More advanced Fault handling (recovers to text mode), Keyboard handler converted to C and improved (shifting, simple get_key added)

Makefile

@@ -1,4 +1,4 @@
-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
+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
 CFLAGS = -target "i686-elf" -m32 -mgeneral-regs-only -ffreestanding -march=pentium-m -fno-stack-protector -Wno-int-conversion -nostdlib -c
 
 %.o: %.nasm

boot.nasm

@@ -47,7 +47,7 @@ out 0x92, al
 after:
 mov esi, 0x8000
 mov edi, 0x100000
-mov ecx, 17000
+mov ecx, 0x10000
 rep movsb
 jmp 08h:0x100000
 gdt_desc:

fault.nasm

@@ -0,0 +1,146 @@
+extern error_screen ; 80x50 words 
+
+; Switches to text mode and shit
+extern error_environment
+_fault_coda:
+xchg bx,bx
+mov ax, 0x10
+mov es, ax
+; move to TOP OF kernel stack
+mov ebp, 0x400000
+mov esp, ebp
+call error_environment
+.hlt:
+hlt
+jmp .hlt
+
+global unhandled_handler
+unhandled_handler:
+mov ax, 0x10
+mov ds, ax
+mov dword [error_screen+0x00], 0x0f000f00 | 'E' | 'R' << 16
+mov dword [error_screen+0x04], 0x0f000f00 | 'R' | 'O' << 16
+mov dword [error_screen+0x08], 0x0f000f00 | 'R' | '!' << 16
+jmp _fault_coda
+
+global pageFaultHandler
+pageFaultHandler:
+mov ax, 0x10
+mov ds, ax
+pop eax ; error code
+mov ebx, 0x0f000f00 | '0' | '!' << 16
+and eax, 0x7 ; U/S,R/W,P
+add ebx, eax
+mov dword [error_screen+0x00], 0x0f000f00 | 'P' | 'G' << 16
+mov dword [error_screen+0x04], 0x0f000f00 | 'F' | 'L' << 16
+mov dword [error_screen+0x08], 0x0f000f00 | 'T' | ':' << 16
+mov dword [error_screen+0x0C], ebx
+jmp _fault_coda
+
+extern gpf_handler_v86
+global gpfHandler
+gpfHandler:
+push eax
+mov ax, 0x10
+mov ds, ax
+mov eax, dword [esp+16] ; EFLAGS
+and eax, 1 << 17 ; VM flag
+test eax, eax
+pop eax
+jnz gpf_handler_v86
+jmp gpf_handler_32
+gpf_unhandled:
+mov dword [error_screen+0x00], 0x0f000f00 | 'G' | 'P' << 16
+mov dword [error_screen+0x04], 0x0f000f00 | 'F' | '!' << 16
+jmp _fault_coda
+
+gpf_handler_32:
+push eax
+mov eax, dword [esp+8] ; EIP
+movzx eax, word [eax]
+cmp eax, 0x30CD ; int 0x30
+jne gpf_unhandled
+pop eax ; return value
+jmp return_prev_task
+
+extern return_prev_task
+
+global divisionErrorHandler
+divisionErrorHandler:
+mov ax, 0x10
+mov ds, ax
+mov dword [error_screen+0x00], 0x0f000f00 | '#' | 'D' << 16
+mov dword [error_screen+0x04], 0x0f000f00 | 'E' | '!' << 16
+jmp _fault_coda
+global boundRangeHandler
+boundRangeHandler:
+mov ax, 0x10
+mov ds, ax
+mov dword [error_screen+0x00], 0x0f000f00 | '#' | 'B' << 16
+mov dword [error_screen+0x04], 0x0f000f00 | 'R' | '!' << 16
+jmp _fault_coda
+global invalidOpcodeHandler
+invalidOpcodeHandler:
+mov ax, 0x10
+mov ds, ax
+mov dword [error_screen+0x00], 0x0f000f00 | '#' | 'U' << 16
+mov dword [error_screen+0x04], 0x0f000f00 | 'D' | '!' << 16
+jmp _fault_coda
+global deviceNotAvailableHandler
+deviceNotAvailableHandler:
+mov ax, 0x10
+mov ds, ax
+mov dword [error_screen+0x00], 0x0f000f00 | '#' | 'N' << 16
+mov dword [error_screen+0x04], 0x0f000f00 | 'D' | '!' << 16
+jmp _fault_coda
+global doubleFaultHandler
+doubleFaultHandler:
+mov ax, 0x10
+mov ds, ax
+mov dword [0xb8000+0x00], 0x0f000f00 | '#' | 'D' << 16
+mov dword [0xb8000+0x04], 0x0f000f00 | 'F' | '!' << 16
+; double faults simply abort right then
+.hlt: hlt
+jmp .hlt
+global invalidTSSHandler
+invalidTSSHandler:
+mov ax, 0x10
+mov ds, ax
+mov dword [error_screen+0x00], 0x0f000f00 | '#' | 'T' << 16
+mov dword [error_screen+0x04], 0x0f000f00 | 'S' | '!' << 16
+jmp _fault_coda
+global segmentNotPresentHandler
+segmentNotPresentHandler:
+mov ax, 0x10
+mov ds, ax
+mov dword [error_screen+0x00], 0x0f000f00 | '#' | 'N' << 16
+mov dword [error_screen+0x04], 0x0f000f00 | 'P' | '!' << 16
+jmp _fault_coda
+global stackSegmentHandler
+stackSegmentHandler:
+mov ax, 0x10
+mov ds, ax
+mov dword [error_screen+0x00], 0x0f000f00 | '#' | 'S' << 16
+mov dword [error_screen+0x04], 0x0f000f00 | 'S' | '!' << 16
+jmp _fault_coda
+global x87FloatingHandler
+x87FloatingHandler:
+mov ax, 0x10
+mov ds, ax
+mov dword [error_screen+0x00], 0x0f000f00 | '#' | 'M' << 16
+mov dword [error_screen+0x04], 0x0f000f00 | 'F' | '!' << 16
+jmp _fault_coda
+global alignmentCheckHandler
+alignmentCheckHandler:
+mov ax, 0x10
+mov ds, ax
+mov dword [error_screen+0x00], 0x0f000f00 | '#' | 'A' << 16
+mov dword [error_screen+0x04], 0x0f000f00 | 'C' | '!' << 16
+jmp _fault_coda
+global controlProtectionHandler
+controlProtectionHandler:
+mov ax, 0x10
+mov ds, ax
+mov dword [error_screen+0x00], 0x0f000f00 | '#' | 'C' << 16
+mov dword [error_screen+0x04], 0x0f000f00 | 'P' | '!' << 16
+jmp _fault_coda

