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H A D | hw_breakpoint.c | c4bed4b9 Thu Feb 04 09:27:06 CST 2021 Lai Jiangshan <laijs@linux.alibaba.com> x86/debug: Prevent data breakpoints on __per_cpu_offset
When FSGSBASE is enabled, paranoid_entry() fetches the per-CPU GSBASE value via __per_cpu_offset or pcpu_unit_offsets.
When a data breakpoint is set on __per_cpu_offset[cpu] (read-write operation), the specific CPU will be stuck in an infinite #DB loop.
RCU will try to send an NMI to the specific CPU, but it is not working either since NMI also relies on paranoid_entry(). Which means it's undebuggable.
Fixes: eaad981291ee3("x86/entry/64: Introduce the FIND_PERCPU_BASE macro") Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20210204152708.21308-1-jiangshanlai@gmail.com
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