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platform_system_core
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debuggerd: fork the signal sender once. 

Bug: http://b/27427439
Change-Id: I6294ff68a150bc9950a300264c31d2141307ac66
(cherry picked from commit f5e8f0b9cd)
This commit is contained in:
Josh Gao 2016-03-16 18:09:15 -07:00
parent 1a69e2811e
commit e5dbdd09c7
4 changed files with 197 additions and 91 deletions
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1
debuggerd/Android.mk
View File

@ -15,6 +15,7 @@ LOCAL_SRC_FILES:= \
debuggerd.cpp \
elf_utils.cpp \
getevent.cpp \
signal_sender.cpp \
tombstone.cpp \
utility.cpp \

105
debuggerd/debuggerd.cpp
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@ -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 @@ static bool perform_dump(const debugger_request_t& request, int fd, int tombston
// 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 @@ static bool drop_privileges() {
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 @@ static void handle_request(int fd) {
// 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 @@ static void handle_request(int fd) {
}
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 @@ static void handle_request(int fd) {
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 @@ static void handle_request(int fd) {
// 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 @@ static void handle_request(int fd) {
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 @@ static int do_server() {
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 (;;) {

152
debuggerd/signal_sender.cpp Normal file
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@ -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;
}

30
debuggerd/signal_sender.h Normal file
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@ -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