handler.nasm

@@ -1,61 +1,4 @@
-extern unhandled_handler
+oldscancodesToAscii: db 0, 0 ; 0x00 - 0x01
-unhandled_handler:
-mov ax, 0x10
-mov ds, ax
-mov dword [0xb8000], 0x0f000f00 | 'E' | 'R' << 16
-mov dword [0xb8004], 0x0f000f00 | 'R' | 'O' << 16
-mov dword [0xb8008], 0x0f000f00 | 'R' | '!' << 16
-.hlt:
-hlt
-jmp .hlt
-
-global pageFaultHandler
-pageFaultHandler:
-mov ax, 0x10
-mov ds, ax
-pop eax ; error code
-mov ebx, 0x0f000f00 | '0' | '!' << 16
-and eax, 0x7 ; U/S,R/W,P
-add ebx, eax
-mov dword [0xb8000], 0x0f000f00 | 'P' | 'G' << 16
-mov dword [0xb8004], 0x0f000f00 | 'F' | 'L' << 16
-mov dword [0xb8008], 0x0f000f00 | 'T' | ':' << 16
-mov dword [0xb800C], ebx
-.hlt:
-hlt
-jmp .hlt
-
-extern gpf_handler_v86
-global gpfHandler
-gpfHandler:
-push eax
-mov ax, 0x10
-mov ds, ax
-mov eax, dword [esp+16] ; EFLAGS
-and eax, 1 << 17 ; VM flag
-test eax, eax
-pop eax
-jnz gpf_handler_v86
-jmp gpf_handler_32
-gpf_unhandled:
-mov dword [0xb8000], 0x0f000f00 | 'G' | 'P' << 16
-mov dword [0xb8004], 0x0f000f00 | 'F' | '!' << 16
-.hlt:
-hlt
-jmp .hlt
-
-gpf_handler_32:
-push eax
-mov eax, dword [esp+8] ; EIP
-movzx eax, word [eax]
-cmp eax, 0x30CD ; int 0x30
-jne gpf_unhandled
-pop eax ; return value
-jmp return_prev_task
-
-extern return_prev_task
-
-scancodesToAscii: db 0, 0 ; 0x00 - 0x01
 db "1234567890" ; 0x02 - 0x0B
 db "-=" ; 0x0C - 0x0D
 db 0, 0 ; 0x0E - 0x0F
@@ -71,8 +14,8 @@ db ' ' ; 0x39
 db 'C'
 scancodesToAsciiEnd:
 cursorCurrent: dd 0xb8000 + (80*6*2)
-global keyboardHandler
+global oldkeyboardHandler
-keyboardHandler:
+oldkeyboardHandler:
 push eax
 push ebx
 push ds
@@ -82,7 +25,7 @@ xor eax, eax
 in al, 0x60
 cmp eax, 0x3A
 jg .done
-mov al, [scancodesToAscii+eax]
+mov al, [oldscancodesToAscii+eax]
 test al, al
 jz .done
 mov ebx, [cursorCurrent]
@@ -98,8 +41,7 @@ pop eax
 iret
 
