debuggerd: fork the signal sender once.
Bug: http://b/27427439
Change-Id: I6294ff68a150bc9950a300264c31d2141307ac66
(cherry picked from commit f5e8f0b9cd9ec0214a6f9cd38dd6d9af3268f9aa)
diff --git a/debuggerd/Android.mk b/debuggerd/Android.mk
index 9e4f1f7..6469db4 100644
--- a/debuggerd/Android.mk
+++ b/debuggerd/Android.mk
@@ -15,6 +15,7 @@
debuggerd.cpp \
elf_utils.cpp \
getevent.cpp \
+ signal_sender.cpp \
tombstone.cpp \
utility.cpp \
diff --git a/debuggerd/debuggerd.cpp b/debuggerd/debuggerd.cpp
index eabbb9a..b6c2f8a 100644
--- a/debuggerd/debuggerd.cpp
+++ b/debuggerd/debuggerd.cpp
@@ -15,21 +15,20 @@
*/
#include <dirent.h>
+#include <elf.h>
#include <errno.h>
#include <fcntl.h>
#include <pthread.h>
#include <signal.h>
#include <stdarg.h>
#include <stdio.h>
-#include <sys/types.h>
-#include <time.h>
-
-#include <elf.h>
#include <sys/poll.h>
#include <sys/prctl.h>
#include <sys/ptrace.h>
#include <sys/stat.h>
+#include <sys/types.h>
#include <sys/wait.h>
+#include <time.h>
#include <set>
@@ -48,6 +47,7 @@
#include "backtrace.h"
#include "getevent.h"
+#include "signal_sender.h"
#include "tombstone.h"
#include "utility.h"
@@ -422,7 +422,7 @@
// this we get a lot of "ptrace detach failed:
// No such process".
*crash_signal = signal;
- kill(request.pid, SIGSTOP);
+ send_signal(request.pid, 0, SIGSTOP);
engrave_tombstone(tombstone_fd, backtrace_map, request.pid, request.tid, siblings, signal,
request.original_si_code, request.abort_msg_address);
break;
@@ -451,60 +451,6 @@
return true;
}
-// Fork a process that listens for signals to send, or 0, to exit.
-static bool fork_signal_sender(int* out_fd, pid_t* sender_pid, pid_t target_pid) {
- int sfd[2];
- if (socketpair(AF_UNIX, SOCK_SEQPACKET, 0, sfd) != 0) {
- ALOGE("debuggerd: failed to create socketpair for signal sender: %s", strerror(errno));
- return false;
- }
-
- pid_t fork_pid = fork();
- if (fork_pid == -1) {
- ALOGE("debuggerd: failed to initialize signal sender: fork failed: %s", strerror(errno));
- return false;
- } else if (fork_pid == 0) {
- close(sfd[1]);
-
- while (true) {
- int signal;
- int rc = TEMP_FAILURE_RETRY(read(sfd[0], &signal, sizeof(signal)));
- if (rc < 0) {
- ALOGE("debuggerd: signal sender failed to read from socket");
- kill(target_pid, SIGKILL);
- exit(1);
- } else if (rc != sizeof(signal)) {
- ALOGE("debuggerd: signal sender read unexpected number of bytes: %d", rc);
- kill(target_pid, SIGKILL);
- exit(1);
- }
-
- // Report success after sending a signal, or before exiting.
- int err = 0;
- if (signal != 0) {
- if (kill(target_pid, signal) != 0) {
- err = errno;
- }
- }
-
- if (TEMP_FAILURE_RETRY(write(sfd[0], &err, sizeof(err))) < 0) {
- ALOGE("debuggerd: signal sender failed to write: %s", strerror(errno));
- kill(target_pid, SIGKILL);
- exit(1);
- }
-
- if (signal == 0) {
- exit(0);
- }
- }
- } else {
- close(sfd[0]);
- *out_fd = sfd[1];
- *sender_pid = fork_pid;
- return true;
- }
-}
-
static void handle_request(int fd) {
ALOGV("handle_request(%d)\n", fd);
@@ -585,15 +531,6 @@
// Don't attach to the sibling threads if we want to attach gdb.
// Supposedly, it makes the process less reliable.
bool attach_gdb = should_attach_gdb(&request);
- int signal_fd = -1;
- pid_t signal_pid = 0;
-
- // Fork a process that stays root, and listens on a pipe to pause and resume the target.
