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//===-- Launcher.cpp --------------------------------------------*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//----------------------------------------------------------------------
// Darwin launch helper
//
// This program was written to allow programs to be launched in a new
// Terminal.app window and have the application be stopped for debugging
// at the program entry point.
//
// Although it uses posix_spawn(), it uses Darwin specific posix spawn
// attribute flags to accomplish its task. It uses an "exec only" flag
// which avoids forking this process, and it uses a "stop at entry"
// flag to stop the program at the entry point.
//
// Since it uses darwin specific flags this code should not be compiled
// on other systems.
//----------------------------------------------------------------------
#if defined (__APPLE__)
#include <getopt.h>
#include <mach/machine.h>
#include <spawn.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#ifndef _POSIX_SPAWN_DISABLE_ASLR
#define _POSIX_SPAWN_DISABLE_ASLR 0x0100
#endif
#define streq(a,b) strcmp(a,b) == 0
static struct option g_long_options[] =
{
{ "arch", required_argument, NULL, 'a' },
{ "disable-aslr", no_argument, NULL, 'd' },
{ "no-env", no_argument, NULL, 'e' },
{ "help", no_argument, NULL, 'h' },
{ "setsid", no_argument, NULL, 's' },
{ NULL, 0, NULL, 0 }
};
static void
usage()
{
puts (
"NAME\n"
" darwin-debug -- posix spawn a process that is stopped at the entry point\n"
" for debugging.\n"
"\n"
"SYNOPSIS\n"
" darwin-debug [--arch=<ARCH>] [--disable-aslr] [--no-env] [--setsid] [--help] -- <PROGRAM> [<PROGRAM-ARG> <PROGRAM-ARG> ....]\n"
"\n"
"DESCRIPTION\n"
" darwin-debug will exec itself into a child process <PROGRAM> that is\n"
" halted for debugging. It does this by using posix_spawn() along with\n"
" darwin specific posix_spawn flags that allows exec only (no fork), and\n"
" stop at the program entry point. Any program arguments <PROGRAM-ARG> are\n"
" passed on to the exec as the arguments for the new process. The current\n"
" environment will be passed to the new process unless the \"--no-env\"\n"
" option is used.\n"
"\n"
"EXAMPLE\n"
" darwin-debug --arch=i386 -- /bin/ls -al /tmp\n"
);
exit (1);
}
static void
exit_with_errno (int err, const char *prefix)
{
if (err)
{
fprintf (stderr,
"%s%s",
prefix ? prefix : "",
strerror(err));
exit (err);
}
}
pid_t
posix_spawn_for_debug (char *const *argv, char *const *envp, cpu_type_t cpu_type, int disable_aslr)
{
pid_t pid = 0;
const char *path = argv[0];
posix_spawnattr_t attr;
exit_with_errno (::posix_spawnattr_init (&attr), "::posix_spawnattr_init (&attr) error: ");
// Here we are using a darwin specific feature that allows us to exec only
// since we want this program to turn into the program we want to debug,
// and also have the new program start suspended (right at __dyld_start)
// so we can debug it
short flags = POSIX_SPAWN_START_SUSPENDED | POSIX_SPAWN_SETEXEC;
// Disable ASLR if we were asked to
if (disable_aslr)
flags |= _POSIX_SPAWN_DISABLE_ASLR;
// Set the flags we just made into our posix spawn attributes
exit_with_errno (::posix_spawnattr_setflags (&attr, flags), "::posix_spawnattr_setflags (&attr, flags) error: ");
// Another darwin specific thing here where we can select the architecture
// of the binary we want to re-exec as.
if (cpu_type != 0)
{
size_t ocount = 0;
exit_with_errno (::posix_spawnattr_setbinpref_np (&attr, 1, &cpu_type, &ocount), "posix_spawnattr_setbinpref_np () error: ");
}
exit_with_errno (::posix_spawnp (&pid, path, NULL, &attr, (char * const*)argv, (char * const*)envp), "posix_spawn() error: ");
// This code will only be reached if the posix_spawn exec failed...
::posix_spawnattr_destroy (&attr);
return pid;
}
int main (int argc, char *const *argv, char *const *envp, const char **apple)
{
const char *program_name = strrchr(apple[0], '/');
if (program_name)
program_name++; // Skip the last slash..
else
program_name = apple[0];
#if defined (DEBUG_LLDB_LAUNCHER)
printf("%s called with:\n", program_name);
for (int i=0; i<argc; ++i)
printf("argv[%u] = '%s'\n", i, argv[i]);
#endif
cpu_type_t cpu_type = 0;
bool show_usage = false;
char ch;
int disable_aslr = 0; // By default we disable ASLR
int pass_env = 1;
while ((ch = getopt_long(argc, argv, "a:dfh?", g_long_options, NULL)) != -1)
{
switch (ch)
{
case 0:
break;
case 'a': // "-a i386" or "--arch=i386"
if (optarg)
{
if (streq (optarg, "i386"))
cpu_type = CPU_TYPE_I386;
else if (streq (optarg, "x86_64"))
cpu_type = CPU_TYPE_X86_64;
else if (strstr (optarg, "arm") == optarg)
cpu_type = CPU_TYPE_ARM;
else
{
::fprintf (stderr, "error: unsupported cpu type '%s'\n", optarg);
::exit (1);
}
}
break;
case 'd':
disable_aslr = 1;
break;
case 'e':
pass_env = 0;
break;
case 's':
// Create a new session to avoid having control-C presses kill our current
// terminal session when this program is launched from a .command file
::setsid();
break;
case 'h':
case '?':
default:
show_usage = true;
break;
}
}
argc -= optind;
argv += optind;
if (show_usage || argc <= 0)
usage();
#if defined (DEBUG_LLDB_LAUNCHER)
printf ("\n%s post options:\n", program_name);
for (int i=0; i<argc; ++i)
printf ("argv[%u] = '%s'\n", i, argv[i]);
#endif
posix_spawn_for_debug (argv,
pass_env ? envp : NULL,
cpu_type,
disable_aslr);
return 0;
}
#endif // #if defined (__APPLE__)
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