335 lines · cpp
1//===-- darwin-debug.cpp ----------------------------------------*- C++ -*-===//2//3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.4// See https://llvm.org/LICENSE.txt for license information.5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception6//7//===----------------------------------------------------------------------===//8 9// Darwin launch helper10//11// This program was written to allow programs to be launched in a new12// Terminal.app window and have the application be stopped for debugging13// at the program entry point.14//15// Although it uses posix_spawn(), it uses Darwin specific posix spawn16// attribute flags to accomplish its task. It uses an "exec only" flag17// which avoids forking this process, and it uses a "stop at entry"18// flag to stop the program at the entry point.19//20// Since it uses darwin specific flags this code should not be compiled21// on other systems.22#if defined(__APPLE__)23 24#include <climits>25#include <crt_externs.h>26#include <csignal>27#include <cstdio>28#include <cstdlib>29#include <cstring>30#include <getopt.h>31#include <mach/machine.h>32#include <spawn.h>33#include <sys/socket.h>34#include <sys/stat.h>35#include <sys/types.h>36#include <sys/un.h>37 38#include <string>39 40#ifndef _POSIX_SPAWN_DISABLE_ASLR41#define _POSIX_SPAWN_DISABLE_ASLR 0x010042#endif43 44#define streq(a, b) strcmp(a, b) == 045 46static struct option g_long_options[] = {47 {"arch", required_argument, NULL, 'a'},48 {"disable-aslr", no_argument, NULL, 'd'},49 {"no-env", no_argument, NULL, 'e'},50 {"help", no_argument, NULL, 'h'},51 {"setsid", no_argument, NULL, 's'},52 {"unix-socket", required_argument, NULL, 'u'},53 {"working-dir", required_argument, NULL, 'w'},54 {"env", required_argument, NULL, 'E'},55 {NULL, 0, NULL, 0}};56 57static void usage() {58 puts("NAME\n"59 " darwin-debug -- posix spawn a process that is stopped at the entry "60 "point\n"61 " for debugging.\n"62 "\n"63 "SYNOPSIS\n"64 " darwin-debug --unix-socket=<SOCKET> [--arch=<ARCH>] "65 "[--working-dir=<PATH>] [--disable-aslr] [--no-env] [--setsid] [--help] "66 "-- <PROGRAM> [<PROGRAM-ARG> <PROGRAM-ARG> ....]\n"67 "\n"68 "DESCRIPTION\n"69 " darwin-debug will exec itself into a child process <PROGRAM> that "70 "is\n"71 " halted for debugging. It does this by using posix_spawn() along "72 "with\n"73 " darwin specific posix_spawn flags that allows exec only (no fork), "74 "and\n"75 " stop at the program entry point. Any program arguments "76 "<PROGRAM-ARG> are\n"77 " passed on to the exec as the arguments for the new process. The "78 "current\n"79 " environment will be passed to the new process unless the "80 "\"--no-env\"\n"81 " option is used. A unix socket must be supplied using the\n"82 " --unix-socket=<SOCKET> option so the calling program can handshake "83 "with\n"84 " this process and get its process id.\n"85 "\n"86 "EXAMPLE\n"87 " darwin-debug --arch=i386 -- /bin/ls -al /tmp\n");88 exit(1);89}90 91static void exit_with_errno(int err, const char *prefix) {92 if (err) {93 fprintf(stderr, "%s%s", prefix ? prefix : "", strerror(err));94 exit(err);95 }96}97 98pid_t posix_spawn_for_debug(char *const *argv, char *const *envp,99 const char *working_dir, cpu_type_t cpu_type,100 int disable_aslr) {101 pid_t pid = 0;102 103 const char *path = argv[0];104 105 posix_spawnattr_t attr;106 107 exit_with_errno(::posix_spawnattr_init(&attr),108 "::posix_spawnattr_init (&attr) error: ");109 110 // Here we are using a darwin specific feature that allows us to exec only111 // since we want this program to turn into the program we want to debug,112 // and also have the new program start suspended (right at __dyld_start)113 // so we can debug it114 short flags = POSIX_SPAWN_START_SUSPENDED | POSIX_SPAWN_SETEXEC |115 POSIX_SPAWN_SETSIGDEF | POSIX_SPAWN_SETSIGMASK;116 117 // Disable ASLR if we were asked to118 if (disable_aslr)119 flags |= _POSIX_SPAWN_DISABLE_ASLR;120 121 sigset_t no_signals;122 sigset_t all_signals;123 sigemptyset(&no_signals);124 sigfillset(&all_signals);125 ::posix_spawnattr_setsigmask(&attr, &no_signals);126 ::posix_spawnattr_setsigdefault(&attr, &all_signals);127 128 // Set the flags we just made into our posix spawn attributes129 exit_with_errno(::posix_spawnattr_setflags(&attr, flags),130 "::posix_spawnattr_setflags (&attr, flags) error: ");131 132 // Another darwin specific thing here where we can select the architecture133 // of the binary we want to re-exec as.134 if (cpu_type != 0) {135 size_t ocount = 0;136 exit_with_errno(137 ::posix_spawnattr_setbinpref_np(&attr, 1, &cpu_type, &ocount),138 "posix_spawnattr_setbinpref_np () error: ");139 }140 141 // I wish there was a posix_spawn flag to change the working directory of142 // the inferior process we will spawn, but there currently isn't. If there143 // ever is a better way to do this, we should use it. I would rather not144 // manually fork, chdir in the child process, and then posix_spawn with exec145 // as the whole reason for doing posix_spawn is to not hose anything