restore floating point registers from stack in reverse order #37
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lukaskubanek
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to structuredpath/InterposeKit
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Oct 21, 2024
lukaskubanek
added a commit
to structuredpath/InterposeKit
that referenced
this pull request
Oct 21, 2024
This commit applies the patch from steipete#37, which resolves an issue affecting swizzled methods that take `CGFloat` parameters or structs containing `CGFloat` (such as `CGPoint` or `CGRect`) on ARM64. The issue occurred because floating-point registers were apparently not being restored in the correct order, causing values in those registers to become shuffled after the trampoline call. The fix ensures that floating-point registers are restored in reverse order, as required by ARM64 calling conventions. According to the referenced PR, regular registers were already handled correctly, so this issue specifically affected floating-point parameters.
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We should restore registers preserved in stack in reverse order. Otherwise, it leads to shuffled values in those registers after trampoline.
The simplest way to reproduce is to swizzle any method from UIKit that accepts CGFloat or plain struct like CGRect. It's relevant only to arm64.
Btw, regular registers get restored correctly.