Properly create BLX instruction #1266
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Rethinked and revised this function. This previous one worked by "accident". More a sheer luck of offsets on current firmware (as of writing) But now, this is more mathematically correct way of creating a THUMB -> ARM BLX instruction. Also setting the new op in a set of 2 u16, because patching code is in thumb.
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Release hotfixed with this PR merged, thanks! |
Sahlo97
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Dec 9, 2021
Properly create BLX instruction
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Sorry I'm coming with a commit post release, but looking at that patch function I made made me think about the maths that were being done.
And this a correction of them.
Better than leaving it uncorrected.
A bit shall never be set on a THUMB -> ARM BLX op, and this bit was what messed with me the first time i made this code but didn't knew about it. Hence now that added
& ~(1<<16).So, the op jump distance math was incorrect because i never fixed that bit, but instead changed the maths of the op distance, originally.
Old code was basically doing
(Destination_offset - blx_op_offset+4) / 2instead of+2, which worked as mentioned on commit message, by sheer luck of offsets.But now this new code is correct.