问题
I keep getting a segmentation fault error when running my code. Everything has compiled well, but I can't seem to get it to do what I want. The program is to ask the user to enter 3 integers, then ask the user what they think the average of the numbers would be, take that into account and then come back with whether or not the user guessed correctly
segment .data
;
; Output strings
;
prompt1 db "Enter a positive integer: ", 0
prompt2 db "Enter a second positive integer: ", 0
prompt3 db "Enter a third positive integer: ", 0
prompt4 db "Enter a guess of their average: ", 0
outmsg1 db "You entered ", 0
outmsg2 db " and ", 0
outmsg3 db " and ", 0
outmsg4 db "You guessed that the average is ", 0
outmsg5 db "You did you guess correctly? (0 = no, 1 = yes)", 0
avermsg db "The average of the numbers is ", 0
segment .bss
input1 resd 1
input2 resd 1
input3 resd 1
input4 resd 1
guess resd 1
segment .text
Global main
main:
enter 0,0 ; setup routine
pusha
mov eax, prompt1 ; print out prompt1
call print_string
call read_int ; read integer
mov [input1], eax ; store integer into input1
mov eax, prompt2 ; print out prompt2
call print_string
call read_int ; read integer
mov [input2], eax ; store integer into input2
mov eax, prompt3 ; print out prompt3
call print_string
call read_int ; read integer
mov [input3], eax ; store integer into input3
mov eax, prompt4 ; print out prompt4
call print_string
call read_int ; read integer
mov [guess], eax
mov eax, [input1] ; eax = dword at input1
add eax, [input2] ; eax += dword at input2
add eax, [input3] ; eax += dword at input3
mov ebx, 3
div ebx ; divides the sum by 3
mov ecx, eax ; freeing up eax, puts quotient into ecx
dump_regs 1 ; print out register values
; next print out results
mov eax, outmsg1
call print_string ; print out first message
mov eax, [input1]
call print_int
mov eax, outmsg2
call print_string ; print out second message
mov eax, [input2]
call print_int
mov eax, outmsg3
call print_string ; print out thrid message
mov eax, [input3]
call print_int
mov eax, outmsg4
call print_string ; print out fourth message
mov eax, [input4]
call print_int
xor ebx, ebx
cmp ecx, [guess]
sete bl
neg ebx
mov edx, ebx
and ecx, edx
not ebx
and ebx, [guess]
or edx, ebx
mov eax, outmsg5
call print_string
mov ecx, eax
call print_int
mov eax, [avermsg]
call print_string ; print out final message
mov ecx, edx
call print_int ; print out average of ebx
call print_nl ; print new line
popa
mov eax, 0 ; return back to C
leave
ret
回答1:
It is not easy to pinpoint the problem without knowing the compiler you use.
Segmentation fault hapens in protected mode, when you try to access a segment you have no permissions to access.
You declare 3 diferent segments here. You have to make sure your ds register is initialized to your .data segment, before calling print_string.
It also seems problematic that after read_int you save the data to the input1 variable which seems to be in a different segment than that you used for printing the message, but you do not change ds.
I'm not familiar how exactly your compiler handles these segments, so please give a link to its documentation.
回答2:
div ebx
the problem seems to be here. You have to zero out edx since is is the high order word of the divisor, so probably you're getting something like a division overflow exception.
If this isn't the case probably the problem is in some of your I/O routines
来源：https://stackoverflow.com/questions/5364755/segmentation-fault-error-happening-with-assembly-code-program