build: replace hosted target with static linux and add kernel target

Co-authored-by: aider (openrouter/moonshotai/kimi-k2.6) <aider@aider.chat>

platform_kernel.c

@@ -0,0 +1,142 @@
+#include "forth.h"
+#include <stdint.h>
+#include <stdarg.h>
+
+// VGA text-mode buffer
+static uint16_t* vga_buffer = (uint16_t*)0xB8000;
+static int vga_row = 0;
+static int vga_col = 0;
+
+static void vga_putchar(char c) {
+    if (c == '\n') {
+        vga_col = 0;
+        vga_row++;
+    } else {
+        int idx = vga_row * 80 + vga_col;
+        vga_buffer[idx] = (uint16_t)((0x0F << 8) | (unsigned char)c);
+        vga_col++;
+        if (vga_col >= 80) {
+            vga_col = 0;
+            vga_row++;
+        }
+    }
+    if (vga_row >= 25) {
+        vga_row = 0;
+        vga_col = 0;
+    }
+}
+
+static inline void outb(uint16_t port, uint8_t val) {
+    __asm__ volatile ("outb %0, %1" : : "a"(val), "Nd"(port));
+}
+
+static inline uint8_t inb(uint16_t port) {
+    uint8_t ret;
+    __asm__ volatile ("inb %1, %0" : "=a"(ret) : "Nd"(port));
+    return ret;
+}
+
+static void serial_init(void) {
+    outb(0x3F8 + 1, 0x00);
+    outb(0x3F8 + 3, 0x80);
+    outb(0x3F8 + 0, 0x01);
+    outb(0x3F8 + 1, 0x00);
+    outb(0x3F8 + 3, 0x03);
+    outb(0x3F8 + 2, 0xC7);
+    outb(0x3F8 + 4, 0x0B);
+}
+
+void forth_putchar(char c) {
+    vga_putchar(c);
+    while ((inb(0x3F8 + 5) & 0x20) == 0) { }
+    outb(0x3F8, (uint8_t)c);
+}
+
+int forth_getchar(void) {
+    if ((inb(0x3F8 + 5) & 1) == 0) {
+        return FORTH_EOF;
+    }
+    return inb(0x3F8);
+}
+
+void forth_fflush(void) {
+}
+
+void forth_panic(void) {
+    __asm__ volatile ("cli; hlt");
+    __builtin_unreachable();
+}
+
+int64_t forth_strtoll(const char* str, char** endptr, int base) {
+    const char* s = str;
+    int neg = 0;
+    int64_t val = 0;
+    while (forth_isspace(*s)) s++;
+    if (*s == '-') { neg = 1; s++; }
+    else if (*s == '+') { s++; }
+    while (*s >= '0' && *s <= '9') {
+        val = val * base + (*s - '0');
+        s++;
+    }
+    if (endptr) *endptr = (char*)s;
+    return neg ? -val : val;
+}
+
+static void print_str(const char* s) {
+    while (*s) forth_putchar(*s++);
+}
+
+static void print_int(long long v) {
+    char buf[32];
+    int i = 30;
+    int neg = 0;
+    if (v < 0) { neg = 1; v = -v; }
+    buf[31] = '\0';
+    if (v == 0) {
+        buf[i--] = '0';
+    } else {
+        while (v > 0 && i >= 0) {
+            buf[i--] = '0' + (v % 10);
+            v /= 10;
+        }
+    }
+    if (neg) buf[i--] = '-';
+    print_str(&buf[i + 1]);
+}
+
+void forth_printf(const char* fmt, ...) {
+    va_list ap;
+    va_start(ap, fmt);
+    while (*fmt) {
+        if (*fmt == '%' && *(fmt + 1)) {
+            fmt++;
+            if (*fmt == 's') {
+                print_str(va_arg(ap, const char*));
+            } else if (*fmt == 'c') {
+                forth_putchar((char)va_arg(ap, int));
+            } else if (*fmt == '%') {
+                forth_putchar('%');
+            } else if (*fmt == 'l') {
+                if (*(fmt + 1) == 'l' && (*(fmt + 2) == 'd' || *(fmt + 2) == 'i' || *(fmt + 2) == 'u')) {
+                    fmt += 2;
+                    print_int(va_arg(ap, long long));
+                }
+            } else if (*fmt == 'd' || *fmt == 'i' || *fmt == 'u') {
+                print_int(va_arg(ap, int));
+            } else {
+                forth_putchar('%');
+                forth_putchar(*fmt);
+            }
+        } else {
+            forth_putchar(*fmt);
+        }
+        fmt++;
+    }
+    va_end(ap);
+}
+
+void kernel_main(void) {
+    serial_init();
+    forth_run();
+    forth_panic();
+}