492 lines
14 KiB
Plaintext
492 lines
14 KiB
Plaintext
include pmem.i
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include cards.i
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include start.i
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section .text,text
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; Initialize the virtual memory manager
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public vmem_init
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vmem_init:
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movem.l d2/d3, -(a7)
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move.w #$5, d0 ; Get the pointer to the MMU card
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jsr find_first_card
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move.l a0, vmem_mmu_base_addr ; Save it for later use
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; Map 3 pages to dummy physical frames for use in accessing user page mappings
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move.l #$FFFFC000, d0
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move.l #3, d1
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move.l #0, d2
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move.l #$2, d3
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jsr vmem_map_free_to
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move.l a0, vmem_active_space_mapping_ptr ; Save the pointer for later use
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; Same as above for the secondary address space
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move.l #$FFFFC000, d0
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move.l #3, d1
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move.l #0, d2
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move.l #$2, d3
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jsr vmem_map_free_to
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move.l a0, vmem_secondary_space_mapping_ptr ; Save the pointer for later use
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movem.l (a7)+, d2/d3
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; Activate the kernel address space
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move.l #kernel_address_space, a0
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jsr vmem_activate_addr_space
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rts
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; Clears the TLB entry of the page pointed to by a0
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public vmem_clear_tlb_entry
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vmem_clear_tlb_entry:
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; Write the address to the TLB clear register of the MMU card
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move.l vmem_mmu_base_addr, a1
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move.l a0, ($10,a1)
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rts
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; Activates the address space pointed to by a0
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public vmem_activate_addr_space
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vmem_activate_addr_space:
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movem.l a2, -(a7)
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move.l a0, vmem_active_space_ptr ; Set the pointer to the current address space
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move.l vmem_mmu_base_addr, a1 ; Get the MMU card base into a1
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move.l vmem_active_space_mapping_ptr, a2 ; Load the pointer to the active space mapping pages into a2
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move.l #2, d0 ; Loop 3 times, count -1 due to dbra looping n+1 times
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vaas_loop:
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move.l (a0)+, d1 ; Read the next mapping frame into d1
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movem.l d0/d1/d2/d3/a0/a1, -(a7)
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; Map the mapping page pointed to by a2 to the mapping frame just read into d1
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move.l a2, a0
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move.l d1, d0
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move.l #1, d1
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move.l #0, d2
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move.l #$2, d3
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jsr vmem_map_to
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movem.l (a7)+, d0/d1/d2/d3/a0/a1
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cmp.l #0, d1 ; If the mapping frame isn't 0, mark it as active
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beq.b .1
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ori.l #3, d1
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.1:
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move.l d1, (a1)+ ; Write the frame to the next quarter mapping register in the MMU
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adda.l #$1000, a2 ; Advance to the next mapping page
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dbra d0, vaas_loop ; Loop back if there are more frames to read
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movem.l (a7)+, a2
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rts
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; Sets the secondary address space
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public vmem_set_secondary_addr_space
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vmem_set_secondary_addr_space:
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move.l a0, vmem_secondary_space_ptr ; Set the pointer to the secondary address space
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move.l vmem_secondary_space_mapping_ptr, a1 ; Load the pointer to the secondary space mapping pages into a1
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move.l #2, d0 ; Loop 3 times, count -1 due to dbra looping n+1 times
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vssas_loop:
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move.l (a0)+, d1 ; Read the next mapping frame into d1
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movem.l d0/d1/d2/d3/a0, -(a7)
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; Map the mapping page pointed to by a1 to the mapping frame just read into d1
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move.l a1, a0
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move.l d1, d0
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move.l #1, d1
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move.l #0, d2
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move.l #$2, d3
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jsr vmem_map_to
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movem.l (a7)+, d0/d1/d2/d3/a0
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adda.l #$1000, a1 ; Advance to the next mapping page
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dbra d0, vssas_loop ; Loop back if there are more frames to read
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rts
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; Get the pointer to the mapping entry for the page in a0
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; Pointer returned in a0
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; Address space number in d0
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public vmem_get_map_ptr
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vmem_get_map_ptr:
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move.l d2, -(a7)
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; Save the space # in d2
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move.l d0, d2
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; Get the quarter number * 4096 in d0 (offset of mapping page), and the page number in the quarter * 4 in d1
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; qnum_x4k = (addr >> 10 & 0x3000)
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; q_pnum_x4 = (addr >> 10 & 0xFFC)
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move.l a0, d0
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lsr.l #8, d0
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lsr.l #2, d0
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move.l d0, d1
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andi.l #$3000, d0
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andi.l #$FFC, d1
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; If the quarter is the kernel quarter, the mapping page is fixed
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; and we can compute the pointer w/o using the user mapping pages
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cmp.l #$3000, d0
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bne.b .1
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move.l #kernel_map, a0
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bra.b .5
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.1:
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; Get the correct pointers for the space #. Active space for 0, secondary space for 1
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cmp.l #0, d2
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bne.b .2
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move.l vmem_active_space_mapping_ptr, a0
