fix: use correct multiboot2 framebuffer info tag type (8 not 5)

Co-authored-by: aider (openrouter/anthropic/claude-opus-4.7) <aider@aider.chat>

Makefile

@@ -1,19 +1,23 @@
-CC = gcc
-CFLAGS = -Wall -Wextra -g -std=c11 -D_POSIX_C_SOURCE=200809L
-LDFLAGS =
-SRCS = forth_core.c forth_dict.c forth_words.c forth_interp.c main.c
-OBJS = $(SRCS:.c=.o)
+CC = clang
+CFLAGS = -Wall -Wextra -g -std=c11
+COMMON_SRCS = forth_core.c forth_dict.c forth_words.c forth_interp.c main.c
+
+LINUX_SRCS = $(COMMON_SRCS) platform_linux.c
+KERNEL_SRCS = $(COMMON_SRCS) platform_kernel.c kernel_entry.S font8x8.c
+KERNEL_LD = kernel.ld
+
 TARGET = forth
+KERNEL_TARGET = forth.kernel
 
 all: $(TARGET)
 
-$(TARGET): $(OBJS)
-	$(CC) $(CFLAGS) -o $@ $^ $(LDFLAGS)
+$(TARGET): $(LINUX_SRCS) forth.h
+	$(CC) $(CFLAGS) -static -nostdlib -ffreestanding -fno-stack-protector -o $@ $(LINUX_SRCS)
 
-%.o: %.c forth.h
-	$(CC) $(CFLAGS) -c $< -o $@
+$(KERNEL_TARGET): $(KERNEL_SRCS) forth.h $(KERNEL_LD)
+	$(CC) $(CFLAGS) -ffreestanding -nostdlib -fno-stack-protector -mno-red-zone -fno-pie -no-pie -o $@ $(KERNEL_SRCS) -T$(KERNEL_LD) -Wl,--build-id=none
 
 clean:
-	rm -f $(OBJS) $(TARGET)
+	rm -f $(TARGET) $(KERNEL_TARGET)
 
