Implemented Paging! Moved Kernel to 0x100000, Moved TSS above 1M, Moved V86 to 0x8000, Moved Usermode test to 0x400000, Moved lots of things!

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
+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
-CFLAGS = -target "i686-elf" -m32 -mgeneral-regs-only -ffreestanding -march=pentium-m -fno-stack-protector -nostdlib -c
+CFLAGS = -target "i686-elf" -m32 -mgeneral-regs-only -ffreestanding -march=pentium-m -fno-stack-protector -Wno-int-conversion -nostdlib -c
 
 %.o: %.nasm
 	nasm -f elf32 -o $@ $<
@@ -9,7 +9,7 @@ CFLAGS = -target "i686-elf" -m32 -mgeneral-regs-only -ffreestanding -march=penti
 
 all: $(objects)
 	nasm boot.nasm -o boot.bin
-	gcc -Tlink.ld -m32 -ffreestanding -nostartfiles -nostdlib -o kernel.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=512 seek=1 conv=notrunc if=kernel.bin of=virtdisk.bin

boot.nasm

@@ -7,7 +7,7 @@ mov es, ax
 mov ah, 0x42
 mov si, addr_packet
 int 0x13
-jnc 0x8000
+jnc entry
 push 0xb800
 pop es
 xor di, di
@@ -21,6 +21,41 @@ loop err_print
 hlt_loop:
 hlt
 jmp hlt_loop
+entry:
+cli             ; no interrupts
+xor ax,ax
+mov ds, ax
+lgdt [gdt_desc]  ; load gdt register
+mov eax, cr0    ; set pmode bit
+or al, 1
+mov cr0, eax
+jmp 08h:Pmode
+[BITS 32]
+Pmode:
+mov ax, 0x10
+mov ds, ax
+mov es, ax
+mov esi, 0x8000
+mov edi, 0x100000
+mov ecx, 0x10000
+rep movsb
+jmp 08h:0x100000
+gdt_desc:
+    dw gdt_end - gdt
+    dd gdt
+gdt:
+gdt_null: dq 0
+gdt_code: dw 0xFFFF, 0     ; bits 0-15 limit (4GB), bits 0-15 base address
+          db 0             ; bits 16-23 base address
+          db 10011010b     ; access byte
+          db 11001111b     ; bits 16-19 limit (4GB), 4 bits flags
+          db 0 ; bits 24-31 base address
+gdt_data: dw 0xFFFF, 0     ; bits 0-15 limit (4GB), bits 0-15 base address
+          db 0             ; bits 16-23 base address
+          db 10010010b     ; access byte
+          db 11001111b     ; bits 16-19 limit (4GB), 4 bits flags
+          db 0 ; bits 24-31 base address
+gdt_end:
 
 string: db 'DISK ERROR'
 

entry.nasm

@@ -1,14 +1,9 @@
-[BITS 16]
 global entry
 entry:
-cli             ; no interrupts
-xor ax,ax
-mov ds, ax
 lgdt [gdt_desc]  ; load gdt register
-mov eax, cr0    ; set pmode bit
+jmp Pmodecode
-or al, 1
+
-mov cr0, eax
+extern gdt_desc
-jmp 08h:Pmodecode
 
