Improved fault handling

boot.nasm

@@ -94,8 +94,8 @@ mov gs, ax
 mov ss, ax
 ; check A20
 .a20:
-mov edi, 0x101337
+mov edi, 0x107C00
-mov esi, 0x001337
+mov esi, 0x007C00
 mov [esi], esi
 mov [edi], edi
 cmpsd

fault.nasm

@@ -8,6 +8,14 @@ mov ax, 0x10
 mov es, ax
 ; move to 'safe' location
 mov ebp, 0x318000
+; copy stack a bit
+mov ecx, 0
+.copy:
+mov eax, [esp+ecx*4]
+mov [ebp+ecx*4], eax
+inc ecx
+cmp ecx, 6
+jl .copy
 mov esp, ebp
 call error_environment
 .hlt:
@@ -47,6 +55,7 @@ mov eax, dword [esp+16] ; EFLAGS
 and eax, 1 << 17 ; VM flag
 test eax, eax
 pop eax
+mov dword [_gpf_eax_save], eax
 jnz gpf_handler_v86
 jmp gpf_handler_32
 gpf_unhandled:

interrupt.c

@@ -99,6 +99,7 @@ __attribute((__no_caller_saved_registers__))
 extern void return_prev_task();
 __attribute((__no_caller_saved_registers__))
 extern void error_environment(); // defined in kernel.c
+extern uint32_t _gpf_eax_save;
 #define VALID_FLAGS 0xDFF
 __attribute__ ((interrupt))
 void gpf_handler_v86(struct interrupt_frame *frame, unsigned long error_code) {
@@ -233,8 +234,11 @@ void gpf_handler_v86(struct interrupt_frame *frame, unsigned long error_code) {
                     uint16_t *e = error_screen;
                     for (int i = 0; i < 80; i++)
                         e[i] = 0x0f00;
-                    e += int_printStr("Unknown instruction caused V86 GPF: ", e);
+                    e += int_printStr("Unknown instruction caused V86 GPF(", e);
-                    *(uint32_t*)e = 0x1f001f00;
+                    int_printWord(error_code, e);
+                    e += 4;
+                    e += int_printStr("):", e);
+                    *(uint32_t*)e = 0x7f007f00;
                     int_printDword(*(uint32_t*)ip, e);
                     e += 9;
                     *(uint8_t*)e = '@';
@@ -293,19 +297,14 @@ void set_trap_gate(uint8_t gate, void (*handler)()) {
     IDT[gate].type_attributes = 0x8F;
 }
 void setup_interrupts() {
+    asm volatile("cli");
     IDTR.size = 256*8 - 1;
     IDTR.offset = (uint32_t)(size_t)IDT;
     for (int i = 0; i < 256; i++) {
         *(uint64_t*)&IDT[i] = 0;
     }
 
-    for (int i = 0; i < 9; i++) {
+    for (int i = 0; i < 256; i++) {
-        set_trap_gate(i, unhandled_handler);
-    }
-    for (int i = 10; i < 15; i++) {
-        set_trap_gate(i, unhandled_handler);
-    }
-    for (int i = 16; i < 22; i++) {
         set_trap_gate(i, unhandled_handler);
     }
 

