diff options
| -rw-r--r-- | src/entry.asm | 194 |
1 files changed, 90 insertions, 104 deletions
diff --git a/src/entry.asm b/src/entry.asm index 5fdf4c2..00b5874 100644 --- a/src/entry.asm +++ b/src/entry.asm @@ -47,12 +47,6 @@ %define EXT2_DIRECT_POINTER_COUNT 0x0c ; Direct pointer count %define EXT2_SIG 0xef53 ; Signature -; MMAP constants -%define MMAP_START 0x400 ; Struct starts at 0x400, ends at 0x500 -%define MMAP_SIZE 0x18 ; Struct size -%define MMAP_SIG 0x0534d4150 ; Signature ("SMAP") -%define MMAP_BIOS_MAGIC 0xe820 ; BIOS int 15h code to get address map - ; Video constants (VESA) %define VESA_START 0x2000 ; Struct starts at 0x2000 %define VESA_END 0x3000 ; Struct ends at 0x3000 @@ -78,10 +72,13 @@ ; GDT constants (bitmap) %define GDT_MAX_LIMIT 0xffff ; I just use the max limit lel %define GDT_PRESENT 0b10000000 ; Is present +%define GDT_RING3 0b01100000 ; Privilege level 3 %define GDT_DESCRIPTOR 0b00010000 ; Descriptor type, set for code/data %define GDT_EXECUTABLE 0b00001000 ; Can be executed %define GDT_READWRITE 0b00000010 ; Read/write access for code/data -%define GDT_GRANULARITY (0xc0 | 0x0f) ; Use paged 32 bit granularity +%define GDT_ACCESSED 0b00000001 ; Whether segment is accessed +%define GDT_GRANULARITY (0x80 | 0x0f) ; Page granularity (4KiB) +%define GDT_SIZE (0x40 | 0x0f) ; Use 32 bit selectors %define GDT_DATA_OFFSET 0x10 ; Offset to GDT data segment ; Kernel constants @@ -297,14 +294,6 @@ stage_two: ; Set video mode call video_map - ; Load mmap - xor eax, eax - mov es, eax - mov edi, MMAP_START - push edi - call memory_map - push edi - jmp protected_mode_enter kernel_load: @@ -322,37 +311,37 @@ kernel_load: call disk_read jmp .end -.indirect: - push di - push bx - push cx - - xor ebx, ebx - - ; Read singly indirect pointer - mov bx, EXT2_GET_ADDRESS(EXT2_KERNEL_INODE) ; First block - lea di, [bx + EXT2_IND_POINTER_OFFSET] ; Address of singly indirect pointer - mov bx, 0x3000 ; Arbitrary address - mov ax, [di] ; Set ax = block pointer - shl ax, 1 ; Multiply ax by 2 - mov [lba], ax - mov [dest], bx - call disk_read - - ; Read data - sub cx, EXT2_DIRECT_POINTER_COUNT - lea di, [ebx + 4 * ecx] - mov bx, 0x4000 ; Arbitrary address - mov ax, [di] - shl ax, 1 - ;sub bx, 0x400 - mov [lba], ax - mov [dest], bx - call disk_read - - pop cx - pop bx - pop di +;.indirect: +; push di +; push bx +; push cx +; +; xor ebx, ebx +; +; ; Read singly indirect pointer +; mov bx, EXT2_GET_ADDRESS(EXT2_KERNEL_INODE) ; First block +; lea di, [bx + EXT2_IND_POINTER_OFFSET] ; Address of singly indirect pointer +; mov bx, 0x3000 ; Arbitrary address +; mov ax, [di] ; Set ax = block pointer +; shl ax, 1 ; Multiply ax by 2 +; mov [lba], ax +; mov [dest], bx +; call disk_read +; +; ; Read data +; sub cx, EXT2_DIRECT_POINTER_COUNT +; lea di, [ebx + 4 * ecx] +; mov bx, 0x4000 ; Arbitrary address +; mov ax, [di] +; shl ax, 1 +; ;sub bx, 0x400 +; mov [lba], ax +; mov [dest], bx +; call disk_read +; +; pop cx +; pop bx +; pop di .end: add bx, 0x400 ; 1kb increase @@ -361,49 +350,6 @@ kernel_load: jnz kernel_load ret -; Tries to load a memory map using BIOS INT 15h and e820h -memory_map: - xor ebx, ebx ; Must be 0 by spec - mov edx, MMAP_SIG ; "SMAP" in hex - mov eax, MMAP_BIOS_MAGIC ; Specify MMAP information - mov [es:di + 20], dword 1 ; Force a valid ACPI entry - mov ecx, MMAP_SIZE ; Request struct size - int MISC_INT ; BIOS interrupt - jc short .fail ; Carry means "unsupported function" - mov edx, MMAP_SIG ; Mov for verification - cmp eax, edx ; Verification: Must be "SMAP" - jne short .fail ; Result wasn't correct signature - test ebx, ebx ; Is size >1 - je short .fail ; Nope, worthless :( - jmp short .loop ; Loop! -.next: - mov eax, MMAP_BIOS_MAGIC ; Re-move because 0x15 clears or sth - mov [es:di + 20], dword 1 ; Force a valid ACPI entry - mov ecx, MMAP_SIZE ; Request struct size - int MISC_INT ; BIOS interrupt - jc short .done ; Carry means "end of list already reached" - mov edx, MMAP_SIG ; Repair register (safety first!) -.loop: - jcxz .skip ; Skip 0-length entries - cmp cl, 20 ; Is the response correct ACPI spec (24 byte)? - jbe short .notext ; Nope? Jump! - test byte [es:di + 20], 1 ; Is the "ignore this data" bit clear? - je short .skip ; Yep? Skip! -.notext: - mov ecx, [es:di + 8] ; Get lower 32 bits of region - or ecx, [es:di + 12] ; "Or" with upper 32 bits to test for zero - jz .skip ; It's zero, skip! - add di, MMAP_SIZE ; Else, next! -.skip: - test ebx, ebx ; If ebx is 0, list is complete - jne short .next ; Else, next! -.done: - clc ; Clear carry - ret ; Finished! -.fail: - stc ; Set "unsupported function" - ret ; Finished! - protected_mode_enter: cli ; Turn off interrupts @@ -425,6 +371,8 @@ protected_mode_enter: mov gs, ax lgdt [gdt_desc] ; Load GDT + mov ax, 0x28 + ltr ax ; Set protected mode via cr0 mov eax, cr0 @@ -435,11 +383,6 @@ protected_mode_enter: bits 32 ; Woah, so big! protected_mode: - pop ecx ; End of memory map - mov [mem_info + 4], ecx ; Ending boundary of struct - pop ecx ; Start of memory map - mov [mem_info], ecx ; Starting boundary of struct - mov ax, GDT_DATA_OFFSET ; Data segment offset of GDT mov ds, ax mov es, ax @@ -452,18 +395,40 @@ protected_mode: mov eax, vid_info ; Pass VBE struct to kernel push eax ; Push as second kernel parameter - mov eax, mem_info ; Pass mmap to kernel - push eax ; Push as first kernel parameter - mov edx, KERNEL_POSITION lea eax, [edx] call eax -; Memory map -align 16 -mem_info: - dd 0 ; Start address - dd 0 ; End address +; TSS +tss_entry: + dd 0 ; Previous TSS + dd STACK_POINTER ; esp0 + dd GDT_DATA_OFFSET ; ss0 + dd 0 ; esp1 + dd 0 ; ss1 + dd 0 ; esp2 + dd 0 ; ss2 + dd 0 ; cr3 + dd 0 ; eip + dd 0 ; eflags + dd 0 ; eax + dd 0 ; ecx + dd 0 ; edx + dd 0 ; ebx + dd 0 ; esp + dd 0 ; ebp + dd 0 ; esi + dd 0 ; edi + dd 0x13 ; es + dd 0x0b ; cs + dd 0x13 ; ss + dd 0x13 ; ds + dd 0x13 ; fs + dd 0x13 ; gs + dd 0 ; ldt + dw 0 ; trap + dw 0 ; iomap base +tss_entry_end: ; GDT align 32 @@ -476,14 +441,35 @@ gdt_code: ; Code segment dw 0 ; First base db 0 ; Second base db (GDT_PRESENT | GDT_DESCRIPTOR | GDT_EXECUTABLE | GDT_READWRITE) ; Configuration - db GDT_GRANULARITY ; Granularity + db (GDT_GRANULARITY | GDT_SIZE) ; Flags db 0 ; Third base gdt_data: ; Data segment dw GDT_MAX_LIMIT ; Limit dw 0 ; First base db 0 ; Second base db (GDT_PRESENT | GDT_DESCRIPTOR | GDT_READWRITE) ; Configuration - db GDT_GRANULARITY ; Granularity + db (GDT_GRANULARITY | GDT_SIZE) ; Flags + db 0 ; Third base +gdt_user_code: ; User code segment + dw GDT_MAX_LIMIT ; Limit + dw 0 ; First base + db 0 ; Second base + db (GDT_PRESENT | GDT_RING3 | GDT_DESCRIPTOR | GDT_EXECUTABLE | GDT_READWRITE) ; Configuration + db (GDT_GRANULARITY | GDT_SIZE) ; Flags + db 0 ; Third base +gdt_user_data: ; Data segment + dw GDT_MAX_LIMIT ; Limit + dw 0 ; First base + db 0 ; Second base + db (GDT_PRESENT | GDT_RING3 | GDT_DESCRIPTOR | GDT_READWRITE) ; Configuration + db (GDT_GRANULARITY | GDT_SIZE) ; Flags + db 0 ; Third base +gdt_tss: ; TSS segment + dw tss_entry + (tss_entry_end - tss_entry) ; Limit + dw tss_entry ; First base + db 0 ; Second base + db (GDT_PRESENT | GDT_RING3 | GDT_EXECUTABLE | GDT_ACCESSED) ; Configuration + db GDT_SIZE ; Flags db 0 ; Third base gdt_end: gdt_desc: |