Messages in this thread | | | Date | Tue, 10 Jun 2014 13:24:36 -0700 | From | "H. Peter Anvin" <> | Subject | Re: [PATCH] x86: be more helpful with SMEP faults |
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On 06/10/2014 01:18 PM, Borislav Petkov wrote: >> static void >> show_fault_oops(struct pt_regs *regs, unsigned long error_code, >> @@ -594,6 +596,11 @@ show_fault_oops(struct pt_regs *regs, unsigned long error_code, >> >> if (pte && pte_present(*pte) && !pte_exec(*pte)) >> printk(nx_warning, from_kuid(&init_user_ns, current_uid())); >> + if (pte && pte_present(*pte) && pte_exec(*pte) && >> + (pgd_flags(*pgd) & _PAGE_USER) && >> + static_cpu_has(X86_FEATURE_SMEP) && > > Btw, we could probably save us this line as CR4 reserved bits should be > Must-Be-Zero and setting any of those should #GP. And I'm talking about > pre-SMEP Intel, and AMD machines. > > IOW, if CR4.SMEP is set, it definitely means SMEP is present and > enabled. > > hpa, that true? >
Yes. Also, the Linux kernel will set or clear X86_FEATURE_SMEP to match, so the two are redundant.
-hpa
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