1 /*
2 * Copyright (C) 2023 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17 #include "process_names.h"
18
19 #include "android-base/file.h"
20
ReadCmdline(uint64_t pid)21 const std::string ProcessNames::ReadCmdline(uint64_t pid) {
22 const std::string path = std::string("/proc/") + std::to_string(pid) + "/cmdline";
23
24 std::string cmdline;
25 if (!android::base::ReadFileToString(path, &cmdline)) {
26 return "";
27 }
28
29 // We need to remove anything that would be part of an absolute path for the executable
30 // but also the parameters. e.g.:
31 // Input : /path/to/myProgram -D --ooo
32 // Output: myProgram
33 return android::base::Basename(cmdline.c_str());
34 }
35
ReadComm(uint64_t pid)36 const std::string ProcessNames::ReadComm(uint64_t pid) {
37 const std::string path = std::string("/proc/") + std::to_string(pid) + "/comm";
38 std::string cmdline;
39 bool success = android::base::ReadFileToString(path, &cmdline);
40 if (!success) {
41 return "";
42 }
43 return cmdline;
44 }
45
Resolve(uint64_t pid)46 const std::string ProcessNames::Resolve(uint64_t pid) {
47 std::string name = ReadCmdline(pid);
48 if (!name.empty()) {
49 return name;
50 }
51
52 // Kernel threads do not have anything in /proc/PID/cmdline. e.g.:
53 // migration/0
54 // cpuhp/0
55 // kworker/7:1-events
56 //
57 // To still have a somewhat relevant name, we check /proc/PID/comm, even though
58 // the max length is 16 characters.
59 name = ReadComm(pid);
60 if (!name.empty()) {
61 return name;
62 }
63
64 return "";
65 }
66
Get(uint64_t pid)67 std::string ProcessNames::Get(uint64_t pid) {
68 // Cache hit!
69 const std::string& cached = cache.get(pid);
70 if (!cached.empty()) {
71 return cached;
72 }
73
74 // Cache miss!
75 std::string name = Resolve(pid);
76 // When an app starts, after it forks from zygote process, the process name remains
77 // zygote/zygote64, then <pre-initialized>, then the package/process name is set.
78 // We don't cache until we know the final value.
79 if (name != "<pre-initialized>" && !name.starts_with("zygote")) {
80 cache.put(pid, name);
81 }
82 return name;
83 }
84