206 lines
5.1 KiB
C
206 lines
5.1 KiB
C
#include <stdio.h>
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#include <unistd.h>
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#include <string.h>
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#include <dirent.h>
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#include <fcntl.h>
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#include <sys/stat.h>
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#include <sys/types.h>
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#include <sys/mount.h>
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#include <sys/sendfile.h>
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#include <sys/sysmacros.h>
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struct cmdline {
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int skip_initramfs;
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char slot[3];
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};
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struct device {
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dev_t major;
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dev_t minor;
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char devname[32];
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char partname[32];
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char path[64];
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};
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static void clone_dir(int src, int dest) {
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struct dirent *entry;
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DIR *dir;
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int srcfd, destfd, newsrc, newdest;
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struct stat st;
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char buf[PATH_MAX];
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ssize_t size;
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dir = fdopendir(src);
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while ((entry = readdir(dir))) {
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if (strcmp(entry->d_name, ".") == 0 || strcmp(entry->d_name, "..") == 0)
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continue;
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fstatat(src, entry->d_name, &st, AT_SYMLINK_NOFOLLOW);
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switch (entry->d_type) {
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case DT_DIR:
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mkdirat(dest, entry->d_name, st.st_mode & 0777);
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fchownat(dest, entry->d_name, st.st_uid, st.st_gid, 0);
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// Don't clone recursive if it's /system
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if (strcmp(entry->d_name, "system") == 0)
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continue;
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newsrc = openat(src, entry->d_name, O_RDONLY | O_CLOEXEC);
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newdest = openat(dest, entry->d_name, O_RDONLY | O_CLOEXEC);
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clone_dir(newsrc, newdest);
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close(newsrc);
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close(newdest);
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break;
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case DT_REG:
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destfd = openat(dest, entry->d_name, O_WRONLY | O_CREAT | O_TRUNC | O_CLOEXEC, st.st_mode & 0777);
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srcfd = openat(src, entry->d_name, O_RDONLY | O_CLOEXEC);
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sendfile(destfd, srcfd, 0, st.st_size);
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fchownat(dest, entry->d_name, st.st_uid, st.st_gid, 0);
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close(destfd);
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close(srcfd);
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break;
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case DT_LNK:
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size = readlinkat(src, entry->d_name, buf, sizeof(buf));
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buf[size] = '\0';
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symlinkat(buf, dest, entry->d_name);
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fchownat(dest, entry->d_name, st.st_uid, st.st_gid, AT_SYMLINK_NOFOLLOW);
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break;
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}
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}
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}
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static void rm_rf(int path) {
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struct dirent *entry;
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int newfd;
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DIR *dir = fdopendir(path);
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while ((entry = readdir(dir))) {
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if (strcmp(entry->d_name, ".") == 0 || strcmp(entry->d_name, "..") == 0)
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continue;
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switch (entry->d_type) {
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case DT_DIR:
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newfd = openat(path, entry->d_name, O_RDONLY | O_CLOEXEC);
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rm_rf(newfd);
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close(newfd);
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unlinkat(path, entry->d_name, AT_REMOVEDIR);
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break;
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default:
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unlinkat(path, entry->d_name, 0);
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break;
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}
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}
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}
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static void parse_cmdline(struct cmdline *cmd) {
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char *tok;
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char buffer[4096];
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mkdir("/proc", 0555);
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mount("proc", "/proc", "proc", 0, NULL);
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int fd = open("/proc/cmdline", O_RDONLY | O_CLOEXEC);
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ssize_t size = read(fd, buffer, sizeof(buffer));
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buffer[size] = '\0';
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close(fd);
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umount("/proc");
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tok = strtok(buffer, " ");
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cmd->skip_initramfs = 0;
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cmd->slot[0] = '\0';
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while (tok != NULL) {
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if (strncmp(tok, "androidboot.slot_suffix", 23) == 0) {
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sscanf(tok, "androidboot.slot_suffix=%s", cmd->slot);
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} else if (strcmp(tok, "skip_initramfs") == 0) {
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cmd->skip_initramfs = 1;
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break;
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}
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tok = strtok(NULL, " ");
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}
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}
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static void parse_device(struct device *dev, char *uevent) {
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char *tok;
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tok = strtok(uevent, "\n");
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while (tok != NULL) {
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if (strncmp(tok, "MAJOR", 5) == 0) {
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sscanf(tok, "MAJOR=%ld", (long*) &dev->major);
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} else if (strncmp(tok, "MINOR", 5) == 0) {
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sscanf(tok, "MINOR=%ld", (long*) &dev->minor);
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} else if (strncmp(tok, "DEVNAME", 7) == 0) {
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sscanf(tok, "DEVNAME=%s", dev->devname);
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} else if (strncmp(tok, "PARTNAME", 8) == 0) {
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sscanf(tok, "PARTNAME=%s", dev->partname);
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}
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tok = strtok(NULL, "\n");
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}
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}
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static int setup_block(struct device *dev, const char *partname) {
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char buffer[1024], path[128];
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mkdir("/sys", 0755);
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mount("sysfs", "/sys", "sysfs", 0, NULL);
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struct dirent *entry;
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DIR *dir = opendir("/sys/dev/block");
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if (dir == NULL)
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return 1;
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int found = 0;
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while ((entry = readdir(dir))) {
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if (strcmp(entry->d_name, ".") == 0 || strcmp(entry->d_name, "..") == 0)
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continue;
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snprintf(path, sizeof(path), "/sys/dev/block/%s/uevent", entry->d_name);
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int fd = open(path, O_RDONLY | O_CLOEXEC);
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ssize_t size = read(fd, buffer, sizeof(buffer));
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buffer[size] = '\0';
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close(fd);
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parse_device(dev, buffer);
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if (strcmp(dev->partname, partname) == 0) {
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snprintf(dev->path, sizeof(dev->path), "/dev/block/%s", dev->devname);
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found = 1;
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break;
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}
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}
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closedir(dir);
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if (!found)
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return 1;
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mkdir("/dev", 0755);
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mkdir("/dev/block", 0755);
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mknod(dev->path, S_IFBLK | 0600, makedev(dev->major, dev->minor));
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return 0;
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}
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int main(int argc, char *argv[]) {
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umask(0);
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struct cmdline cmd;
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parse_cmdline(&cmd);
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if (cmd.skip_initramfs) {
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// Normal boot mode
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// Clear rootfs
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int root = open("/", O_RDONLY | O_CLOEXEC);
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rm_rf(root);
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char partname[32];
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snprintf(partname, sizeof(partname), "system%s", cmd.slot);
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struct device dev;
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setup_block(&dev, partname);
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mkdir("/system_root", 0755);
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mount(dev.path, "/system_root", "ext4", MS_RDONLY, NULL);
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int system_root = open("/system_root", O_RDONLY | O_CLOEXEC);
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clone_dir(system_root, root);
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mount("/system_root/system", "/system", NULL, MS_BIND, NULL);
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close(root);
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close(system_root);
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} else {
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// Recovery mode
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// Revert original init binary
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unlink("/init");
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rename("/init_orig", "/init");
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}
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execv("/init", argv);
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return 0;
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}
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