kernel.c

@@ -109,18 +109,31 @@ void ensure_v86env() {
 __attribute((__no_caller_saved_registers__))
 extern void return_prev_task();
 __attribute((__no_caller_saved_registers__))
-void error_environment() {
+void error_environment(uint32_t stack0, uint32_t stack1, uint32_t stack2, uint32_t stack3, uint32_t stack4, uint32_t stack5) {
     ensure_v86env();
+    setup_interrupts(); // just in case
     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);
-    char str0[] = "Oh noes!!! System error! ;c    ";
+    char str0[] = "Oh noes!!! System error! ;c     STKDMP:";
     printStr(str0, &error_screen[80]);
-    printStr("Press E for a fun recovery :3", &error_screen[80+sizeof(str0)]);
+    uint16_t *tmp = &error_screen[80+sizeof(str0)-1];
-    printStr("Press R to return to previous task", &error_screen[160+sizeof(str0)]);
+    tmp += printDword(stack0, tmp);
+    tmp++;
+    tmp += printDword(stack1, tmp);
+    tmp++;
+    tmp += printDword(stack2, tmp);
+    tmp = &error_screen[80*2+sizeof(str0)-1];
+    tmp += printDword(stack3, tmp);
+    tmp++;
+    tmp += printDword(stack4, tmp);
+    tmp++;
+    tmp += printDword(stack5, tmp);
+    printStr("Press E for a fun recovery :3", &error_screen[80*2]);
+    printStr("Press R to return to previous task", &error_screen[80*3]);
     uint16_t *vga_text = ((uint16_t*)0xB8000);
     for (int i = 0; i < 80*50; i++)
         vga_text[i] = error_screen[i];
@@ -225,6 +238,7 @@ void FileSelect() {
     int32_t fileHovered = 0, lastFileHovered = 0;
     for (char reload = 1;;) {
         // Info line (4)
+        DrawScreen();
         printStr("T to run tests - X to view in hex - V to view as text - P to load as program", &vga_text[80*4+2]);
         VOLINFO vi; DIRINFO di;
         if (reload) {
@@ -253,7 +267,6 @@ void FileSelect() {
             case 0x14: // t
                 create_child(0x380000, (uintptr_t)RunTests, 0);
                 SetCursorDisabled();
-                DrawScreen();
                 reload = 1;
                 break;
             case KEY_P:
@@ -261,7 +274,6 @@ void FileSelect() {
                 create_child(0x380000, (uintptr_t)ProgramLoadTest, 2, path, &vi);
                 SetVideo25Lines();
                 SetCursorDisabled();
-                DrawScreen();
                 reload = 1;
                 break;
             case KEY_X:
@@ -270,7 +282,6 @@ void FileSelect() {
                 create_child(0x380000, (uintptr_t)HexViewTest, 2, path, &vi);
                 SetVideo25Lines();
                 SetCursorDisabled();
-                DrawScreen();
                 break;
             case KEY_V:
                 File83ToPath((char*)entries[fileHovered].name, (char*)path);
@@ -278,7 +289,6 @@ void FileSelect() {
                 create_child(0x380000, (uintptr_t)TextViewTest, 2, path, &vi);
                 SetVideo25Lines();
                 SetCursorDisabled();
-                DrawScreen();
                 reload = 1;
                 break;
             default:
@@ -346,6 +356,21 @@ void start() {
     SetVideo25Lines();
     SetCursorDisabled();
     DrawScreen();
-    FileSelect();
+    uint32_t stack;
+    asm volatile("mov %%esp,%%eax":"=a"(stack));
+    stack = ((stack - 0x4000) / 0x1000) * 0x1000;
+    for (;;) {
+        create_child(stack, (uintptr_t)FileSelect, 0);
+        // should never return, so if it does,
+        // we have an error
+        SetVideo25Lines();
+        SetCursorDisabled();
+        DrawScreen();
+        vga_text = &((word*)0xb8000)[80*4 + 2];
+        vga_text += printStr("Error loading file select. Ensure the disk has a valid MBR and FAT partition.", vga_text);
+        vga_text = &((word*)0xb8000)[80*5 + 2];
+        vga_text += printStr("Press R to retry.", vga_text);
+        for (;(get_scancode() & 0xff) != KEY_R;);
+    }
 }
 

