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    SubjectRe: [PATCH 1/2] x86/hw_breakpoint: Prevent data breakpoints on __per_cpu_offset
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    On Thu, Feb 04 2021 at 16:11, Andy Lutomirski wrote:
    > On Thu, Feb 4, 2021 at 6:26 AM Lai Jiangshan <jiangshanlai@gmail.com> wrote:
    >> When FSGSBASE is enabled, paranoid_entry() fetches the per-CPU
    >> GSBASE value via __per_cpu_offset or pcpu_unit_offsets.
    >>
    >> When data breakpoint is set on __per_cpu_offset[cpu] (read-write
    >> operation), the specific cpu will be stuck in the infinite #DB loop.
    >> RCU will try to send NMI to the specific cpu, but it is not working
    >> either since NMI also relies on paranoid_entry().
    >
    > Should we consider having a .percpu..noinstr section and having
    > objtool enforce this?

    I think so.

    Thanks,

    tglx

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