114 lines
3.9 KiB
NASM
114 lines
3.9 KiB
NASM
; Copyright (C) 2025 Elaina Claus
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;
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; This program is free software: you can redistribute it and/or modify
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; it under the terms of the GNU General Public License as published by
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; the Free Software Foundation, either version 3 of the License, or
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; (at your option) any later version.
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;
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; This program is distributed in the hope that it will be useful,
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; but WITHOUT ANY WARRANTY; without even the implied warranty of
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; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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; GNU General Public License for more details.
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;
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; You should have received a copy of the GNU General Public License
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; along with this program. If not, see <https://www.gnu.org/licenses/>.
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%ifndef __INC_E820MEMORY_MAP
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; Address Range Descriptor Structure
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;
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; Offset in Bytes Name Description
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; 0 BaseAddrLow u32 - Low 32 Bits of Base Address
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; 4 BaseAddrHigh u32 - High 32 Bits of Base Address
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; 8 LengthLow u32 - Low 32 Bits of Length in Bytes
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; 12 LengthHigh u32 - High 32 Bits of Length in Bytes
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; 16 Type u32 - Address type of this range.
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; 20 ExtType u32 - ACPI 3.0 extended type
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struc AddressRangeDescStruct_t
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.BaseAddrLow resd 1
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.BaseAddrHigh resd 1
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.LengthLow resd 1
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.LengthHigh resd 1
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.Type resd 1
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.ExtType resd 1
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endstruc
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; !!! this procedure changes ES !!!
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ALIGN 4, db 0x90
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GetMemoryMap:
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__CDECL16_PROC_ENTRY
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push es ; save segment register
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.func:
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mov word [SteviaInfo + SteviaInfoStruct_t.u16_E820MMapEntryCount], 0
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xor ebx, ebx ; Continuation value, 0 for the first call
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mov di, BIOSMemoryMap ; destination is es:di, es should == ds
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mov ecx, AddressRangeDescStruct_t_size ; hard request ACPI 3.0 table versions (24 bytes)
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.loop_L1:
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mov eax, 0x0000E820 ; select 0xE820 function
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mov edx, 0x534D4150 ; 'SMAP' magic
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clc ; clear carry
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int 0x15 ; data will be stored at es:di by e820 call
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jc GetMemoryMap.error
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cmp eax, 0x534D4150
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jne GetMemoryMap.no_smap_returned
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.no_error:
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inc word [SteviaInfo + SteviaInfoStruct_t.u16_E820MMapEntryCount]
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cmp ecx, 20 ; TODO: maybe this could be handled better than just panicing
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jb GetMemoryMap.nonstandard_e820 ; non-standard entry found
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cmp ebx, 0
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je GetMemoryMap.endp ; 0 in ebx means we have reached the end of memory ranges
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; setup for next loop, ebx is our next index and has already been set.
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xor ecx, ecx
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mov ecx, AddressRangeDescStruct_t_size ; set ecx (requested_size) to 24 bytes
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add di, cx ; increment di to next descriptor so es:di points to the next free space
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jmp GetMemoryMap.loop_L1
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.error:
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ERROR STAGE2_MM_E820_MISC_ERR
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.nonstandard_e820:
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ERROR STAGE2_MM_E820_NONSTANDARD
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.no_smap_returned:
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ERROR STAGE2_MM_E820_NO_SMAP
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.endp:
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pop es
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__CDECL16_PROC_EXIT
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ret
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PrintMemoryMap:
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__CDECL16_PROC_ENTRY
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.func:
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mov eax, dword [SteviaInfo + SteviaInfoStruct_t.u16_E820MMapEntryCount]
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cmp eax, 0
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je PrintMemoryMap.endp ; if entries == 0, exit
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mov ecx, eax ; store # of entries in counter
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mov eax, BIOSMemoryMap ; address to start of e820 mmap
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push dword ecx
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push dword eax
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call FormatMemoryMapEntry
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add sp, 0x8
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; ax contains segment offset to string after call
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; TODO: going to need an allocator for strings and stuff...
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; print_string strformat_buffer
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.endp:
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__CDECL16_PROC_EXIT
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ret
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FormatMemoryMapEntry:
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__CDECL16_PROC_ENTRY
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.func:
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; create a string buffer somewhere and return address to result string in ax
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.endp:
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__CDECL16_PROC_EXIT
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ret
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%endif
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%define __INC_E820MEMORY_MAP |