Messages in this thread | | | Date | Mon, 24 Feb 2014 20:30:43 +0100 | From | Peter Zijlstra <> | Subject | Re: perf_fuzzer compiled for x32 causes reboot |
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On Mon, Feb 24, 2014 at 02:13:29PM -0500, Steven Rostedt wrote: > Ah, and x86_64 saves off the cr2 register when entering NMI and restores > it before returning. But it seems to be missing from the i386 code.
arch/x86/kernel/nmi.c:
#define nmi_nesting_preprocess(regs) \ do { \ if (this_cpu_read(nmi_state) != NMI_NOT_RUNNING) { \ this_cpu_write(nmi_state, NMI_LATCHED); \ return; \ } \ this_cpu_write(nmi_state, NMI_EXECUTING); \ this_cpu_write(nmi_cr2, read_cr2()); \ } while (0); \ nmi_restart:
#define nmi_nesting_postprocess() \ do { \ if (unlikely(this_cpu_read(nmi_cr2) != read_cr2())) \ write_cr2(this_cpu_read(nmi_cr2)); \ if (this_cpu_dec_return(nmi_state)) \ goto nmi_restart; \ } while (0)
That very much looks like saving/restoring CR2 to me.
FWIW; I hate how the x86_64 and i386 versions of this NMI nesting magic are so completely different.
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