 [BITS 32]
 Pmodecode:
@@ -30,110 +25,3 @@ hlt
 jmp hlt_loop
 
 extern start
-
-; currently unused first 8MB identity paging
-; taken from Linux 0.01
-setup_paging:
-mov ecx, 1024*3 ; 3K?
-xor eax, eax
-mov edi, 0x1000
-rep stosd ; zero first 3K for some reason
-mov edi, 0x4000
-mov eax, 0x800007 ; 8MB + 7
-std ; fill backwards
-.fill:
-stosd
-sub eax, 0x1000
-jge .fill
-cld ; fix direction
-mov dword [0x0000], 0x2000 + 7
-mov dword [0x0004], 0x3000 + 7
-mov eax, 0x1000
-mov cr3, eax ; page dir start 0x1000
-mov eax, cr0
-or eax, 0x80000000
-mov cr0, eax ; set paging bit
-ret ; flushes pre-fetch queue
-
-user_test:
-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 edi, 0xA0000
-xor eax, eax
-.loop:
-mov ecx, 320
-rep stosb
-inc al
-cmp eax, 200
-jl .loop
-mov eax, 0xA0000
-int 0x30 ; Exit
-xor ebx, ebx
-div bl ; Unhandled DIV0 exception
-
-global jmp_usermode_test
-jmp_usermode_test:
-pop eax ; return address
-mov ecx, esp ; return stack
-call save_current_task
-mov esp, 0x500000 ; usermode stack
-mov eax, 0x20 | 3
-mov ds, ax
-mov es, ax
-mov fs, ax
-mov gs, ax
-mov eax, esp
-push 0x20 | 3
-push eax
-pushfd
-push 0x18 | 3
-push user_test
-iret
-
-extern save_current_task
-
-global flushTSS
-flushTSS:
-mov ax, 0x28
-ltr ax
-ret
-
-extern tss_data
-
-global ivt
-ivt: dd 0x00000000
-
-gdt_desc:
-    dw gdt_end - gdt
-    dd gdt
-gdt:
-gdt_null: dq 0
-gdt_code: dw 0xFFFF, 0     ; bits 0-15 limit (4GB), bits 0-15 base address
-          db 0             ; bits 16-23 base address
-          db 10011010b     ; access byte
-          db 11001111b     ; bits 16-19 limit (4GB), 4 bits flags
-          db 0 ; bits 24-31 base address
-gdt_data: dw 0xFFFF, 0     ; bits 0-15 limit (4GB), bits 0-15 base address
-          db 0             ; bits 16-23 base address
-          db 10010010b     ; access byte
-          db 11001111b     ; bits 16-19 limit (4GB), 4 bits flags
-          db 0 ; bits 24-31 base address
-gdt_r3code: dw 0xFFFF, 0     ; bits 0-15 limit (4GB), bits 0-15 base address
-          db 0             ; bits 16-23 base address
-          db 0xFA     ; access byte
-          db 11001111b     ; bits 16-19 limit (4GB), 4 bits flags
-          db 0 ; bits 24-31 base address
-gdt_r3data: dw 0xFFFF, 0     ; bits 0-15 limit (4GB), bits 0-15 base address
-          db 0             ; bits 16-23 base address
-          db 0xF2     ; access byte
-          db 11001111b     ; bits 16-19 limit (4GB), 4 bits flags
-          db 0 ; bits 24-31 base address
-gdt_tss:  dw 0x2080, 0x0000;26*4, tss_data     ; bits 0-15 limit (4GB), bits 0-15 base address
-          db 0x2             ; bits 16-23 base address
-          db 0x89     ; access byte
-          db 00000000b     ; bits 16-19 limit (4GB), 4 bits flags
-          db 0 ; bits 24-31 base address
-gdt_end:

gdt.nasm

@@ -0,0 +1,35 @@
+global ivt
+ivt: dd 0x00000000
+
+global gdt_desc
+gdt_desc:
+    dw gdt_end - gdt
+    dd gdt
+gdt:
+gdt_null: dq 0
+gdt_code: dw 0xFFFF, 0     ; bits 0-15 limit (4GB), bits 0-15 base address
+          db 0             ; bits 16-23 base address
+          db 10011010b     ; access byte
+          db 11001111b     ; bits 16-19 limit (4GB), 4 bits flags
+          db 0 ; bits 24-31 base address
+gdt_data: dw 0xFFFF, 0     ; bits 0-15 limit (4GB), bits 0-15 base address
+          db 0             ; bits 16-23 base address
+          db 10010010b     ; access byte
+          db 11001111b     ; bits 16-19 limit (4GB), 4 bits flags
+          db 0 ; bits 24-31 base address
+gdt_r3code: dw 0xFFFF, 0     ; bits 0-15 limit (4GB), bits 0-15 base address
+          db 0             ; bits 16-23 base address
+          db 0xFA     ; access byte
+          db 11001111b     ; bits 16-19 limit (4GB), 4 bits flags
+          db 0 ; bits 24-31 base address
+gdt_r3data: dw 0xFFFF, 0     ; bits 0-15 limit (4GB), bits 0-15 base address
+          db 0             ; bits 16-23 base address
+          db 0xF2     ; access byte
+          db 11001111b     ; bits 16-19 limit (4GB), 4 bits flags
+          db 0 ; bits 24-31 base address
+gdt_tss:  dw 0x2080, 0x0000;26*4, tss_data     ; bits 0-15 limit (4GB), bits 0-15 base address
+          db 0x20            ; bits 16-23 base address
+          db 0x89     ; access byte
+          db 00000000b     ; bits 16-19 limit (4GB), 4 bits flags
+          db 0 ; bits 24-31 base address
+gdt_end:

handler.nasm

@@ -9,6 +9,22 @@ mov dword [0xb8008], 0x0f000f00 | 'R' | '!' << 16
 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:

interrupt.c

@@ -237,6 +237,7 @@ void gpf_handler_v86(struct interrupt_frame *frame, unsigned long error_code) {
 extern void timerHandler();
 extern void keyboardHandler();
 extern void gpfHandler();
+extern void pageFaultHandler();
 extern void unhandled_handler();
 extern void picInit();
 void set_system_gate(uint8_t gate, void (*handler)()) {
@@ -272,6 +273,7 @@ void setup_interrupts() {
     set_system_gate(0x21, keyboardHandler);
     //set_trap_gate(13, gpf_handler_v86);
     set_trap_gate(13, gpfHandler);
+    set_trap_gate(14, pageFaultHandler);
 
     asm volatile("lidt %0": : "m"(IDTR));
     picInit();

kernel.c

@@ -3,8 +3,8 @@
 #include "dosfs/dosfs.h"
 #include "print.h"
 #include "interrupt.h"
-
 #include "tss.h"
+#include "paging.h"
 
 typedef unsigned short word;
 
@@ -72,29 +72,49 @@ 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)
+        *d++ = *s++;
+
+    // Put Usermode code in proper place based on linker
+    s = &_loadusercode;
+    d = &_usercode;
+    while (d < &_eusercode)
+        *d++ = *s++;
+
+    // Clear BSS area
+    for (d = &_bstart; d < &_bend; d++)
+        *d = 0;
+}
+
 /*
 Real Mode Accessible (First MB)
  00000 -  00400 IVT (1kB)
  00400 -  01000 Unused (3kB)
- 01000 -  04000 Paging (12kB)
+ 01000 -  04000 Free (12kB)
  04000 -  07C00 Free (15kB)
  07C00 -  08000 Boot (512B)
- 08000 -  20000 Kernel Code (96kB)
+ 08000 -  20000 V86 Code (96kB)
- 20000 -  20080 TSS (128B)
+ 20000 -  30000 Disk Buffer (64kB)
- 20080 -  22080 TSS IOMAP (8kB)
- 22080 -  22400 Unused (896B)
- 22400 -  23000 Free (3kB)
- 23000 -  30000 Disk Buffer (52kB)
  30000 -  80000 Free (320kB)
  80000 -  90000 Real Mode Stack (64kB)
  90000 -  A0000 Free (64kB)
- A0000 -  FFFFF BIOS Area (384kB)
+ A0000 -  C0000 VGA (128kB)
+ C0000 -  FFFFF BIOS Area (256kB)
 Protected Only (1MB+)
-100000 - 300000 Free (2mB)
+100000 - 200000 Kernel Code (1mB)
+200000 - 200080 TSS (128B)
+200080 - 202080 TSS IOMAP (8kB)
+202080 - 300000 Free (~1mB)
 300000 - 310000 Task Stack (64kB)
 310000 - 320000 Interrupt Stack (64kB)
 320000 - 400000 Kernel Stack (896kB)
-400000 - 500000 Usermode Stack (1mB)
+400000 - 700000 Usermode Code (3mB)
+700000 - 800000 Usermode Stack (1mB)
 */
 
 void TestV86() {
@@ -218,14 +238,16 @@ void start() {
     if (!sse) return;
     enable_sse();
 