- if (!fork_signal_sender(&signal_fd, &signal_pid, request.pid)) {
- ALOGE("debuggerd: failed to fork signal sender");
- exit(1);
- }
-
if (attach_gdb) {
// Open all of the input devices we need to listen for VOLUMEDOWN before dropping privileges.
if (init_getevent() != 0) {
@@ -603,21 +540,6 @@
}
- auto send_signal = [=](int signal) {
- int error;
- if (TEMP_FAILURE_RETRY(write(signal_fd, &signal, sizeof(signal))) < 0) {
- ALOGE("debuggerd: failed to notify signal process: %s", strerror(errno));
- return false;
- } else if (TEMP_FAILURE_RETRY(read(signal_fd, &error, sizeof(error))) < 0) {
- ALOGE("debuggerd: failed to read response from signal process: %s", strerror(errno));
- return false;
- } else if (error != 0) {
- errno = error;
- return false;
- }
- return true;
- };
-
std::set<pid_t> siblings;
if (!attach_gdb) {
ptrace_siblings(request.pid, request.tid, siblings);
@@ -646,7 +568,7 @@
if (attach_gdb) {
// Tell the signal process to send SIGSTOP to the target.
- if (!send_signal(SIGSTOP)) {
+ if (!send_signal(request.pid, 0, SIGSTOP)) {
ALOGE("debuggerd: failed to stop process for gdb attach: %s", strerror(errno));
attach_gdb = false;
}
@@ -662,7 +584,7 @@
// Send the signal back to the process if it crashed and we're not waiting for gdb.
if (!attach_gdb && request.action == DEBUGGER_ACTION_CRASH) {
- if (!send_signal(crash_signal)) {
+ if (!send_signal(request.pid, request.tid, crash_signal)) {
ALOGE("debuggerd: failed to kill process %d: %s", request.pid, strerror(errno));
}
}
@@ -672,18 +594,13 @@
wait_for_user_action(request);
// Tell the signal process to send SIGCONT to the target.
- if (!send_signal(SIGCONT)) {
+ if (!send_signal(request.pid, 0, SIGCONT)) {
ALOGE("debuggerd: failed to resume process %d: %s", request.pid, strerror(errno));
}
uninit_getevent();
}
- if (!send_signal(0)) {
- ALOGE("debuggerd: failed to notify signal sender to finish");
- kill(signal_pid, SIGKILL);
- }
- waitpid(signal_pid, nullptr, 0);
exit(!succeeded);
}
@@ -714,6 +631,12 @@
SOCK_STREAM | SOCK_CLOEXEC);
if (s == -1) return 1;
+ // Fork a process that stays root, and listens on a pipe to pause and resume the target.
+ if (!start_signal_sender()) {
+ ALOGE("debuggerd: failed to fork signal sender");
+ return 1;
+ }
+
ALOGI("debuggerd: starting\n");
for (;;) {
diff --git a/debuggerd/signal_sender.cpp b/debuggerd/signal_sender.cpp
new file mode 100644
index 0000000..35e0c0b
--- /dev/null
+++ b/debuggerd/signal_sender.cpp
@@ -0,0 +1,152 @@
+/*
+ * Copyright (C) 2016 The Android Open Source Project
+ *
+ * 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.
+ */
+
+#include <errno.h>
+#include <signal.h>
+#include <string.h>
+#include <sys/socket.h>
+#include <sys/syscall.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <unistd.h>
+
+#include <log/logger.h>
+
+#include "signal_sender.h"
+
+static int signal_fd = -1;
+static pid_t signal_pid;
+struct signal_message {
+ pid_t pid;
+ pid_t tid;
+ int signal;
+};
+
+// Fork a process to send signals for the worker processes to use after they've dropped privileges.
