what's wrong with relative jump?

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shoorick

Joined: 25 Feb 2005
Posts: 1614
Location: Ukraine

shoorick 21 Dec 2005, 06:07

here is a part of code (proc/endp)

Code:

@@:    
    push 0
    push edx
    invoke GetPrivateProfileInt,[ebx + S_CH.sect],\
             [ebx + S_CH.var],[ebx + S_CH.default],[ecx]
    and [esp],eax
    invoke SendMessage,[ebx + S_CH.hWnd],edi
    jmp .next    

.check:
    mov edx,1
    mov edi,BM_SETCHECK
    mov ecx,[ebx + S_CH.ini]
    test ecx,ecx
    jne @B
    mov eax,[S_CH.default]
    jmp .r_noini

this is from olly (starts from .check:):

Code:

004011F5   > BA 01000000    MOV EDX,1
004011FA   . BF F1000000    MOV EDI,0F1
004011FF   . 8B4B 10        MOV ECX,DWORD PTR DS:[EBX+10]
00401202   . 85C9           TEST ECX,ECX
00401204   .^75 C9          JNZ SHORT install.004011CF
00401206     A1             DB A1
00401207     1C             DB 1C
00401208     00             DB 00
00401209     00             DB 00
0040120A   . 00EB           ADD BL,CH
0040120C   . 55             PUSH EBP
0040120D   > 31C0           XOR EAX,EAX
0040120F   . 8945 FC        MOV DWORD PTR SS:[EBP-4],EAX
00401212   . 8B53 10        MOV EDX,DWORD PTR DS:[EBX+10]
00401215   . 8955 F8        MOV DWORD PTR SS:[EBP-8],EDX
00401218   . 85D2           TEST EDX,EDX
0040121A   . 74 18          JE SHORT install.00401234

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Last edited by shoorick on 21 Dec 2005, 06:15; edited 1 time in total

21 Dec 2005, 06:07

shoorick

Joined: 25 Feb 2005
Posts: 1614
Location: Ukraine

shoorick 21 Dec 2005, 06:14

oh! just saw: it is not same. i tried move instructions here/there and use different registers, but got same result after jmp @B.
i'll update it.

21 Dec 2005, 06:14

shoorick

Joined: 25 Feb 2005
Posts: 1614
Location: Ukraine

shoorick 21 Dec 2005, 06:24

before was like this:

Code:

.check:
    mov edx,1
    mov edi,BM_SETCHECK
    jmp @B

and everything was right. maybe it is because of distance?

while messing i found dramatically another way to make this part, but think this report will be interesting. thanks!

21 Dec 2005, 06:24

shoorick

Joined: 25 Feb 2005
Posts: 1614
Location: Ukraine

shoorick 21 Dec 2005, 06:28

it seems i found error:

Code:

    mov eax,[S_CH.default]

should be

Code:

    mov eax,[ebx + S_CH.default]

21 Dec 2005, 06:28

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