dualinit

A meta-init system for linux
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dualinit.c (3341B)

      1 #include "common.h"
      2 #include "config.h"
      3 #include "console.h"
      4 #include "default.h"
      5 
      6 #include <dirent.h>
      7 #include <errno.h>
      8 #include <fcntl.h>
      9 #include <stdio.h>
     10 #include <stdlib.h>
     11 #include <string.h>
     12 #include <sys/mount.h>
     13 #include <unistd.h>
     14 
     15 // mounts `mnt` relative to `root`
     16 static void mount_chroot(const char* root, const mount_t* mnt) {
     17 	static char dest[100];
     18 	strcpy(dest, root);
     19 	strcat(dest, mnt->target);
     20 
     21 	INFO("mounting %s -> %s", mnt->source, dest);
     22 	if (mnt->type != NULL)
     23 		printf(" (%s)", mnt->type);
     24 	if (mnt->options != NULL)
     25 		printf(" [%s]", mnt->options);
     26 
     27 	printf("\n");
     28 
     29 	if (mount(mnt->source, dest, mnt->type, mnt->flags, mnt->options) != 0) {
     30 		if (mnt->try) {
     31 			WARN("mounting %s to %s failed: %s\n", mnt->source, dest, strerror(errno));
     32 		} else {
     33 			PANIC("mounting %s to %s failed: %s\n", mnt->source, dest, strerror(errno));
     34 		}
     35 	}
     36 }
     37 
     38 int main() {
     39 	if (getpid() != 1) {
     40 		PANIC("must run as PID 1\n");
     41 	}
     42 
     43 	// initiates the console as it's not initiated if init-system
     44 	init_console();
     45 
     46 	// opens the config file (`fopen` is not working yet)
     47 	int config_file = open(DEFAULT_CONFIG, O_RDONLY | O_NONBLOCK);
     48 	if (config_file == -1) {
     49 		// if it can't be opened, die!
     50 		PANIC("cannot open %s: %s\n", DEFAULT_CONFIG, strerror(errno));
     51 	}
     52 
     53 	// parse the config
     54 	parse_error_t parse_code = config_parse(config_file, DEFAULT_CONFIG);
     55 	if (parse_code != 0) {
     56 		// if config can't be parse, die! (again lol)
     57 		PANIC("invalid config");
     58 	}
     59 	// and close the file as it's not needed anymore
     60 	close(config_file);
     61 
     62 	int section_index;
     63 	while (1) {
     64 		// politely asking for which init you want to load
     65 		printf("which init do you want to start?\n");
     66 		// listing the sections
     67 		for (int i = 0; i < section_size; i++) {
     68 			printf("[%d] %s at %s\n", i, sections[i].name, sections[i].root);
     69 		}
     70 
     71 		printf(": ");
     72 		fflush(stdout);
     73 
     74 		scanf("%d", &section_index);
     75 		if (section_index >= 0 && section_index < section_size)
     76 			break;
     77 
     78 		// mmph, you didn't enter a valid number
     79 		WARN("your choice %d must be lower than %d\n\n", section_index, section_size);
     80 	}
     81 
     82 	section_t* section = &sections[section_index];
     83 	bool	   is_root = strcmp(section->root, "/") == 0;
     84 
     85 	// if the section is not `/` (as it should be), mount everything
     86 	if (!is_root) {
     87 		mount_t self_mount = {
     88 			.type	 = NULL,
     89 			.source	 = section->root,
     90 			.target	 = "/",
     91 			.options = NULL,
     92 			.flags	 = MS_BIND,
     93 			.try	 = false,
     94 		};
     95 
     96 		mount_chroot(section->root, &self_mount);
     97 
     98 		for (int i = 0; i < mount_size; i++) {
     99 			mount_chroot(section->root, &mounts[i]);
    100 		}
    101 	}
    102 
    103 	for (int i = 0; i < section->mount_size; i++) {
    104 		mount_chroot(section->root, &section->mounts[i]);
    105 	}
    106 
    107 	if (!is_root) {
    108 		// if it's not '/', chroot into it
    109 		INFO("chrooting into %s\n", section->root);
    110 
    111 		if (chroot(section->root) == -1) {
    112 			PANIC("cannot chroot into %s: %s\n", section->root, strerror(errno));
    113 		}
    114 	}
    115 
    116 	// chdir '/', otherwise the init-system will have funny errors
    117 	if (chdir("/") == -1) {
    118 		PANIC("error: cannot chdir into '/': %s\n", strerror(errno));
    119 	}
    120 
    121 	// aaand finally entering `init`
    122 	char init[PATH_MAX] = DEFAULT_INIT;
    123 	if (section->init != NULL)
    124 		strcpy(init, section->init);
    125 
    126 	config_cleanup();
    127 
    128 	INFO("entering %s\n\n", init);
    129 
    130 	execlp(section->init, section->init, NULL);
    131 
    132 	PANIC("error: cannot execute %s: %s\n", section->init, strerror(errno));
    133 }