From 0a32c0235744191947a6bf890031026e06788837 Mon Sep 17 00:00:00 2001
From: Zach Koopmans <zkoopmans@google.com>
Date: Thu, 5 Dec 2019 13:22:31 -0800
Subject: Create correct file for /proc/[pid]/task/[tid]/io

PiperOrigin-RevId: 284038840
---
 pkg/sentry/fs/proc/task.go  | 32 +++++++++++++++++---------------
 test/syscalls/linux/proc.cc | 40 ++++++++++++++++++++++++++++++++++++++++
 2 files changed, 57 insertions(+), 15 deletions(-)

diff --git a/pkg/sentry/fs/proc/task.go b/pkg/sentry/fs/proc/task.go
index 2a598149d..0e46c5fb7 100644
--- a/pkg/sentry/fs/proc/task.go
+++ b/pkg/sentry/fs/proc/task.go
@@ -67,29 +67,28 @@ type taskDir struct {
 var _ fs.InodeOperations = (*taskDir)(nil)
 
 // newTaskDir creates a new proc task entry.
-func (p *proc) newTaskDir(t *kernel.Task, msrc *fs.MountSource, showSubtasks bool) *fs.Inode {
+func (p *proc) newTaskDir(t *kernel.Task, msrc *fs.MountSource, isThreadGroup bool) *fs.Inode {
 	contents := map[string]*fs.Inode{
-		"auxv":    newAuxvec(t, msrc),
-		"cmdline": newExecArgInode(t, msrc, cmdlineExecArg),
-		"comm":    newComm(t, msrc),
-		"environ": newExecArgInode(t, msrc, environExecArg),
-		"exe":     newExe(t, msrc),
-		"fd":      newFdDir(t, msrc),
-		"fdinfo":  newFdInfoDir(t, msrc),
-		"gid_map": newGIDMap(t, msrc),
-		// FIXME(b/123511468): create the correct io file for threads.
-		"io":        newIO(t, msrc),
+		"auxv":      newAuxvec(t, msrc),
+		"cmdline":   newExecArgInode(t, msrc, cmdlineExecArg),
+		"comm":      newComm(t, msrc),
+		"environ":   newExecArgInode(t, msrc, environExecArg),
+		"exe":       newExe(t, msrc),
+		"fd":        newFdDir(t, msrc),
+		"fdinfo":    newFdInfoDir(t, msrc),
+		"gid_map":   newGIDMap(t, msrc),
+		"io":        newIO(t, msrc, isThreadGroup),
 		"maps":      newMaps(t, msrc),
 		"mountinfo": seqfile.NewSeqFileInode(t, &mountInfoFile{t: t}, msrc),
 		"mounts":    seqfile.NewSeqFileInode(t, &mountsFile{t: t}, msrc),
 		"ns":        newNamespaceDir(t, msrc),
 		"smaps":     newSmaps(t, msrc),
-		"stat":      newTaskStat(t, msrc, showSubtasks, p.pidns),
+		"stat":      newTaskStat(t, msrc, isThreadGroup, p.pidns),
 		"statm":     newStatm(t, msrc),
 		"status":    newStatus(t, msrc, p.pidns),
 		"uid_map":   newUIDMap(t, msrc),
 	}
-	if showSubtasks {
+	if isThreadGroup {
 		contents["task"] = p.newSubtasks(t, msrc)
 	}
 	if len(p.cgroupControllers) > 0 {
@@ -619,8 +618,11 @@ type ioData struct {
 	ioUsage
 }
 
-func newIO(t *kernel.Task, msrc *fs.MountSource) *fs.Inode {
-	return newProcInode(t, seqfile.NewSeqFile(t, &ioData{t.ThreadGroup()}), msrc, fs.SpecialFile, t)
+func newIO(t *kernel.Task, msrc *fs.MountSource, isThreadGroup bool) *fs.Inode {
+	if isThreadGroup {
+		return newProcInode(t, seqfile.NewSeqFile(t, &ioData{t.ThreadGroup()}), msrc, fs.SpecialFile, t)
+	}
+	return newProcInode(t, seqfile.NewSeqFile(t, &ioData{t}), msrc, fs.SpecialFile, t)
 }
 
 // NeedsUpdate returns whether the generation is old or not.
diff --git a/test/syscalls/linux/proc.cc b/test/syscalls/linux/proc.cc
index 512de5ee0..8cf08991b 100644
--- a/test/syscalls/linux/proc.cc
+++ b/test/syscalls/linux/proc.cc
@@ -37,6 +37,7 @@
 #include <map>
 #include <memory>
 #include <ostream>
+#include <regex>
 #include <string>
 #include <unordered_set>
 #include <utility>
@@ -51,6 +52,7 @@
 #include "absl/strings/str_split.h"
 #include "absl/strings/string_view.h"
 #include "absl/synchronization/mutex.h"
+#include "absl/synchronization/notification.h"
 #include "absl/time/clock.h"
 #include "absl/time/time.h"
 #include "test/util/capability_util.h"
@@ -1988,6 +1990,44 @@ TEST(Proc, GetdentsEnoent) {
               SyscallFailsWithErrno(ENOENT));
 }
 
+void CheckSyscwFromIOFile(const std::string& path, const std::string& regex) {
+  std::string output;
+  ASSERT_NO_ERRNO(GetContents(path, &output));
+  ASSERT_THAT(output, ContainsRegex(absl::StrCat("syscw:\\s+", regex, "\n")));
+}
+
+// Checks that there is variable accounting of IO between threads/tasks.
+TEST(Proc, PidTidIOAccounting) {
+  absl::Notification notification;
+
+  // Run a thread with a bunch of writes. Check that io account records exactly
+  // the number of write calls. File open/close is there to prevent buffering.
+  ScopedThread writer([&notification] {
+    const int num_writes = 100;
+    for (int i = 0; i < num_writes; i++) {
+      auto path = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateFile());
+      ASSERT_NO_ERRNO(SetContents(path.path(), "a"));
+    }
+    notification.Notify();
+    const std::string& writer_dir =
+        absl::StrCat("/proc/", getpid(), "/task/", gettid(), "/io");
+
+    CheckSyscwFromIOFile(writer_dir, std::to_string(num_writes));
+  });
+
+  // Run a thread and do no writes. Check that no writes are recorded.
+  ScopedThread noop([&notification] {
+    notification.WaitForNotification();
+    const std::string& noop_dir =
+        absl::StrCat("/proc/", getpid(), "/task/", gettid(), "/io");
+
+    CheckSyscwFromIOFile(noop_dir, "0");
+  });
+
+  writer.Join();
+  noop.Join();
+}
+
 }  // namespace
 }  // namespace testing
 }  // namespace gvisor
-- 
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