Advance on 8086 emulator

lib/fcbparse.asm

@@ -0,0 +1,46 @@
+; Parse ASCIIZ string into FCB
+; IN	SI	ptr to filename
+;       BX	ptr to FCB
+fcb_parse:
+  push di
+  push ax
+  mov di, bx
+  xor ax, ax
+  stosb
+.cleanout:
+  push di
+  mov cx, 0x0A
+  mov al, 0x20
+  rep stosb
+  pop di
+.base_loop:
+  call .read
+  cmp al, 0x2E
+  je .ext_start
+  cmp al, 0x20
+  je .ret
+  stosb
+  jmp .base_loop
+.ext_start:
+  mov di, bx
+  add di, 9
+.ext_loop:
+  call .read
+  cmp al, 0x20
+  je .ret
+  stosb
+  jmp .ext_loop
+.read:
+  lodsb
+  test al, al
+  jz .eret
+  cmp al, 0x0D
+  je .eret
+  ret
+.eret:
+  dec si
+  pop ax
+.ret:
+  pop ax
+  pop di
+  ret

programs/lst2bin.asm

@@ -0,0 +1,18 @@
+org 0x100
+
+jmp start
+
+%include "fcbparse.asm"
+
+fcb_in:
+  times 20 db 0
+
+fcb_out:
+  times 20 db 0
+
+start:
+  mov si, 0x81
+  mov bx, fcb_in
+  mov ax, 0x1234
+  call fcb_parse
+  ret

utils/emul.c

@@ -13,6 +13,7 @@ union regset {
 int carry, zero;
 
 uint16_t ip = 0x100;
+uint16_t flags = 0;
 uint16_t scratch;
 uint16_t reg;
 int off;
@@ -54,7 +55,29 @@ void dump() {
     printf("%s=%04X ", regnames[i], regset.r16[i]);
   }
   printf("\n");
-  printf("IP=%04X : %X\n", ip, mem[ip]);
+  printf("IP=%04X : %02X %02X\n", ip, mem[ip], mem[ip+1]);
+}
+
+void arith8(int op, int8_t* dst, int src) {
+  // I'll just assume this sign-extends
+  int t = *dst;
+  int p = *dst;
+  switch (op) {
+  case ADD:  t += src; break;
+  case OR:   t |= src; break;
+  case ADC:  t += (src + carry); break;
+  case SBB:  t -= (src + carry); break;
+  case AND:  t &= src; break;
+  case SUB:  t -= src; break;
+  case XOR:  t ^= src; break;
+  case CMP:  t -= src; break;
+  case TEST: t &= src; break;
+  }
+  zero=!t;
+  // I dont think the following is correct
+  carry=((t ^ p) >> 8) & 1;
+  if (op==CMP || op==TEST) return;
+  *dst = t;
 }
 
 void arith16(int op, int16_t* dst, int src) {
@@ -192,6 +215,28 @@ void step() {
   uint8_t opcode = mem[ip];
   ip++;
   switch(opcode) {
+  case 0x00: // ARITH r/m8,reg8
+  case 0x08:
+  case 0x10:
+  case 0x18:
+  case 0x20:
+  case 0x28:
+  case 0x30:
+  case 0x38:
+    modrm(BIT8);
+    arith8(opcode >> 3, &RM8, R8(reg));
+    break;
+  case 0x01: // ARITH r/m16,reg16
+  case 0x09:
+  case 0x11:
+  case 0x19:
+  case 0x21:
+  case 0x29:
+  case 0x31:
+  case 0x39:
+    modrm(BIT16);
+    arith16(opcode >> 3, &RM16, R16(reg));
+    break;
   case 0x50 ... 0x57: // PUSH reg16
     push(R16(opcode-0x50));
     break;
@@ -216,6 +261,10 @@ void step() {
     modrm(BIT8);
     RM8 = R8(reg);
     break;
+  case 0x89: // MOV r/m16,reg16
+    modrm(BIT16);
+    RM16 = R16(reg);
+    break;
   case 0x8B: // MOV reg16,r/m16
     modrm(BIT16);
     R16(reg) = RM16;
@@ -303,5 +352,6 @@ int main(int argc, char** argv) {
   fread(mem + ip, 1, sizeof(mem) - ip, fd);
   while(1) {
     step();
+    dump();
   }
 }