 KBDWAIT: db 0
-global kbd_wait
+oldkbd_wait:
-kbd_wait:
 mov byte [KBDWAIT], 0
 .loop:
 hlt
@@ -108,13 +50,15 @@ test eax, eax
 jz .loop
 ret
 
+TIMERVAL: dd 0
 global timerHandler
 timerHandler:
 push eax
 push ds
 mov ax, 0x10
 mov ds, ax
-inc byte [(0xb8000 + (80*8*2))]
+;inc byte [(0xb8000 + (80*8*2))]
+inc dword [TIMERVAL]
 mov al, 0x20
 out 0x20, al
 pop ds
@@ -159,103 +103,3 @@ jmp $+2
 jmp $+2
 out 0xA1, al
 ret
-
-global divisionErrorHandler
-divisionErrorHandler:
-mov ax, 0x10
-mov ds, ax
-mov dword [0xb8000], 0x0f000f00 | '#' | 'D' << 16
-mov dword [0xb8004], 0x0f000f00 | 'E' | '!' << 16
-.hlt:
-hlt
-jmp .hlt
-global boundRangeHandler
-boundRangeHandler:
-mov ax, 0x10
-mov ds, ax
-mov dword [0xb8000], 0x0f000f00 | '#' | 'B' << 16
-mov dword [0xb8004], 0x0f000f00 | 'R' | '!' << 16
-.hlt:
-hlt
-jmp .hlt
-global invalidOpcodeHandler
-invalidOpcodeHandler:
-mov ax, 0x10
-mov ds, ax
-mov dword [0xb8000], 0x0f000f00 | '#' | 'U' << 16
-mov dword [0xb8004], 0x0f000f00 | 'D' | '!' << 16
-.hlt:
-hlt
-jmp .hlt
-global deviceNotAvailableHandler
-deviceNotAvailableHandler:
-mov ax, 0x10
-mov ds, ax
-mov dword [0xb8000], 0x0f000f00 | '#' | 'N' << 16
-mov dword [0xb8004], 0x0f000f00 | 'D' | '!' << 16
-.hlt:
-hlt
-jmp .hlt
-global doubleFaultHandler
-doubleFaultHandler:
-mov ax, 0x10
-mov ds, ax
-mov dword [0xb8000], 0x0f000f00 | '#' | 'D' << 16
-mov dword [0xb8004], 0x0f000f00 | 'F' | '!' << 16
-.hlt:
-hlt
-jmp .hlt
-global invalidTSSHandler
-invalidTSSHandler:
-mov ax, 0x10
-mov ds, ax
-mov dword [0xb8000], 0x0f000f00 | '#' | 'T' << 16
-mov dword [0xb8004], 0x0f000f00 | 'S' | '!' << 16
-.hlt:
-hlt
-jmp .hlt
-global segmentNotPresentHandler
-segmentNotPresentHandler:
-mov ax, 0x10
-mov ds, ax
-mov dword [0xb8000], 0x0f000f00 | '#' | 'N' << 16
-mov dword [0xb8004], 0x0f000f00 | 'P' | '!' << 16
-.hlt:
-hlt
-jmp .hlt
-global stackSegmentHandler
-stackSegmentHandler:
-mov ax, 0x10
-mov ds, ax
-mov dword [0xb8000], 0x0f000f00 | '#' | 'S' << 16
-mov dword [0xb8004], 0x0f000f00 | 'S' | '!' << 16
-.hlt:
-hlt
-jmp .hlt
-global x87FloatingHandler
-x87FloatingHandler:
-mov ax, 0x10
-mov ds, ax
-mov dword [0xb8000], 0x0f000f00 | '#' | 'M' << 16
-mov dword [0xb8004], 0x0f000f00 | 'F' | '!' << 16
-.hlt:
-hlt
-jmp .hlt
-global alignmentCheckHandler
-alignmentCheckHandler:
-mov ax, 0x10
-mov ds, ax
-mov dword [0xb8000], 0x0f000f00 | '#' | 'A' << 16
-mov dword [0xb8004], 0x0f000f00 | 'C' | '!' << 16
-.hlt:
-hlt
-jmp .hlt
-global controlProtectionHandler
-controlProtectionHandler:
-mov ax, 0x10
-mov ds, ax
-mov dword [0xb8000], 0x0f000f00 | '#' | 'C' << 16
-mov dword [0xb8004], 0x0f000f00 | 'P' | '!' << 16
-.hlt:
-hlt
-jmp .hlt

interrupt.c

@@ -84,8 +84,6 @@ void IRQ_clear_mask(char IRQline) {
 char v86_if = 0;
 extern uint16_t *ivt;
 extern void real_test();
-__attribute((__no_caller_saved_registers__))
-extern void kbd_wait();
 extern void jmp_usermode_test();
 __attribute((__no_caller_saved_registers__))
 extern void return_prev_task();
@@ -236,8 +234,81 @@ void gpf_handler_v86(struct interrupt_frame *frame, unsigned long error_code) {
     vga[0] = 'G'; vga[2] = 'S'; int_printWord(frame->gs, (uint16_t*)&vga[4]); vga += 14;
 }
 
+uint8_t scancodesToAscii[0x3B] =
+"\0\0" // 0x00 - 0x01
+"1234567890" // 0x02 - 0x0B
+"-=" // 0x0C - 0x0D
+"\0\0" // 0x0E - 0x0F
+"qwertyuiop[]" // 0x10 - 0x1B
+"\0\0" // 0x1C - 0x1D
+"asdfghjkl;'`" // 0x1E - 0x29
+"\0" // 0x2A
+"\\zxcvbnm,./" // 0x2B - 0x35
+"\0" // 0x36
+"*" // 0x37
+"\0" // 0x38
+" " // 0x39
+"\0"; // 0x3A
+uint8_t scancodesToAsciiShift[0x3B] =
+"\0\0" // 0x00 - 0x01
+"!@#$%^&*()" // 0x02 - 0x0B
+"_+" // 0x0C - 0x0D
+"\0\0" // 0x0E - 0x0F
+"QWERTYUIOP{}" // 0x10 - 0x1B
+"\0\0" // 0x1C - 0x1D
+"ASDFGHJKL:\"~" // 0x1E - 0x29
+"\0" // 0x2A
+"|ZXCVBNM<>?" // 0x2B - 0x35
+"\0" // 0x36
+"*" // 0x37
+"\0" // 0x38
+" " // 0x39
+"\0"; // 0x3A
+uint8_t _KBDWAIT;
+uint8_t _KEYCAPS = 0, _KEYSHIFT = 0;
+uint8_t _LSTKEY = 0;
+__attribute__ ((interrupt))
+void keyboardHandler(struct interrupt_frame *frame) {
+    uint8_t key;
+    asm volatile("inb $0x60, %%al":"=a"(key));
+    if (key == 0x3A) { // caps lock press
+        _KEYCAPS = !_KEYCAPS;
+    } else if (key == 0x2A || key == 0x36) { // left and right shift press
+        _KEYSHIFT = 1;
+    } else if (key == 0xAA || key == 0xB6) { // left and right shift release
+        _KEYSHIFT = 0;
+    } else if (key < 0x3B) {
+        uint8_t ascii = _KEYCAPS != _KEYSHIFT ?
+            scancodesToAsciiShift[key] :
+            scancodesToAscii[key];
+        if (ascii) {
+            _LSTKEY = ascii;
+            _KBDWAIT = 1;
+        }
+    }
+    asm volatile("outb %%al, $0x20"::"a"(0x20));
+}
+
+__attribute((__no_caller_saved_registers__))
+void kbd_wait() {
+    _KBDWAIT = 0;
+    while(!_KBDWAIT) {
+        asm volatile("hlt");
+    }
+}
+
+__attribute((__no_caller_saved_registers__))
+uint8_t get_key() {
+    while(!_LSTKEY) {
+        asm volatile("hlt");
+    }
+    uint8_t k = _LSTKEY;
+    _LSTKEY = 0;
+    return k;
+}
+
 extern void timerHandler();
-extern void keyboardHandler();
+//extern void keyboardHandler();
 extern void gpfHandler();
 extern void pageFaultHandler();
 extern void unhandled_handler();

interrupt.h

@@ -28,6 +28,11 @@ typedef uint32_t FARPTR;
 
 FARPTR i386LinearToFp(void *ptr);
 
+__attribute((__no_caller_saved_registers__))
+void kbd_wait();
+
+__attribute((__no_caller_saved_registers__))
+uint8_t get_key();
 
