Messages in this thread | | | Date | Wed, 04 Sep 2019 20:12:34 +0530 | From | "Naveen N. Rao" <> | Subject | Re: [PATCH v3 2/3] Powerpc64/Watchpoint: Don't ignore extraneous exceptions |
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Ravi Bangoria wrote: > On Powerpc64, watchpoint match range is double-word granular. On > a watchpoint hit, DAR is set to the first byte of overlap between > actual access and watched range. And thus it's quite possible that > DAR does not point inside user specified range. Ex, say user creates > a watchpoint with address range 0x1004 to 0x1007. So hw would be > configured to watch from 0x1000 to 0x1007. If there is a 4 byte > access from 0x1002 to 0x1005, DAR will point to 0x1002 and thus > interrupt handler considers it as extraneous, but it's actually not, > because part of the access belongs to what user has asked. So, let > kernel pass it on to user and let user decide what to do with it > instead of silently ignoring it. The drawback is, it can generate > false positive events.
I think you should do the additional validation here, instead of generating false positives. You should be able to read the instruction, run it through analyse_instr(), and then use OP_IS_LOAD_STORE() and GETSIZE() to understand the access range. This can be used to then perform a better match against what the user asked for.
- Naveen
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