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Im trying code in Assembly, and i have a little problem. My program stoped with SIGSEV segmentation fault. GDB stops at

cmpb %bl, 0x41

in check_loop. Program just check every single char and modify it when it is lowercase, great or other 

.bss
.comm textin, 512
.comm textout, 512

.text

.global main
main:

movq $SYSREAD, %rax
movq $STDIN, %rdi
movq $textin, %rsi
movq $BUFLEN, %rdx
syscall

CALL changing

changing:
movl $0, %edi
jmp check_loop

check_loop:
movb textin(,%edi,1),%bl
cmpb %bl, 0x41
jl other
cmpb %bl, 0x5A
jl great
cmpb %bl, 0x61
jl other
cmpb %bl, 0x7a
jg other

lower:
addb %bl, 0x06
movb %bl,textout(,%edi,1)
jmp isEND

great:
addb %bl, 0x08
movb %bl,textout(,%edi,1)
jmp isEND

other:
movb %bl,textout(,%edi,1)
jmp isEND

isEND:
incl %edi
cmpl %eax, %edi
jl check_loop
ret
Steve Obbayi
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user3703028
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    at&t syntax requires `$` prefix on immediate numbers or else they will be treated as addresses which will then fault. – Jester Mar 15 '16 at 23:02

0 Answers0