[HCS12] fix memory mapping local -> physical #7261
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The first quarter of the local space should be used to access IO / RAM / EEPROM, FLASH should be mapped only to the 0x4000..0xffff
JMP [D,PC] instruction that is the 'core' for switch/case statement should use physical address, not logical to fetch branch table. PC register (inst_next in terms of Ghidra) is already contains physical address, so there is no need to extend it.
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To reproduse you can use this binary. It's a old vehicle dashboard, based on MC9S12HZ256. Flash image should be loaded at 0x0c0000. |
ryanmkurtz
added
Feature: Processor/HCS12
Status: Triage
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There are a few commits to improve HSC12 decompilation.
first one is just cosmetic changes, removed a few spaces to align similar lines into one column. If you want, I can remove this commitit (as I know, such 'useless' changes are not much appreciated)
Local addresses 0..0x3fff had a reference to flash page 3D, which is wrong.
AN3784 "Understanding the Memory Scheme in the S12(X) Architecture" (as well as datasheets for particular MC9S12xxxx chips) says that the first quarter of the local memory should point to the IO area, RAM and EEPROM.
there is the issue with reading data relative to PC register. In particular I found that
JMP [D,PC]reads the jump address from some weird location, while typically these addresses located immediately after it. I'm not sure about the other PC-related operands, but perhaps it also broken.