1 /*
2  * Copyright (C) 2016 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 <procinfo/process.h>
18 
19 #include <fcntl.h>
20 #include <stdio.h>
21 #include <stdlib.h>
22 #include <string.h>
23 #include <unistd.h>
24 
25 #include <string>
26 
27 #include <android-base/unique_fd.h>
28 
29 using android::base::unique_fd;
30 
31 namespace android {
32 namespace procinfo {
33 
34 bool GetProcessInfo(pid_t tid, ProcessInfo* process_info, std::string* error) {
35   char path[PATH_MAX];
36   snprintf(path, sizeof(path), "/proc/%d", tid);
37 
38   unique_fd dirfd(open(path, O_DIRECTORY | O_RDONLY));
39   if (dirfd == -1) {
40     if (error != nullptr) {
41       *error = std::string("failed to open ") + path;
42     }
43     return false;
44   }
45 
46   return GetProcessInfoFromProcPidFd(dirfd.get(), process_info, error);
47 }
48 
49 static ProcessState parse_state(char state) {
50   switch (state) {
51     case 'R':
52       return kProcessStateRunning;
53     case 'S':
54       return kProcessStateSleeping;
55     case 'D':
56       return kProcessStateUninterruptibleWait;
57     case 'T':
58       return kProcessStateStopped;
59     case 'Z':
60       return kProcessStateZombie;
61     default:
62       return kProcessStateUnknown;
63   }
64 }
65 
66 bool GetProcessInfoFromProcPidFd(int fd, ProcessInfo* process_info,
67                                  std::string* error /* can be nullptr */) {
68   int status_fd = openat(fd, "status", O_RDONLY | O_CLOEXEC);
69 
70   auto set_error = [&error](const char* err) {
71     if (error != nullptr) {
72       *error = err;
73     }
74   };
75 
76   if (status_fd == -1) {
77     set_error("failed to open status fd in GetProcessInfoFromProcPidFd");
78     return false;
79   }
80 
81   std::unique_ptr<FILE, decltype(&fclose)> fp(fdopen(status_fd, "r"), fclose);
82   if (!fp) {
83     set_error("failed to open status file in GetProcessInfoFromProcPidFd");
84     close(status_fd);
85     return false;
86   }
87 
88   int field_bitmap = 0;
89   static constexpr int finished_bitmap = 63;
90   char* line = nullptr;
91   size_t len = 0;
92 
93   while (getline(&line, &len, fp.get()) != -1 && field_bitmap != finished_bitmap) {
94     char* tab = strchr(line, '\t');
95     if (tab == nullptr) {
96       continue;
97     }
98 
99     size_t header_len = tab - line;
100     std::string header = std::string(line, header_len);
101     if (header == "Name:") {
102       std::string name = line + header_len + 1;
103 
104       // line includes the trailing newline.
105       name.pop_back();
106       process_info->name = std::move(name);
107 
108       field_bitmap |= 1;
109     }  else if (header == "Tgid:") {
110       process_info->pid = atoi(tab + 1);
111       field_bitmap |= 2;
112     } else if (header == "Pid:") {
113       process_info->tid = atoi(tab + 1);
114       field_bitmap |= 4;
115     } else if (header == "TracerPid:") {
116       process_info->tracer = atoi(tab + 1);
117       field_bitmap |= 8;
118     } else if (header == "Uid:") {
119       process_info->uid = atoi(tab + 1);
120       field_bitmap |= 16;
121     } else if (header == "Gid:") {
122       process_info->gid = atoi(tab + 1);
123       field_bitmap |= 32;
124     }
125   }
126 
127   free(line);
128   if (field_bitmap != finished_bitmap) {
129     set_error("failed to parse /proc/<pid>/status");
130     return false;
131   }
132 
133   unique_fd stat_fd(openat(fd, "stat", O_RDONLY | O_CLOEXEC));
134   if (stat_fd == -1) {
135     set_error("failed to open /proc/<pid>/stat");
136   }
137 
138   std::string stat;
139   if (!android::base::ReadFdToString(stat_fd, &stat)) {
140     set_error("failed to read /proc/<pid>/stat");
141     return false;
142   }
143 
144   // See man 5 proc. There's no reason comm can't contain ' ' or ')',
145   // so we search backwards for the end of it.
146   const char* end_of_comm = strrchr(stat.c_str(), ')');
147 
148   static constexpr const char* pattern =
149       "%c "    // state
150       "%d "    // ppid
151       "%*d "   // pgrp
152       "%*d "   // session
153       "%*d "   // tty_nr
154       "%*d "   // tpgid
155       "%*u "   // flags
156       "%*lu "  // minflt
157       "%*lu "  // cminflt
158       "%*lu "  // majflt
159       "%*lu "  // cmajflt
160       "%*lu "  // utime
161       "%*lu "  // stime
162       "%*ld "  // cutime
163       "%*ld "  // cstime
164       "%*ld "  // priority
165       "%*ld "  // nice
166       "%*ld "  // num_threads
167       "%*ld "  // itrealvalue
168       "%llu "  // starttime
169       ;
170 
171   char state = '\0';
172   int ppid = 0;
173   unsigned long long start_time = 0;
174   int rc = sscanf(end_of_comm + 2, pattern, &state, &ppid, &start_time);
175   if (rc != 3) {
176     set_error("failed to parse /proc/<pid>/stat");
177     return false;
178   }
179 
180   process_info->state = parse_state(state);
181   process_info->ppid = ppid;
182   process_info->starttime = start_time;
183   return true;
184 }
185 
186 } /* namespace procinfo */
187 } /* namespace android */
188