+    setup_binary();
+
     // edit
     setup_interrupts();
     setup_tss();
-    print_flags();
+    init_paging();
+    //print_flags();
     print_cr0();
-    print_cr3();
+    //print_cr3();
-    print_cr4();
+    //print_cr4();
-    //asm ("xchgw %bx, %bx");
 
     TestV86(); // has int 3 wait in v86
     TestGfx();

link.ld

@@ -2,18 +2,34 @@ OUTPUT_FORMAT(binary)
 ENTRY(entry)
 
 SECTIONS {
-    . = 0x8000;
+    . = 0x100000;
 
     .text : ALIGN(0x1000) {
-        *(.text)
+        *(.text);
     }
 
     .data : ALIGN(0x1000) {
-        *(.data)
+        *(.data);
-        *(.rodata)
+        *(.rodata);
+        *(.rodata*);
+        _edata = .;
     }
 
-    .bss : ALIGN(0x1000) {
+    .realmode 0x8000 :
-        *(.bss)
+        AT ( ADDR(.data) + SIZEOF(.data) )
+        { _v86code = .; *(.v86); _ev86code = .; }
+
+    . = ADDR(.data) + SIZEOF(.data) + SIZEOF(.realmode);
+    .thing : { _loadusercode = .; }
+
+    .usermode 0x400000 :
+        AT ( ADDR(.data) + SIZEOF(.data) + SIZEOF(.realmode) )
+        { _usercode = .; *(.user); _eusercode = .; }
+
+    . = ADDR(.data) + SIZEOF(.data) + SIZEOF(.realmode) + SIZEOF(.usermode);
+
+    .bss : ALIGN(0x1000)
+    {
+        _bstart = .; *(.bss); _bend = .;
     }
 }

paging.c

@@ -0,0 +1,50 @@
+#include "paging.h"
+
+uint32_t page_directory[1024] __attribute__((aligned(4096)));
+uint32_t first_page_table[1024] __attribute__((aligned(4096))); // 0x00000000 - 0x00400000
+uint32_t second_page_table[1024] __attribute__((aligned(4096))); // 0x00400000 - 0x00800000
+
+void enable_paging() {
+    asm(
+        "mov %%eax, %%cr3\n"
+        "mov %%cr0, %%eax\n"
+        "or $0x80000001, %%eax\n"
+        "mov %%eax, %%cr0\n"
+    ::"a"(page_directory));
+}
+
+void init_paging() {
+    for (int i = 0; i < 1024; i++)
+        // Supervisor, R/W, Not Present
+        page_directory[i] = 2;
+
+    // First Page Table
+    // First MB: Real Mode
+    {
+        int i;
+        // Up to 0xC0000
+        // TODO make some areas here Read Only
+        for (i = 0;i < 16*0xC; i++)
+            // User, R/W, Present
+            first_page_table[i] = (i * 0x1000) |4|2|1;
+        // Remainder of first MB BIOS Area (writable?)
+        for (;i < 256; i++)
+            // User, R/W, Present
+            first_page_table[i] = (i * 0x1000) |4|2|1;
+    }
+    // Next 3MB: Kernel
+    for (int i = 256; i < 1024; i++)
+        // Supervisor, R/W, Present
+        first_page_table[i] = (i * 0x1000) |2|1;
+
+    // Usermode Page Table
+    for (int i = 0; i < 1024; i++)
+        // User, R/W, Present
+        second_page_table[i] = (i * 0x1000 + 0x400000) |4|2|1;
+
+    // User, R/W, Present
+    page_directory[0] = ((uintptr_t)first_page_table)|4|2|1;
+    page_directory[1] = ((uintptr_t)second_page_table)|4|2|1;
+
+    enable_paging();
+}

paging.h

@@ -0,0 +1,3 @@
+#include <stdint.h>
+
+void init_paging();

task.nasm

@@ -1,3 +1,9 @@
+global flushTSS
+flushTSS:
+mov ax, 0x28
+ltr ax
+ret
+
 task_ptr: equ (0x310000-4)
 