 .PHONY: all clean

font8x8.c

@@ -0,0 +1,100 @@
+#include <stdint.h>
+
+const uint8_t font8x8[96][8] = {
+    {0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00}, /* 32 ' ' */
+    {0x18,0x18,0x18,0x18,0x18,0x00,0x18,0x00}, /* 33 '!' */
+    {0x66,0x66,0x66,0x00,0x00,0x00,0x00,0x00}, /* 34 '"' */
+    {0x66,0x66,0xFF,0x66,0xFF,0x66,0x66,0x00}, /* 35 '#' */
+    {0x18,0x3E,0x60,0x3C,0x06,0x7C,0x18,0x00}, /* 36 '$' */
+    {0x62,0x66,0x0C,0x18,0x30,0x66,0x46,0x00}, /* 37 '%' */
+    {0x3C,0x66,0x3C,0x38,0x67,0x66,0x3F,0x00}, /* 38 '&' */
+    {0x06,0x0C,0x18,0x00,0x00,0x00,0x00,0x00}, /* 39 ''' */
+    {0x0C,0x18,0x30,0x30,0x30,0x18,0x0C,0x00}, /* 40 '(' */
+    {0x30,0x18,0x0C,0x0C,0x0C,0x18,0x30,0x00}, /* 41 ')' */
+    {0x00,0x66,0x3C,0xFF,0x3C,0x66,0x00,0x00}, /* 42 '*' */
+    {0x00,0x18,0x18,0x7E,0x18,0x18,0x00,0x00}, /* 43 '+' */
+    {0x00,0x00,0x00,0x00,0x00,0x18,0x18,0x30}, /* 44 ',' */
+    {0x00,0x00,0x00,0x7E,0x00,0x00,0x00,0x00}, /* 45 '-' */
+    {0x00,0x00,0x00,0x00,0x00,0x18,0x18,0x00}, /* 46 '.' */
+    {0x00,0x03,0x06,0x0C,0x18,0x30,0x60,0x00}, /* 47 '/' */
+    {0x3C,0x66,0x6E,0x76,0x66,0x66,0x3C,0x00}, /* 48 '0' */
+    {0x18,0x18,0x38,0x18,0x18,0x18,0x7E,0x00}, /* 49 '1' */
+    {0x3C,0x66,0x06,0x0C,0x30,0x60,0x7E,0x00}, /* 50 '2' */
+    {0x3C,0x66,0x06,0x1C,0x06,0x66,0x3C,0x00}, /* 51 '3' */
+    {0x06,0x0E,0x1E,0x66,0x7F,0x06,0x06,0x00}, /* 52 '4' */
+    {0x7E,0x60,0x7C,0x06,0x06,0x66,0x3C,0x00}, /* 53 '5' */
+    {0x3C,0x60,0x60,0x7C,0x66,0x66,0x3C,0x00}, /* 54 '6' */
+    {0x7E,0x06,0x0C,0x18,0x30,0x30,0x30,0x00}, /* 55 '7' */
+    {0x3C,0x66,0x66,0x3C,0x66,0x66,0x3C,0x00}, /* 56 '8' */
+    {0x3C,0x66,0x66,0x3E,0x06,0x06,0x3C,0x00}, /* 57 '9' */
+    {0x00,0x00,0x18,0x00,0x00,0x18,0x00,0x00}, /* 58 ':' */
+    {0x00,0x00,0x18,0x00,0x00,0x18,0x18,0x30}, /* 59 ';' */
+    {0x0C,0x18,0x30,0x60,0x30,0x18,0x0C,0x00}, /* 60 '<' */
+    {0x00,0x00,0x7E,0x00,0x7E,0x00,0x00,0x00}, /* 61 '=' */
+    {0x30,0x18,0x0C,0x06,0x0C,0x18,0x30,0x00}, /* 62 '>' */
+    {0x3C,0x66,0x06,0x0C,0x18,0x00,0x18,0x00}, /* 63 '?' */
+    {0x3C,0x66,0x6E,0x6E,0x60,0x62,0x3C,0x00}, /* 64 '@' */
+    {0x18,0x3C,0x66,0x7E,0x66,0x66,0x66,0x00}, /* 65 'A' */
+    {0x7C,0x66,0x66,0x7C,0x66,0x66,0x7C,0x00}, /* 66 'B' */
+    {0x3C,0x66,0x60,0x60,0x60,0x66,0x3C,0x00}, /* 67 'C' */
+    {0x78,0x6C,0x66,0x66,0x66,0x6C,0x78,0x00}, /* 68 'D' */
+    {0x7E,0x60,0x60,0x78,0x60,0x60,0x7E,0x00}, /* 69 'E' */
+    {0x7E,0x60,0x60,0x78,0x60,0x60,0x60,0x00}, /* 70 'F' */
+    {0x3C,0x66,0x60,0x6E,0x66,0x66,0x3C,0x00}, /* 71 'G' */
+    {0x66,0x66,0x66,0x7E,0x66,0x66,0x66,0x00}, /* 72 'H' */
+    {0x3C,0x18,0x18,0x18,0x18,0x18,0x3C,0x00}, /* 73 'I' */
+    {0x1E,0x0C,0x0C,0x0C,0x0C,0x6C,0x38,0x00}, /* 74 'J' */
+    {0x66,0x6C,0x78,0x70,0x78,0x6C,0x66,0x00}, /* 75 'K' */
+    {0x60,0x60,0x60,0x60,0x60,0x60,0x7E,0x00}, /* 76 'L' */
+    {0x63,0x77,0x7F,0x6B,0x63,0x63,0x63,0x00}, /* 77 'M' */
+    {0x66,0x76,0x7E,0x7E,0x6E,0x66,0x66,0x00}, /* 78 'N' */
+    {0x3C,0x66,0x66,0x66,0x66,0x66,0x3C,0x00}, /* 79 'O' */
+    {0x7C,0x66,0x66,0x7C,0x60,0x60,0x60,0x00}, /* 80 'P' */
+    {0x3C,0x66,0x66,0x66,0x66,0x3C,0x0E,0x00}, /* 81 'Q' */
+    {0x7C,0x66,0x66,0x7C,0x78,0x6C,0x66,0x00}, /* 82 'R' */
+    {0x3C,0x66,0x60,0x3C,0x06,0x66,0x3C,0x00}, /* 83 'S' */
+    {0x7E,0x18,0x18,0x18,0x18,0x18,0x18,0x00}, /* 84 'T' */
+    {0x66,0x66,0x66,0x66,0x66,0x66,0x3C,0x00}, /* 85 'U' */
+    {0x66,0x66,0x66,0x66,0x66,0x3C,0x18,0x00}, /* 86 'V' */
+    {0x63,0x63,0x63,0x6B,0x7F,0x77,0x63,0x00}, /* 87 'W' */
+    {0x66,0x66,0x3C,0x18,0x3C,0x66,0x66,0x00}, /* 88 'X' */
+    {0x66,0x66,0x66,0x3C,0x18,0x18,0x18,0x00}, /* 89 'Y' */
+    {0x7E,0x06,0x0C,0x18,0x30,0x60,0x7E,0x00}, /* 90 'Z' */
+    {0x3C,0x30,0x30,0x30,0x30,0x30,0x3C,0x00}, /* 91 '[' */
+    {0x00,0x60,0x30,0x18,0x0C,0x06,0x03,0x00}, /* 92 '\' */
+    {0x3C,0x0C,0x0C,0x0C,0x0C,0x0C,0x3C,0x00}, /* 93 ']' */
+    {0x18,0x3C,0x66,0x00,0x00,0x00,0x00,0x00}, /* 94 '^' */
+    {0x00,0x00,0x00,0x00,0x00,0x00,0x7E,0x00}, /* 95 '_' */
+    {0x18,0x18,0x0C,0x00,0x00,0x00,0x00,0x00}, /* 96 '`' */
+    {0x00,0x00,0x3C,0x06,0x3E,0x66,0x3E,0x00}, /* 97 'a' */
+    {0x00,0x60,0x60,0x7C,0x66,0x66,0x7C,0x00}, /* 98 'b' */
+    {0x00,0x00,0x3C,0x60,0x60,0x60,0x3C,0x00}, /* 99 'c' */
+    {0x00,0x06,0x06,0x3E,0x66,0x66,0x3E,0x00}, /* 100 'd' */
+    {0x00,0x00,0x3C,0x66,0x7E,0x60,0x3C,0x00}, /* 101 'e' */
+    {0x00,0x0E,0x18,0x3E,0x18,0x18,0x18,0x00}, /* 102 'f' */
+    {0x00,0x00,0x3E,0x66,0x66,0x3E,0x06,0x7C}, /* 103 'g' */
+    {0x00,0x60,0x60,0x7C,0x66,0x66,0x66,0x00}, /* 104 'h' */
+    {0x00,0x18,0x00,0x38,0x18,0x18,0x3C,0x00}, /* 105 'i' */
+    {0x00,0x06,0x00,0x06,0x06,0x06,0x06,0x3C}, /* 106 'j' */
+    {0x00,0x60,0x60,0x6C,0x78,0x6C,0x66,0x00}, /* 107 'k' */
+    {0x00,0x38,0x18,0x18,0x18,0x18,0x3C,0x00}, /* 108 'l' */
+    {0x00,0x00,0x66,0x7F,0x6B,0x63,0x63,0x00}, /* 109 'm' */
+    {0x00,0x00,0x7C,0x66,0x66,0x66,0x66,0x00}, /* 110 'n' */
+    {0x00,0x00,0x3C,0x66,0x66,0x66,0x3C,0x00}, /* 111 'o' */
+    {0x00,0x00,0x7C,0x66,0x66,0x7C,0x60,0x60}, /* 112 'p' */
+    {0x00,0x00,0x3E,0x66,0x66,0x3E,0x06,0x06}, /* 113 'q' */
+    {0x00,0x00,0x7C,0x66,0x60,0x60,0x60,0x00}, /* 114 'r' */
+    {0x00,0x00,0x3E,0x60,0x3C,0x06,0x7C,0x00}, /* 115 's' */
+    {0x00,0x18,0x18,0x7E,0x18,0x18,0x0C,0x00}, /* 116 't' */
+    {0x00,0x00,0x66,0x66,0x66,0x66,0x3E,0x00}, /* 117 'u' */
+    {0x00,0x00,0x66,0x66,0x66,0x3C,0x18,0x00}, /* 118 'v' */
+    {0x00,0x00,0x63,0x6B,0x7F,0x3E,0x36,0x00}, /* 119 'w' */
+    {0x00,0x00,0x66,0x3C,0x18,0x3C,0x66,0x00}, /* 120 'x' */
+    {0x00,0x00,0x66,0x66,0x66,0x3E,0x0C,0x78}, /* 121 'y' */
+    {0x00,0x00,0x7E,0x0C,0x18,0x30,0x7E,0x00}, /* 122 'z' */
+    {0x0C,0x18,0x18,0x30,0x18,0x18,0x0C,0x00}, /* 123 '{' */
+    {0x18,0x18,0x18,0x18,0x18,0x18,0x18,0x00}, /* 124 '|' */
+    {0x30,0x18,0x18,0x0C,0x18,0x18,0x30,0x00}, /* 125 '}' */
+    {0x00,0x00,0x66,0x3C,0x00,0x00,0x00,0x00}, /* 126 '~' */
+    {0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00}, /* 127 DEL */
+};