up146 // after the fork and prior to the exec...147 if (working_dir)148 ::chdir(working_dir);149 150 exit_with_errno(::posix_spawnp(&pid, path, NULL, &attr, (char *const *)argv,151 (char *const *)envp),152 "posix_spawn() error: ");153 154 // This code will only be reached if the posix_spawn exec failed...155 ::posix_spawnattr_destroy(&attr);156 157 return pid;158}159 160int main(int argc, char *const *argv, char *const *envp, const char **apple) {161#if defined(DEBUG_LLDB_LAUNCHER)162 const char *program_name = strrchr(apple[0], '/');163 164 if (program_name)165 program_name++; // Skip the last slash..166 else167 program_name = apple[0];168 169 printf("%s called with:\n", program_name);170 for (int i = 0; i < argc; ++i)171 printf("argv[%u] = '%s'\n", i, argv[i]);172#endif173 174 cpu_type_t cpu_type = 0;175 bool show_usage = false;176 int ch;177 int disable_aslr = 0; // By default we disable ASLR178 bool pass_env = true;179 std::string unix_socket_name;180 std::string working_dir;181 182#if __GLIBC__183 optind = 0;184#else185 optreset = 1;186 optind = 1;187#endif188 189 while ((ch = getopt_long_only(argc, argv, "a:deE:hsu:?", g_long_options,190 NULL)) != -1) {191 switch (ch) {192 case 0:193 break;194 195 case 'a': // "-a i386" or "--arch=i386"196 if (optarg) {197 if (streq(optarg, "i386"))198 cpu_type = CPU_TYPE_I386;199 else if (streq(optarg, "x86_64"))200 cpu_type = CPU_TYPE_X86_64;201 else if (streq(optarg, "x86_64h"))202 cpu_type = 0; // Don't set CPU type when we have x86_64h203 else if (strstr(optarg, "arm") == optarg)204 cpu_type = CPU_TYPE_ARM;205 else {206 ::fprintf(stderr, "error: unsupported cpu type '%s'\n", optarg);207 ::exit(1);208 }209 }210 break;211 212 case 'd':213 disable_aslr = 1;214 break;215 216 case 'e':217 pass_env = false;218 break;219 220 case 'E': {221 // Since we will exec this program into our new program, we can just set222 // environment223 // variables in this process and they will make it into the child process.224 std::string name;225 std::string value;226 const char *equal_pos = strchr(optarg, '=');227 if (equal_pos) {228 name.assign(optarg, equal_pos - optarg);229 value.assign(equal_pos + 1);230 } else {231 name = optarg;232 }233 ::setenv(name.c_str(), value.c_str(), 1);234 } break;235 236 case 's':237 // Create a new session to avoid having control-C presses kill our current238 // terminal session when this program is launched from a .command file239 ::setsid();240 break;241 242 case 'u':243 unix_socket_name.assign(optarg);244 break;245 246 case 'w': {247 struct stat working_dir_stat;248 if (stat(optarg, &working_dir_stat) == 0)249 working_dir.assign(optarg);250 else251 ::fprintf(stderr, "warning: working directory doesn't exist: '%s'\n",252 optarg);253 } break;254 255 case 'h':256 case '?':257 default:258 show_usage = true;259 break;260 }261 }262 argc -= optind;263 argv += optind;264 265 if (show_usage || argc <= 0 || unix_socket_name.empty())266 usage();267 268#if defined(DEBUG_LLDB_LAUNCHER)269 printf("\n%s post options:\n", program_name);270 for (int i = 0; i < argc; ++i)271 printf("argv[%u] = '%s'\n", i, argv[i]);272#endif273 274 // Open the socket that was passed in as an option275 struct sockaddr_un saddr_un;276 int s = ::socket(AF_UNIX, SOCK_STREAM, 0);277 if (s < 0) {278 perror("error: socket (AF_UNIX, SOCK_STREAM, 0)");279 exit(1);280 }281 282 saddr_un.sun_family = AF_UNIX;283 ::strncpy(saddr_un.sun_path, unix_socket_name.c_str(),284 sizeof(saddr_un.sun_path) - 1);285 saddr_un.sun_path[sizeof(saddr_un.sun_path) - 1] = '\0';286 saddr_un.sun_len = SUN_LEN(&saddr_un);287 288 if (::connect(s, (struct sockaddr *)&saddr_un, SUN_LEN(&saddr_un)) < 0) {289 perror("error: connect (socket, &saddr_un, saddr_un_len)");290 exit(1);291 }292 293 // We were able to connect to the socket, now write our PID so whomever294 // launched us will know this process's ID295 char pid_str[64];296 const int pid_str_len =297 ::snprintf(pid_str, sizeof(pid_str), "%i", ::getpid());298 const int bytes_sent = ::send(s, pid_str, pid_str_len, 0);299 300 if (pid_str_len != bytes_sent) {301 perror("error: send (s, pid_str, pid_str_len, 0)");302 exit(1);303 }304 305 // We are done with the socket306 close(s);307 308 system("clear");309 printf("Launching: '%s'\n", argv[0]);310 if (working_dir.empty()) {311 char cwd[PATH_MAX];312 const char *cwd_ptr = getcwd(cwd, sizeof(cwd));313 printf("Working directory: '%s'\n", cwd_ptr);314 } else {315 printf("Working directory: '%s'\n", working_dir.c_str());316 }317 printf("%i arguments:\n", argc);318 319 for (int i = 0; i < argc; ++i)320 printf("argv[%u] = '%s'\n", i, argv[i]);321 322 // Now we posix spawn to exec this process into the inferior that we want323 // to debug.324 posix_spawn_for_debug(325 argv,326 pass_env ? *_NSGetEnviron() : NULL, // Pass current environment as we may327 // have modified it if "--env" options328 // was used, do NOT pass "envp" here329 working_dir.empty() ? NULL : working_dir.c_str(), cpu_type, disable_aslr);330 331 return 0;332}333 334#endif // #if defined (__APPLE__)335