1 /*
2 * Copyright (C) 2018 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 <sys/capability.h>
18 #include <sys/reboot.h>
19 #include <sys/syscall.h>
20 #include <unistd.h>
21
22 #include <optional>
23 #include <string>
24
25 #include <android-base/file.h>
26 #include <android-base/logging.h>
27 #include <android-base/properties.h>
28 #include <android-base/strings.h>
29 #include <cutils/android_reboot.h>
30 #include <fs_mgr.h>
31 #include <unwindstack/AndroidUnwinder.h>
32
33 #include "capabilities.h"
34 #include "reboot_utils.h"
35 #include "util.h"
36
37 namespace android {
38 namespace init {
39
40 static std::string init_fatal_reboot_target = "bootloader";
41 static bool init_fatal_panic = false;
42
43 // this needs to read the /proc/* files directly because it is called before
44 // ro.boot.* properties are initialized
SetFatalRebootTarget(const std::optional<std::string> & reboot_target)45 void SetFatalRebootTarget(const std::optional<std::string>& reboot_target) {
46 std::string cmdline;
47 android::base::ReadFileToString("/proc/cmdline", &cmdline);
48 cmdline = android::base::Trim(cmdline);
49
50 const std::string kInitFatalPanicParamString = "androidboot.init_fatal_panic";
51 if (cmdline.find(kInitFatalPanicParamString) == std::string::npos) {
52 std::string value;
53 init_fatal_panic = (android::fs_mgr::GetBootconfig(kInitFatalPanicParamString, &value) &&
54 value == "true");
55 } else {
56 const std::string kInitFatalPanicString = kInitFatalPanicParamString + "=true";
57 init_fatal_panic = cmdline.find(kInitFatalPanicString) != std::string::npos;
58 }
59
60 if (reboot_target) {
61 init_fatal_reboot_target = *reboot_target;
62 return;
63 }
64
65 const std::string kRebootTargetString = "androidboot.init_fatal_reboot_target";
66 auto start_pos = cmdline.find(kRebootTargetString);
67 if (start_pos == std::string::npos) {
68 android::fs_mgr::GetBootconfig(kRebootTargetString, &init_fatal_reboot_target);
69 // We already default to bootloader if no setting is provided.
70 } else {
71 const std::string kRebootTargetStringPattern = kRebootTargetString + "=";
72 start_pos += sizeof(kRebootTargetStringPattern) - 1;
73
74 auto end_pos = cmdline.find(' ', start_pos);
75 // if end_pos isn't found, then we've run off the end, but this is okay as this is the last
76 // entry, and -1 is a valid size for string::substr();
77 auto size = end_pos == std::string::npos ? -1 : end_pos - start_pos;
78 init_fatal_reboot_target = cmdline.substr(start_pos, size);
79 }
80 }
81
IsRebootCapable()82 bool IsRebootCapable() {
83 if (!CAP_IS_SUPPORTED(CAP_SYS_BOOT)) {
84 PLOG(WARNING) << "CAP_SYS_BOOT is not supported";
85 return true;
86 }
87
88 ScopedCaps caps(cap_get_proc());
89 if (!caps) {
90 PLOG(WARNING) << "cap_get_proc() failed";
91 return true;
92 }
93
94 cap_flag_value_t value = CAP_SET;
95 if (cap_get_flag(caps.get(), CAP_SYS_BOOT, CAP_EFFECTIVE, &value) != 0) {
96 PLOG(WARNING) << "cap_get_flag(CAP_SYS_BOOT, EFFECTIVE) failed";
97 return true;
98 }
99 return value == CAP_SET;
100 }
101
102 void __attribute__((noreturn))
RebootSystem(unsigned int cmd,const std::string & rebootTarget,const std::string & reboot_reason)103 RebootSystem(unsigned int cmd, const std::string& rebootTarget, const std::string& reboot_reason) {
104 LOG(INFO) << "Reboot ending, jumping to kernel";
105
106 if (!IsRebootCapable()) {
107 // On systems where init does not have the capability of rebooting the
108 // device, just exit cleanly.