 ; return address in EAX
@@ -56,3 +62,42 @@ mov eax, [edx+12+16] ; ds
 mov ds, ax
 mov eax, ecx ; restore return value
 iret
+
+; extern void enter_v86(uint32_t ss, uint32_t esp, uint32_t cs, uint32_t eip);
+global enter_v86
+enter_v86:
+pop eax ; return address
+mov ecx, esp ; return stack
+call save_current_task
+mov ebp, esp               ; save stack pointer
+push dword  [ebp+0]        ; ss
+push dword  [ebp+4]        ; esp
+pushfd                     ; eflags
+or dword [esp], (1 << 17)  ; set VM flags
+;or dword [esp], (3 << 12) ; IOPL 3
+push dword [ebp+8]        ; cs
+push dword  [ebp+12]       ; eip
+iret
+
+; return address in eax, return stack in ebp
+;extern save_current_task
+
+extern user_test
+global jmp_usermode_test
+jmp_usermode_test:
+pop eax ; return address
+mov ecx, esp ; return stack
+call save_current_task
+mov esp, 0x800000 ; usermode stack
+mov eax, 0x20 | 3
+mov ds, ax
+mov es, ax
+mov fs, ax
+mov gs, ax
+mov eax, esp
+push 0x20 | 3
+push eax
+pushfd
+push 0x18 | 3
+push user_test
+iret

tss.c

@@ -33,7 +33,7 @@ struct __attribute__((__packed__)) tss_entry_struct {
 };
 struct tss_entry_struct *tss_data;
 void write_tss() {
-    tss_data = (struct tss_entry_struct *)0x20000;
+    tss_data = (struct tss_entry_struct *)0x200000;
     for (int i = 0; i < 0x2080; i++)
         ((uint8_t*)tss_data)[i] = 0;
     tss_data->ss0 = 0x10;

usermode.nasm

@@ -0,0 +1,20 @@
+[SECTION .user]
+global user_test
+user_test:
+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 edi, 0xA0000
+xor eax, eax
+.loop:
+mov ecx, 320
+rep stosb
+inc al
+cmp eax, 200
+jl .loop
+mov eax, 0xA0000
+int 0x30 ; Exit
+xor ebx, ebx
+div bl ; Unhandled DIV0 exception

v86.nasm

@@ -1,4 +1,5 @@
 [BITS 16]
+[SECTION .v86]
 real_hexprint:
 xor cx, cx
 mov bl, al
@@ -77,23 +78,3 @@ db 0x10, 0x00 ; size, reserved
 dw 0x1 ; blocks
 dd 0x23000000 ; transfer buffer 0x23000
 dq 0x1 ; start block
-
-[BITS 32]
-; extern void enter_v86(uint32_t ss, uint32_t esp, uint32_t cs, uint32_t eip);
-global enter_v86
-enter_v86:
-pop eax ; return address
-mov ecx, esp ; return stack
-call save_current_task
-mov ebp, esp               ; save stack pointer
-push dword  [ebp+0]        ; ss
-push dword  [ebp+4]        ; esp
-pushfd                     ; eflags
-or dword [esp], (1 << 17)  ; set VM flags
-;or dword [esp], (3 << 12) ; IOPL 3
-push dword [ebp+8]        ; cs
-push dword  [ebp+12]       ; eip
-iret
-
-; return address in eax, return stack in ebp
-extern save_current_task