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    x86,kgdb: fix debugger hw breakpoint test regression in 2.6.35 · fad99fac
    Jason Wessel 提交于
    HW breakpoints events stopped working correctly with kgdb as a result
    of commit: 018cbffe (Merge commit
    'v2.6.33' into perf/core), later commit:
    ba773f7c (x86,kgdb: Fix hw breakpoint
    regression) allowed breakpoints to propagate to the debugger core but
    did not completely address the original regression in functionality
    found in 2.6.35.
    
    When the DR_STEP flag is set in dr6 along with any of the DR_TRAP
    bits, the kgdb exception handler will enter once from the
    hw_breakpoint API call back and again from the die notifier for
    do_debug(), which causes the debugger to stop twice and also for the
    kgdb regression tests to fail running under kvm with:
    
    echo V2I1 > /sys/module/kgdbts/parameters/kgdbts
    
    To address the problem, the kgdb overflow handler needs to implement
    the same logic as the ptrace overflow handler call back with respect
    to updating the virtual copy of dr6.  This will allow the kgdb
    do_debug() die notifier to properly handle the exception and the
    attached debugger, or kgdb test suite, will only receive a single
    notification.
    Signed-off-by: NJason Wessel <jason.wessel@windriver.com>
    CC: Frederic Weisbecker <fweisbec@gmail.com>
    CC: x86@kernel.org
    fad99fac
kgdb.c 18.7 KB