From 2935d7ee6cfc482fc753dc976eb09b105d8deec8 Mon Sep 17 00:00:00 2001
From: Ain <41307858+nero@users.noreply.github.com>
Date: Sat, 28 Sep 2019 20:38:35 +0000
Subject: [PATCH] Improve emulator

---
 programs/hello.asm |  6 +++---
 utils/emul.c       | 31 ++++++++++++++++++++++++++++++-
 2 files changed, 33 insertions(+), 4 deletions(-)

diff --git a/programs/hello.asm b/programs/hello.asm
index 71ed1b5..ff02195 100644
--- a/programs/hello.asm
+++ b/programs/hello.asm
@@ -7,11 +7,11 @@ main:
   test al, al
   jz .ret
   mov dl, al
-  mov ah, 0x02
-  int 0x21
+  mov cl, 0x02
+  call 5
   jmp .loop
 .ret:
   ret
 
 hello:
-  db "Hello!", 0
+  db "Hello!", 0x0A, 0x0D, 0
diff --git a/utils/emul.c b/utils/emul.c
index 1b4f2d8..b5e59f2 100644
--- a/utils/emul.c
+++ b/utils/emul.c
@@ -27,6 +27,7 @@ void* rmptr;
 #define AL regset.r8[0]
 #define CL regset.r8[2]
 #define DL regset.r8[4]
+#define AX regset.r16[0]
 #define BX regset.r16[3]
 #define SP regset.r16[4]
 #define BP regset.r16[5]
@@ -169,6 +170,13 @@ void step() {
     modrm(BIT8);
     RM8 = R8(reg);
     break;
+  case 0x8B: // MOV reg16,r/m16
+    modrm(BIT16);
+    R16(reg) = RM16;
+    break;
+  case 0xA1: // MOV AX,memoffs16
+    AX = *(uint16_t*)&mem[imm16()];
+    break;
   case 0xAC: // LODSB
     AL = mem[SI];
     SI++;
@@ -196,7 +204,7 @@ void step() {
       handle_syscall(CL);
     } else {
       push(ip);
-      ip += reg;
+      ip = reg;
     }
     break;
   case 0xEB: // JMP rb
@@ -214,6 +222,21 @@ void step() {
   }
 }
 
+void copy_cmdline(char* str) {
+  int i, c;
+  uint8_t *len = &mem[0x80];
+  char* ptr = (char*)&mem[0x81];
+  c = strlen(str);
+  // Clip at max length
+  if (c>0x7E) {
+    fprintf(stderr, "Command line too long, max is 126 bytes\n");
+    exit(1);
+  }
+  memcpy(ptr, str, c);
+  ptr[c]=0x0D;
+  *len=c;
+}
+
 int main(int argc, char** argv) {
   memset(&mem, sizeof(mem), 0);
   memset(&regset, sizeof(regset), 0);
@@ -221,6 +244,12 @@ int main(int argc, char** argv) {
   mem[1]=0x20;
   push(0);
 
+  if (argc>2) {
+    copy_cmdline(argv[2]);
+  } else {
+    copy_cmdline("");
+  }
+
   FILE* fd = fopen(argv[1], "r");
   fread(mem + ip, 1, sizeof(mem) - ip, fd);
   while(1) {