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Add physical memory frame stack

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This commit is contained in:
pjht 2023-03-27 14:31:40 -05:00
parent 0368408636
commit 6aaf71f214
Signed by: pjht
GPG Key ID: 7B5F6AFBEC7EE78E
3 changed files with 67 additions and 3 deletions
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4
kernel/kernel.ld
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@ -41,5 +41,9 @@ SECTIONS
*(.bss)
}
.pagereserve ALIGN (4K) : {
*(.pagereserve)
}
kernel_map_page = 0xFEF000;
}

12
kernel/main.68k
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@ -1,9 +1,15 @@
.global main
main:
move.l #inital_stack, a7 | Load the initial stack pointer
move.b #'H', 0xFF0200
move.b #'i', 0xFF0200
move.b #0xA, 0xFF0200
jsr pmem_init
move.l #0x1000, d0
jsr push_page
move.l #0x2000, d0
jsr push_page
move.l #0, d0
jsr pop_page
jsr pop_page
jsr pop_page
stop #0x2700
.bss

54
kernel/pmem.68k Normal file
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@ -0,0 +1,54 @@
.text
.global pmem_init
pmem_init:
move.b #0x5, d0 | Get the pointer to the MMU card
jsr find_first_card
adda.l #0x10, a0
move.l a0, mmu_tlb_clear_addr
move.l #((map_page - 0xC00000)), d1 | Get the entry offset for the mapping page in d1
lsr.l #8, d1
lsr.l #2, d1
move.l #kernel_map_page, a0 | Get the address of the mapping entry for the mapping page in a0
adda.l d1, a0
move.l a0, map_page_entry_addr
rts
.global push_page
| Page to push in d0
push_page:
move.l map_page_entry_addr, a0
move.l (a0), d1 | Read the mapping entry into d1
andi.l #(~0xFFF), d1 | Clear the entry's flags to get the pointer to it's physical page
ori.l #0x3, d0 | Map the mapping page to the passed in frame
move.l d0, (a0)
move.l #map_page, mmu_tlb_clear_addr | Clear the TLB entry for the mapping page
move.l d1, (map_page)
rts
.global pop_page
pop_page:
move.l map_page_entry_addr, a0
move.l (a0), d0 | Read the mapping entry into d0
btst #0, d0 | Check the entry's present flag
bne.b pop_no_page | If the entry isn't present, halt the CPU
andi.l #(~0xFFF), d0 | Clear the entry's flags to get the pointer to it's physical frame
move.l (map_page), d1 | Get the address of the frame pointed to by the top of the stack
cmpi.l #0x0, d1 | Compare the pointed-to frame to the null frame
beq.b 1f | If it is, unmap the mapping_page
ori.l #0x3, d1 | Map the mapping page to the frame pointed to by the top of the stack
1: move.l d1, (a0)
move.l #map_page, mmu_tlb_clear_addr | Clear the TLB entry for the mapping page
rts
pop_no_page:
stop #2700
.bss
mmu_tlb_clear_addr:
.ds.b 4
map_page_entry_addr:
.ds.b 4
.section .pagereserve
.balign 4096
map_page:
.ds.b 4096