 __attribute__ ((interrupt))
 void gpf_handler_v86(struct interrupt_frame *frame, unsigned long error_code);

kernel.c

@@ -69,16 +69,14 @@ extern void v86GfxMode();
 extern void v86TextMode();
 extern void v86DiskRead();
 extern char *jmp_usermode_test();
-__attribute((__no_caller_saved_registers__))
-extern void kbd_wait();
 
 extern char _edata, _v86code, _ev86code, _bstart, _bend, _loadusercode, _usercode, _eusercode;
 void setup_binary() {
     // Put V86 code in proper place based on linker
     char *s = &_edata;
     char *d = &_v86code;
-    //while (d < &_ev86code)
+    while (d < &_ev86code)
-    //    *d++ = *s++;
+        *d++ = *s++;
 
     // Put Usermode code in proper place based on linker
     s = &_loadusercode;
@@ -91,6 +89,42 @@ void setup_binary() {
         *d = 0;
 }
 
+uint16_t error_screen[80*50]; // 50-line VGA screen of error content
+
+extern uint16_t *ivt;
+uint16_t ivt_bkup[0x200];
+uint8_t bios_bkup[0x40000];
+void backup_ivtbios() {
+    for (int i = 0; i < 0x200; i++)
+        ivt_bkup[i] = ivt[i];
+    for (int i = 0; i < 0x40000; i++)
+        bios_bkup[i] = ((uint8_t*)0xC0000)[i];
+}
+
+// This should only be used during fault handling, as it is expensive
+void ensure_v86env() {
+    for (int i = 0; i < 0x200; i++)
+        ivt[i] = ivt_bkup[i];
+    for (int i = 0; i < 0x40000; i++)
+        ((uint8_t*)0xC0000)[i] = bios_bkup[i];
+    char *s = &_edata;
+    char *d = &_v86code;
+    while (d < &_ev86code)
+        *d++ = *s++;
+    for (int i = 0; i < 80*50; i++)
+        if (!error_screen[i]) error_screen[i] = 0x0f00;
+}
+
+void error_environment() {
+    ensure_v86env();
+    FARPTR v86_entry = i386LinearToFp(v86TextMode);
+    enter_v86(0x8000, 0xFF00, FP_SEG(v86_entry), FP_OFF(v86_entry));
+    printStr("Oh noes!!! System error! ;c", &error_screen[80]);
+    uint16_t *vga_text = ((uint16_t*)0xB8000);
+    for (int i = 0; i < 80*50; i++)
+        vga_text[i] = error_screen[i];
+}
+
 /*
 Real Mode Accessible (First MB)
  00000 -  00400 IVT (1kB)
@@ -260,14 +294,30 @@ void start() {
     //print_cr4();
 
     vga_text += printStr("V86 Test... ", vga_text);
+    //asm ("xchgw %bx, %bx");
     TestV86(); // has int 3 wait in v86
     vga_text = (word *)0xb8000 + (80*3);
-    printStr("Done. Press any key for next test.", vga_text);
+    backup_ivtbios();
+    vga_text += printStr("Done. Press 'N' for next test.", vga_text);
+    uint8_t key;
+    while ((key = get_key()) != 'N') {
+        *vga_text = (*vga_text & 0xFF00) | key;
+        vga_text++;
+    }
     TestGfx();
     kbd_wait();
     TestDiskRead();
     kbd_wait();
     TestFAT();
     kbd_wait();
+
+    vga_text = &((uint16_t*)0xB8000)[80*16];
+    vga_text += printStr("Press ` for a flagrant system error... ", vga_text);
+    while ((key = get_key()) != '`') {
+        *vga_text = (*vga_text & 0xFF00) | key;
+        vga_text++;
+    }
+    // flagrant system error
+    *((uint8_t*)0x1000000) = 0;
 }
 

link.ld

@@ -15,7 +15,7 @@ SECTIONS {
         _edata = .;
     }
 
-    .realmode (0x8000 + ADDR(.data) + SIZEOF(.data) - 0x100000) :
+    .realmode 0x8000 :
         AT ( ADDR(.data) + SIZEOF(.data) )
         { _v86code = .; *(.v86); _ev86code = .; }
 

usermode.nasm

@@ -16,5 +16,7 @@ cmp eax, 200
 jl .loop
 mov eax, 0xA0000
 int 0x30 ; Exit
+mov edx, 0x105000 ; somewhere in kernel mem
+mov edx, [edx] ; should page fault
 xor ebx, ebx
 div bl ; Unhandled DIV0 exception