C kernel runs now after fixing bootloader and build, beginnings of a REPL

Makefile

@@ -1,15 +1,15 @@
 all: boot.img kernel.bin
 
 src/%.o: src/%.c
-	bcc -ansi -3 -c -o $@ $<
+	bcc -ansi -0 -c -o $@ $<
 
 kernel.bin: src/kernel.o
-	ld86 -T0x1000 -M -o $@ $^
+	ld86 -d -M -o $@ $^ | tee ld86.out
 
 asm/kernel_syms.S: kernel.bin
-	objdump86 kernel.bin | \
-		grep -E "^[0-9]+ T _.*" | \
-		python -c "import sys; print '\n'.join([\"_extern_c%s:\n    jmp 0x1000:0x%04x\" % (x.split(' ')[2].strip('\n'), int(x.split(' ')[0].lstrip('0'), 16)-0x1000) for x in sys.stdin.readlines()])" > asm/kernel_syms.S
+	cat ld86.out | \
+		grep -E "^\s+kernel\s+[a-zA-Z0-9_]+  0  [0-9]+" | \
+		python -c "import sys; print '\n'.join([\"_extern_c%s:\n    jmp 0x1000:0x%04x\" % (x.lstrip(' ').replace('kernel', '').lstrip(' ').split(' ')[0], int(x.lstrip(' ').replace('kernel', '').lstrip(' ').split(' ')[4], 16)) for x in sys.stdin.readlines()])" > asm/kernel_syms.S
 
 boot.bin: asm/kernel_syms.S asm/bootloader.S asm/bootloader.S
 	cd asm && nasm bootloader.S -f bin -o ../$@
@@ -18,7 +18,10 @@ asm/%.o: asm/%.S
 	nasm $< -f as86 -o $@
 
 boot.img: boot.bin kernel.bin
-	cat $^ > $@
+	dd if=/dev/zero of=boot.img ibs=1k count=1440
+	cat $^ > boot.tmp
+	dd if=boot.tmp of=boot.img conv=notrunc
+	rm -f boot.tmp
 
 test: boot.img
 	bochs -f bochsrc -q

asm/bootloader.S

@@ -2,6 +2,10 @@
 [org 0x7C00]                   ; Origin at 0x7C00 (upper end of memory)
 
 start:
+	;; FIXME - we need to relocate ourselves to the
+	;; upper end of memory somewhere so we can overwrite
+	;; ourselves with the kernel at 0x0000
+	
 	call blankScreen
 
 	mov dx, 0x0
@@ -13,10 +17,10 @@ start:
 	mov dl, 0x0
 	call setCursorPosition
 	
-	mov al, 0x1            ; read the remaining 16 tracks 
+	mov al, 0x10           ; read the remaining 16 tracks 
 	mov ch, 0x0            ; .... on track 0 ....
 	mov cl, 0x2            ; .... starting at sector 2
-	mov bx, 0x1000         ; 0x1000 is a standard kernel start location
+	mov bx, 0x1000         ; Load the kernel into the bottom of memory
 	mov es, bx
 	mov bx, 0x0            ; bx = 0, es:bx = 0x1000:0
 	call loadFloppyDiskSectors
@@ -58,6 +62,11 @@ _end_floppy_read:
 	call setCursorPosition
 	mov si, _str_floppydone
 	call printString
+	mov ax, 0x1000
+	mov ds, ax
+	mov ax, 0x1000
+	mov ss, ax
+	mov sp, 0xFFFF
 	jmp _extern_c_main
 
 %include "libinterrupt.S"
@@ -69,4 +78,3 @@ _end_floppy_read:
 
 times 510 - ($ - $$) db 0      ; fill up to 510 bytes with 0
 dw 0xAA55                      ; magic bootloader signature
-

asm/kernel_syms.S

@@ -1,4 +1,26 @@
+_extern_c_backupCursor:
+    jmp 0x1000:0x001e
+_extern_c_blankScreen:
+    jmp 0x1000:0x03b6
+_extern_c_strlen:
+    jmp 0x1000:0x00ba
 _extern_c_main:
-    jmp 0x1000:0x0049
-_extern_c_printCh:
+    jmp 0x1000:0x0412
+_extern_c_getkey:
+    jmp 0x1000:0x0155
+_extern_c_repl:
+    jmp 0x1000:0x02ea
+_extern_c_strcmp:
+    jmp 0x1000:0x0265
+_extern_c_advanceCursor:
+    jmp 0x1000:0x0067
+_extern_c_setCursorPosition:
     jmp 0x1000:0x0000
+_extern_c_memset:
+    jmp 0x1000:0x0227
+_extern_c_putc:
+    jmp 0x1000:0x00a0
+_extern_c_puts:
+    jmp 0x1000:0x00f4
+_extern_c_gets:
+    jmp 0x1000:0x017b

src/kernel.c

@@ -1,34 +1,238 @@
-void printChar(char c)
+char _cursor_x = 0;
+char _cursor_y = 0;
+
+#define NULL 0x0
+typedef int size_t;
+
+void setCursorPosition(char x, char y)
 {
 #asm
-#if !__FIRST_ARG_IN_AX__
-  mov bx, sp
-#endif
-#if __FIRST_ARG_IN_AX__
-  mov si, ax
-#else
-  mov si, [bx+2]
-#endif
-    mov ah, 0x0e
-    mov bh, 0x00
-    mov bl, 0x07
-    int 0x10
+  push bx;
+  mov bx, sp;
+  mov dl, [bx+4];
+  mov dh, [bx+6];
+  pop bx;
+  push ax;
+  push bx;
+  mov ah, #0x02;
+  mov bx, #0x0;
+  int 0x10;
+  pop bx;
+  pop ax;
 #endasm
   return;
 }
 