+bool start_signal_sender() {
+ if (signal_pid == 0) {
+ ALOGE("debuggerd: attempted to start signal sender multiple times");
+ return false;
+ }
+
+ int sfd[2];
+ if (socketpair(AF_UNIX, SOCK_SEQPACKET | SOCK_CLOEXEC, 0, sfd) != 0) {
+ ALOGE("debuggerd: failed to create socketpair for signal sender: %s", strerror(errno));
+ return false;
+ }
+
+ pid_t parent = getpid();
+ pid_t fork_pid = fork();
+ if (fork_pid == -1) {
+ ALOGE("debuggerd: failed to initialize signal sender: fork failed: %s", strerror(errno));
+ return false;
+ } else if (fork_pid == 0) {
+ close(sfd[1]);
+
+ while (true) {
+ signal_message msg;
+ int rc = TEMP_FAILURE_RETRY(read(sfd[0], &msg, sizeof(msg)));
+ if (rc < 0) {
+ ALOGE("debuggerd: signal sender failed to read from socket");
+ break;
+ } else if (rc != sizeof(msg)) {
+ ALOGE("debuggerd: signal sender read unexpected number of bytes: %d", rc);
+ break;
+ }
+
+ // Report success after sending a signal
+ int err = 0;
+ if (msg.tid > 0) {
+ if (syscall(SYS_tgkill, msg.pid, msg.tid, msg.signal) != 0) {
+ err = errno;
+ }
+ } else {
+ if (kill(msg.pid, msg.signal) != 0) {
+ err = errno;
+ }
+ }
+
+ if (TEMP_FAILURE_RETRY(write(sfd[0], &err, sizeof(err))) < 0) {
+ ALOGE("debuggerd: signal sender failed to write: %s", strerror(errno));
+ }
+ }
+
+ // Our parent proably died, but if not, kill them.
+ if (getppid() == parent) {
+ kill(parent, SIGKILL);
+ }
+ _exit(1);
+ } else {
+ close(sfd[0]);
+ signal_fd = sfd[1];
+ signal_pid = fork_pid;
+ return true;
+ }
+}
+
+bool stop_signal_sender() {
+ if (signal_pid <= 0) {
+ return false;
+ }
+
+ if (kill(signal_pid, SIGKILL) != 0) {
+ ALOGE("debuggerd: failed to kill signal sender: %s", strerror(errno));
+ return false;
+ }
+
+ close(signal_fd);
+ signal_fd = -1;
+
+ int status;
+ waitpid(signal_pid, &status, 0);
+ signal_pid = 0;
+
+ return true;
+}
+
+bool send_signal(pid_t pid, pid_t tid, int signal) {
+ if (signal_fd == -1) {
+ ALOGE("debuggerd: attempted to send signal before signal sender was started");
+ errno = EHOSTUNREACH;
+ return false;
+ }
+
+ signal_message msg = {.pid = pid, .tid = tid, .signal = signal };
+ if (TEMP_FAILURE_RETRY(write(signal_fd, &msg, sizeof(msg))) < 0) {
+ ALOGE("debuggerd: failed to send message to signal sender: %s", strerror(errno));
+ errno = EHOSTUNREACH;
+ return false;
+ }
+
+ int response;
+ ssize_t rc = TEMP_FAILURE_RETRY(read(signal_fd, &response, sizeof(response)));
+ if (rc == 0) {
+ ALOGE("debuggerd: received EOF from signal sender");
+ errno = EHOSTUNREACH;
+ return false;
+ } else if (rc < 0) {
+ ALOGE("debuggerd: failed to receive response from signal sender: %s", strerror(errno));
+ errno = EHOSTUNREACH;
+ return false;
+ }
+
+ if (response == 0) {
+ return true;
+ }
+
+ errno = response;
+ return false;
+}
diff --git a/debuggerd/signal_sender.h b/debuggerd/signal_sender.h
new file mode 100644
index 0000000..0443272
--- /dev/null
+++ b/debuggerd/signal_sender.h
@@ -0,0 +1,30 @@
+/*
+ * Copyright (C) 2016 The Android Open Source Project
+ *
+ * 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.
+ */
+
+#ifndef _DEBUGGERD_SIGNAL_SENDER_H
+#define _DEBUGGERD_SIGNAL_SENDER_H
+
+#include <sys/types.h>
+
+bool start_signal_sender();
+bool stop_signal_sender();
+
+// Sends a signal to a target process or thread.
+// If tid is greater than zero, this performs tgkill(pid, tid, signal).
+// Otherwise, it performs kill(pid, signal).
+bool send_signal(pid_t pid, pid_t tid, int signal);
+
+#endif