mirror of
https://github.com/gbowne1/ClassicOS.git
synced 2025-11-16 22:35:26 -08:00
99 lines
2.3 KiB
NASM
99 lines
2.3 KiB
NASM
[BITS 32]
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global _start
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global ata_lba_read
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extern load_kernel
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_start:
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; Set up segments
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; Data segments
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mov ax, 0x10
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mov ds, ax
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mov es, ax
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mov fs, ax
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mov gs, ax
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mov ss, ax
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; Code segment
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mov ax, 0x08
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mov cs, ax
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; Stack (must be identity-mapped)
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mov esp, 0x90000
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call load_kernel
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jmp eax
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; ----------------------------------------------------------------------------
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; ATA read sectors (LBA mode)
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;
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; sysv32 abi signature:
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; void ata_lba_read(uint32_t lba, uint8_t nsect, void *addr);
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; ----------------------------------------------------------------------------
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ata_lba_read:
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push ebp
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mov ebp, esp
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push ebx
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push ecx
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push edx
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push edi
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mov eax, [ebp+8] ; arg #1 = LBA
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mov cl, [ebp+12] ; arg #2 = # of sectors
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mov edi, [ebp+16] ; arg #3 = buffer address
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and eax, 0x0FFFFFFF
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mov ebx, eax ; Save LBA in RBX
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mov edx, 0x01F6 ; Port to send drive and bit 24 - 27 of LBA
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shr eax, 24 ; Get bit 24 - 27 in al
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or al, 11100000b ; Set bit 6 in al for LBA mode
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out dx, al
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mov edx, 0x01F2 ; Port to send number of sectors
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mov al, cl ; Get number of sectors from CL
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out dx, al
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mov edx, 0x1F3 ; Port to send bit 0 - 7 of LBA
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mov eax, ebx ; Get LBA from EBX
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out dx, al
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mov edx, 0x1F4 ; Port to send bit 8 - 15 of LBA
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mov eax, ebx ; Get LBA from EBX
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shr eax, 8 ; Get bit 8 - 15 in AL
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out dx, al
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mov edx, 0x1F5 ; Port to send bit 16 - 23 of LBA
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mov eax, ebx ; Get LBA from EBX
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shr eax, 16 ; Get bit 16 - 23 in AL
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out dx, al
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mov edx, 0x1F7 ; Command port
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mov al, 0x20 ; Read with retry.
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out dx, al
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mov bl, cl ; Save # of sectors in BL
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.wait_drq:
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mov edx, 0x1F7
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.do_wait_drq:
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in al, dx
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test al, 8 ; the sector buffer requires servicing.
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jz .do_wait_drq ; keep polling until the sector buffer is ready.
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mov edx, 0x1F0 ; Data port, in and out
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mov ecx, 256
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rep insw ; in to [RDI]
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dec bl ; are we...
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jnz .wait_drq ; ...done?
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pop edi
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pop edx
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pop ecx
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pop ebx
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pop ebp
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ret
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