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CRISPR todo

  • rewrite the patcher
    • step 1: drop LIEF, we use it only for convenience
    • step 2: rewrite it in C++ and make CRISPR a single executable
  • invoke lld in-process
  • size optimizations
  • support PE/COFF binaries
  • support MachO binaries
  • support codegen for other architectures
  • create a comprehensive testsuite

Size optimization ideas

Here are some ideas which we could implement to avoid increasing the memory footprint and/or file size of the binary. TODO: document the other ideas we discussed.

Extending segments

Often segments are not placed contiguously in memory due to alignment. If the gap between a segment and the next is big enough, we could extend the first segment and place our new data there, to avoid extending and moving the PHDRs.

GNU_NOTES

The GNU_NOTES program header can be replaced with a different PHDR. If we need to add a single PHDR we can replace GNU_NOTES instead and avoid moving PHDRs.

Fitting the code over multiple functions/places

We could get a list of unneded ranges in the binary, and try to split the new data to distribute it over them. We can try to do this either:

  • by solving a sort-of knapsack problem, or
  • by splitting every function and placing every piece in a different spot, joining pieces with jumps