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platform_system_core/libprocessgroup/processgroup.cpp
Elliott Hughes dc80312628 libbase: add host properties support. 
Move init and libprocessgroup away from their existing hacks.

Bug: N/A
Test: ran tests
Change-Id: Ifabdd38e0cc4ab2582f1ea59d32159d386f48eb6
2018-05-24 18:04:31 -07:00

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/*
* Copyright 2014 Google, Inc
*
* 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.
*/
//#define LOG_NDEBUG 0
#define LOG_TAG "libprocessgroup"
#include <assert.h>
#include <dirent.h>
#include <errno.h>
#include <fcntl.h>
#include <inttypes.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>
#include <chrono>
#include <memory>
#include <mutex>
#include <set>
#include <string>
#include <thread>
#include <android-base/file.h>
#include <android-base/logging.h>
#include <android-base/properties.h>
#include <android-base/stringprintf.h>
#include <android-base/strings.h>
#include <private/android_filesystem_config.h>
#include <processgroup/processgroup.h>
using android::base::GetBoolProperty;
using android::base::StartsWith;
using android::base::StringPrintf;
using android::base::WriteStringToFile;
using namespace std::chrono_literals;
#define MEM_CGROUP_PATH "/dev/memcg/apps"
#define MEM_CGROUP_TASKS "/dev/memcg/apps/tasks"
#define ACCT_CGROUP_PATH "/acct"
#define PROCESSGROUP_CGROUP_PROCS_FILE "/cgroup.procs"
std::once_flag init_path_flag;
static const std::string& GetCgroupRootPath() {
static std::string cgroup_root_path;
std::call_once(init_path_flag, [&]() {
// low-ram devices use per-app memcg by default, unlike high-end ones
bool low_ram_device = GetBoolProperty("ro.config.low_ram", false);
bool per_app_memcg =
GetBoolProperty("ro.config.per_app_memcg", low_ram_device);
if (per_app_memcg) {
// Check if mem cgroup is mounted, only then check for
// write-access to avoid SELinux denials
cgroup_root_path =
(access(MEM_CGROUP_TASKS, F_OK) || access(MEM_CGROUP_PATH, W_OK) ?
ACCT_CGROUP_PATH : MEM_CGROUP_PATH);
} else {
cgroup_root_path = ACCT_CGROUP_PATH;
}
});
return cgroup_root_path;
}
static std::string ConvertUidToPath(uid_t uid) {
return StringPrintf("%s/uid_%d", GetCgroupRootPath().c_str(), uid);
}
static std::string ConvertUidPidToPath(uid_t uid, int pid) {
return StringPrintf("%s/uid_%d/pid_%d", GetCgroupRootPath().c_str(), uid, pid);
}
static int RemoveProcessGroup(uid_t uid, int pid) {
int ret;
auto uid_pid_path = ConvertUidPidToPath(uid, pid);
ret = rmdir(uid_pid_path.c_str());
auto uid_path = ConvertUidToPath(uid);
rmdir(uid_path.c_str());
return ret;
}
static void RemoveUidProcessGroups(const std::string& uid_path) {
std::unique_ptr<DIR, decltype(&closedir)> uid(opendir(uid_path.c_str()), closedir);
if (uid != NULL) {
dirent* dir;
while ((dir = readdir(uid.get())) != nullptr) {
if (dir->d_type != DT_DIR) {
continue;
}
if (!StartsWith(dir->d_name, "pid_")) {
continue;
}
auto path = StringPrintf("%s/%s", uid_path.c_str(), dir->d_name);
LOG(VERBOSE) << "Removing " << path;
if (rmdir(path.c_str()) == -1) PLOG(WARNING) << "Failed to remove " << path;
}
}
}
void removeAllProcessGroups()
{
LOG(VERBOSE) << "removeAllProcessGroups()";
const auto& cgroup_root_path = GetCgroupRootPath();
std::unique_ptr<DIR, decltype(&closedir)> root(opendir(cgroup_root_path.c_str()), closedir);
if (root == NULL) {
PLOG(ERROR) << "Failed to open " << cgroup_root_path;
} else {
dirent* dir;
while ((dir = readdir(root.get())) != nullptr) {
if (dir->d_type != DT_DIR) {
continue;
}
if (!StartsWith(dir->d_name, "uid_")) {
continue;
}
auto path = StringPrintf("%s/%s", cgroup_root_path.c_str(), dir->d_name);
RemoveUidProcessGroups(path);
LOG(VERBOSE) << "Removing " << path;
if (rmdir(path.c_str()) == -1) PLOG(WARNING) << "Failed to remove " << path;
}
}
}
// Returns number of processes killed on success
// Returns 0 if there are no processes in the process cgroup left to kill
// Returns -1 on error
static int DoKillProcessGroupOnce(uid_t uid, int initialPid, int signal) {
auto path = ConvertUidPidToPath(uid, initialPid) + PROCESSGROUP_CGROUP_PROCS_FILE;
std::unique_ptr<FILE, decltype(&fclose)> fd(fopen(path.c_str(), "re"), fclose);
if (!fd) {
PLOG(WARNING) << "Failed to open process cgroup uid " << uid << " pid " << initialPid;
return -1;
}
// We separate all of the pids in the cgroup into those pids that are also the leaders of
// process groups (stored in the pgids set) and those that are not (stored in the pids set).
std::set<pid_t> pgids;
pgids.emplace(initialPid);
std::set<pid_t> pids;
pid_t pid;
int processes = 0;
while (fscanf(fd.get(), "%d\n", &pid) == 1 && pid >= 0) {
processes++;
if (pid == 0) {
// Should never happen... but if it does, trying to kill this
// will boomerang right back and kill us! Let's not let that happen.
