Added example disk, Made some minor changes to error output

.gitignore

@@ -1,5 +1,6 @@
 *.o
 *.bin
+*.img
 *.lock
 *.com
 bx_enh_dbg.ini

Makefile

@@ -1,5 +1,5 @@
 objects = entry.o kernel.o task.o handler.o interrupt.o v86.o print.o tss.o dosfs/dosfs.o gdt.o usermode.o paging.o fault.o tests.o kbd.o helper.o progs.o
-CFLAGS = -target "i686-elf" -m32 -mgeneral-regs-only -ffreestanding -march=pentium-m -fno-stack-protector -Wno-int-conversion -nostdlib -c
+CFLAGS = -target "i486-elf" -m32 -mgeneral-regs-only -ffreestanding -march=pentium-m -fno-stack-protector -Wno-int-conversion -nostdlib -c
 
 %.o: %.nasm
 	nasm -f elf32 -o $@ $<
@@ -11,7 +11,7 @@ all: $(objects)
 	nasm boot.nasm -o boot.bin
 	gcc -Tlink.ld -Wl,-M -m32 -ffreestanding -nostartfiles -nostdlib -o kernel.bin\
 		$(objects)
-	dd bs=256 count=1 conv=notrunc if=boot.bin of=virtdisk.bin
+	dd bs=400 count=1 conv=notrunc if=boot.bin of=virtdisk.bin
 	dd bs=512 seek=1 conv=notrunc if=kernel.bin of=virtdisk.bin
 virtdisk:
 	dd bs=1M count=32 if=/dev/zero of=virtdisk.bin

boot.nasm

@@ -8,6 +8,10 @@ mov es, ax
 mov ax, 0x8000
 mov ss, ax
 mov sp, 0xFF00
+mov ah, 0x41 ; int 13 extensions check
+mov bx, 0x55AA
+int 0x13
+jc no_exten
 mov cx, kernelreads
 read_loop:
 xor ax, ax
@@ -19,6 +23,14 @@ add word [addr_packet_transfer_buff_seg], (secreadcnt*512)/16
 add word [addr_packet_start_block], secreadcnt
 loop read_loop
 entry:
+mov ax,0x2403 ; A20 BIOS Support
+int 0x15
+jb .no_a20
+cmp ah,0
+jnz .no_a20
+mov ax,0x2401 ; A20 BIOS Activate
+int 0x15
+.no_a20:
 cli             ; no interrupts
 xor ax,ax
 mov ds, ax
@@ -28,19 +40,50 @@ or al, 1
 mov cr0, eax
 jmp 08h:Pmode
 err:
+mov bx, ax
+mov si, string
+mov cx, string_end - string
+jmp print
+no_exten:
+mov bx, ax
+mov si, no_exten_str
+mov cx, no_exten_str_end - no_exten_str
+print:
 push 0xb800
 pop es
 xor di, di
-mov si, string
-mov cx, 10
 mov ah, 0x7
 err_print:
 lodsb
 stosw
 loop err_print
+add di, 2
+mov ax, bx
+call hexprint
 hlt_loop:
 hlt
 jmp hlt_loop
+hexprint:
+xor cx, cx
+mov bl, al
+shr al, 4
+jmp .donibble
+.nibble2:
+mov al, bl
+inc cx
+.donibble:
+and al, 0x0F
+cmp al, 0x0A
+jl .noadjust
+add al, 'A' - '0' - 10
+.noadjust:
+add al, '0'
+mov ah, 0x7
+stosw
+test cx, cx
+jz .nibble2
+ret
+
 [BITS 32]
 Pmode:
 mov eax, 0x10
@@ -49,18 +92,29 @@ mov es, ax
 mov fs, ax
 mov gs, ax
 mov ss, ax
-in al, 0x92
+; check A20
+.a20:
+mov edi, 0x101337
+mov esi, 0x001337
+mov [esi], esi
+mov [edi], edi
+cmpsd
+jne .kernel
+in al, 0x92 ; fast A20
 test al, 2
-jnz after
+jnz .fa20_end
 or al, 2
 and al, 0xFE
 out 0x92, al
-after:
+.fa20_end:
+jmp .a20
+.kernel:
 mov esi, 0x8000
 mov edi, 0x100000
 mov ecx, 0x10000
 rep movsb
 jmp 08h:0x100000
+
 gdt_desc:
     dw gdt_end - gdt
     dd gdt
@@ -79,6 +133,9 @@ gdt_data: dw 0xFFFF, 0     ; bits 0-15 limit (4GB), bits 0-15 base address
 gdt_end:
 
 string: db 'DISK ERROR'
+string_end:
+no_exten_str: db 'NO INT13 EXTEN'
+no_exten_str_end:
 
 addr_packet:
 db 0x10, 0x00 ; size, reserved

interrupt.c

@@ -22,6 +22,13 @@ void int_printDword(uint32_t v, uint16_t *buff) {
     int_printWord(v >> 16, buff);
     int_printWord(v, &buff[4]);
 }
+__attribute((__no_caller_saved_registers__))
+uintptr_t int_printStr(char *v, uint16_t *buff) {
+    char *s;
+    for (s = v;*s;s++,buff++)
+        *(char*)buff = *s;
+    return s - v;
+}
 
