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    SubjectRe: [PATCH v3 2/3] Powerpc64/Watchpoint: Don't ignore extraneous exceptions
    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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