109 exit(0);
110 }
111
112 switch (cmd) {
113 case ANDROID_RB_POWEROFF:
114 reboot(RB_POWER_OFF);
115 break;
116
117 case ANDROID_RB_RESTART2:
118 syscall(__NR_reboot, LINUX_REBOOT_MAGIC1, LINUX_REBOOT_MAGIC2,
119 LINUX_REBOOT_CMD_RESTART2, rebootTarget.c_str());
120 break;
121
122 case ANDROID_RB_THERMOFF:
123 if (android::base::GetBoolProperty("ro.thermal_warmreset", false)) {
124 std::string reason = "shutdown,thermal";
125 if (!reboot_reason.empty()) reason = reboot_reason;
126
127 LOG(INFO) << "Try to trigger a warm reset for thermal shutdown";
128 syscall(__NR_reboot, LINUX_REBOOT_MAGIC1, LINUX_REBOOT_MAGIC2,
129 LINUX_REBOOT_CMD_RESTART2, reason.c_str());
130 } else {
131 reboot(RB_POWER_OFF);
132 }
133 break;
134 }
135 // In normal case, reboot should not return.
136 PLOG(ERROR) << "reboot call returned";
137 abort();
138 }
139
InitFatalReboot(int signal_number)140 void __attribute__((noreturn)) InitFatalReboot(int signal_number) {
141 auto pid = fork();
142
143 if (pid == -1) {
144 // Couldn't fork, don't even try to backtrace, just reboot.
145 RebootSystem(ANDROID_RB_RESTART2, init_fatal_reboot_target);
146 } else if (pid == 0) {
147 // Fork a child for safety, since we always want to shut down if something goes wrong, but
148 // its worth trying to get the backtrace, even in the signal handler, since typically it
149 // does work despite not being async-signal-safe.
150 sleep(5);
151 RebootSystem(ANDROID_RB_RESTART2, init_fatal_reboot_target);
152 }
153
154 // In the parent, let's try to get a backtrace then shutdown.
155 LOG(ERROR) << __FUNCTION__ << ": signal " << signal_number;
156 unwindstack::AndroidLocalUnwinder unwinder;
157 unwindstack::AndroidUnwinderData data;
158 if (!unwinder.Unwind(data)) {
159 LOG(ERROR) << __FUNCTION__ << ": Failed to unwind callstack: " << data.GetErrorString();
160 }
161 for (const auto& frame : data.frames) {
162 LOG(ERROR) << unwinder.FormatFrame(frame);
163 }
164 if (init_fatal_panic) {
165 LOG(ERROR) << __FUNCTION__ << ": Trigger crash";
166 android::base::WriteStringToFile("c", PROC_SYSRQ);
167 LOG(ERROR) << __FUNCTION__ << ": Sys-Rq failed to crash the system; fallback to exit().";
168 _exit(signal_number);
169 }
170 RebootSystem(ANDROID_RB_RESTART2, init_fatal_reboot_target);
171 }
172
InstallRebootSignalHandlers()173 void InstallRebootSignalHandlers() {
174 // Instead of panic'ing the kernel as is the default behavior when init crashes,
175 // we prefer to reboot to bootloader on development builds, as this will prevent
176 // boot looping bad configurations and allow both developers and test farms to easily
177 // recover.
178 struct sigaction action;
179 memset(&action, 0, sizeof(action));
180 sigfillset(&action.sa_mask);
181 action.sa_handler = [](int signal) {
182 // These signal handlers are also caught for processes forked from init, however we do not
183 // want them to trigger reboot, so we directly call _exit() for children processes here.
184 if (getpid() != 1) {
185 _exit(signal);
186 }
187
188 // Calling DoReboot() or LOG(FATAL) is not a good option as this is a signal handler.
189 // RebootSystem uses syscall() which isn't actually async-signal-safe, but our only option
190 // and probably good enough given this is already an error case and only enabled for
191 // development builds.
192 InitFatalReboot(signal);
193 };
194 action.sa_flags = SA_RESTART;
195 sigaction(SIGABRT, &action, nullptr);
196 sigaction(SIGBUS, &action, nullptr);
197 sigaction(SIGFPE, &action, nullptr);
198 sigaction(SIGILL, &action, nullptr);
199 sigaction(SIGSEGV, &action, nullptr);
200 #if defined(SIGSTKFLT)
201 sigaction(SIGSTKFLT, &action, nullptr);
202 #endif
203 sigaction(SIGSYS, &action, nullptr);
204 sigaction(SIGTRAP, &action, nullptr);
205 }
206
207 } // namespace init
208 } // namespace android
209