfs.FileDescription, error) {
+	fd := &kernfs.GenericDirectoryFD{}
+	fd.Init(rp.Mount(), vfsd, &d.OrderedChildren, flags)
+	return fd.VFSFileDescription(), nil
+}
+
+// cpuFile implements kernfs.Inode.
+type cpuFile struct {
+	kernfs.DynamicBytesFile
+	maxCores uint
+}
+
+// Generate implements vfs.DynamicBytesSource.Generate.
+func (c *cpuFile) Generate(ctx context.Context, buf *bytes.Buffer) error {
+	fmt.Fprintf(buf, "0-%d", c.maxCores-1)
+	return nil
+}
+
+func (fs *filesystem) newCPUFile(creds *auth.Credentials, maxCores uint, mode linux.FileMode) *kernfs.Dentry {
+	c := &cpuFile{maxCores: maxCores}
+	c.DynamicBytesFile.Init(creds, fs.NextIno(), c, mode)
+	d := &kernfs.Dentry{}
+	d.Init(c)
+	return d
+}
diff --git a/pkg/sentry/fsimpl/sys/sys_test.go b/pkg/sentry/fsimpl/sys/sys_test.go
new file mode 100644
index 000000000..60a1634a9
--- /dev/null
+++ b/pkg/sentry/fsimpl/sys/sys_test.go
@@ -0,0 +1,90 @@
+// 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 sys_test
+
+import (
+	"fmt"
+	"testing"
+
+	"github.com/google/go-cmp/cmp"
+	"gvisor.dev/gvisor/pkg/abi/linux"
+	"gvisor.dev/gvisor/pkg/sentry/fsimpl/sys"
+	"gvisor.dev/gvisor/pkg/sentry/fsimpl/testutil"
+	"gvisor.dev/gvisor/pkg/sentry/kernel"
+	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
+	"gvisor.dev/gvisor/pkg/sentry/vfs"
+)
+
+func newTestSystem(t *testing.T) *testutil.System {
+	k, err := testutil.Boot()
+	if err != nil {
+		t.Fatalf("Failed to create test kernel: %v", err)
+	}
+	ctx := k.SupervisorContext()
+	creds := auth.CredentialsFromContext(ctx)
+	v := vfs.New()
+	v.MustRegisterFilesystemType("sysfs", sys.FilesystemType{}, &vfs.RegisterFilesystemTypeOptions{
+		AllowUserMount: true,
+	})
+
+	mns, err := v.NewMountNamespace(ctx, creds, "", "sysfs", &vfs.GetFilesystemOptions{})
+	if err != nil {
+		t.Fatalf("Failed to create new mount namespace: %v", err)
+	}
+	return testutil.NewSystem(ctx, t, v, mns)
+}
+
+func TestReadCPUFile(t *testing.T) {
+	s := newTestSystem(t)
+	defer s.Destroy()
+	k := kernel.KernelFromContext(s.Ctx)
+	maxCPUCores := k.ApplicationCores()
+
+	expected := fmt.Sprintf("0-%d", maxCPUCores-1)
+
+	for _, fname := range []string{"online", "possible", "present"} {
+		pop := s.PathOpAtRoot(fmt.Sprintf("devices/system/cpu/%s", fname))
+		fd, err := s.VFS.OpenAt(s.Ctx, s.Creds, &pop, &vfs.OpenOptions{})
+		if err != nil {
+			t.Fatalf("OpenAt(pop:%+v) = %+v failed: %v", pop, fd, err)
+		}
+		defer fd.DecRef()
+		content, err := s.ReadToEnd(fd)
+		if err != nil {
+			t.Fatalf("Read failed: %v", err)
+		}
+		if diff := cmp.Diff(expected, content); diff != "" {
+			t.Fatalf("Read returned unexpected data:\n--- want\n+++ got\n%v", diff)
+		}
+	}
+}
+
+func TestSysRootContainsExpectedEntries(t *testing.T) {
+	s := newTestSystem(t)
+	defer s.Destroy()
+	pop := s.PathOpAtRoot("/")
+	s.AssertDirectoryContains(&pop, map[string]testutil.DirentType{
+		"block":    linux.DT_DIR,
+		"bus":      linux.DT_DIR,
+		"class":    linux.DT_DIR,
+		"dev":      linux.DT_DIR,
+		"devices":  linux.DT_DIR,
+		"firmware": linux.DT_DIR,
+		"fs":       linux.DT_DIR,
+		"kernel":   linux.DT_DIR,
+		"module":   linux.DT_DIR,
+		"power":    linux.DT_DIR,
+	})
+}