procfs: Migrate seqfile implementations.

Migrates all (except 3) seqfile implementations to the vfs.DynamicBytesSource
interface. There should not be any change in functionality due to this migration
itself.

Please note that the following seqfile implementations have not been migrated:
- /proc/filesystems in proc/filesystems.go
- /proc/[pid]/mountinfo in proc/mounts.go
- /proc/[pid]/mounts in proc/mounts.go
This is because these depend on pending changes in /pkg/senty/vfs.

PiperOrigin-RevId: 263880719

1 files changed, 40 insertions, 0 deletions

diff --git a/pkg/sentry/fsimpl/proc/loadavg.go b/pkg/sentry/fsimpl/proc/loadavg.go
new file mode 100644
index 000000000..9135afef1
--- /dev/null
+++ b/pkg/sentry/fsimpl/proc/loadavg.go
@@ -0,0 +1,40 @@
+// 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 proc
+
+import (
+	"bytes"
+	"fmt"
+
+	"gvisor.dev/gvisor/pkg/sentry/context"
+	"gvisor.dev/gvisor/pkg/sentry/vfs"
+)
+
+// loadavgData backs /proc/loadavg.
+//
+// +stateify savable
+type loadavgData struct{}
+
+var _ vfs.DynamicBytesSource = (*loadavgData)(nil)
+
+// Generate implements vfs.DynamicBytesSource.Generate.
+func (d *loadavgData) Generate(ctx context.Context, buf *bytes.Buffer) error {
+	// TODO(b/62345059): Include real data in fields.
+	// Column 1-3: CPU and IO utilization of the last 1, 5, and 10 minute periods.
+	// Column 4-5: currently running processes and the total number of processes.
+	// Column 6: the last process ID used.
+	fmt.Fprintf(buf, "%.2f %.2f %.2f %d/%d %d\n", 0.00, 0.00, 0.00, 0, 0, 0)
+	return nil
+}