From 0697694564c84f4c9320e5d103d0191297a20023 Mon Sep 17 00:00:00 2001 From: Dave Hansen Date: Fri, 12 Feb 2016 13:02:29 -0800 Subject: [PATCH] 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: Dave Hansen Reviewed-by: Thomas Gleixner Cc: Andrew Morton Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Brian Gerst Cc: Dave Hansen Cc: Denys Vlasenko Cc: H. Peter Anvin Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Rik van Riel Cc: linux-mm@kvack.org Link: http://lkml.kernel.org/r/20160212210229.6708027C@viggo.jf.intel.com [ Small readability edits. ] Signed-off-by: Ingo Molnar --- Documentation/kernel-parameters.txt | 3 ++ arch/x86/kernel/cpu/common.c | 43 +++++++++++++++++++++++++++++ 2 files changed, 46 insertions(+) diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt index a37b5bb03e51..acf467d44e39 100644 --- a/Documentation/kernel-parameters.txt +++ b/Documentation/kernel-parameters.txt @@ -976,6 +976,9 @@ bytes respectively. Such letter suffixes can also be entirely omitted. See Documentation/x86/intel_mpx.txt for more information about the feature. + nopku [X86] Disable Memory Protection Keys CPU feature found + in some Intel CPUs. + eagerfpu= [X86] on enable eager fpu restore off disable eager fpu restore diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c index a719ad7551d2..4fac2634ba19 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -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 * 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); x86_init_rdrand(c); x86_init_cache_qos(c); + setup_pku(c); /* * Clear/Set all flags overriden by options, need do it -- 2.30.2