nt-lite/code/user/system/init/init.c

// init.c - first user-mode process
#include <stdint.h>
#include <stdbool.h>
#include <stddef.h>
#include <ntlite/syscall.h>

#define STATUS_SUCCESS 0u

void itoa(int num, char* str) {
    int i = 0;
    int is_negative = 0;

    // Handle 0 explicitly
    if (num == 0) {
        str[i++] = '0';
        str[i] = '\0';
        return;
    }

    // Handle negative numbers
    if (num < 0) {
        is_negative = 1;
        num = -num;
    }

    // Process individual digits (result is in reverse)
    while (num != 0) {
        int rem = num % 10;
        str[i++] = rem + '0';
        num = num / 10;
    }

    if (is_negative) {
        str[i++] = '-';
    }

    str[i] = '\0'; // Null terminate

    // Reverse the string
    int start = 0;
    int end = i - 1;
    while (start < end) {
        char temp = str[start];
        str[start] = str[end];
        str[end] = temp;
        start++;
        end--;
    }
}

static void debug_print(const char* s) {
    SYS_DEBUG_PRINT_REQUEST req = { SysSvFromCstr(s) };
    (void)SysDebugPrint(&req);
}

void _start(void)
{
    SYS_STRING_VIEW args = SysGetPeb()->CommandLine;
    uint32_t h = 0;
    uint32_t s = 0;

    while (true) {
        debug_print("[init] starting\n");
        SYS_CREATE_PROCESS_REQUEST cp = { args, SysSvFromParts(0, 0), &h };
        s = SysCreateProcess(&cp);
        if (s != STATUS_SUCCESS) {
            debug_print("[init] FATAL: failed to start!\n");
            char buffer[12];
            itoa(s, buffer);
            debug_print(buffer);
            debug_print("\n");
            SysExitProcess(1);
        }

        debug_print("[init] waiting\n");
        s = SysWaitForProcess(h);
        if (s != STATUS_SUCCESS)
            debug_print("[init] WARNING: SysWaitForProcess returned error\n");

        int exitCode = 0;
        if (SysGetProcessExitCode(h, &exitCode) != STATUS_SUCCESS) {
            debug_print("[init] WARNING: failed to read exit code\n");
            exitCode = 1;
        }

        SysCloseHandle(h);

        if (exitCode == 0)
            break;

        debug_print("[init] child crashed, restarting\n");
    }

    debug_print("[init] done\n");
    SysExitProcess(0);
}