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move.l vmem_active_space_ptr, a1
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bra.b .4
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.2:
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cmp.l #1, d2
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bne.b .3
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move.l vmem_secondary_space_mapping_ptr, a0
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move.l vmem_secondary_space_ptr, a1
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bra.b .4
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.3:
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; Halt if invalid space # passed
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stop #2700
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.4:
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; Add the mapping page offset to the base of the mapping pages for the space
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adda.l d0, a0
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; Shift the mapping page offset to get the quarter # * 4 in d0
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lsr.l #8, d0
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lsr.l #2, d0
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; Get the mapping frame for that quarter
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move.l (a1,d0), d0
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; Return 0 if the frame is not present
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cmp.l #0, d0
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bne.b .5
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move.l #0, a0
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move.l (a7)+, d2
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rts
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.5:
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; Return the mapping page address + (page # * 4)
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lea.l (a0,d1), a0
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move.l (a7)+, d2
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rts
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; Unmaps the virtual page at address a0
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; Address space number in d0
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public vmem_unmap_page
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vmem_unmap_page:
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movem.l d0/a0, -(a7)
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; Clear the page's TLB entry
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bsr.w vmem_clear_tlb_entry
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movem.l (a7)+, d0/a0
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; Set the page entry to 0
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bsr.w vmem_get_map_ptr
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move.l #0, (a0)
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rts
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; Sets the mapping for the virtual page at address a0 to d0
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; Address space number in d1
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vmem_set_page_mapping:
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movem.l d2/a2, -(a7)
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movem.l d0/d1/a0, -(a7)
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; Clear the page's TLB entry
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bsr.w vmem_clear_tlb_entry
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movem.l (a7)+, d0/d1/a0
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movem.l d0/d1/a0, -(a7)
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; Get the mapping pointer for the passed-in page
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move.l d1, d0
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bsr.w vmem_get_map_ptr
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move.l a0, a2 ; Save it in a2
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movem.l (a7)+, d0/d1/a0
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; If there is no pointer, a mapping frame must be allocated, else write the mapping
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cmpa.l #0, a2
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bne.b .4
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move.l d0, -(a7)
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movem.l d1/a0, -(a7)
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jsr pmem_pop_frame ; Get a physical frame to use
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movem.l (a7)+, d1/a0
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; Get the passed-in page's quarter # * 4 in d2
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move.l a0, d2
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lsr.l #8, d2
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lsr.l #8, d2
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lsr.l #4, d2
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andi.l #%1100, d2
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; Set the new physical frame as the mapping for the passed-in page's quarter and update the specified address space
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cmp.l #0, d1
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bne.b .1
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movem.l d1/a0, -(a7)
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move.l vmem_active_space_ptr, a0
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move.l d0, (a0,d2)
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bsr.w vmem_activate_addr_space
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movem.l (a7)+, d1/a0
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bra.b .3
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.1:
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cmp.l #1, d1
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bne.b .2
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movem.l d1/a0, -(a7)
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move.l vmem_secondary_space_ptr, a0
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move.l d0, (a0,d2)
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bsr.w vmem_set_secondary_addr_space
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movem.l (a7)+, d1/a0
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bra.b .3
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.2:
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; Halt if invalid space # passed
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stop #2700
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.3:
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; Get the new mapping pointer
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move.l d1, d0
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bsr.w vmem_get_map_ptr
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move.l a0, a2
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move.l (a7)+, d0
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.4:
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move.l d0, (a2) ; Write the mapping to the mapping page
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movem.l (a7)+, d2/a2
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rts
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; Sets the permission flags for the virtual page at address a0 to d0
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; Address space number in d1
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vmem_set_page_flags:
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movem.l d2/a2, -(a7)
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movem.l d0/d1/a0, -(a7)
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; Clear the page's TLB entry
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bsr.w vmem_clear_tlb_entry
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movem.l (a7)+, d0/d1/a0
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movem.l d0/d1/a0, -(a7)
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move.l d1, d0
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; Get the mapping pointer for the passed-in page
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bsr.w vmem_get_map_ptr
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move.l a0, a2
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movem.l (a7)+, d0/d1/a1
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; If there is no pointer, return
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cmpa.l #0, a2
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beq.b .1
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move.l (a2), d1 ; Read the old entry
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andi.l #(~$FFE), d1 ; Clear the permission flags on the old entry
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or.l d0, d1 ; Set the new permission flags
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move.l d1, (a2) ; Write the entry
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.1:
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movem.l (a7)+, d2/a2
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rts
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; Maps the virtual page at address a0 to the physical frame at address d0
