A poorly written OS for the x86 arch. (WIP)
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; SRs to find memory size and leave it as a "note" for the kernel
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mmap_probe: ; literally just test the memory boundaries
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push eax
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push ebx
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push edx
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push ebp
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mov ebp, esi
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add esi, 0x00000ff
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and esi, ~0x00000ff
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mmap_probe_addr:
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mmap_probe_done:
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mmap_e820:
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mov di, 0x8004
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mov ebx, 0 ; Must be 0
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mov bp, 0 ; entry count
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mov eax, 0xe820 ; function reg
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mov edx, 'SMAP'
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; TODO: update es:di to e820_dt
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mov [es:di + 20], dword 1 ; fill
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mov ecx, 24 ; ask for 24 bytes
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int 0x15 ; Do the interupt
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; carry flag = (un)supported function
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jc mmap_e820_fail ; Try probing instead
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cmp eax, edx ; eax should be = 'SMAP'
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jne mmap_e820_fail ; if not then fail
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test ebx, ebx
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je mmap_e820_fail
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mmap_e820_fail:
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stc
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ret
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e820_dt_start:
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e820_low: dd 0
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e820_high: dd 0
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e820_len_low: dd 0
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e820_len_high: dd 0
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e820_type: dd 0
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e820_dt_end:
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