forth.h

@@ -1,29 +1,46 @@
 #ifndef FORTH_H
 #define FORTH_H
 
-#include <stdio.h>
-#include <stdlib.h>
-#include <string.h>
-#include <ctype.h>
 #include <stdint.h>
-#include <inttypes.h>
+#include <stddef.h>
+#include <stdarg.h>
 
 // Configuration (all hard limits removed)
 #define MAX_NAME_LEN 31
+#define FORTH_EOF (-1)
 
-/* Portable panic hook. Override for bare-metal reset/handling. */
-#ifndef forth_panic
-#define forth_panic() do { for (;;) ; } while (0)
-#endif
+/* Platform interface -- must be provided by the target platform layer. */
+void forth_putchar(char c);
+int forth_getchar(void);
+void forth_printf(const char* fmt, ...);
+void forth_fflush(void);
+void forth_panic(void);
 
-/* Portable I/O hooks. Define FORTH_CUSTOM_IO before including this header
- * to provide bare-metal UART (or other) implementations. */
-#ifndef FORTH_CUSTOM_IO
-#define forth_putchar(c) putchar(c)
-#define forth_getchar() getchar()
-#define forth_printf(...) printf(__VA_ARGS__)
-#define forth_fflush() fflush(stdout)
-#endif
+/* Platform string-to-number (base 10 is required). */
+int64_t forth_strtoll(const char* str, char** endptr, int base);
+
+/* Portable character classification. */
+static inline int forth_isspace(int c) {
+    return c == ' ' || c == '\t' || c == '\n' || c == '\r' || c == '\f' || c == '\v';
+}
+
+/* Portable string operations. */
+static inline size_t forth_strlen(const char* s) {
+    size_t n = 0;
+    while (s[n]) n++;
+    return n;
+}
+
+static inline void forth_memcpy(void* dst, const void* src, size_t n) {
+    char* d = dst;
+    const char* s = src;
+    while (n--) *d++ = *s++;
+}
+
+static inline int forth_strcmp(const char* a, const char* b) {
+    while (*a && *a == *b) { a++; b++; }
+    return (unsigned char)*a - (unsigned char)*b;
+}
 
 /* Static memory sizes (override before including forth.h) */
 #ifndef FORTH_DATA_STACK_SIZE
@@ -105,6 +122,9 @@ extern Word* w_branch;
 extern Word* w_zbranch;
 extern Word* w_dot_quote_inner;
 
+// Entry point
+void forth_run(void);
+
 // Core function prototypes
 void data_push(int64_t val);
 int64_t data_pop(void);
@@ -184,6 +204,14 @@ void do_dot_quote(Word* w);
 void do_dot_quote_inner(Word* w);
 void do_words(Word* w);
 
+// Framebuffer
+void do_fb_addr(Word* w);
+void do_fb_width(Word* w);
+void do_fb_height(Word* w);
+void do_fb_pitch(Word* w);
+void do_fb_bpp(Word* w);
+void do_fb_plot(Word* w);
+
 // Memory
 void do_fetch(Word* w);
 void do_store(Word* w);
@@ -196,6 +224,7 @@ void do_do_var(Word* w);
 void do_do_const(Word* w);
 void do_here(Word* w);
 void do_allot(Word* w);
+void do_comma(Word* w);
 
 // Return stack
 void do_to_r(Word* w);

forth_core.c

@@ -1,13 +1,21 @@
 #include "forth.h"
 
 // Static storage for bare-metal portability
+#ifndef FORTH_CUSTOM_MEMORY
 static int64_t data_stack_storage[FORTH_DATA_STACK_SIZE];
 int64_t *data_stack = data_stack_storage;
+#else
+int64_t *data_stack;
+#endif
 int32_t data_sp = -1;
 int32_t data_cap = FORTH_DATA_STACK_SIZE;
 
+#ifndef FORTH_CUSTOM_MEMORY
 static Cell ret_stack_storage[FORTH_RET_STACK_SIZE];
 Cell *ret_stack = ret_stack_storage;
+#else
+Cell *ret_stack;
+#endif
 int32_t rp = -1;
 int32_t ret_cap = FORTH_RET_STACK_SIZE;
 Cell* ip = NULL;
@@ -16,8 +24,12 @@ Word* dict_head = NULL;
 
 int state = 0;
 
+#ifndef FORTH_CUSTOM_MEMORY
 static Cell compile_buf_storage[FORTH_COMPILE_BUF_SIZE];
 Cell *compile_buf = compile_buf_storage;
+#else
+Cell *compile_buf;
+#endif
 int32_t compile_idx = 0;
 int32_t compile_cap = FORTH_COMPILE_BUF_SIZE;
 char compiling_name[MAX_NAME_LEN + 1] = {0};
@@ -26,15 +38,24 @@ char* input_buf = NULL;
 size_t input_buf_cap = 0;
 char* input_ptr = NULL;
 
+#ifndef FORTH_CUSTOM_MEMORY
 static int64_t compile_stack_storage[FORTH_COMPILE_STACK_SIZE];
 int64_t *compile_stack = compile_stack_storage;
+#else
+int64_t *compile_stack;
+#endif
 int32_t compile_sp = -1;
 int32_t compile_stack_cap = FORTH_COMPILE_STACK_SIZE;
 