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; d0 must have none of its lower 12 bits set
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; Address space number in d1
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; Permission flags in d2
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vmem_map_page_to:
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; Set the passed-in permission flags and the present flag on the passed-in page number
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or.l d2, d0
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or.l #1, d0
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bra.w vmem_set_page_mapping
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; Maps the virtual page at address a0 to a free physical frame
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; Address space number in d0
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; Permission flags in d1
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vmem_map_page:
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; Separate the register pushes to allow popping them directly
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; into the right registers for vmem_map_page_to's arguments
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move.l d2, -(a7)
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move.l a0, -(a7)
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move.l d0, -(a7)
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move.l d1, -(a7)
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jsr pmem_pop_frame
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movem.l (a7)+, d2
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movem.l (a7)+, d1
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movem.l (a7)+, a0
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bsr.w vmem_map_page_to
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move.l (a7)+, d2
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rts
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; Unmaps the range of virtual pages at address a0 with length d0
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; Address space number in d1
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public vmem_unmap
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vmem_unmap:
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subi.l #1, d0 ; Subtract 1 to account for the extra loop done by dbra
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vmem_um_loop:
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movem.l d0/d1/a0, -(a7)
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move.l d1, d0
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bsr.w vmem_unmap_page
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movem.l (a7)+, d0/d1/a0
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adda.l #$1000, a0
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dbra d0, vmem_um_loop
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rts
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; Sets the permission flags of the range of virtual pages starting at address a0 with length d1 to d0
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; Address space number in d2
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public vmem_set_flags
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vmem_set_flags:
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subi.l #1, d1 ; Subtract 1 to account for the extra loop done by dbra
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vmem_sf_loop:
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movem.l d0/d1/a0, -(a7)
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move.l d2, d1
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bsr.w vmem_set_page_flags
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movem.l (a7)+, d0/d1/a0
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adda.l #$1000, a0
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dbra d1, vmem_sf_loop
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rts
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; Maps the range of virtual pages starting at address a0 with length d1 to the range of physical frames starting at d0
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; d0 must have none of its lower 12 bits set
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; Address space number in d2
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; Permission flags in d3
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public vmem_map_to
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vmem_map_to:
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subi.l #1, d1 ; Subtract 1 to account for the extra loop done by dbra
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vmem_mt_loop:
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movem.l d0/d1/d2/a0, -(a7)
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move.l d2, d1
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move.l d3, d2
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bsr.w vmem_map_page_to
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movem.l (a7)+, d0/d1/d2/a0
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adda.l #$1000, a0
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add.l #$1000, d0
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dbra d1, vmem_mt_loop
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rts
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; Maps the range of virtual pages starting at address a0 with length d0 to free physical frames
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; Address space number in d1
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; Permission flags in d2
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public vmem_map
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vmem_map:
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subi.l #1, d0 ; Subtract 1 to account for the extra loop done by dbra
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vmem_m_loop:
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movem.l d0/d1/a0, -(a7)
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move.l d1, d0
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move.l d2, d1
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bsr.w vmem_map_page
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movem.l (a7)+, d0/d1/a0
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adda.l #$1000, a0
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dbra d0, vmem_m_loop
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rts
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; Maps a free range of virtual pages with length d0 to free physical frames
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; Returns the range start in a0
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; Address space number in d1
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; Permission flags in d2
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public vmem_map_free
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vmem_map_free:
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movem.l d0/d1/d3, -(a7)
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move.l d1, d3
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; Use bit 2 of the address space # to choose between getting free user or kernel
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; pages as only 0 and 1 are valid address space #s, requiring only bit 0.
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andi.l #$2, d3
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beq.b .1
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bsr.w vmem_get_free_user_pages
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bra.b .2
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.1:
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bsr.b vmem_get_free_kernel_pages
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.2:
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movem.l (a7)+, d0/d1/d3
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; Clear bit 2 to make the passed-in address space # valid for the rest of the VMM code
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andi.l #$1, d1
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move.l a0, -(a7)
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bsr.b vmem_map
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move.l (a7)+, a0
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rts
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; Maps a free range of virtual pages with length d1 to the range of physical frames starting at d0
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; Returns the range start in a0
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; Address space number in d2
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; Permission flags in d3
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public vmem_map_free_to
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vmem_map_free_to:
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movem.l d0/d1/d3, -(a7)
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move.l d1, d0
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move.l d2, d3
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; Use bit 2 of the address space # to choose between getting free user or kernel
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; pages as only 0 and 1 are valid address space #s, requiring only bit 0.