-void printString(char *ptr) 
+void backupCursor()
 {
-  while ((char)*ptr != '\0') { 
-    printChar((char)*ptr);
-    ptr++;
+  
+  if ( _cursor_x == 0 && _cursor_y > 0 ) {
+    _cursor_x = 80;
+    _cursor_y -= 1;
+  } else if ( _cursor_x > 0 ) {
+    _cursor_x -= 1;
+  }
+  setCursorPosition(_cursor_x, _cursor_y);
 }
 
+void advanceCursor()
+{
+  _cursor_x += 1;
+  if ( _cursor_x > 79 ) {
+    _cursor_x = 0;
+    _cursor_y += 1;
+  }
+  setCursorPosition(_cursor_x, _cursor_y);
+}
+
+void putc(char c)
+{
+#asm
+  push bx;
+  push ax;
+  mov bx, sp;
+  mov al, [bx+6];
+  mov ah, #0x0e;
+  mov bh, #0x00;
+  mov bl, #0x07;
+  int 0x10;
+  pop ax;
+  pop bx;
+#endasm
     return;
 }
 
+int strlen(char *ptr)
+{
+  char *ptr2 = ptr;
+  if ( ptr == NULL ) {
+    return 0;
+  }
+
+  while (*ptr2 != 0x0 ) {
+    ptr2 += 1;
+  }
+
+  return ptr2 - ptr;
+}
+
+void puts(char *ptr, char x, char y) 
+{
+  if ( ptr == NULL ) {
+    return;
+  }
+  while ((char)*ptr != 0x0) { 
+    putc((char)*ptr);
+    if (*ptr == '\n') {
+      _cursor_y += 1;
+      _cursor_x = 0;
+      setCursorPosition(_cursor_x, _cursor_y);
+    } else {
+      advanceCursor();
+    }
+    ptr += 1;
+  }
+  return;
+}
+
+char getkey(char *dest)
+{
+  char echo;
+  char scancode;
+#asm
+  push ax;
+  mov ah, 0x10;
+  int 0x16;
+  mov [bp-6], ah;
+  mov [bp-5], al;
+  pop ax;
+#endasm
+  *dest = echo;
+  return scancode;
+}
+
+char *gets(char *d)
+{
+  char *orig = d;
+  char scancode;
+  char printable;
+
+  if ( d == NULL ) {
+    return NULL;
+  }
+
+  scancode = getkey(&printable);
+
+  while ( scancode != NULL ) {
+    if ( scancode == 0x0e ) {
+      if ( d > orig ) {
+	backupCursor();
+	setCursorPosition(_cursor_x, _cursor_y);
+	d -= 1;
+	putc(0x0);
+      }
+    } else if ( scancode == 0x1c ) {
+      break;
+    } else {
+      *(d++) = printable;
+      putc(printable);
+      advanceCursor();
+    } 
+    scancode = getkey(&printable);
+  }
+  
+ _gets_finish_loop:
+  *d = NULL;
+  return orig;
+}
+
+void memset(void *s, int c, size_t n)
+{
+  int *d = (int *)s;
+  if ( s == NULL ) {
+    return;
+  }
+  while ( ((int)d - (int)s) <= n ) {
+    *d = c;
+    d += sizeof(int);
+  }
+}
+
+signed int strcmp(char *s1, char *s2)
+{
+  int d = 0;
+  int s1len = 0;
+
+  if ( s1 == NULL || s2 == NULL ) {
+    return 1;
+  }
+
+  s1len = strlen(s1);
+  if ( s1len != strlen(s2) ) {
+    return 1;
+  }
+
+  while ( *s1 != '\0' ) {
+    if ( *s1 != *s2 ) {
+      return 1;
+    }
+    s1 += sizeof(char);
+    s2 += sizeof(char);
+  }
+
+  return 0;
+}
+
+void repl(void)
+{
+  char keybuff[512];
+
+  while ( 1 ) {
+    puts("> ");
+    memset((void *)&keybuff, 0x00, 512);
+    if ( gets((char *)&keybuff) != NULL ) {
+      puts("\n");
+      if ( strcmp(&keybuff, "quit") == 0 ) {
+	puts("You asked for it\n");
+	#asm
+	hlt;
+	#endasm
+
+      } else if ( strcmp(&keybuff, "reset") == 0 ) {
+	puts("Resetting PC ... ");
+	#asm
+	jmp 0xf000:0xfff0;
+	#endasm
+
+      } else if ( strcmp(&keybuff, "help") == 0 ) {
+	puts("help : Show this help message\n");
+	puts("quit : Halt the computer\n");
+	puts("reset : Reset the PC\n");
+	puts("\n");
+      } else {
+	puts("Wat?\n");
+      }
+    }
+  }
+}
+
+void blankScreen(void)
+{
+  char i = 0;
+  char j = 0;
+  for ( i = 0 ; i < 26 ; i++ ) {
+    for ( j = 0; j < 81 ; j++ ) {
+      setCursorPosition(j, i);
+      putc(' ');
+    }
+  }
+}
+
 void main(void)
 {
-  //printString("Piquant Kernel v0.1\n");
-  while(1);
+  blankScreen();
+  setCursorPosition(0, 0);
+  puts("Piquant Kernel v0.1\n");
+  puts("\n");
+  repl();
 }