Messages in this thread | | | Date | Fri, 28 Feb 2014 12:11:11 +0100 | From | Peter Zijlstra <> | Subject | Re: perf_fuzzer compiled for x32 causes reboot |
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On Thu, Feb 27, 2014 at 09:57:26PM -0500, Steven Rostedt wrote: > @@ -512,8 +508,21 @@ static inline void nmi_nesting_postprocess(void) > dotraplinkage notrace __kprobes void > do_nmi(struct pt_regs *regs, long error_code) > { > + unsigned long cr2; > + > nmi_nesting_preprocess(regs); > > + /* > + * Save off the CR2 register. If we take a page fault in the NMI then > + * it could corrupt the CR2 value. If the NMI preempts a page fault > + * handler before it was able to read the CR2 register, and then the > + * NMI itself takes a page fault, the page fault that was preempted > + * will read the information from the NMI page fault and not the > + * origin fault. Save it off and restore it if it changes.
> + * Use the r12 callee-saved register.
You might want to make that line go away :-)
> + */ > + cr2 = read_cr2(); > + > nmi_enter(); > > inc_irq_stat(__nmi_count); > @@ -523,6 +532,10 @@ do_nmi(struct pt_regs *regs, long error_code) > > nmi_exit(); > > + /* Reads are cheaper than writes */ > + if (unlikely(cr2 != read_cr2())) > + write_cr2(cr2); > + > /* On i386, may loop back to preprocess */ > nmi_nesting_postprocess(); > }
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