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make sure eax and edx are set each call to E820

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This commit is contained in:
Elaina Claus
2025-09-04 15:32:28 -04:00
parent 7fd5b9b85d
commit 105ceb8b8b
1 changed files with 14 additions and 8 deletions
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22
include/BIOS/func/E820_memory_map.nasm
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@@ -40,23 +40,27 @@ GetMemoryMap:
.func: .func:
mov dword [SteviaInfo + SteviaInfoStruct_t.MemoryMapEntries], 0 mov dword [SteviaInfo + SteviaInfoStruct_t.MemoryMapEntries], 0
mov eax, 0xE820 ; select 0xE820 function
xor ebx, ebx ; Continuation value, 0 for the first call xor ebx, ebx ; Continuation value, 0 for the first call
lea dx, [BIOSMemoryMap] mov dx, BIOSMemoryMap
shr dx, 4 shr dx, 4
mov es, dx mov es, dx
xor di, di ; (BIOSMemoryMap >> 4):0 makes di an index into BIOSMemoryMap xor di, di ; (BIOSMemoryMap >> 4):0 makes di an index into BIOSMemoryMap
mov ecx, AddressRangeDescStruct_t_size mov ecx, AddressRangeDescStruct_t_size ; hard request ACPI 3.0 table versions (24 bytes)
mov edx, 0x534D4150 ; 'SMAP' magic
.loop_L1: .loop_L1:
mov eax, 0x0000E820 ; select 0xE820 function
mov edx, 0x534D4150 ; 'SMAP' magic
int 0x15 int 0x15
jc GetMemoryMap.error jc GetMemoryMap.error
cmp eax, 0x534D4150 cmp eax, 0x534D4150
jne GetMemoryMap.no_smap_returned jne GetMemoryMap.no_smap_returned
.no_error: .no_error:
inc dword [SteviaInfo + SteviaInfoStruct_t.MemoryMapEntries] mov eax, dword [SteviaInfo + SteviaInfoStruct_t.MemoryMapEntries]
add eax, 1
mov dword [SteviaInfo + SteviaInfoStruct_t.MemoryMapEntries], eax
cmp ecx, 20 ; TODO: maybe this could be handled better than just panicing cmp ecx, 20 ; TODO: maybe this could be handled better than just panicing
jb GetMemoryMap.nonstandard_e820 ; non-standard entry found jb GetMemoryMap.nonstandard_e820 ; non-standard entry found
@@ -64,9 +68,11 @@ GetMemoryMap:
cmp ebx, 0 cmp ebx, 0
je GetMemoryMap.endp ; 0 in ebx means we have reached the end of memory ranges je GetMemoryMap.endp ; 0 in ebx means we have reached the end of memory ranges
add di, AddressRangeDescStruct_t_size ; increment di to next descriptor ; setup for next loop, ebx is our next index and has already been set.
mov edx, eax ; 'SMAP' to edx xor ecx, ecx
mov eax, 0xE820 ; select E820 function mov ecx, AddressRangeDescStruct_t_size ; set ecx (requested_size) to 24 bytes
add di, cx ; increment di to next descriptor so es:di points to the next free space
jmp GetMemoryMap.loop_L1 jmp GetMemoryMap.loop_L1
.error: .error:
ERROR STAGE2_MM_E820_MISC_ERR ERROR STAGE2_MM_E820_MISC_ERR