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104 lines
2.4 KiB
ArmAsm
104 lines
2.4 KiB
ArmAsm
;
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; Ullrich von Bassewitz, 2002-11-29
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;
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; Common functions of the extended memory API.
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;
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.export em_clear_ptr
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.import return0
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.importzp ptr1
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.include "em-kernel.inc"
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.include "em-error.inc"
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;----------------------------------------------------------------------------
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; Variables
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.bss
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_em_drv: .res 2 ; Pointer to driver
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; Jump table for the driver functions.
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.data
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emd_vectors:
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emd_install: jmp return0
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emd_uninstall: jmp return0
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emd_pagecount: jmp return0
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emd_map: jmp return0
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emd_use: jmp return0
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emd_commit: jmp return0
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emd_copyfrom: jmp return0
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emd_copyto: jmp return0
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; Driver header signature
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.rodata
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emd_sig: .byte $65, $6d, $64, $00 ; "emd", version
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emd_sig_len = * - emd_sig
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;----------------------------------------------------------------------------
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; unsigned char __fastcall__ em_install (void* driver);
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; /* Install the driver once it is loaded */
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_em_install:
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sta _em_drv
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sta ptr1
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stx _em_drv+1
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stx ptr1+1
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; Check the driver signature
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ldy #emd_sig_len-1
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@L0: lda (ptr1),y
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cmp emd_sig,y
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bne inv_drv
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dey
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bpl @L0
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; Copy the jump vectors
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ldy #EMD_HDR_JUMPTAB
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ldx #0
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@L1: inx ; Skip the JMP opcode
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jsr copy ; Copy one byte
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jsr copy ; Copy one byte
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cpx #(EMD_HDR_JUMPCOUNT*3)
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bne @L1
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jmp emd_install ; Call driver install routine
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; Driver signature invalid
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inv_drv:
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lda #EM_ERR_INV_DRIVER
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ldx #0
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rts
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; Copy one byte from the jump vectors
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copy: lda (ptr1),y
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sta emd_vectors,x
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iny
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inx
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rts
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;----------------------------------------------------------------------------
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; unsigned char __fastcall__ em_uninstall (void);
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; /* Uninstall the currently loaded driver and return an error code.
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; * Note: This call does not free allocated memory.
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; */
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_em_uninstall:
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jsr emd_uninstall ; Call driver routine
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em_clear_ptr: ; External entry point
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lda #0
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sta _em_drv
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sta _em_drv+1 ; Clear the driver pointer
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tax
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rts ; Return zero
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