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// SPDX-License-Identifier: GPL-2.0
/*
* Copyright (c) 2025, Google LLC.
* Pasha Tatashin <pasha.tatashin@soleen.com>
*/
#include <fcntl.h>
#include <linux/kexec.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/mount.h>
#include <sys/reboot.h>
#include <sys/syscall.h>
#include <sys/wait.h>
#include <unistd.h>
#define COMMAND_LINE_SIZE 2048
#define KERNEL_IMAGE "/kernel"
#define INITRD_IMAGE "/initrd.img"
#define TEST_BINARY "/test_binary"
static int mount_filesystems(void)
{
if (mount("devtmpfs", "/dev", "devtmpfs", 0, NULL) < 0) {
fprintf(stderr, "INIT: Warning: Failed to mount devtmpfs\n");
return -1;
}
if (mount("debugfs", "/debugfs", "debugfs", 0, NULL) < 0) {
fprintf(stderr, "INIT: Failed to mount debugfs\n");
return -1;
}
if (mount("proc", "/proc", "proc", 0, NULL) < 0) {
fprintf(stderr, "INIT: Failed to mount proc\n");
return -1;
}
return 0;
}
static long kexec_file_load(int kernel_fd, int initrd_fd,
unsigned long cmdline_len, const char *cmdline,
unsigned long flags)
{
return syscall(__NR_kexec_file_load, kernel_fd, initrd_fd, cmdline_len,
cmdline, flags);
}
static int kexec_load(void)
{
char cmdline[COMMAND_LINE_SIZE];
int kernel_fd, initrd_fd, err;
ssize_t len;
int fd;
fd = open("/proc/cmdline", O_RDONLY);
if (fd < 0) {
fprintf(stderr, "INIT: Failed to read /proc/cmdline\n");
return -1;
}
len = read(fd, cmdline, sizeof(cmdline) - 1);
close(fd);
if (len < 0)
return -1;
cmdline[len] = 0;
if (len > 0 && cmdline[len - 1] == '\n')
cmdline[len - 1] = 0;
strncat(cmdline, " luo_stage=2", sizeof(cmdline) - strlen(cmdline) - 1);
kernel_fd = open(KERNEL_IMAGE, O_RDONLY);
if (kernel_fd < 0) {
fprintf(stderr, "INIT: Failed to open kernel image\n");
return -1;
}
initrd_fd = open(INITRD_IMAGE, O_RDONLY);
if (initrd_fd < 0) {
fprintf(stderr, "INIT: Failed to open initrd image\n");
close(kernel_fd);
return -1;
}
err = kexec_file_load(kernel_fd, initrd_fd, strlen(cmdline) + 1,
cmdline, 0);
close(initrd_fd);
close(kernel_fd);
return err;
}
static int run_test(int stage)
{
char stage_arg[32];
int status;
pid_t pid;
snprintf(stage_arg, sizeof(stage_arg), "%d", stage);
pid = fork();
if (pid < 0)
return -1;
if (!pid) {
char *const argv[] = {TEST_BINARY, "-s", stage_arg, NULL};
execve(TEST_BINARY, argv, NULL);
fprintf(stderr, "INIT: execve failed\n");
_exit(1);
}
waitpid(pid, &status, 0);
return (WIFEXITED(status) && WEXITSTATUS(status) == 0) ? 0 : -1;
}
static int get_current_stage(void)
{
char cmdline[COMMAND_LINE_SIZE];
ssize_t len;
int fd;
fd = open("/proc/cmdline", O_RDONLY);
if (fd < 0)
return -1;
len = read(fd, cmdline, sizeof(cmdline) - 1);
close(fd);
if (len < 0)
return -1;
cmdline[len] = 0;
return strstr(cmdline, "luo_stage=2") ? 2 : 1;
}
int main(int argc, char *argv[])
{
int current_stage;
int err;
if (mount_filesystems())
goto err_reboot;
current_stage = get_current_stage();
if (current_stage < 0) {
fprintf(stderr, "INIT: Failed to read cmdline");
goto err_reboot;
}
printf("INIT: Starting Stage %d\n", current_stage);
if (current_stage == 1 && kexec_load()) {
fprintf(stderr, "INIT: Failed to load kexec kernel\n");
goto err_reboot;
}
if (run_test(current_stage)) {
fprintf(stderr, "INIT: Test binary returned failure\n");
goto err_reboot;
}
printf("INIT: Stage %d completed successfully.\n", current_stage);
reboot(current_stage == 1 ? RB_KEXEC : RB_AUTOBOOT);
return 0;
err_reboot:
reboot(RB_AUTOBOOT);
return -1;
}
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