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/**
* Copyright (C) 2018-present MongoDB, Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the Server Side Public License, version 1,
* as published by MongoDB, Inc.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* Server Side Public License for more details.
*
* You should have received a copy of the Server Side Public License
* along with this program. If not, see
* <http://www.mongodb.com/licensing/server-side-public-license>.
*
* As a special exception, the copyright holders give permission to link the
* code of portions of this program with the OpenSSL library under certain
* conditions as described in each individual source file and distribute
* linked combinations including the program with the OpenSSL library. You
* must comply with the Server Side Public License in all respects for
* all of the code used other than as permitted herein. If you modify file(s)
* with this exception, you may extend this exception to your version of the
* file(s), but you are not obligated to do so. If you do not wish to do so,
* delete this exception statement from your version. If you delete this
* exception statement from all source files in the program, then also delete
* it in the license file.
*/
#include "mongo/platform/basic.h"
#include "mongo/util/debugger.h"
#include <cstdlib>
#include <mutex>
#ifndef _WIN32
#include <csignal>
#include <cstdio>
#include <unistd.h>
#endif
#include "mongo/util/debug_util.h"
#ifndef _WIN32
namespace {
std::once_flag breakpointOnceFlag;
} // namespace
#endif
namespace mongo {
void breakpoint() {
#ifdef _WIN32
if (IsDebuggerPresent()) {
DebugBreak();
};
#endif
#ifndef _WIN32
// code to raise a breakpoint in GDB
std::call_once(breakpointOnceFlag, []() {
// prevent SIGTRAP from crashing the program if default action is specified and we are not
// in gdb
struct sigaction current;
if (sigaction(SIGTRAP, nullptr, ¤t) != 0) {
std::abort();
}
if (current.sa_handler == SIG_DFL) {
signal(SIGTRAP, SIG_IGN);
}
});
raise(SIGTRAP);
#endif
}
/* Magic debugging trampoline
* Do not call directly! call setupSIGTRAPforDebugger()
* Assumptions:
* 1) the debugging server binary is on your path
* 2) You have run "handle SIGSTOP noprint" in gdb
* 3) serverGlobalParams.port + 2000 is free
*/
namespace {
#ifndef _WIN32
template <typename Exec>
void launchDebugger(Exec debugger) {
// Don't come back here
signal(SIGTRAP, SIG_IGN);
char pidToDebug[16];
int pidRet = snprintf(pidToDebug, sizeof(pidToDebug), "%d", getpid());
if (!(pidRet >= 0 && size_t(pidRet) < sizeof(pidToDebug)))
std::abort();
char msg[128];
int msgRet = snprintf(msg,
sizeof(msg),
"\n\n\t**** Launching debugging server (ensure binary is in PATH, use "
"lsof to find port) ****\n\n");
if (!(msgRet >= 0 && size_t(msgRet) < sizeof(msg)))
std::abort();
if (!(write(STDERR_FILENO, msg, msgRet) == msgRet))
std::abort();
if (fork() == 0) {
// child
debugger(pidToDebug);
perror(nullptr);
_exit(1);
} else {
// parent
raise(SIGSTOP); // pause all threads until debugger connects and continues
raise(SIGTRAP); // break inside server
}
}
#if defined(USE_GDBSERVER)
extern "C" void execCallback(int) {
launchDebugger([](char* pidToDebug) {
execlp("gdbserver", "gdbserver", "--attach", ":0", pidToDebug, nullptr);
});
}
#elif defined(USE_LLDB_SERVER)
extern "C" void execCallback(int) {
launchDebugger([](char* pidToDebug) {
#ifdef __linux__
execlp("lldb-server", "lldb-server", "g", "--attach", pidToDebug, "*:12345", nullptr);
#else
execlp("debugserver", "debugserver", "*:12345", "--attach", pidToDebug, nullptr);
#endif
});
}
#endif
} // namespace
void setupSIGTRAPforDebugger() {
#if defined(USE_GDBSERVER) || defined(USE_LLDB_SERVER)
if (signal(SIGTRAP, execCallback) == SIG_ERR) {
std::abort();
}
#endif
#endif
}
} // namespace mongo
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