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I am trying to reverse engineer a raw binary image from an nrf24le1 SoC that (I think) has been compiled with the Keil toolchain. Specifically, I see that C functions in this image usually expect their arguments in r7/r5/r3 as described here and that the return value lives in r7. The behavior I'm seeing is:

  • Ghidra thinks that every function in this image takes 0 parameters, even if it's obvious that the function is immediately looking at r7 for its first argument
  • Ghidra thinks the return value lives in ACC

I have to manually override this for every function. I would like for Ghidra to automatically figure out when a function has arguments based on the Keil ABI.

By contrast, when I run Ghidra on a raw arm32 binary, it notices when a function looks for arguments in r0/r1/r2/... and it adjusts the function declaration accordingly. So Ghidra behaves correctly for arm32, but incorrectly for 8051.

Is there a way to fix this (or is there a better tool I should be using instead of Ghidra)?

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You need to use the mx51 variant of the 8051 processor when loading the binary.

The file in the link uses the calling convention found in your link.

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