Luna/apps/src/init.c

#include <luna.h>
#include <setjmp.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/stat.h>
#include <unistd.h>

int print_version()
{
    char version[4096];

    FILE* fp = fopen("/dev/version", "r");
    if (!fp)
    {
        perror("fopen");
        return 1;
    }

    size_t nread = fread(version, 4096, 1, fp);
    if (ferror(fp))
    {
        perror("fread");
        return 1;
    }

    version[nread] = 0;

    if (fclose(fp) < 0)
    {
        perror("fclose");
        return 1;
    }

    printf("Your kernel version is %s\n\n", version);

    return 0;
}

int main()
{
    if (getpid() != 1)
    {
        fprintf(stderr, "init should be started as PID 1\n");
        return 1;
    }

    FILE* serial = fopen("/dev/serial", "r");
    if (!serial)
    {
        perror("fopen");
        return 1;
    }
    if (fputs("Hello from init!\n", serial) < 0)
    {
        perror("fputs");
        return 1;
    }
    if (fclose(serial) < 0)
    {
        perror("fclose");
        return 1;
    }

    printf("Welcome to Luna!\n");

    printf("Running as PID %ld, PPID %ld\n\n", getpid(), getppid());

    sleep(1);

    if (print_version()) return 1;

    sleep(2);

    const char* filename = "/sys/config";

    printf("Opening %s for reading...\n", filename);

    FILE* config = fopen(filename, "r");
    if (!config)
    {
        perror("fopen");
        return 1;
    }

    if (fseek(config, 0, SEEK_END) < 0)
    {
        perror("fseek");
        return 1;
    }

    long offset = ftell(config);
    if (offset < 0)
    {
        perror("ftell");
        return 1;
    }

    printf("%s is %ld bytes long\n", filename, offset);

    rewind(config);

    char buf[4096];

    size_t nread = fread(buf, sizeof(buf), 1, config);
    if (ferror(config)) { perror("fread"); }
    else
    {
        buf[nread] = 0;

        printf("Read %zd bytes\n\n", nread);

        printf("%s", buf);
    }

    if (fclose(config) < 0) { perror("fclose"); }

    printf("\n\nGot random number %d\n\n", rand());

    sleep(2);

    printf("Press any key to restart.\n\n");

    int stderr_fd = fileno(stderr);
    int new_stderr_fd = dup(stderr_fd);
    if (new_stderr_fd < 0)
    {
        perror("dup");
        return 1;
    }
    FILE* new_stderr = fdopen(new_stderr_fd, "rw");
    if (!new_stderr)
    {
        perror("fdopen");
        return 1;
    }

    fprintf(new_stderr, "Bye!\n\n");

    fclose(new_stderr);

    const char* pathname = "/etc";

    printf("Creating directory %s\n", pathname);

    if (mkdir(pathname, 0) < 0)
    {
        perror("mkdir");
        return 1;
    }

    printf("Success!!\n");

    printf("Forking...\n");

    pid_t child = fork();

    if (child < 0)
    {
        perror("fork");
        return 1;
    }
    if (child == 0)
    {
        msleep(500);
        printf("I am the child (PID %ld), my parent is PID %ld!!\n", getpid(), getppid());
        execv("/bin/sym", NULL);
        perror("execv");
        return 1;
    }
    else { printf("Success!! Got PID %ld\n", child); }

    jmp_buf env;
    int val = setjmp(env);
    if (val == 0) { printf("Returning from setjmp!\n"); }
    else
    {
        printf("Returning from longjmp! val=%d\n", val);
        return 0;
    }

    longjmp(env, 3);
}