When using rep insw in 32-bit protected mode to load my kernel from disk to memory, how do I properly write the data to memory, and then execute it?
If I understand correctly, the data segment can be written to, but not executed, and the code segment can be executed but not written to.
I'm not having any problems doing this below the 1MB memory mark, but I want to load it right at 0x00100000.
My loading subroutine:
edi - destination in memory
esi - source LBA
ecx - number of sectors to write
ebx - return point
load32_source dd 0
load32:
mov dword [load32_source], esi
mov al, byte [load32_source + 3]
or al, 0xe0
mov dx, 0x1f6
out dx, al
mov dx, 0x1f1
mov al, 0x00 ; null to error
out dx, al
mov dx, 0x1f2 ; sector count
mov al, cl
out dx, al
mov al, byte [load32_source]
mov dx, 0x1f3
out dx, al
mov al, byte [load32_source + 1]
mov dx, 0x1f4
out dx, al
mov al, byte [load32_source + 2]
mov dx, 0x1f5
out dx, al
mov dx, 0x1f7
mov al, 0x20 ; read sectors
out dx, al
waitforit:
in al, dx
test al, 0x08
jz waitforit
mov eax, ecx
mov ecx, 0x00000100
mul ecx
mov ecx, eax
mov edx, 0x000001f0
rep insw
jmp ebx