tests.c

@@ -39,13 +39,13 @@ void TestDiskRead() {
     vga_text += printStr("Setting Text Mode... ", vga_text);
     regs.w.ax = 3; // text mode
     V8086Int(0x10, &regs); 
-    vga_text += printStr("Done. Starting Disk Read... ", vga_text);
+    //vga_text += printStr("Done. Starting Disk Read... ", vga_text);
-    char *diskReadBuf = (char *)0x8000;
+    char *diskReadBuf = (char *)0x20000;
 	v86disk_addr_packet.transfer_buffer =
 		(uintptr_t)diskReadBuf & 0x000F |
 		(((uintptr_t)diskReadBuf & 0xFFFF0) << 12);
     FARPTR v86_entry = i386LinearToFp(v86DiskRead);
-    enter_v86(0x8000, 0xFF00, FP_SEG(v86_entry), FP_OFF(v86_entry), &regs);
+    enter_v86(0x0000, 0x8000, FP_SEG(v86_entry), FP_OFF(v86_entry), &regs);
     vga_text = (uint16_t *)0xb8000;
     for (int i = 0; i < (80*25)/2; i++) {
         printByte(diskReadBuf[i], &vga_text[i*2]);

usermode.nasm

@@ -5,7 +5,7 @@ mov dword [0xb8000], 0x0f000f00 | 'U' | 's' << 16
 mov dword [0xb8004], 0x0f000f00 | 'e' | 'r' << 16
 mov dword [0xb8008], 0x0f000f00 | 'm' | 'o' << 16
 mov dword [0xb800C], 0x0f000f00 | 'd' | 'e' << 16
-mov word [0xb8010], 0x0f00 | '!'
+mov dword [0xb8010], 0x0f000f00 | '!'
 mov dword [0xb8000+160], 0x0f000f00 | 'F' | 'a' << 16
 mov dword [0xb8004+160], 0x0f000f00 | 'u' | 'l' << 16
 mov dword [0xb8008+160], 0x0f000f00 | 't' | 's' << 16
@@ -18,12 +18,24 @@ mov dword [0xb8000+480], 0x0f000f00 | 'p' | ':' << 16
 mov dword [0xb8004+480], 0x0f000f00 | ' ' | 'P' << 16
 mov dword [0xb8008+480], 0x0f000f00 | 'G' | 'F' << 16
 mov dword [0xb800C+480], 0x0f000f00 | 'L' | 'T' << 16
+mov dword [0xb8000+640], 0x0f000f00 | 'u' | ':' << 16
+mov dword [0xb8004+640], 0x0f000f00 | ' ' | '#' << 16
+mov dword [0xb8008+640], 0x0f000f00 | 'U' | 'D' << 16
+mov dword [0xb800C+640], 0x0f000f00 | '2' | ' ' << 16
+mov dword [0xb8000+800], 0x0f000f00 | 'g' | ':' << 16
+mov dword [0xb8004+800], 0x0f000f00 | ' ' | '#' << 16
+mov dword [0xb8008+800], 0x0f000f00 | 'G' | 'P' << 16
+mov dword [0xb800C+800], 0x0f000f00 | 'F' | ' ' << 16
 mov eax, 0 ; command = 00h, get key
 int 0x21 ; OS call
 cmp al, 'd'
 je .div_err
 cmp al, 'p'
 je .page_err
+cmp al, 'u'
+je .undefined_err
+cmp al, 'g'
+je .gpf_err
 push 0x00000013 ; eax  AH=0,AL=3 set video mode 3
 push 0x00000000 ; ecx
 push 0x00000000 ; edx
@@ -43,9 +55,6 @@ inc al
 cmp eax, 200
 jl .loop
 mov eax, 0xA0000
-;mov ecx, 1000000000
-;.dbg:
-;loop .dbg
 int 0x30 ; Exit
 .page_err:
 mov edx, 0x105000 ; somewhere in kernel mem
@@ -53,3 +62,8 @@ mov edx, [edx] ; should page fault
 .div_err:
 xor ebx, ebx
 div bl ; Unhandled DIV0 exception
+.undefined_err:
+ud2 ; undefined instruction
+.gpf_err:
+mov ax, 0x10
+mov ds, ax   ; load ds with bad value

v86.nasm

@@ -97,7 +97,10 @@ mov ah, 0x42
 mov dl, 0x80 ; TODO get this from BIOS or something
 mov si, v86disk_addr_packet ; ds:si
 int 0x13
+jc .err
 int 0x30
+.err:
+ud2
 jmp $
 global v86disk_addr_packet
 v86disk_addr_packet: