Mercurial > hg > toybox
annotate toys/other/oneit.c @ 1776:7bf68329eb3b draft default tip
Repository switched to git at https://github.com/landley/toybox
author | Rob Landley <rob@landley.net> |
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date | Thu, 09 Apr 2015 02:28:32 -0500 |
parents | b2b2d214727a |
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1 /* oneit.c - tiny init replacement to launch a single child process. |
34 | 2 * |
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3 * Copyright 2005, 2007 by Rob Landley <rob@landley.net>. |
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4 |
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5 USE_ONEIT(NEWTOY(oneit, "^<1nc:p3[!pn]", TOYFLAG_SBIN)) |
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6 |
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7 config ONEIT |
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8 bool "oneit" |
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9 default y |
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10 help |
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11 usage: oneit [-p] [-c /dev/tty0] command [...] |
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12 |
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13 Simple init program that runs a single supplied command line with a |
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14 controlling tty (so CTRL-C can kill it). |
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15 |
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16 -c Which console device to use (/dev/console doesn't do CTRL-C, etc). |
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17 -p Power off instead of rebooting when command exits. |
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18 -r Restart child when it exits. |
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19 -3 Write 32 bit PID of each exiting reparented process to fd 3 of child. |
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20 (Blocking writes, child must read to avoid eventual deadlock.) |
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21 |
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22 Spawns a single child process (because PID 1 has signals blocked) |
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23 in its own session, reaps zombies until the child exits, then |
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24 reboots the system (or powers off with -p, or restarts the child with -r). |
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25 */ |
34 | 26 |
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27 #define FOR_oneit |
34 | 28 #include "toys.h" |
29 #include <sys/reboot.h> | |
30 | |
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31 GLOBALS( |
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32 char *console; |
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33 ) |
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34 |
34 | 35 // The minimum amount of work necessary to get ctrl-c and such to work is: |
36 // | |
37 // - Fork a child (PID 1 is special: can't exit, has various signals blocked). | |
38 // - Do a setsid() (so we have our own session). | |
39 // - In the child, attach stdio to /dev/tty0 (/dev/console is special) | |
40 // - Exec the rest of the command line. | |
41 // | |
42 // PID 1 then reaps zombies until the child process it spawned exits, at which | |
43 // point it calls sync() and reboot(). I could stick a kill -1 in there. | |
44 | |
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45 // Perform actions in response to signals. (Only root can send us signals.) |
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46 static void oneit_signaled(int signal) |
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47 { |
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48 int action = RB_AUTOBOOT; |
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49 |
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50 toys.signal = signal; |
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51 if (signal == SIGUSR1) action = RB_HALT_SYSTEM; |
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52 if (signal == SIGUSR2) action = RB_POWER_OFF; |
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53 |
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54 // PID 1 can't call reboot() because it kills the task that calls it, |
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55 // which causes the kernel to panic before the actual reboot happens. |
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56 sync(); |
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57 if (!vfork()) reboot(action); |
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58 } |
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59 |
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60 void oneit_main(void) |
34 | 61 { |
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62 int i, pid, pipes[] = {SIGUSR1, SIGUSR2, SIGTERM, SIGINT}; |
34 | 63 |
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64 if (FLAG_3) { |
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65 // Ensure next available filehandle is #3 |
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66 while (open("/", 0) < 3); |
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67 close(3); |
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68 close(4); |
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69 if (pipe(pipes)) perror_exit("pipe"); |
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70 fcntl(4, F_SETFD, FD_CLOEXEC); |
34 | 71 } |
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72 |
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73 // Setup signal handlers for signals of interest |
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74 for (i = 0; i<ARRAY_LEN(pipes); i++) xsignal(pipes[i], oneit_signaled); |
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75 |
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76 while (!toys.signal) { |
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77 |
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78 // Create a new child process. |
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79 pid = vfork(); |
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80 if (pid) { |
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81 |
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82 // pid 1 reaps zombies until it gets its child, then halts system. |
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83 // We ignore the return value of write (what would we do with it?) |
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84 // but save it in a variable we never read to make fortify shut up. |
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85 // (Real problem is if pid2 never reads, write() fills pipe and blocks.) |
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86 while (pid != wait(&i)) if (FLAG_3) i = write(4, &pid, 4); |
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87 if (toys.optflags & FLAG_n) continue; |
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88 |
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89 oneit_signaled((toys.optflags & FLAG_p) ? SIGUSR2 : SIGTERM); |
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90 } else { |
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91 // Redirect stdio to /dev/tty0, with new session ID, so ctrl-c works. |
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92 setsid(); |
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93 for (i=0; i<3; i++) { |
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94 close(i); |
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95 // Remember, O_CLOEXEC is backwards for xopen() |
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96 xopen(TT.console ? TT.console : "/dev/tty0", O_RDWR|O_CLOEXEC); |
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97 } |
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98 |
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99 // Can't xexec() here, we vforked so we don't want to error_exit(). |
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100 toy_exec(toys.optargs); |
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101 execvp(*toys.optargs, toys.optargs); |
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102 perror_msg("%s not in PATH=%s", *toys.optargs, getenv("PATH")); |
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103 |
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104 break; |
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105 } |
34 | 106 } |
107 | |
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108 // Give reboot() time to kick in, or avoid rapid spinning if exec failed |
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109 sleep(5); |
34 | 110 _exit(127); |
111 } |