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-exception
6//
7//===----------------------------------------------------------------------===//
8
9// Darwin launch helper
10//
11// This program was written to allow programs to be launched in a new
12// Terminal.app window and have the application be stopped for debugging
13// at the program entry point.
14//
15// Although it uses posix_spawn(), it uses Darwin specific posix spawn
16// attribute flags to accomplish its task. It uses an "exec only" flag
17// 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 compiled
21// 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_ASLR
41#define _POSIX_SPAWN_DISABLE_ASLR 0x0100
42#endif
43
44#define streq(a, b) strcmp(a, b) == 0
45
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 only
111 // 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 it
114 short flags = POSIX_SPAWN_START_SUSPENDED | POSIX_SPAWN_SETEXEC |
115 POSIX_SPAWN_SETSIGDEF | POSIX_SPAWN_SETSIGMASK;
116
117 // Disable ASLR if we were asked to
118 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 attributes
129 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 architecture
133 // 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 of
142 // the inferior process we will spawn, but there currently isn't. If there
143 // ever is a better way to do this, we should use it. I would rather not
144 // manually fork, chdir in the child process, and then posix_spawn with exec
145 // as the whole reason for doing posix_spawn is to not hose anything up
146 // 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 else
167 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#endif
173
174 cpu_type_t cpu_type = 0;
175 bool show_usage = false;
176 int ch;
177 int disable_aslr = 0; // By default we disable ASLR
178 bool pass_env = true;
179 std::string unix_socket_name;
180 std::string working_dir;
181
182#if __GLIBC__
183 optind = 0;
184#else
185 optreset = 1;
186 optind = 1;
187#endif
188
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_64h
203 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 set
222 // environment
223 // 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 current
238 // terminal session when this program is launched from a .command file
239 ::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 else
251 ::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#endif
273
274 // Open the socket that was passed in as an option
275 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 whomever
294 // launched us will know this process's ID
295 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 socket
306 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 want
323 // to debug.
324 posix_spawn_for_debug(
325 argv,
326 pass_env ? *_NSGetEnviron() : NULL, // Pass current environment as we may
327 // have modified it if "--env" options
328 // was used, do NOT pass "envp" here
329 working_dir.empty() ? NULL : working_dir.c_str(), cpu_type, disable_aslr);
330
331 return 0;
332}
333
334#endif // #if defined (__APPLE__)
335

source code of lldb/tools/darwin-debug/darwin-debug.cpp