LOG(WARNING) << "Yikes, we've been told to kill pid 0! How about we don't do that?";
continue;
}
pid_t pgid = getpgid(pid);
if (pgid == -1) PLOG(ERROR) << "getpgid(" << pid << ") failed";
if (pgid == pid) {
pgids.emplace(pid);
} else {
pids.emplace(pid);
}
}
// Erase all pids that will be killed when we kill the process groups.
for (auto it = pids.begin(); it != pids.end();) {
pid_t pgid = getpgid(pid);
if (pgids.count(pgid) == 1) {
it = pids.erase(it);
} else {
++it;
}
}
// Kill all process groups.
for (const auto pgid : pgids) {
LOG(VERBOSE) << "Killing process group " << -pgid << " in uid " << uid
<< " as part of process cgroup " << initialPid;
if (kill(-pgid, signal) == -1) {
PLOG(WARNING) << "kill(" << -pgid << ", " << signal << ") failed";
}
}
// Kill remaining pids.
for (const auto pid : pids) {
LOG(VERBOSE) << "Killing pid " << pid << " in uid " << uid << " as part of process cgroup "
<< initialPid;
if (kill(pid, signal) == -1) {
PLOG(WARNING) << "kill(" << pid << ", " << signal << ") failed";
}
}
return feof(fd.get()) ? processes : -1;
}
static int KillProcessGroup(uid_t uid, int initialPid, int signal, int retries) {
std::chrono::steady_clock::time_point start = std::chrono::steady_clock::now();
int retry = retries;
int processes;
while ((processes = DoKillProcessGroupOnce(uid, initialPid, signal)) > 0) {
LOG(VERBOSE) << "Killed " << processes << " processes for processgroup " << initialPid;
if (retry > 0) {
std::this_thread::sleep_for(5ms);
--retry;
} else {
break;
}
}
if (processes < 0) {
PLOG(ERROR) << "Error encountered killing process cgroup uid " << uid << " pid "
<< initialPid;
return -1;
}
std::chrono::steady_clock::time_point end = std::chrono::steady_clock::now();
auto ms = std::chrono::duration_cast<std::chrono::milliseconds>(end - start).count();
// We only calculate the number of 'processes' when killing the processes.
// In the retries == 0 case, we only kill the processes once and therefore
// will not have waited then recalculated how many processes are remaining
// after the first signals have been sent.
// Logging anything regarding the number of 'processes' here does not make sense.
if (processes == 0) {
if (retries > 0) {
LOG(INFO) << "Successfully killed process cgroup uid " << uid << " pid " << initialPid
<< " in " << static_cast<int>(ms) << "ms";
}
return RemoveProcessGroup(uid, initialPid);
} else {
if (retries > 0) {
LOG(ERROR) << "Failed to kill process cgroup uid " << uid << " pid " << initialPid
<< " in " << static_cast<int>(ms) << "ms, " << processes
<< " processes remain";
}
return -1;
}
}
int killProcessGroup(uid_t uid, int initialPid, int signal) {
return KillProcessGroup(uid, initialPid, signal, 40 /*retries*/);
}
int killProcessGroupOnce(uid_t uid, int initialPid, int signal) {
return KillProcessGroup(uid, initialPid, signal, 0 /*retries*/);
}
static bool MkdirAndChown(const std::string& path, mode_t mode, uid_t uid, gid_t gid) {
if (mkdir(path.c_str(), mode) == -1 && errno != EEXIST) {
return false;
}
if (chown(path.c_str(), uid, gid) == -1) {
int saved_errno = errno;
rmdir(path.c_str());
errno = saved_errno;
return false;
}
return true;
}
int createProcessGroup(uid_t uid, int initialPid)
{
auto uid_path = ConvertUidToPath(uid);
if (!MkdirAndChown(uid_path, 0750, AID_SYSTEM, AID_SYSTEM)) {
PLOG(ERROR) << "Failed to make and chown " << uid_path;
return -errno;
}
auto uid_pid_path = ConvertUidPidToPath(uid, initialPid);
if (!MkdirAndChown(uid_pid_path, 0750, AID_SYSTEM, AID_SYSTEM)) {
PLOG(ERROR) << "Failed to make and chown " << uid_pid_path;
return -errno;
}
auto uid_pid_procs_file = uid_pid_path + PROCESSGROUP_CGROUP_PROCS_FILE;
int ret = 0;
if (!WriteStringToFile(std::to_string(initialPid), uid_pid_procs_file)) {
ret = -errno;
PLOG(ERROR) << "Failed to write '" << initialPid << "' to " << uid_pid_procs_file;
}
return ret;
}
static bool SetProcessGroupValue(uid_t uid, int pid, const std::string& file_name, int64_t value) {
if (GetCgroupRootPath() != MEM_CGROUP_PATH) {
PLOG(ERROR) << "Memcg is not mounted.";
return false;
}
auto path = ConvertUidPidToPath(uid, pid) + file_name;
if (!WriteStringToFile(std::to_string(value), path)) {
PLOG(ERROR) << "Failed to write '" << value << "' to " << path;
return false;
}
return true;
}
bool setProcessGroupSwappiness(uid_t uid, int pid, int swappiness) {
return SetProcessGroupValue(uid, pid, "/memory.swappiness", swappiness);
}
bool setProcessGroupSoftLimit(uid_t uid, int pid, int64_t soft_limit_in_bytes) {
return SetProcessGroupValue(uid, pid, "/memory.soft_limit_in_bytes", soft_limit_in_bytes);
}
bool setProcessGroupLimit(uid_t uid, int pid, int64_t limit_in_bytes) {
return SetProcessGroupValue(uid, pid, "/memory.limit_in_bytes", limit_in_bytes);
}
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