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; check whether the end of the loaded image contains in fact the magic
; string (avoid truncation of image)
check_magic:
push ebx
push ecx
push edx
push esi
push edi
mov eax, NOF_LOAD_SECTORS ; number of 512-byte sectors
shl eax, 9 ; 512 bytes per sector
mov edx, 0x8800 ; offset of kernel
add edx, eax
sub edx, MAGICLEN ; subtract the length of the magic string
mov esi, edx ; now use edx as first string address to compare to
mov edi, COMPARE_MAGIC ; position of second string
mov ecx, MAGICLEN ; length of the magic string
repe cmpsb
jne .ok
jmp .mismatch
.ok:
xor esi, esi
mov si, MAGIC_OK_MSG
call pm_print_string
call pm_print_hex
shr edx, 16
call pm_print_hex
call pm_print_newline
xor eax, eax
jmp .end
.mismatch:
xor esi, esi
mov si, MAGIC_NOT_OK_MSG
call pm_print_string
call pm_print_hex
shr edx, 16
call pm_print_hex
call pm_print_newline
xor eax, eax
mov eax, 1
.end:
pop edi
pop esi
pop edx
pop ecx
pop ebx
ret
COMPARE_MAGIC:
db "ABAOS", %[MAGIC], 0
MAGICLEN equ $ - COMPARE_MAGIC
MAGIC_NOT_OK_MSG:
db "Magic signature found at ", 0
MAGIC_OK_MSG:
db "Magic signature not found at ", 0
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