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    SubjectRe: [PATCH 1/2] x86/hw_breakpoint: Prevent data breakpoints on __per_cpu_offset
    On Thu, Feb 4, 2021 at 6:26 AM Lai Jiangshan <jiangshanlai@gmail.com> wrote:
    >
    > From: Lai Jiangshan <laijs@linux.alibaba.com>
    >
    > 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?

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