1 | /* vi: set sw=4 ts=4: */
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2 | /*
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3 | * Rexec program for system have fork() as vfork() with foreground option
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4 | *
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5 | * Copyright (C) Vladimir N. Oleynik <dzo@simtreas.ru>
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6 | * Copyright (C) 2003 Russ Dill <Russ.Dill@asu.edu>
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7 | *
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8 | * daemon() portion taken from uClibc:
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9 | *
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10 | * Copyright (c) 1991, 1993
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11 | * The Regents of the University of California. All rights reserved.
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12 | *
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13 | * Modified for uClibc by Erik Andersen <andersee@debian.org>
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14 | *
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15 | * Licensed under GPLv2 or later, see file LICENSE in this source tree.
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16 | */
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17 |
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18 | #include "busybox.h" /* uses applet tables */
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19 |
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20 | /* This does a fork/exec in one call, using vfork(). Returns PID of new child,
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21 | * -1 for failure. Runs argv[0], searching path if that has no / in it. */
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22 | pid_t FAST_FUNC spawn(char **argv)
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23 | {
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24 | /* Compiler should not optimize stores here */
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25 | volatile int failed;
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26 | pid_t pid;
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27 |
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28 | fflush_all();
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29 |
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30 | /* Be nice to nommu machines. */
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31 | failed = 0;
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32 | pid = vfork();
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33 | if (pid < 0) /* error */
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34 | return pid;
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35 | if (!pid) { /* child */
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36 | /* This macro is ok - it doesn't do NOEXEC/NOFORK tricks */
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37 | BB_EXECVP(argv[0], argv);
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38 |
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39 | /* We are (maybe) sharing a stack with blocked parent,
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40 | * let parent know we failed and then exit to unblock parent
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41 | * (but don't run atexit() stuff, which would screw up parent.)
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42 | */
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43 | failed = errno;
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44 | /* mount, for example, does not want the message */
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45 | /*bb_perror_msg("can't execute '%s'", argv[0]);*/
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46 | _exit(111);
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47 | }
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48 | /* parent */
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49 | /* Unfortunately, this is not reliable: according to standards
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50 | * vfork() can be equivalent to fork() and we won't see value
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51 | * of 'failed'.
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52 | * Interested party can wait on pid and learn exit code.
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53 | * If 111 - then it (most probably) failed to exec */
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54 | if (failed) {
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55 | safe_waitpid(pid, NULL, 0); /* prevent zombie */
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56 | errno = failed;
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57 | return -1;
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58 | }
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59 | return pid;
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60 | }
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61 |
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62 | /* Die with an error message if we can't spawn a child process. */
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63 | pid_t FAST_FUNC xspawn(char **argv)
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64 | {
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65 | pid_t pid = spawn(argv);
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66 | if (pid < 0)
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67 | bb_simple_perror_msg_and_die(*argv);
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68 | return pid;
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69 | }
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70 |
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71 | #if ENABLE_FEATURE_PREFER_APPLETS
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72 | void FAST_FUNC save_nofork_data(struct nofork_save_area *save)
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73 | {
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74 | memcpy(&save->die_jmp, &die_jmp, sizeof(die_jmp));
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75 | save->applet_name = applet_name;
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76 | save->xfunc_error_retval = xfunc_error_retval;
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77 | save->option_mask32 = option_mask32;
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78 | save->die_sleep = die_sleep;
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79 | save->saved = 1;
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80 | }
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81 |
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82 | void FAST_FUNC restore_nofork_data(struct nofork_save_area *save)
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83 | {
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84 | memcpy(&die_jmp, &save->die_jmp, sizeof(die_jmp));
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85 | applet_name = save->applet_name;
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86 | xfunc_error_retval = save->xfunc_error_retval;
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87 | option_mask32 = save->option_mask32;
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88 | die_sleep = save->die_sleep;
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89 | }
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90 |
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91 | int FAST_FUNC run_nofork_applet_prime(struct nofork_save_area *old, int applet_no, char **argv)
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92 | {
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93 | int rc, argc;
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94 |
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95 | applet_name = APPLET_NAME(applet_no);
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96 |
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97 | xfunc_error_retval = EXIT_FAILURE;
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98 |
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99 | /* Special flag for xfunc_die(). If xfunc will "die"
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100 | * in NOFORK applet, xfunc_die() sees negative
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101 | * die_sleep and longjmp here instead. */
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102 | die_sleep = -1;
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103 |
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104 | /* In case getopt() or getopt32() was already called:
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105 | * reset the libc getopt() function, which keeps internal state.
