352 lines
4.6 KiB
NASM
352 lines
4.6 KiB
NASM
; asmfuncs.asm
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; Josh Holtrop
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; Created: 10/23/03
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; Modified: 07/11/04
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%macro jzfar 1
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jnz %%skip
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jmp %1
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%%skip:
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%endmacro
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;stores the parameter to the CR0 register
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;extern dword write_cr0(dword cr0);
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[global _write_cr0]
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_write_cr0:
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push ebp
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mov ebp, esp
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mov eax, [ebp+8]
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mov cr0, eax
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pop ebp
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ret
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;returns the value in the CR0 register
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;extern dword read_cr0();
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[global _read_cr0]
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_read_cr0:
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mov eax, cr0;
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ret
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;stores the parameter to the CR3 register
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;extern dword write_cr3(dword cr3);
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[global _write_cr3]
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_write_cr3:
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push ebp
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mov ebp, esp
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mov eax, [ebp+8]
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mov cr3, eax
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pop ebp
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ret
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;returns the value in the CR2 register
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;extern dword read_cr2();
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[global _read_cr2]
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_read_cr2:
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mov eax, cr2;
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ret
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;returns the value in the CR3 register
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;extern dword read_cr3();
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[global _read_cr3]
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_read_cr3:
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mov eax, cr3;
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ret
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;compares one string to another
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;returns 0 if the strings are different
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;extern dword strcmp(char *str1, char *str2);
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[global _strcmp]
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_strcmp:
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push ebp
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mov ebp, esp
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push esi
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push edi
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mov esi, [ebp+8]
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mov edi, [ebp+12]
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strcmp_loop1:
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lodsb
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mov ah, [edi]
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inc edi
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cmp ah, al
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jnz strcmp_ne
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or al, al
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jz strcmp_e
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jmp strcmp_loop1
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strcmp_e:
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mov eax, 1
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jmp short strcmp_done
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strcmp_ne:
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xor eax, eax
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strcmp_done:
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pop edi
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pop esi
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pop ebp
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ret
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;copies a string from the source to the destination parameter
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;extern void strcpy(char *dest, char *src);
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[global _strcpy]
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_strcpy:
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push ebp
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mov ebp, esp
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push esi
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push edi
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mov edi, [ebp+8]
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mov esi, [ebp+12]
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strcpyloop:
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lodsb
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stosb
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or al, al
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jnz strcpyloop
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pop edi
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pop esi
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pop ebp
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ret
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;copies memory of n bytes from src to destination
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;void memcpy(void *dest, void *src, dword n);
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[global _memcpy]
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_memcpy:
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push ebp
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mov ebp, esp
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push esi
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push edi
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push ecx
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mov edi, [ebp+8]
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mov esi, [ebp+12]
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mov ecx, [ebp+16]
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cld
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rep movsb
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pop ecx
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pop edi
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pop esi
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pop ebp
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ret
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;copies memory of n words (n*2 bytes) from src to destination
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;void memcpyw(void *dest, void *src, dword n);
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[global _memcpyw]
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_memcpyw:
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push ebp
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mov ebp, esp
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push esi
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push edi
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push ecx
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mov edi, [ebp+8]
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mov esi, [ebp+12]
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mov ecx, [ebp+16]
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cld
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rep movsw
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pop ecx
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pop edi
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pop esi
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pop ebp
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ret
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;copies memory of n dwords (n*4 bytes) from src to destination
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;void memcpyd(void *dest, void *src, dword n);
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[global _memcpyd]
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_memcpyd:
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push ebp
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mov ebp, esp
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push esi
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push edi
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push ecx
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mov edi, [ebp+8]
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mov esi, [ebp+12]
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mov ecx, [ebp+16]
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cld
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rep movsd
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pop ecx
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pop edi
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pop esi
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pop ebp
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ret
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;sets num bytes at buffer to the value of c
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;void *memset(void *buffer, int c, int num);
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[global _memset]
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_memset:
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push ebp
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mov ebp, esp
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push edi
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push ecx
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mov edi, [ebp+8]
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push edi ;save for return address
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mov eax, [ebp+12]
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mov ecx, [ebp+16]
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rep stosb
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pop eax
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pop ecx
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pop edi
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pop ebp
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ret
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;sets num words at buffer to the value of c
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;void *memsetw(void *buffer, int c, int num);
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[global _memsetw]
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_memsetw:
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push ebp
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mov ebp, esp
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push edi
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push ecx
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mov edi, [ebp+8]
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push edi ;save for return address
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mov eax, [ebp+12]
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mov ecx, [ebp+16]
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rep stosw
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pop eax
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pop ecx
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pop edi
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pop ebp
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ret
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;sets num dwords at buffer to the value of c
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;void *memsetd(void *buffer, int c, int num);
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[global _memsetd]
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_memsetd:
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push ebp
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mov ebp, esp
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push edi
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push ecx
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mov edi, [ebp+8]
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push edi ;save for return address
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mov eax, [ebp+12]
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mov ecx, [ebp+16]
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rep stosd
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pop eax
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pop ecx
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pop edi
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pop ebp
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ret
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;returns the number of characters in a string
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;extern dword strlen(char *str);
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[global _strlen]
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_strlen:
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push ebp
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mov ebp, esp
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push esi
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push ebx
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mov esi, [ebp+8]
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xor ebx, ebx
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strlenloop:
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lodsb
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or al, al
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jz strlendone
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inc ebx
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jmp strlenloop
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strlendone:
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mov eax, ebx
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pop ebx
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pop esi
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pop ebp
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ret
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;this function invalidates the page directory/table entry that
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; would be used to access the memory address given in the parameter
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;extern void invlpg_(dword addr);
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[global _invlpg_]
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_invlpg_:
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mov eax, [esp+4]
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invlpg [eax]
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ret
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;
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;void writeCursorPosition(word pos)
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;
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[global _writeCursorPosition]
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_writeCursorPosition:
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push ebp
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mov ebp, esp
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push eax
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push ebx
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push edx
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mov eax, [ebp+8] ;cursor position in ax
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mov bl, al
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mov dx, 0x03D4
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mov al, 0x0E
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out dx, al
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inc dx
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mov al, ah
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out dx, al
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dec dx
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mov al, 0x0F
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out dx, al
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inc dx
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mov al, bl
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out dx, al
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pop edx
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pop ebx
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pop eax
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pop ebp
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ret
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;
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;word getCursorPosition()
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;
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[global _getCursorPosition]
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_getCursorPosition:
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push ebx
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push edx
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xor eax, eax
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mov dx, 0x03D4
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mov al, 0x0E
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out dx, al
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inc dx
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in al, dx
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mov bl, al
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dec dx
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mov al, 0x0F
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out dx, al
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inc dx
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in al, dx
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mov ah, bl
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pop edx
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pop ebx
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ret
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