From 9e3ace52bba69b3fb9b6700e02c9380bd06b0351 Mon Sep 17 00:00:00 2001
From: Suren Baghdasaryan <surenb@google.com>
Date: Wed, 16 Jun 2021 17:01:19 -0700
Subject: [PATCH] libprocessgroup: Add CgroupGetControllerFromPath API function

Add new CgroupGetControllerFromPath function to retrieve the name of the
cgroup using a file path. If the file does not belong to any cgroup, the
function returns false.

Bug: 191283136
Test: build and boot
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Change-Id: Ic17a474cb25a80a3339b33ed8bc27b07af053abb
---
 libprocessgroup/cgroup_map.cpp                | 20 +++++++++++++++++++
 libprocessgroup/cgroup_map.h                  |  1 +
 .../include/processgroup/processgroup.h       |  1 +
 libprocessgroup/processgroup.cpp              | 14 +++++++++++++
 4 files changed, 36 insertions(+)

diff --git a/libprocessgroup/cgroup_map.cpp b/libprocessgroup/cgroup_map.cpp
index 0734f2565..352847a1c 100644
--- a/libprocessgroup/cgroup_map.cpp
+++ b/libprocessgroup/cgroup_map.cpp
@@ -34,6 +34,7 @@
 #include <android-base/logging.h>
 #include <android-base/properties.h>
 #include <android-base/stringprintf.h>
+#include <android-base/strings.h>
 #include <android-base/unique_fd.h>
 #include <cgroup_map.h>
 #include <json/reader.h>
@@ -41,6 +42,7 @@
 #include <processgroup/processgroup.h>
 
 using android::base::GetBoolProperty;
+using android::base::StartsWith;
 using android::base::StringPrintf;
 using android::base::unique_fd;
 using android::base::WriteStringToFile;
@@ -204,6 +206,24 @@ CgroupController CgroupMap::FindController(const std::string& name) const {
     return CgroupController(nullptr);
 }
 
+CgroupController CgroupMap::FindControllerByPath(const std::string& path) const {
+    if (!loaded_) {
+        LOG(ERROR) << "CgroupMap::FindControllerByPath called for [" << getpid()
+                   << "] failed, RC file was not initialized properly";
+        return CgroupController(nullptr);
+    }
+
+    auto controller_count = ACgroupFile_getControllerCount();
+    for (uint32_t i = 0; i < controller_count; ++i) {
+        const ACgroupController* controller = ACgroupFile_getController(i);
+        if (StartsWith(path, ACgroupController_getPath(controller))) {
+            return CgroupController(controller);
+        }
+    }
+
+    return CgroupController(nullptr);
+}
+
 int CgroupMap::ActivateControllers(const std::string& path) const {
     if (__builtin_available(android 30, *)) {
         auto controller_count = ACgroupFile_getControllerCount();
diff --git a/libprocessgroup/cgroup_map.h b/libprocessgroup/cgroup_map.h
index 22d717b32..5cdf8b28c 100644
--- a/libprocessgroup/cgroup_map.h
+++ b/libprocessgroup/cgroup_map.h
@@ -62,6 +62,7 @@ class CgroupMap {
 
     static CgroupMap& GetInstance();
     CgroupController FindController(const std::string& name) const;
+    CgroupController FindControllerByPath(const std::string& path) const;
     int ActivateControllers(const std::string& path) const;
 
   private:
diff --git a/libprocessgroup/include/processgroup/processgroup.h b/libprocessgroup/include/processgroup/processgroup.h
index fa2642d86..be34f9513 100644
--- a/libprocessgroup/include/processgroup/processgroup.h
+++ b/libprocessgroup/include/processgroup/processgroup.h
@@ -26,6 +26,7 @@ __BEGIN_DECLS
 static constexpr const char* CGROUPV2_CONTROLLER_NAME = "cgroup2";
 
 bool CgroupGetControllerPath(const std::string& cgroup_name, std::string* path);
+bool CgroupGetControllerFromPath(const std::string& path, std::string* cgroup_name);
 bool CgroupGetAttributePath(const std::string& attr_name, std::string* path);
 bool CgroupGetAttributePathForTask(const std::string& attr_name, int tid, std::string* path);
 
diff --git a/libprocessgroup/processgroup.cpp b/libprocessgroup/processgroup.cpp
index faf945cfc..0320b0263 100644
--- a/libprocessgroup/processgroup.cpp
+++ b/libprocessgroup/processgroup.cpp
@@ -69,6 +69,20 @@ bool CgroupGetControllerPath(const std::string& cgroup_name, std::string* path)
     return true;
 }
 
+bool CgroupGetControllerFromPath(const std::string& path, std::string* cgroup_name) {
+    auto controller = CgroupMap::GetInstance().FindControllerByPath(path);
+
+    if (!controller.HasValue()) {
+        return false;
+    }
+
+    if (cgroup_name) {
+        *cgroup_name = controller.name();
+    }
+
+    return true;
+}
+
 bool CgroupGetAttributePath(const std::string& attr_name, std::string* path) {
     const TaskProfiles& tp = TaskProfiles::GetInstance();
     const ProfileAttribute* attr = tp.GetAttribute(attr_name);