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andi.l #$2, d3
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beq.b .1
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bsr.w vmem_get_free_user_pages
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bra.b .2
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.1:
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bsr.b vmem_get_free_kernel_pages
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.2:
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movem.l (a7)+, d0/d1/d3
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; Clear bit 2 to make the passed-in address space # valid for the rest of the VMM code
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andi.l #$1, d2
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move.l a0, -(a7)
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bsr.w vmem_map_to
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move.l (a7)+, a0
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rts
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; Copies the range of page mappings at address a0 in the primary space with length d0 to the secondary space starting at address a1
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public vmem_copy_to_secondary
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vmem_copy_to_secondary:
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move.l d0, -(a7)
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; Get the mapping pointer for the start page in the primary address space
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move.l #0, d0
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bsr.w vmem_get_map_ptr
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move.l (a7)+, d0
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subi.l #1, d0 ; Subtract 1 to account for the extra loop done by dbra
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vmem_cts_loop:
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; Read the next page mapping and increment the pointer
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move.l (a0)+, d1
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movem.l d0/a0/a1, -(a7)
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; Set the same mapping in the secondary address space at address a1
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move.l d1, d0
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move.l #1, d1
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move.l a1, a0
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bsr.w vmem_set_page_mapping
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movem.l (a7)+, d0/a0/a1
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adda.l #$1000, a1
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dbra d0, vmem_cts_loop
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rts
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; Get a range of free kernel pages with length in d0 and return its start in a0
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public vmem_get_free_kernel_pages
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vmem_get_free_kernel_pages:
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move.l d2, -(a7)
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move.l d0, d1 ; Set the remaining page # count to the length of the requested range
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move.l #$C00000, a0 ; Put the start page of the search in a0
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vmem_gfkp_loop:
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movem.l d0/d1/a0, -(a7)
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move.l #0, d0 ; Get the pointer for the current page
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bsr.w vmem_get_map_ptr
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; If NULL, load dummy free mapping, otherwise read page mapping into d2
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cmpa.l #0, a0
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beq.b .1
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move.l (a0), d2
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bra.b .2
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.1:
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move.l #0, d2
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.2:
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movem.l (a7)+, d0/d1/a0
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btst #0, d2 ; If the page is not free, skip it
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beq.b .3
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subi.l #1, d1
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bne.b .4 ; If we have not found a run of pages of the right length, continue to check for free pages
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adda.l #$1000, a0 ; Start address is (current_page + $1000 - (length * $1000)), compute this in d0 and return
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lsl.l #8, d0
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lsl.l #4, d0
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suba.l d0, a0
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move.l (a7)+, d2
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rts
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.3:
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move.l d0, d1 ; Page not free, reset the page # count and try again
|
|
.4:
|
|
adda.l #$1000, a0 ; Move to the next page and continue the search
|
|
bra.b vmem_gfkp_loop
|
|
|
|
; Get a range of free user pages with length in d0 and return its start in a0
|
|
public vmem_get_free_user_pages
|
|
vmem_get_free_user_pages:
|
|
move.l d2, -(a7)
|
|
move.l d0, d1 ; Set the remaining page # count to the length of the requested range
|
|
move.l #$1000, a0 ; Put the start page of the search in a0
|
|
vmem_gfup_loop:
|
|
movem.l d0/d1/a0, -(a7)
|
|
move.l #0, d0 ; Get the pointer for the current page
|
|
bsr.w vmem_get_map_ptr
|
|
; If NULL, load dummy free mapping, otherwise read page mapping into d2
|
|
cmpa.l #0, a0
|
|
beq.b .1
|
|
move.l (a0), d2
|
|
bra.b .2
|
|
.1:
|
|
move.l #0, d2
|
|
.2:
|
|
movem.l (a7)+, d0/d1/a0
|
|
btst #0, d2 ; If the page is not free, skip it
|
|
beq.b .3
|
|
subi.l #1, d1
|
|
bne.b .4 ; If we have not found a run of pages of the right length, continue to check for free pages
|
|
adda.l #$1000, a0 ; Start address is (current_page + $1000 - (length * $1000)), compute this in d0 and return
|
|
lsl.l #8, d0
|
|
lsl.l #4, d0
|
|
suba.l d0, a0
|
|
move.l (a7)+, d2
|
|
rts
|
|
.3:
|
|
move.l d0, d1 ; Page not free, reset the page # count and try again
|
|
.4:
|
|
adda.l #$1000, a0 ; Move to the next page and continue the search
|
|
bra.b vmem_gfup_loop
|
|
|
|
section .data,data
|
|
public kernel_address_space
|
|
kernel_address_space:
|
|
dc.l $0, $0, $0, kernel_map - $C00000
|
|
vmem_active_space_ptr: dc.l kernel_address_space
|
|
|
|
section .bss,bss
|
|
public vmem_mmu_base_addr
|
|
vmem_mmu_base_addr: ds.l 1
|
|
vmem_secondary_space_ptr: ds.l 1
|
|
vmem_active_space_mapping_ptr: ds.l 1
|
|
vmem_secondary_space_mapping_ptr: ds.l 1
|