80 lines
1.4 KiB
NASM
80 lines
1.4 KiB
NASM
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format MS COFF
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extrn _acpi_rsdt_base
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public _acpi_locate
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public @rsdt_find@8
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OS_BASE equ 0x80000000
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ACPI_HI_RSDP_WINDOW_START equ (OS_BASE+0x000E0000)
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ACPI_HI_RSDP_WINDOW_END equ (OS_BASE+0x00100000)
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ACPI_RSDP_CHECKSUM_LENGTH equ 20
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section '.text' code readable executable align 16
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_acpi_locate:
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push ebx
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mov ebx, ACPI_HI_RSDP_WINDOW_START
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.check:
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cmp [ebx], dword 0x20445352
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jne .next
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cmp [ebx+4], dword 0x20525450
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jne .next
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mov edx, ebx
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mov ecx, ACPI_RSDP_CHECKSUM_LENGTH
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xor eax, eax
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.sum:
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add al, [edx]
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inc edx
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loop .sum
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test al, al
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jnz .next
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mov eax, ebx
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pop ebx
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ret
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.next:
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add ebx, 16
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cmp ebx, ACPI_HI_RSDP_WINDOW_END
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jb .check
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pop ebx
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xor eax, eax
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ret
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align 4
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@rsdt_find@8: ;ecx= rsdt edx= SIG
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push ebx
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push esi
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lea ebx, [ecx+36]
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mov esi, [ecx+4]
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add esi, ecx
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.next:
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mov eax, [ebx]
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sub eax, [_acpi_rsdt_base]
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add eax, ecx
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cmp [eax], edx
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je .done
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add ebx, 4
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cmp ebx, esi
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jb .next
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xor eax, eax
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pop esi
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pop ebx
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ret
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.done:
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mov eax, [ebx]
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pop esi
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pop ebx
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ret
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