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106 | *
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107 | * BSD-derived getopt() functions require that optind be set to 1 in
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108 | * order to reset getopt() state. This used to be generally accepted
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109 | * way of resetting getopt(). However, glibc's getopt()
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110 | * has additional getopt() state beyond optind, and requires that
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111 | * optind be set to zero to reset its state. So the unfortunate state of
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112 | * affairs is that BSD-derived versions of getopt() misbehave if
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113 | * optind is set to 0 in order to reset getopt(), and glibc's getopt()
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114 | * will core dump if optind is set 1 in order to reset getopt().
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115 | *
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116 | * More modern versions of BSD require that optreset be set to 1 in
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117 | * order to reset getopt(). Sigh. Standards, anyone?
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118 | */
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119 | #ifdef __GLIBC__
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120 | optind = 0;
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121 | #else /* BSD style */
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122 | optind = 1;
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123 | /* optreset = 1; */
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124 | #endif
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125 | /* optarg = NULL; opterr = 1; optopt = 63; - do we need this too? */
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126 | /* (values above are what they initialized to in glibc and uclibc) */
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127 | /* option_mask32 = 0; - not needed, no applet depends on it being 0 */
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128 |
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129 | argc = 1;
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130 | while (argv[argc])
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131 | argc++;
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132 |
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133 | rc = setjmp(die_jmp);
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134 | if (!rc) {
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135 | /* Some callers (xargs)
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136 | * need argv untouched because they free argv[i]! */
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137 | char *tmp_argv[argc+1];
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138 | memcpy(tmp_argv, argv, (argc+1) * sizeof(tmp_argv[0]));
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139 | /* Finally we can call NOFORK applet's main() */
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140 | rc = applet_main[applet_no](argc, tmp_argv);
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141 |
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142 | /* The whole reason behind nofork_save_area is that <applet>_main
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143 | * may exit non-locally! For example, in hush Ctrl-Z tries
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144 | * (modulo bugs) to dynamically create a child (backgrounded task)
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145 | * if it detects that Ctrl-Z was pressed when a NOFORK was running.
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146 | * Testcase: interactive "rm -i".
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147 | * Don't fool yourself into thinking "and <applet>_main() returns
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148 | * quickly here" and removing "useless" nofork_save_area code. */
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149 |
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150 | } else { /* xfunc died in NOFORK applet */
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151 | /* in case they meant to return 0... */
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152 | if (rc == -2222)
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153 | rc = 0;
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154 | }
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155 |
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156 | /* Restoring some globals */
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157 | restore_nofork_data(old);
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158 |
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159 | /* Other globals can be simply reset to defaults */
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160 | #ifdef __GLIBC__
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161 | optind = 0;
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162 | #else /* BSD style */
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163 | optind = 1;
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164 | #endif
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165 |
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166 | return rc & 0xff; /* don't confuse people with "exitcodes" >255 */
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167 | }
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168 |
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169 | int FAST_FUNC run_nofork_applet(int applet_no, char **argv)
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170 | {
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171 | struct nofork_save_area old;
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172 |
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173 | /* Saving globals */
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174 | save_nofork_data(&old);
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175 | return run_nofork_applet_prime(&old, applet_no, argv);
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176 | }
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177 | #endif /* FEATURE_PREFER_APPLETS */
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178 |
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179 | int FAST_FUNC spawn_and_wait(char **argv)
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180 | {
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181 | int rc;
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182 | #if ENABLE_FEATURE_PREFER_APPLETS
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183 | int a = find_applet_by_name(argv[0]);
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184 |
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185 | if (a >= 0 && (APPLET_IS_NOFORK(a)
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186 | #if BB_MMU
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187 | || APPLET_IS_NOEXEC(a) /* NOEXEC trick needs fork() */
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188 | #endif
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189 | )) {
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190 | #if BB_MMU