+#ifndef FORTH_CUSTOM_MEMORY
 static Cell user_mem_storage[FORTH_USER_MEM_CELLS];
 Cell *user_mem = user_mem_storage;
-int64_t user_mem_size = FORTH_USER_MEM_CELLS;
 Cell* here = user_mem_storage;
+#else
+Cell *user_mem;
+Cell* here;
+#endif
+int64_t user_mem_size = FORTH_USER_MEM_CELLS;
 
 Word* w_exit = NULL;
 Word* w_docolon = NULL;
@@ -78,7 +99,7 @@ void data_push(int64_t val) {
 
 int64_t data_pop(void) {
     if (data_sp < 0) {
-        fprintf(stderr, "Data stack underflow\n");
+        forth_printf("Data stack underflow\n");
         return 0;
     }
     return data_stack[data_sp--];

forth_dict.c

@@ -5,10 +5,10 @@ Word* add_primitive(const char* name, void (*code)(Word*), uint8_t flags) {
     w->prev = dict_head;
     dict_head = w;
 
-    size_t len = strlen(name);
+    size_t len = forth_strlen(name);
     if (len > MAX_NAME_LEN) len = MAX_NAME_LEN;
     w->flags = flags | (uint8_t)len;
-    memcpy(w->name, name, len);
+    forth_memcpy(w->name, name, len);
     w->name[len] = '\0';
     w->code = code;
     w->body = NULL;
@@ -18,14 +18,14 @@ Word* add_primitive(const char* name, void (*code)(Word*), uint8_t flags) {
 Word* lookup_word(const char* name) {
     for (Word* w = dict_head; w != NULL; w = w->prev) {
         if (w->flags & (1 << 6)) continue;
-        if (strcmp(w->name, name) == 0) return w;
+        if (forth_strcmp(w->name, name) == 0) return w;
     }
     return NULL;
 }
 
 Word* lookup_word_internal(const char* name) {
     for (Word* w = dict_head; w != NULL; w = w->prev) {
-        if (strcmp(w->name, name) == 0) return w;
+        if (forth_strcmp(w->name, name) == 0) return w;
     }
     return NULL;
 }

forth_interp.c

@@ -3,12 +3,12 @@
 // Input tokenizer (unchanged)
 char* next_token(void) {
     if (input_ptr == NULL) return NULL;
-    while (*input_ptr != '\0' && isspace((unsigned char)*input_ptr)) {
+    while (*input_ptr != '\0' && forth_isspace((unsigned char)*input_ptr)) {
         input_ptr++;
     }
     if (*input_ptr == '\0') return NULL;
     char* start = input_ptr;
-    while (*input_ptr != '\0' && !isspace((unsigned char)*input_ptr)) {
+    while (*input_ptr != '\0' && !forth_isspace((unsigned char)*input_ptr)) {
         input_ptr++;
     }
     if (*input_ptr != '\0') {
@@ -63,10 +63,10 @@ void process_token(const char* token) {
         }
     } else { // Try to parse as number
         char* end;
-        long long v = strtoll(token, &end, 10);
+        int64_t v = forth_strtoll(token, &end, 10);
         if (end != token && *end == '\0') {
             if (state == 0) {
-                data_push((int64_t)v);
+                data_push(v);
             } else { // Compile lit + number
                 if (!w_lit) {
                     forth_printf("Fatal: lit word not found\n");
@@ -87,15 +87,21 @@ void outer_interpreter(void) {
     while (1) {
         forth_printf("ok ");
         forth_fflush();
-        if (fgets(line_buf, sizeof(line_buf), stdin) == NULL) {
+        size_t i = 0;
+        int c;
+        while (i < sizeof(line_buf) - 1) {
+            c = forth_getchar();
+            if (c == FORTH_EOF || c == '\n' || c == '\r') {
+                break;
+            }
+            line_buf[i++] = (char)c;
+        }
+        line_buf[i] = '\0';
+        if (i == 0 && c == FORTH_EOF) {
             break;
         }
         input_buf = line_buf;
         input_buf_cap = sizeof(line_buf);
-        size_t n = strlen(input_buf);
-        if (n > 0 && input_buf[n - 1] == '\n') {
-            input_buf[n - 1] = '\0';
-        }
         input_ptr = input_buf;
         char* tok;
         while ((tok = next_token()) != NULL) {

forth_words.c

@@ -309,7 +309,7 @@ void do_zero_gt(Word* w) {
 void do_dot(Word* w) {
     (void)w;
     if (data_sp < 0) return;
-    forth_printf("%" PRId64 " ", data_pop());
+    forth_printf("%lld ", (long long)data_pop());
     forth_fflush();
 }
 
@@ -329,7 +329,7 @@ void do_emit(Word* w) {
 void do_key(Word* w) {
     (void)w;
     int c = forth_getchar();
-    data_push(c == EOF ? -1 : c);
+    data_push(c == FORTH_EOF ? -1 : c);
 }
 
 void do_dot_quote(Word* w) {
@@ -337,7 +337,7 @@ void do_dot_quote(Word* w) {
     if (state == 0) {
         // Interpret mode: print immediately
         if (input_ptr == NULL) { forth_printf("Missing string\n"); return; }
-        while (*input_ptr && isspace((unsigned char)*input_ptr)) input_ptr++;
+        while (*input_ptr && forth_isspace((unsigned char)*input_ptr)) input_ptr++;
         if (*input_ptr != '"') { forth_printf("Expected \" to start string\n"); return; }
         input_ptr++;
         char* start = input_ptr;
@@ -349,7 +349,7 @@ void do_dot_quote(Word* w) {
     } else {
         // Compile mode: compile string for runtime
         if (input_ptr == NULL) { forth_printf("Missing string\n"); return; }
-        while (*input_ptr && isspace((unsigned char)*input_ptr)) input_ptr++;
+        while (*input_ptr && forth_isspace((unsigned char)*input_ptr)) input_ptr++;
         if (*input_ptr != '"') { forth_printf("Expected \" to start string\n"); return; }
         input_ptr++;
         char* start = input_ptr;
@@ -456,13 +456,25 @@ void do_here(Word* w) {
 void do_allot(Word* w) {
     (void)w;
     int64_t n = data_pop();
-    if (here + n > user_mem + user_mem_size) {
-        forth_printf("User memory overflow\n");
+    int64_t idx = here - user_mem;
+    if (idx + n < 0 || idx + n > user_mem_size) {
+        forth_printf("User memory out of bounds\n");
         return;
     }
     here += n;
 }
 
+void do_comma(Word* w) {
+    (void)w;
+    int64_t val = data_pop();
+    if (here + 1 > user_mem + user_mem_size) {
+        forth_printf("User memory overflow\n");
+        return;
+    }
+    here->num = val;
+    here++;
+}
+
 // Variable and constant
 void do_variable(Word* w) {
     (void)w;
@@ -483,10 +495,10 @@ void do_variable(Word* w) {
     new_w->prev = dict_head;
     dict_head = new_w;
 
-    size_t len = strlen(name);
+    size_t len = forth_strlen(name);
     if (len > MAX_NAME_LEN) len = MAX_NAME_LEN;
     new_w->flags = (uint8_t)len;
-    memcpy(new_w->name, name, len);
+    forth_memcpy(new_w->name, name, len);
     new_w->name[len] = '\0';
     new_w->code = do_do_var;
     new_w->body = var_cell;   // body points directly to the data cell in user_mem
@@ -512,10 +524,10 @@ void do_constant(Word* w) {
     new_w->prev = dict_head;
     dict_head = new_w;
 
-    size_t len = strlen(name);
+    size_t len = forth_strlen(name);
     if (len > MAX_NAME_LEN) len = MAX_NAME_LEN;
     new_w->flags = (uint8_t)len;
-    memcpy(new_w->name, name, len);
+    forth_memcpy(new_w->name, name, len);
     new_w->name[len] = '\0';
     new_w->code = do_do_const;
     new_w->body = val_cell;   // body points to the cell that holds the value
@@ -571,9 +583,9 @@ void do_colon(Word* w) {
     (void)w;
     char* name = next_token();
     if (!name) { forth_printf("':' expects a name\n"); return; }
-    size_t len = strlen(name);
+    size_t len = forth_strlen(name);
     if (len > MAX_NAME_LEN) len = MAX_NAME_LEN;
-    memcpy(compiling_name, name, len);
+    forth_memcpy(compiling_name, name, len);
     compiling_name[len] = '\0';
     state = 1;
     compile_idx = 0;
@@ -591,7 +603,7 @@ void do_semicolon(Word* w) {
     // Create body copy of compiled cells
     Cell* body_copy = forth_alloc_body(compile_idx);
     if (!body_copy) { forth_printf("Out of memory\n"); return; }
-    memcpy(body_copy, compile_buf, compile_idx * sizeof(Cell));
+    forth_memcpy(body_copy, compile_buf, compile_idx * sizeof(Cell));
 
     // Create new word entry
     Word* new_w = forth_alloc_word();
@@ -599,10 +611,10 @@ void do_semicolon(Word* w) {
     new_w->prev = dict_head;
     dict_head = new_w;
 
-    size_t len = strlen(compiling_name);
+    size_t len = forth_strlen(compiling_name);
     if (len > MAX_NAME_LEN) len = MAX_NAME_LEN;
     new_w->flags = (uint8_t)len;   // no hidden, no immediate
-    memcpy(new_w->name, compiling_name, len);
+    forth_memcpy(new_w->name, compiling_name, len);
     new_w->name[len] = '\0';
     new_w->code = do_docolon;
     new_w->body = body_copy;
@@ -680,7 +692,8 @@ void do_until(Word* w) {
     if (!w_zbranch) { forth_printf("Fatal: 0branch not found\n"); return; }
     if (!ensure_compile_cap(2)) return;
     compile_buf[compile_idx++] = (Cell){.word = w_zbranch};
-    compile_buf[compile_idx++] = (Cell){.num = begin_idx - compile_idx};
+    compile_buf[compile_idx] = (Cell){.num = begin_idx - compile_idx};
+    compile_idx++;
 }
 
 void do_while(Word* w) {
@@ -710,7 +723,8 @@ void do_repeat(Word* w) {
     if (!w_branch) { forth_printf("Fatal: branch not found\n"); return; }
     if (!ensure_compile_cap(2)) return;
     compile_buf[compile_idx++] = (Cell){.word = w_branch};
-    compile_buf[compile_idx++] = (Cell){.num = begin_idx - compile_idx};
+    compile_buf[compile_idx] = (Cell){.num = begin_idx - compile_idx};
+    compile_idx++;
 
     compile_buf[while_offset_idx].num = compile_idx - while_offset_idx;
 }

kernel.ld

@@ -0,0 +1,35 @@
+ENTRY(_start)
+
+SECTIONS
+{
+    . = 0x100000;
+
+    .text : ALIGN(4K)
+    {
+        *(.multiboot2)
+        *(.text)
+    }
+
+    .rodata : ALIGN(4K)
+    {
+        *(.rodata)
+    }
+
+    .data : ALIGN(4K)
+    {
+        *(.data)
+    }
+
+    .bss : ALIGN(4K)
+    {
+        __bss_start = .;
+        *(.bss)
+        *(COMMON)
+        __bss_end = .;
+    }
+
+    .note : ALIGN(4)
+    {
+        *(.note.Xen)
+    }
+}