 struct __attribute__((__packed__)) IDTR_t {
     uint16_t size;
@@ -90,6 +97,8 @@ extern void real_test();
 extern void jmp_usermode_test();
 __attribute((__no_caller_saved_registers__))
 extern void return_prev_task();
+__attribute((__no_caller_saved_registers__))
+extern void error_environment(); // defined in kernel.c
 #define VALID_FLAGS 0xDFF
 __attribute__ ((interrupt))
 void gpf_handler_v86(struct interrupt_frame *frame, unsigned long error_code) {
@@ -220,6 +229,23 @@ void gpf_handler_v86(struct interrupt_frame *frame, unsigned long error_code) {
                 frame->eip = (uint16_t) (frame->eip + 1);
                 goto done;
             default:
+                {
+                    uint16_t *e = error_screen;
+                    for (int i = 0; i < 80; i++)
+                        e[i] = 0x0f00;
+                    e += int_printStr("Unknown instruction caused V86 GPF: ", e);
+                    *(uint32_t*)e = 0x1f001f00;
+                    int_printDword(*(uint32_t*)ip, e);
+                    e += 9;
+                    *(uint8_t*)e = '@';
+                    e += 1;
+                    int_printWord(frame->cs, e);
+                    e += 4;
+                    *(uint8_t*)e = ':';
+                    e += 1;
+                    int_printWord(frame->eip, e);
+                    error_environment();
+                }
                 for(;;);
         }
     }

kernel.c

@@ -104,15 +104,16 @@ void ensure_v86env() {
     char *d = &_v86code;
     while (d < &_ev86code)
         *d++ = *s++;
-    for (int i = 0; i < 80*50; i++)
-        if (!(error_screen[i] & 0xFF00))
-            error_screen[i] = 0x0f00 | (error_screen[i] & 0x00FF);
 }
 
 __attribute((__no_caller_saved_registers__))
 extern void return_prev_task();
+__attribute((__no_caller_saved_registers__))
 void error_environment() {
     ensure_v86env();
+    for (int i = 0; i < 80*50; i++)
+        if (!(error_screen[i] & 0xFF00))
+            error_screen[i] = 0x0f00 | (error_screen[i] & 0x00FF);
     union V86Regs_t regs;
     FARPTR v86_entry = i386LinearToFp(v86TextMode);
     enter_v86(0x8000, 0xFF00, FP_SEG(v86_entry), FP_OFF(v86_entry), &regs);
@@ -126,7 +127,12 @@ void error_environment() {
     for(;;) {
         uint8_t key = get_scancode() & 0xff;
         if (key == KEY_E) break;
-        if (key == KEY_R) return_prev_task();
+        if (key == KEY_R) {
+            // reset error screen
+            for (int i = 0; i < (80*50)/2; i++)
+                ((uint32_t*)error_screen)[i] = 0x0f000f00;
+            return_prev_task();
+        }
     }
     v86_entry = i386LinearToFp(v86TransFlag);
     enter_v86(0x8000, 0xFF00, FP_SEG(v86_entry), FP_OFF(v86_entry), &regs);
@@ -288,6 +294,12 @@ void start() {
         *(char *)&vga_text[i] = h[i];
     vga_text = &vga_text[80];
 
+    // DL *should* be preserved
+    uint8_t dl;
+    asm volatile("nop":"=d"(dl));
+    vga_text += printByte(dl, vga_text);
+    vga_text++;
+
     uint32_t o;
     asm("mov %%esp, %%eax" : "=a"(o) : :);
     vga_text += printDword(o, vga_text);
@@ -303,15 +315,14 @@ void start() {
     //    *(char *)&vga_text[i+(80*3)] = c[i];
     //if (!apic) return;
 
-    char sse_str[] = "SSE support: ";
-    vga_text += printStr("SSE: ", vga_text);
-    char sse = check_sse();
-    if (!sse) {
-        *vga_text = 'N';
-        return;
-    }
-    vga_text += printStr("Y ", vga_text);
-    enable_sse();
+    //char sse_str[] = "SSE support: ";
+    //vga_text += printStr("SSE: ", vga_text);
+    //char sse = check_sse();
+    //if (!sse) {
+    //    *vga_text = 'N';
+    //}
+    //vga_text += printStr("Y ", vga_text);
+    //enable_sse();
 
     setup_binary();
 
@@ -327,7 +338,7 @@ void start() {
     //print_cr4();
     backup_ivtbios();
 
-    vga_text = &((word *)0xb8000)[80];
+    vga_text = &((word *)0xb8000)[160];
     vga_text += printStr("Press T for tests, or any key to continue... ", vga_text);
     uint8_t key = get_key();
     if (key == 't' || key == 'T')

tests.c

@@ -40,7 +40,7 @@ void TestDiskRead() {
     regs.w.ax = 3; // text mode
     V8086Int(0x10, &regs); 
     vga_text += printStr("Done. Starting Disk Read... ", vga_text);
-    char *diskReadBuf = (char *)0x23000;
+    char *diskReadBuf = (char *)0x8000;
 	v86disk_addr_packet.transfer_buffer =
 		(uintptr_t)diskReadBuf & 0x000F |
 		(((uintptr_t)diskReadBuf & 0xFFFF0) << 12);

v86.nasm

@@ -1,6 +1,5 @@
 [BITS 16]
 [SECTION .v86]
-
 global v86Interrupt
 v86Interrupt:
 int 0x00

v86defs.h

@@ -41,7 +41,7 @@ union __attribute((__packed__)) V86Regs_t {
     } h;
 };
 
-extern void enter_v86(uint32_t ss, uint32_t esp, uint32_t cs, uint32_t eip, union V86Regs_t *regs);
+extern uint32_t enter_v86(uint32_t ss, uint32_t esp, uint32_t cs, uint32_t eip, union V86Regs_t *regs);
 
 void V8086Int(uint8_t interrupt, union V86Regs_t *regs);
 
@@ -76,3 +76,4 @@ typedef uint32_t FARPTR;
 
 FARPTR i386LinearToFp(void *ptr);
 
+void ensure_v86env();