Added function to calculate and encode relative operands#368
Merged
athre0z merged 4 commits intozyantific:masterfrom Jul 25, 2022
Merged
Added function to calculate and encode relative operands#368athre0z merged 4 commits intozyantific:masterfrom
athre0z merged 4 commits intozyantific:masterfrom
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Pushed some tests, CI fails because I cannot commit workflow change: - name: Running regression tests (encoder)
run: |
cd tests
- python3 regression_encoder.py ../build/ZydisFuzzReEncoding ../build/ZydisFuzzEncoder
+ python3 regression_encoder.py ../build/ZydisFuzzReEncoding ../build/ZydisFuzzEncoder ../build/ZydisTestEncoderAbsolute |
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Thanks a lot @mappzor 👍 I just pushed the workflow changes. There seems to be a minor string format issue, but other than that it looks very good 🙂 |
flobernd
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Jul 22, 2022
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LGTM! Thanks again, that will make a lot of users happy!
Is there a python script to generate the new .inc file or was it rather "generated" by hand? 😄
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There's a new mode added to the script, will push it in a moment. It's not the prettiest thing but it does the job. |
athre0z
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Jul 25, 2022
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LGTM as well, thanks a lot for tackling this!
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Related to 268 and #345.
This PR introduces
ZydisEncoderEncodeInstructionAbsolutefunction which accepts absolute addresses instead of:First group of instructions is handled by patching displacement after encoding. Second group uses fast size prediction algorithm to find the right variant and calculate relative operand prior to encoding. This has less overhead than trying to brute-force encode different variants. Solutions exploits simplicity of branching instructions as they have less "moving parts" such as prefixes, ModR/M, SIB, etc. This allows for fast table lookups with some minor adjustments.
Let me know if you have any feedback. If we want to proceed with this solution I will clean up my test code and add it to this PR. Final test suite would be a small C tool triggered from usual python test scripts.