kernel_entry.S

@@ -0,0 +1,184 @@
+# Multiboot2 header and x86_64 long-mode bootstrap
+
+.section .multiboot2, "a"
+.align 8
+multiboot_header:
+    .long 0xe85250d6
+    .long 0
+    .long multiboot_header_end - multiboot_header
+    .long -(0xe85250d6 + 0 + (multiboot_header_end - multiboot_header))
+
+    /* Framebuffer tag: type=5, size=20, width=height=0 (any), depth=32.
+     * Layout per multiboot2 spec:
+     *   u16 type, u16 flags, u32 size, u32 width, u32 height, u32 depth
+     * Padded to 8-byte alignment. */
+    .align 8
+    .word 5
+    .word 0
+    .long 20
+    .long 0
+    .long 0
+    .long 32
+    .long 0       /* padding to 8-byte alignment */
+
+    .align 8
+    .word 0
+    .word 0
+    .long 8
+multiboot_header_end:
+
+.section .bss, "aw", @nobits
+.align 4096
+pml4:
+    .space 4096
+pdpt:
+    .space 4096
+pd:
+    .space 4096 * 4
+
+.align 16
+stack_bottom:
+    .space 16384
+stack_top:
+
+.align 8
+mboot_info_ptr:
+    .space 8
+
+.section .text
+.code32
+.global _start
+.type _start, @function
+_start:
+    movl $stack_top, %esp
+    movl %ebx, mboot_info_ptr
+
+    cld
+    movl $__bss_start, %edi
+    movl $__bss_end, %ecx
+    subl %edi, %ecx
+    xorl %eax, %eax
+    rep stosb
+
+    movl $pdpt, %eax
+    orl $0x03, %eax
+    movl %eax, pml4
+
+    /* Populate 4 PDPT entries, each pointing to one of 4 PDs.
+     * This identity-maps the first 4 GiB using 2 MiB pages,
+     * which covers typical framebuffer/MMIO regions. */
+    movl $pd, %eax
+    orl $0x03, %eax
+    movl %eax, pdpt + 0
+    addl $4096, %eax
+    movl %eax, pdpt + 8
+    addl $4096, %eax
+    movl %eax, pdpt + 16
+    addl $4096, %eax
+    movl %eax, pdpt + 24
+
+    movl $0x00000083, %eax
+    movl $pd, %edi
+    movl $2048, %ecx
+1:
+    movl %eax, (%edi)
+    addl $0x200000, %eax
+    addl $8, %edi
+    loop 1b
+
+    movl $pml4, %eax
+    movl %eax, %cr3
+
+    movl %cr4, %eax
+    orl $0x20, %eax
+    movl %eax, %cr4
+
+    movl $0xC0000080, %ecx
+    rdmsr
+    orl $0x100, %eax
+    wrmsr
+
+    movl %cr0, %eax
+    orl $0x80000000, %eax
+    movl %eax, %cr0
+
+    lgdt gdt64_pointer
+    ljmp $0x08, $long_mode_start
+
+.code64
+long_mode_start:
+    /* Load data segment registers with the data descriptor (0x10).
+     * In long mode most of these are ignored for access checks, but
+     * %ss must be a valid (or null) selector so that iretq from an
+     * interrupt can safely reload it. */
+    movw $0x10, %ax
+    movw %ax, %ds
+    movw %ax, %es
+    movw %ax, %fs
+    movw %ax, %gs
+    movw %ax, %ss
+
+    movabsq $stack_top, %rax
+    movq %rax, %rsp
+    /* Ensure 16-byte alignment for the System V AMD64 ABI. */
+    andq $-16, %rsp
+
+    movq mboot_info_ptr, %rdi
+    call kernel_main
+    cli
+1:
+    hlt
+    jmp 1b
+
+.code64
+.global isr_keyboard
+.align 16
+isr_keyboard:
+    /* Save all caller-saved registers used by the SysV AMD64 ABI. */
+    pushq %rax
+    pushq %rcx
+    pushq %rdx
+    pushq %rsi
+    pushq %rdi
+    pushq %r8
+    pushq %r9
+    pushq %r10
+    pushq %r11
+    /* On interrupt entry the CPU pushed 5 qwords (40 bytes), and we
+     * pushed 9 more (72 bytes) = 112 bytes total. That leaves %rsp
+     * misaligned by 8 relative to a 16-byte boundary after the
+     * upcoming `call`. Push one dummy qword to realign. */
+    subq $8, %rsp
+    cld
+    call keyboard_handler
+    addq $8, %rsp
+    popq %r11
+    popq %r10
+    popq %r9
+    popq %r8
+    popq %rdi
+    popq %rsi
+    popq %rdx
+    popq %rcx
+    popq %rax
+    iretq
+
+.section .note.Xen, "a", @note
+.align 4
+.long 4
+.long 4
+.long 18
+.asciz "Xen"
+.align 4
+.long _start
+
+.section .rodata
+.align 8
+gdt64:
+    .quad 0x0000000000000000         /* 0x00: null descriptor         */
+    .quad 0x00209A0000000000         /* 0x08: 64-bit code, DPL=0      */
+    .quad 0x0000920000000000         /* 0x10: data, writable, present */
+gdt64_end:
+gdt64_pointer:
+    .word gdt64_end - gdt64 - 1
+    .quad gdt64

main.c

@@ -1,6 +1,6 @@
 #include "forth.h"
 
-int main(void) {
+void forth_run(void) {
     here = user_mem;
 
     // Hidden words first
@@ -65,6 +65,14 @@ int main(void) {
     add_primitive(".\"",   do_dot_quote, F_IMMEDIATE); // immediate
     add_primitive("words", do_words, 0);
 
+    // Framebuffer
+    add_primitive("fb-addr",  do_fb_addr, 0);
+    add_primitive("fb-width", do_fb_width, 0);
+    add_primitive("fb-height", do_fb_height, 0);
+    add_primitive("fb-pitch", do_fb_pitch, 0);
+    add_primitive("fb-bpp",   do_fb_bpp, 0);
+    add_primitive("fb-plot",  do_fb_plot, 0);
+
     // Memory
     add_primitive("@",  do_fetch, 0);
     add_primitive("!",  do_store, 0);
@@ -75,6 +83,7 @@ int main(void) {
     add_primitive("constant", do_constant, 0);
     add_primitive("here",  do_here, 0);
     add_primitive("allot", do_allot, 0);
+    add_primitive(",",     do_comma, 0);
 
     // Return stack
     add_primitive(">r", do_to_r, 0);
@@ -103,5 +112,4 @@ int main(void) {
 
