Results 1 to 3 of 3

Thread: Jump if not below | another question to moderators

  1. #1
    __DuDu__
    Guest

    Jump if not below | another question to moderators

    i did a question about hash and i can't find it anymore i did +- 25 days ago and it's not on database someone deleted it ?

    my other question is

    add edx, 34
    shl edx, 32
    jnb 00404123

    how can i check in what condidtion it'll jump if below ? the program is always jumping and i need to make it continue the xecution without jumping so i need to know how to find what makes it jump if below coz there's no cmp edx, eax \ jnb xxx !

    of course i don't wanna patch

    tnx
    __DuDu__
    I promise that I have read the FAQ and tried to use the Search to answer my question.

  2. #2
    CoDe_InSiDe
    Guest
    Hi __DuDu__

    It depends that when your on the jnb xxxxxxxx the value in EDX is equal or above the value 00000000.
    If it's equal or above it'll jump, otherwise it'll continue.
    There's no need for a "cmp xxx, xxx" to make something jump, look at this example:

    mov eax, 01
    sub eax, 01
    jz xxxxxxxx

    In this example it'll jump because the value in EAX is 00000000 and so the "Z" flag is set when you enter the "jz xxxxxxxx".
    Hope this helps.

    Cya...

    CoDe_InSiDe
    I promise that I have read the FAQ and tried to use the Search to answer my question.

  3. #3
    Solomon
    Guest
    According to the "Art of ASM",

    JNB: jump if Carry = 0

    The SHL instruction sets the condition code bits as follows:
    1. If the shift count is zero, SHL will not affect any flags.
    2. The Carry flag contains the last bit shifted out of the High Order bit of the operand.

    So if u want it not to jump, the following condition should be satisfied:
    (edx + 0x34) & 1 = 1 => edx & 1 = 1

    regards
    I promise that I have read the FAQ and tried to use the Search to answer my question.

Similar Threads

  1. Jump tables
    By Hex Blog in forum Blogs Forum
    Replies: 0
    Last Post: January 31st, 2008, 11:30
  2. Jump to address
    By monu in forum OllyDbg Support Forums
    Replies: 0
    Last Post: August 29th, 2006, 14:37
  3. Jump analysis
    By peterg70 in forum Plugins (General)
    Replies: 7
    Last Post: February 13th, 2003, 22:57
  4. Replies: 8
    Last Post: November 8th, 2000, 08:48

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •