Messages in this thread | | | From | Ravi Bangoria <> | Subject | Re: [PATCH v3 2/3] Powerpc64/Watchpoint: Don't ignore extraneous exceptions | Date | Thu, 5 Sep 2019 09:26:44 +0530 |
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On 9/4/19 8:12 PM, Naveen N. Rao wrote: > 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.
Ok. Let me see how feasible that is.
But patch 1 and 3 are independent of this and can still go in. mpe?
-Ravi
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