     // Start outer interpreter
     outer_interpreter();
-    return 0;
 }

platform_kernel.c

@@ -0,0 +1,397 @@
+#include "forth.h"
+#include <stdint.h>
+#include <stdarg.h>
+
+extern const uint8_t font8x8[96][8];
+
+struct mboot_tag {
+    uint32_t type;
+    uint32_t size;
+};
+
+struct mboot_tag_framebuffer {
+    uint32_t type;
+    uint32_t size;
+    uint64_t framebuffer_addr;
+    uint32_t framebuffer_pitch;
+    uint32_t framebuffer_width;
+    uint32_t framebuffer_height;
+    uint8_t framebuffer_bpp;
+    uint8_t framebuffer_type;
+    uint16_t reserved;
+};
+
+static uint64_t fb_addr = 0;
+static uint32_t fb_pitch = 0;
+static uint32_t fb_width = 0;
+static uint32_t fb_height = 0;
+static uint8_t fb_bpp = 0;
+static int fb_cols = 0;
+static int fb_rows = 0;
+static int fb_col = 0;
+static int fb_row = 0;
+
+static void fb_draw_pixel(int x, int y, uint32_t color) {
+    if (x < 0 || y < 0 || (uint32_t)x >= fb_width || (uint32_t)y >= fb_height) return;
+    if (!fb_addr) return;
+    if (fb_bpp == 32) {
+        uint32_t* p = (uint32_t*)(fb_addr + y * fb_pitch + x * 4);
+        *p = color;
+    } else if (fb_bpp == 24) {
+        uint8_t* p = (uint8_t*)(fb_addr + y * fb_pitch + x * 3);
+        p[0] = color & 0xFF;
+        p[1] = (color >> 8) & 0xFF;
+        p[2] = (color >> 16) & 0xFF;
+    }
+}
+
+static void fb_scroll(void) {
+    int line_height = 8;
+    uint32_t bytes_per_pixel = (fb_bpp + 7) / 8;
+    uint32_t copy_bytes = fb_width * bytes_per_pixel;
+    for (uint32_t y = 0; y < fb_height - line_height; y++) {
+        uint8_t* dst = (uint8_t*)(fb_addr + y * fb_pitch);
+        uint8_t* src = (uint8_t*)(fb_addr + (y + line_height) * fb_pitch);
+        for (uint32_t i = 0; i < copy_bytes; i++) {
+            dst[i] = src[i];
+        }
+    }
+    for (uint32_t y = fb_height - line_height; y < fb_height; y++) {
+        uint8_t* row = (uint8_t*)(fb_addr + y * fb_pitch);
+        for (uint32_t i = 0; i < copy_bytes; i++) {
+            row[i] = 0;
+        }
+    }
+}
+
+static void fb_draw_char(char c) {
+    if (!fb_addr || fb_cols == 0) return;
+    if (c == '\n') {
+        fb_col = 0;
+        fb_row++;
+    } else if (c == '\r') {
+        fb_col = 0;
+    } else if (c == '\b') {
+        if (fb_col > 0) fb_col--;
+    } else {
+        unsigned char ch = (unsigned char)c;
+        if (ch < 32 || ch > 126) ch = '?';
+        const uint8_t* glyph = font8x8[ch - 32];
+        int start_x = fb_col * 8;
+        int start_y = fb_row * 8;
+        for (int dy = 0; dy < 8; dy++) {
+            uint8_t row = glyph[dy];
+            for (int dx = 0; dx < 8; dx++) {
+                if (row & (0x80 >> dx)) {
+                    fb_draw_pixel(start_x + dx, start_y + dy, 0xFFFFFF);
+                } else {
+                    fb_draw_pixel(start_x + dx, start_y + dy, 0x000000);
+                }
+            }
+        }
+        fb_col++;
+    }
+    if (fb_col >= fb_cols) {
+        fb_col = 0;
+        fb_row++;
+    }
+    if (fb_row >= fb_rows) {
+        fb_scroll();
+        fb_row = fb_rows - 1;
+    }
+}
+
+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 inline void io_wait(void) {
+    __asm__ volatile ("outb %0, %1" : : "a"((uint8_t)0), "Nd"((uint16_t)0x80));
+}
+
+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);
+}
+
+/* Each 64-bit IDT entry is 16 bytes = two uint64_t words.
+ *
+ * Word 0 layout:
+ *   [15: 0] offset[15:0]
+ *   [31:16] segment selector
+ *   [34:32] IST (0 = no IST)
+ *   [39:35] reserved (0)
+ *   [47:40] type+attr  (0x8E = present, DPL=0, 64-bit interrupt gate)
+ *   [63:48] offset[31:16]
+ *
+ * Word 1 layout:
+ *   [31: 0] offset[63:32]
+ *   [63:32] reserved (0)
+ */
+typedef struct {
+    uint64_t low;
+    uint64_t high;
+} __attribute__((packed)) IdtEntry;
+
+static IdtEntry idt_entries[256];
+
+static void idt_set_gate(int vector, uint64_t offset, uint16_t selector, uint8_t type_attr) {
+    uint64_t low =
+        (offset & 0x000000000000FFFFULL)          |   /* offset[15:0]  */
+        ((uint64_t)selector          << 16)        |   /* selector      */
+        /* bits 34:32 = IST=0, bits 39:35 = 0 */
+        ((uint64_t)type_attr         << 40)        |   /* type+attr     */
+        ((offset  & 0x00000000FFFF0000ULL) << 32); /* offset[31:16] */
+    uint64_t high = offset >> 32;                      /* offset[63:32] */
+    idt_entries[vector].low  = low;
+    idt_entries[vector].high = high;
+}
+
+static struct {
+    uint16_t limit;
+    uint64_t base;
+} __attribute__((packed)) idt_ptr;
+
+static void pic_remap(void) {
+    uint8_t a1 = inb(0x21);
+    uint8_t a2 = inb(0xA1);
+
+    outb(0x20, 0x11);
+    io_wait();
+    outb(0xA0, 0x11);
+    io_wait();
+    outb(0x21, 0x20);
+    io_wait();
+    outb(0xA1, 0x28);
+    io_wait();
+    outb(0x21, 0x04);
+    io_wait();
+    outb(0xA1, 0x02);
+    io_wait();
+    outb(0x21, 0x01);
+    io_wait();
+    outb(0xA1, 0x01);
+    io_wait();
+
+    outb(0x21, a1);
+    outb(0xA1, a2);
+}
+
+static void pic_unmask_keyboard(void) {
+    uint8_t mask = inb(0x21);
+    mask &= ~(1 << 1);
+    outb(0x21, mask);
+}
+
+#define KEYBUF_SIZE 256
+static volatile char keybuf[KEYBUF_SIZE];
+static volatile int keybuf_head = 0;
+static volatile int keybuf_tail = 0;
+
+static const char scancode_map[] = {
+    0,  27, '1', '2', '3', '4', '5', '6', '7', '8', '9', '0', '-', '=', '\b',
+    '\t', 'q', 'w', 'e', 'r', 't', 'y', 'u', 'i', 'o', 'p', '[', ']', '\n',
+    0, 'a', 's', 'd', 'f', 'g', 'h', 'j', 'k', 'l', ';', '\'', '`',
+    0, '\\', 'z', 'x', 'c', 'v', 'b', 'n', 'm', ',', '.', '/', 0,
+    '*', 0, ' ', 0
+};
+
+void keyboard_handler(void) {
+    uint8_t scancode = inb(0x60);
+    if (scancode < sizeof(scancode_map)) {
+        char c = scancode_map[scancode];
+        if (c) {
+            int next = (keybuf_tail + 1) % KEYBUF_SIZE;
+            if (next != keybuf_head) {
+                keybuf[keybuf_tail] = c;
+                keybuf_tail = next;
+                forth_putchar(c);
+            }
+        }
+    }
+    outb(0x20, 0x20);
+}
+
+void forth_putchar(char c) {
+    fb_draw_char(c);
+    while ((inb(0x3F8 + 5) & 0x20) == 0) { }
+    outb(0x3F8, (uint8_t)c);
+}
+
+int forth_getchar(void) {
+    while (keybuf_head == keybuf_tail) {
+        __asm__ volatile ("pause");
+    }
+    char c = keybuf[keybuf_head];
+    keybuf_head = (keybuf_head + 1) % KEYBUF_SIZE;
+    return (int)c;
+}
+
+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(uint64_t mboot_ptr) {
+    extern void isr_keyboard(void);
+
+    /* Multiboot2 info tag types:
+     *   5 = BIOS boot device, 6 = memory map, 8 = framebuffer info, ...
+     * Note: in the *header* (request side), type 5 means "framebuffer
+     * request", but the bootloader's *response* tag uses type 8. */
+    struct mboot_tag* tag = (struct mboot_tag*)(mboot_ptr + 8);
+    while (tag->type != 0) {
+        if (tag->type == 8) {
+            struct mboot_tag_framebuffer* fb = (struct mboot_tag_framebuffer*)tag;
+            fb_addr = fb->framebuffer_addr;
+            fb_pitch = fb->framebuffer_pitch;
+            fb_width = fb->framebuffer_width;
+            fb_height = fb->framebuffer_height;
+            fb_bpp = fb->framebuffer_bpp;
+        }
+        tag = (struct mboot_tag*)((uint8_t*)tag + ((tag->size + 7) & ~7));
+    }
+
+    if (fb_addr && fb_bpp >= 24) {
+        fb_cols = fb_width / 8;
+        fb_rows = fb_height / 8;
+        for (uint32_t y = 0; y < fb_height; y++) {
+            for (uint32_t x = 0; x < fb_width; x++) {
+                fb_draw_pixel(x, y, 0);
+            }
+        }
+    }
+
+    serial_init();
+
+    idt_set_gate(0x21, (uint64_t)isr_keyboard, 0x08, 0x8E);
+    idt_ptr.limit = (uint16_t)(sizeof(idt_entries) - 1);
+    idt_ptr.base  = (uint64_t)(uintptr_t)idt_entries;
+    __asm__ volatile ("lidt %0" : : "m"(idt_ptr));
+
+    pic_remap();
+    outb(0x21, 0xFF); // mask all IRQs on master
+    outb(0xA1, 0xFF); // mask all IRQs on slave
+    pic_unmask_keyboard();
+
+    __asm__ volatile ("sti");
+
+    forth_printf("Kernel started\n");
+    forth_run();
+    forth_panic();
+}
+
+void do_fb_addr(Word* w) {
+    (void)w;
+    data_push((int64_t)fb_addr);
+}
+
+void do_fb_width(Word* w) {
+    (void)w;
+    data_push((int64_t)fb_width);
+}
+
+void do_fb_height(Word* w) {
+    (void)w;
+    data_push((int64_t)fb_height);
+}
+
+void do_fb_pitch(Word* w) {
+    (void)w;
+    data_push((int64_t)fb_pitch);
+}
+
+void do_fb_bpp(Word* w) {
+    (void)w;
+    data_push((int64_t)fb_bpp);
+}
+
+void do_fb_plot(Word* w) {
+    (void)w;
+    int64_t color = data_pop();
+    int64_t y = data_pop();
+    int64_t x = data_pop();
+    fb_draw_pixel((int)x, (int)y, (uint32_t)color);
+}

