objc2_class_ro_item.base_meths incorect value

[lfuret]

Problem

• Platform: iOS
• Arch: arm64e
• lang: Objective-C

For some obscure reason the upper word of objc2_class_ro_item.base_meths in ktool/src/ktool/objc.py is shift one nibble to the left. This result in an invalid method's pointer.

Example:

BEFORE FIX: objc2_class_ro_item.base_meths: 0x800dc310000678b0   # 0x10000678b0 INVALID POINTER
 AFTER FIX: objc2_class_ro_item.base_meths: 0x800dc31000678b0    # 0x1000678b0 VALID POINTER

Temporary fix:

I add a line in ktool/src/ktool/objc.py at line 774, to manually fix the upper word.

objc2_class_ro_item.base_meths =  (objc2_class_ro_item.base_meths & 0xffffffff00000000) >> 4| (objc2_class_ro_item.base_meths & 0xffffffff)

TODO:

• What's the root cause ?
• Reproduce with other binary