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191 | if (APPLET_IS_NOFORK(a))
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192 | #endif
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193 | {
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194 | return run_nofork_applet(a, argv);
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195 | }
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196 | #if BB_MMU
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197 | /* MMU only */
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198 | /* a->noexec is true */
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199 | rc = fork();
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200 | if (rc) /* parent or error */
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201 | return wait4pid(rc);
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202 | /* child */
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203 | xfunc_error_retval = EXIT_FAILURE;
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204 | run_applet_no_and_exit(a, argv);
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205 | #endif
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206 | }
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207 | #endif /* FEATURE_PREFER_APPLETS */
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208 | rc = spawn(argv);
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209 | return wait4pid(rc);
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210 | }
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211 |
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212 | #if !BB_MMU
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213 | void FAST_FUNC re_exec(char **argv)
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214 | {
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215 | /* high-order bit of first char in argv[0] is a hidden
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216 | * "we have (already) re-execed, don't do it again" flag */
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217 | argv[0][0] |= 0x80;
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218 | execv(bb_busybox_exec_path, argv);
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219 | bb_perror_msg_and_die("can't execute '%s'", bb_busybox_exec_path);
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220 | }
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221 |
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222 | pid_t FAST_FUNC fork_or_rexec(char **argv)
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223 | {
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224 | pid_t pid;
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225 | /* Maybe we are already re-execed and come here again? */
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226 | if (re_execed)
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227 | return 0;
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228 | pid = xvfork();
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229 | if (pid) /* parent */
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230 | return pid;
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231 | /* child - re-exec ourself */
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232 | re_exec(argv);
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233 | }
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234 | #endif
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235 |
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236 | /* Due to a #define in libbb.h on MMU systems we actually have 1 argument -
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237 | * char **argv "vanishes" */
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238 | void FAST_FUNC bb_daemonize_or_rexec(int flags, char **argv)
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239 | {
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240 | int fd;
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241 |
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242 | if (flags & DAEMON_CHDIR_ROOT)
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243 | xchdir("/");
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244 |
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245 | if (flags & DAEMON_DEVNULL_STDIO) {
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246 | close(0);
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247 | close(1);
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248 | close(2);
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249 | }
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250 |
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251 | fd = open(bb_dev_null, O_RDWR);
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252 | if (fd < 0) {
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253 | /* NB: we can be called as bb_sanitize_stdio() from init
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254 | * or mdev, and there /dev/null may legitimately not (yet) exist!
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255 | * Do not use xopen above, but obtain _ANY_ open descriptor,
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256 | * even bogus one as below. */
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257 | fd = xopen("/", O_RDONLY); /* don't believe this can fail */
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258 | }
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259 |
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260 | while ((unsigned)fd < 2)
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261 | fd = dup(fd); /* have 0,1,2 open at least to /dev/null */
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262 |
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263 | if (!(flags & DAEMON_ONLY_SANITIZE)) {
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264 | if (fork_or_rexec(argv))
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265 | exit(EXIT_SUCCESS); /* parent */
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266 | /* if daemonizing, make sure we detach from stdio & ctty */
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267 | setsid();
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268 | dup2(fd, 0);
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269 | dup2(fd, 1);
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270 | dup2(fd, 2);
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271 | }
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272 | while (fd > 2) {
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273 | close(fd--);
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274 | if (!(flags & DAEMON_CLOSE_EXTRA_FDS))
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275 | return;
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276 | /* else close everything after fd#2 */
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277 | }
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278 | }
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279 |
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280 | void FAST_FUNC bb_sanitize_stdio(void)
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281 | {
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282 | bb_daemonize_or_rexec(DAEMON_ONLY_SANITIZE, NULL);
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283 | }
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