platform_linux.c

@@ -0,0 +1,121 @@
+#include "forth.h"
+#include <stdarg.h>
+
+static inline long syscall3(long n, long a1, long a2, long a3) {
+    long ret;
+    __asm__ volatile ("syscall"
+        : "=a"(ret)
+        : "a"(n), "D"(a1), "S"(a2), "d"(a3)
+        : "rcx", "r11", "memory");
+    return ret;
+}
+
+static inline long syscall1(long n, long a1) {
+    long ret;
+    __asm__ volatile ("syscall"
+        : "=a"(ret)
+        : "a"(n), "D"(a1)
+        : "rcx", "r11", "memory");
+    return ret;
+}
+
+void forth_putchar(char c) {
+    char ch = c;
+    syscall3(1, 1, (long)&ch, 1);
+}
+
+void forth_fflush(void) {
+}
+
+int forth_getchar(void) {
+    unsigned char c;
+    long n = syscall3(0, 0, (long)&c, 1);
+    if (n <= 0) return FORTH_EOF;
+    return (int)c;
+}
+
+void forth_panic(void) {
+    syscall1(60, 1);
+    __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 do_fb_addr(Word* w) { (void)w; data_push(0); }
+void do_fb_width(Word* w) { (void)w; data_push(0); }
+void do_fb_height(Word* w) { (void)w; data_push(0); }
+void do_fb_pitch(Word* w) { (void)w; data_push(0); }
+void do_fb_bpp(Word* w) { (void)w; data_push(0); }
+void do_fb_plot(Word* w) { (void)w; data_pop(); data_pop(); data_pop(); }
+
+void _start(void) {
+    forth_run();
+    syscall1(60, 0);
+    __builtin_unreachable();
+}