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Commit 06976945 authored by Dave Hansen's avatar Dave Hansen Committed by Ingo Molnar
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x86/mm/pkeys: Actually enable Memory Protection Keys in the CPU 



This sets the bit in 'cr4' to actually enable the protection
keys feature.  We also include a boot-time disable for the
feature "nopku".

Seting X86_CR4_PKE will cause the X86_FEATURE_OSPKE cpuid
bit to appear set.  At this point in boot, identify_cpu()
has already run the actual CPUID instructions and populated
the "cpu features" structures.  We need to go back and
re-run identify_cpu() to make sure it gets updated values.

We *could* simply re-populate the 11th word of the cpuid
data, but this is probably quick enough.

Also note that with the cpu_has() check and X86_FEATURE_PKU
present in disabled-features.h, we do not need an #ifdef
for setup_pku().

Signed-off-by: default avatarDave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: default avatarThomas Gleixner <tglx@linutronix.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Dave Hansen <dave@sr71.net>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: linux-mm@kvack.org
Link: http://lkml.kernel.org/r/20160212210229.6708027C@viggo.jf.intel.com


[ Small readability edits. ]
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 284244a9

Documentation/kernel-parameters.txt

+3 −0
Original line number Original line Diff line number Diff line
@@ -976,6 +976,9 @@ bytes respectively. Such letter suffixes can also be entirely omitted. 
			See Documentation/x86/intel_mpx.txt for more

			See Documentation/x86/intel_mpx.txt for more

			information about the feature.

			information about the feature.





	nopku		[X86] Disable Memory Protection Keys CPU feature found

			in some Intel CPUs.



	eagerfpu=	[X86]

	eagerfpu=	[X86]

			on	enable eager fpu restore

			on	enable eager fpu restore

			off	disable eager fpu restore

			off	disable eager fpu restore

arch/x86/kernel/cpu/common.c

+43 −0
Original line number Original line Diff line number Diff line
@@ -303,6 +303,48 @@ static __always_inline void setup_smap(struct cpuinfo_x86 *c) 
	}

	}

}

}





/*

 * Protection Keys are not available in 32-bit mode.

 */

static bool pku_disabled;



static __always_inline void setup_pku(struct cpuinfo_x86 *c)

{

	if (!cpu_has(c, X86_FEATURE_PKU))

		return;

	if (pku_disabled)

		return;



	cr4_set_bits(X86_CR4_PKE);

	/*

	 * Seting X86_CR4_PKE will cause the X86_FEATURE_OSPKE

	 * cpuid bit to be set.  We need to ensure that we

	 * update that bit in this CPU's "cpu_info".

	 */

	get_cpu_cap(c);

}



#ifdef CONFIG_X86_INTEL_MEMORY_PROTECTION_KEYS

static __init int setup_disable_pku(char *arg)

{

	/*

	 * Do not clear the X86_FEATURE_PKU bit.  All of the

	 * runtime checks are against OSPKE so clearing the

	 * bit does nothing.

	 *

	 * This way, we will see "pku" in cpuinfo, but not

	 * "ospke", which is exactly what we want.  It shows

	 * that the CPU has PKU, but the OS has not enabled it.

	 * This happens to be exactly how a system would look

	 * if we disabled the config option.

	 */

	pr_info("x86: 'nopku' specified, disabling Memory Protection Keys\n");

	pku_disabled = true;

	return 1;

}

__setup("nopku", setup_disable_pku);

#endif /* CONFIG_X86_64 */



/*

/*

 * Some CPU features depend on higher CPUID levels, which may not always

 * Some CPU features depend on higher CPUID levels, which may not always

 * be available due to CPUID level capping or broken virtualization

 * be available due to CPUID level capping or broken virtualization
@@ -960,6 +1002,7 @@ static void identify_cpu(struct cpuinfo_x86 *c) 
	init_hypervisor(c);

	init_hypervisor(c);

	x86_init_rdrand(c);

	x86_init_rdrand(c);

	x86_init_cache_qos(c);

	x86_init_cache_qos(c);

	setup_pku(c);





	/*

	/*

	 * Clear/Set all flags overriden by options, need do it

	 * Clear/Set all flags overriden by options, need do it