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GJDuck / e9patch

A powerful static binary rewriting tool

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Find patch misses

task3r opened this issue · comments

commented

Hi! Is it possible to know which matches could not be patched? Ideally the addresses of the instructions that could not be patched. Additionally, is there any way to give a "fallback" match pattern, that is only considered if the first pattern is not "patchable"? Thank you.

commented

Is it possible to know which matches could not be patched?

You can try passing --option --debug=true to E9Tool, which will cause E9Patch to print more detailed information. E.g.:

    debug: failed to patch instruction at address 0xc21

Currently there is no machine-readable information, but maybe I should look into this.

is there any way to give a "fallback" match pattern, that is only considered if the first pattern is not "patchable"?

Do you mean something like: "patch instruction B instead of instruction A if A is unpatchable?"

There is not really an automated way to do this currently. There is however:

  • BB.best selects the "best" instruction to patch from a basic block (if your application is interested in BBs)
  • Use the -CFR mode, which makes it more likely that patching will succeed, although it may introduce rewriting errors for some binaries.
commented

Thank you! I did try the debug option but failed to find those lines in the middle of all the output. As for the second part, I knew of those alternatives but they do not fit my current problem. I might use the debug information to do multiple instrumentation attempts. Thanks once again!

EDIT Actually, I previously used --debug and not --option --debug=true as you suggest. The second does show that info