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    Subject[083/104] perf/x86: Fix PEBS instruction unwind
    3.1-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Peter Zijlstra <a.p.zijlstra@chello.nl>

    commit 57d1c0c03c6b48b2b96870d831b9ce6b917f53ac upstream.

    Masami spotted that we always try to decode the instruction stream as
    64bit instructions when running a 64bit kernel, this doesn't work for
    ia32-compat proglets.

    Use TIF_IA32 to detect if we need to use the 32bit instruction
    decoder.

    Reported-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
    Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
    Signed-off-by: Ingo Molnar <mingo@elte.hu>
    Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

    ---
    arch/x86/kernel/cpu/perf_event_intel_ds.c | 6 +++++-
    1 file changed, 5 insertions(+), 1 deletion(-)

    --- a/arch/x86/kernel/cpu/perf_event_intel_ds.c
    +++ b/arch/x86/kernel/cpu/perf_event_intel_ds.c
    @@ -508,6 +508,7 @@ static int intel_pmu_pebs_fixup_ip(struc
    unsigned long from = cpuc->lbr_entries[0].from;
    unsigned long old_to, to = cpuc->lbr_entries[0].to;
    unsigned long ip = regs->ip;
    + int is_64bit = 0;

    /*
    * We don't need to fixup if the PEBS assist is fault like
    @@ -559,7 +560,10 @@ static int intel_pmu_pebs_fixup_ip(struc
    } else
    kaddr = (void *)to;

    - kernel_insn_init(&insn, kaddr);
    +#ifdef CONFIG_X86_64
    + is_64bit = kernel_ip(to) || !test_thread_flag(TIF_IA32);
    +#endif
    + insn_init(&insn, kaddr, is_64bit);
    insn_get_length(&insn);
    to += insn.length;
    } while (to < ip);



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