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 tarball for details.
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16 | */
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17 |
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18 | #include <paths.h>
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19 | #include "busybox.h" /* for struct bb_applet */
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20 |
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21 | /* This does a fork/exec in one call, using vfork(). Returns PID of new child,
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22 | * -1 for failure. Runs argv[0], searching path if that has no / in it. */
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23 | pid_t spawn(char **argv)
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24 | {
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25 | /* Compiler should not optimize stores here */
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26 | volatile int failed;
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27 | pid_t pid;
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28 |
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29 | // Ain't it a good place to fflush(NULL)?
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30 |
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31 | /* Be nice to nommu machines. */
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32 | failed = 0;
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33 | pid = vfork();
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34 | if (pid < 0) /* error */
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35 | return pid;
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36 | if (!pid) { /* child */
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37 | /* This macro is ok - it doesn't do NOEXEC/NOFORK tricks */
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38 | BB_EXECVP(argv[0], argv);
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39 |
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40 | /* We are (maybe) sharing a stack with blocked parent,
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41 | * let parent know we failed and then exit to unblock parent
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42 | * (but don't run atexit() stuff, which would screw up parent.)
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43 | */
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44 | failed = errno;
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45 | _exit(111);
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46 | }
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47 | /* parent */
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48 | /* Unfortunately, this is not reliable: according to standards
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49 | * vfork() can be equivalent to fork() and we won't see value
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50 | * of 'failed'.
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51 | * Interested party can wait on pid and learn exit code.
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52 | * If 111 - then it (most probably) failed to exec */
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53 | if (failed) {
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54 | errno = failed;
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55 | return -1;
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56 | }
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57 | return pid;
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58 | }
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59 |
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60 | /* Die with an error message if we can't spawn a child process. */
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61 | pid_t xspawn(char **argv)
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62 | {
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63 | pid_t pid = spawn(argv);
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64 | if (pid < 0)
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65 | bb_perror_msg_and_die("%s", *argv);
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66 | return pid;
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67 | }
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68 |
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69 | // Wait for the specified child PID to exit, returning child's error return.
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70 | int wait4pid(int pid)
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71 | {
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72 | int status;
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73 |
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74 | if (pid <= 0) {
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75 | /*errno = ECHILD; -- wrong. */
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76 | /* we expect errno to be already set from failed [v]fork/exec */
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77 | return -1;
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78 | }
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79 | if (waitpid(pid, &status, 0) == -1)
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80 | return -1;
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81 | if (WIFEXITED(status))
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82 | return WEXITSTATUS(status);
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83 | if (WIFSIGNALED(status))
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84 | return WTERMSIG(status) + 1000;
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85 | return 0;
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86 | }
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87 |
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88 | int wait_nohang(int *wstat)
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89 | {
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90 | return waitpid(-1, wstat, WNOHANG);
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91 | }
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92 |
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93 | int wait_pid(int *wstat, int pid)
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94 | {
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95 | int r;
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96 |
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97 | do
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98 | r = waitpid(pid, wstat, 0);
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99 | while ((r == -1) && (errno == EINTR));
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100 | return r;
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101 | }
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102 |
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103 | #if ENABLE_FEATURE_PREFER_APPLETS
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104 | void save_nofork_data(struct nofork_save_area *save)
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105 | {
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106 | memcpy(&save->die_jmp, &die_jmp, sizeof(die_jmp));
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107 | save->current_applet = current_applet;
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108 | save->xfunc_error_retval = xfunc_error_retval;
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109 | save->option_mask32 = option_mask32;
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110 | save->die_sleep = die_sleep;
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111 | save->saved = 1;
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112 | }
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113 |
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114 | void restore_nofork_data(struct nofork_save_area *save)
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115 | {
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116 | memcpy(&die_jmp, &save->die_jmp, sizeof(die_jmp));
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117 | current_applet = save->current_applet;
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118 | xfunc_error_retval = save->xfunc_error_retval;
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119 | option_mask32 = save->option_mask32;
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120 | die_sleep = save->die_sleep;
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121 |
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122 | applet_name = current_applet->name;
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123 | }
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124 |
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125 | int run_nofork_applet_prime(struct nofork_save_area *old, const struct bb_applet *a, char **argv)
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126 | {
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127 | int rc, argc;
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128 |
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129 | current_applet = a;
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130 | applet_name = a->name;
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131 | xfunc_error_retval = EXIT_FAILURE;
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132 | /*option_mask32 = 0; - not needed */
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133 | /* special flag for xfunc_die(). If xfunc will "die"
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134 | * in NOFORK applet, xfunc_die() sees negative
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135 | * die_sleep and longjmp here instead. */
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136 | die_sleep = -1;
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137 |
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138 | argc = 1;
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139 | while (argv[argc])
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140 | argc++;
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141 |
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142 | rc = setjmp(die_jmp);
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143 | if (!rc) {
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144 | /* Some callers (xargs)
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145 | * need argv untouched because they free argv[i]! */
