fix: remove redundant .bss zeroing that destroyed page tables

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

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);

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");
@@ -91,13 +91,13 @@ void outer_interpreter(void) {
         int c;
         while (i < sizeof(line_buf) - 1) {
             c = forth_getchar();
-            if (c == EOF || c == '\n' || c == '\r') {
+            if (c == FORTH_EOF || c == '\n' || c == '\r') {
                 break;
             }
             line_buf[i++] = (char)c;
         }
         line_buf[i] = '\0';
-        if (i == 0 && c == EOF) {
+        if (i == 0 && c == FORTH_EOF) {
             break;
         }
         input_buf = line_buf;

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;
@@ -495,10 +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
@@ -524,10 +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
@@ -583,9 +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;
@@ -603,7 +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();
@@ -611,10 +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;
@@ -692,7 +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) {
@@ -722,7 +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 +1,108 @@
+# 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))
+
+    .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
+
+.align 16
+stack_bottom:
+    .space 16384
+stack_top:
+
+.section .text
+.code32
+.global _start
+.type _start, @function
+_start:
+    movl $stack_top, %esp
+
+    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
+
+    movl $pd, %eax
+    orl $0x03, %eax
+    movl %eax, pdpt
+
+    movl $0x00000083, %eax
+    movl $pd, %edi
+    movl $512, %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:
+    movabsq $stack_top, %rax
+    movq %rax, %rsp
+
+    call kernel_main
+    cli
+1:
+    hlt
+    jmp 1b
+
+.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
+    .quad 0x00209A0000000000
+gdt64_pointer:
+    .word gdt64_pointer - 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
@@ -104,5 +104,4 @@ int main(void) {
 
     // Start outer interpreter
     outer_interpreter();
-    return 0;
 }

platform_kernel.c

@@ -0,0 +1,143 @@
+#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_printf("Kernel started\n");
+    forth_run();
+    forth_panic();
+}

platform_linux.c

@@ -0,0 +1,114 @@
+#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 _start(void) {
+    forth_run();
+    syscall1(60, 0);
+    __builtin_unreachable();
+}