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146 | char *tmp_argv[argc+1];
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147 | memcpy(tmp_argv, argv, (argc+1) * sizeof(tmp_argv[0]));
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148 | /* Finally we can call NOFORK applet's main() */
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149 | rc = a->main(argc, tmp_argv);
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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 globals */
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157 | restore_nofork_data(old);
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158 | return rc;
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159 | }
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160 |
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161 | int run_nofork_applet(const struct bb_applet *a, char **argv)
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162 | {
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163 | struct nofork_save_area old;
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164 |
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165 | /* Saving globals */
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166 | save_nofork_data(&old);
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167 | return run_nofork_applet_prime(&old, a, argv);
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168 | }
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169 | #endif /* FEATURE_PREFER_APPLETS */
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170 |
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171 | int spawn_and_wait(char **argv)
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172 | {
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173 | int rc;
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174 | #if ENABLE_FEATURE_PREFER_APPLETS
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175 | const struct bb_applet *a = find_applet_by_name(argv[0]);
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176 |
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177 | if (a && (a->nofork
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178 | #if BB_MMU
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179 | || a->noexec /* NOEXEC trick needs fork() */
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180 | #endif
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181 | )) {
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182 | #if BB_MMU
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183 | if (a->nofork)
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184 | #endif
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185 | {
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186 | return run_nofork_applet(a, argv);
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187 | }
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188 | #if BB_MMU
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189 | /* MMU only */
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190 | /* a->noexec is true */
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191 | rc = fork();
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192 | if (rc) /* parent or error */
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193 | return wait4pid(rc);
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194 | /* child */
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195 | xfunc_error_retval = EXIT_FAILURE;
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196 | current_applet = a;
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197 | run_current_applet_and_exit(argv);
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198 | #endif
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199 | }
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200 | #endif /* FEATURE_PREFER_APPLETS */
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201 | rc = spawn(argv);
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202 | return wait4pid(rc);
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203 | }
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204 |
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205 | #if !BB_MMU
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206 | void re_exec(char **argv)
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207 | {
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208 | /* high-order bit of first char in argv[0] is a hidden
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209 | * "we have (already) re-execed, don't do it again" flag */
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210 | argv[0][0] |= 0x80;
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211 | execv(bb_busybox_exec_path, argv);
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212 | bb_perror_msg_and_die("exec %s", bb_busybox_exec_path);
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213 | }
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214 |
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215 | void forkexit_or_rexec(char **argv)
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216 | {
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217 | pid_t pid;
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218 | /* Maybe we are already re-execed and come here again? */
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219 | if (re_execed)
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220 | return;
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221 |
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222 | pid = vfork();
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223 | if (pid < 0) /* wtf? */
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224 | bb_perror_msg_and_die("vfork");
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225 | if (pid) /* parent */
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226 | exit(0);
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227 | /* child - re-exec ourself */
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228 | re_exec(argv);
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229 | }
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230 | #else
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231 | /* Dance around (void)...*/
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232 | #undef forkexit_or_rexec
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233 | void forkexit_or_rexec(void)
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234 | {
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235 | pid_t pid;
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236 | pid = fork();
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237 | if (pid < 0) /* wtf? */
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238 | bb_perror_msg_and_die("fork");
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239 | if (pid) /* parent */
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240 | exit(0);
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241 | /* child */
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242 | }
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243 | #define forkexit_or_rexec(argv) forkexit_or_rexec()
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244 | #endif
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245 |
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246 | /* Due to a #define in libbb.h on MMU systems we actually have 1 argument -
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247 | * char **argv "vanishes" */
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248 | void bb_daemonize_or_rexec(int flags, char **argv)
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249 | {
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250 | int fd;
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251 |
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252 | if (flags & DAEMON_CHDIR_ROOT)
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253 | xchdir("/");
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254 |
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255 | if (flags & DAEMON_DEVNULL_STDIO) {
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256 | close(0);
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257 | close(1);
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258 | close(2);
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259 | }
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260 |
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261 | fd = xopen(bb_dev_null, O_RDWR);
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262 |
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263 | while ((unsigned)fd < 2)
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264 | fd = dup(fd); /* have 0,1,2 open at least to /dev/null */
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265 |
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266 | if (!(flags & DAEMON_ONLY_SANITIZE)) {
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267 | forkexit_or_rexec(argv);
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268 | /* if daemonizing, make sure we detach from stdio & ctty */
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269 | setsid();
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270 | dup2(fd, 0);
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271 | dup2(fd, 1);
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272 | dup2(fd, 2);
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273 | }
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274 | while (fd > 2) {
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275 | close(fd--);
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276 | if (!(flags & DAEMON_CLOSE_EXTRA_FDS))
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277 | return;
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278 | /* else close everything after fd#2 */
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279 | }
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280 | }
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281 |
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282 | void bb_sanitize_stdio(void)
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283 | {
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284 | bb_daemonize_or_rexec(DAEMON_ONLY_SANITIZE, NULL);
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285 | }
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