[PATCH 03/10] x86/pks: Enable Protection Keys Supervisor (PKS)

ira.weiny
2020-10-22T22:27:21Z

From: Fenghua Yu <fenghua.yu@intel.com>

Protection Keys for Supervisor pages (PKS) enables fast, hardware thread
specific, manipulation of permission restrictions on supervisor page
mappings. It uses the same mechanism of Protection Keys as those on
User mappings but applies that mechanism to supervisor mappings using a
supervisor specific MSR.

Kernel users can thus defines 'domains' of page mappings which have an
extra level of protection beyond those specified in the supervisor page
table entries.

Define ARCH_HAS_SUPERVISOR_PKEYS to distinguish this functionality from
the existing ARCH_HAS_PKEYS and then enable PKS when configured and
indicated by the CPU instance. While not strictly necessary in this
patch, ARCH_HAS_SUPERVISOR_PKEYS separates this functionality through
the patch series so it is introduced here.

Co-developed-by: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: Fenghua Yu <fenghua.yu@intel.com>

---
Changes since RFC V3
Per Dave Hansen
Update comment
Add X86_FEATURE_PKS to disabled-features.h
Rebase based on latest TIP tree
---
arch/x86/Kconfig | 1 +
arch/x86/include/asm/cpufeatures.h | 1 +
arch/x86/include/asm/disabled-features.h | 8 +++++++-
arch/x86/include/uapi/asm/processor-flags.h | 2 ++
arch/x86/kernel/cpu/common.c | 13 +++++++++++++
mm/Kconfig | 2 ++
6 files changed, 26 insertions(+), 1 deletion(-)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index f6946b81f74a..78c4c749c6a9 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1876,6 +1876,7 @@ config X86_INTEL_MEMORY_PROTECTION_KEYS
depends on X86_64 && (CPU_SUP_INTEL || CPU_SUP_AMD)
select ARCH_USES_HIGH_VMA_FLAGS
select ARCH_HAS_PKEYS
+ select ARCH_HAS_SUPERVISOR_PKEYS
help
Memory Protection Keys provides a mechanism for enforcing
page-based protections, but without requiring modification of the
diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
index dad350d42ecf..4deb580324e8 100644
--- a/arch/x86/include/asm/cpufeatures.h
+++ b/arch/x86/include/asm/cpufeatures.h
@@ -356,6 +356,7 @@
#define X86_FEATURE_MOVDIRI (16*32+27) /* MOVDIRI instruction */
#define X86_FEATURE_MOVDIR64B (16*32+28) /* MOVDIR64B instruction */
#define X86_FEATURE_ENQCMD (16*32+29) /* ENQCMD and ENQCMDS instructions */
+#define X86_FEATURE_PKS (16*32+31) /* Protection Keys for Supervisor pages */

/* AMD-defined CPU features, CPUID level 0x80000007 (EBX), word 17 */
#define X86_FEATURE_OVERFLOW_RECOV (17*32+ 0) /* MCA overflow recovery support */
diff --git a/arch/x86/include/asm/disabled-features.h b/arch/x86/include/asm/disabled-features.h
index 5861d34f9771..82540f0c5b6c 100644
--- a/arch/x86/include/asm/disabled-features.h
+++ b/arch/x86/include/asm/disabled-features.h
@@ -44,6 +44,12 @@
# define DISABLE_OSPKE (1<<(X86_FEATURE_OSPKE & 31))
#endif /* CONFIG_X86_INTEL_MEMORY_PROTECTION_KEYS */

+#ifdef CONFIG_ARCH_HAS_SUPERVISOR_PKEYS
+# define DISABLE_PKS 0
+#else
+# define DISABLE_PKS (1<<(X86_FEATURE_PKS & 31))
+#endif
+
#ifdef CONFIG_X86_5LEVEL
# define DISABLE_LA57 0
#else
@@ -82,7 +88,7 @@
#define DISABLED_MASK14 0
#define DISABLED_MASK15 0
#define DISABLED_MASK16 (DISABLE_PKU|DISABLE_OSPKE|DISABLE_LA57|DISABLE_UMIP| \
- DISABLE_ENQCMD)
+ DISABLE_ENQCMD|DISABLE_PKS)
#define DISABLED_MASK17 0
#define DISABLED_MASK18 0
#define DISABLED_MASK_CHECK BUILD_BUG_ON_ZERO(NCAPINTS != 19)
diff --git a/arch/x86/include/uapi/asm/processor-flags.h b/arch/x86/include/uapi/asm/processor-flags.h
index bcba3c643e63..191c574b2390 100644
--- a/arch/x86/include/uapi/asm/processor-flags.h
+++ b/arch/x86/include/uapi/asm/processor-flags.h
@@ -130,6 +130,8 @@
#define X86_CR4_SMAP _BITUL(X86_CR4_SMAP_BIT)
#define X86_CR4_PKE_BIT 22 /* enable Protection Keys support */
#define X86_CR4_PKE _BITUL(X86_CR4_PKE_BIT)
+#define X86_CR4_PKS_BIT 24 /* enable Protection Keys for Supervisor */
+#define X86_CR4_PKS _BITUL(X86_CR4_PKS_BIT)

/*
* x86-64 Task Priority Register, CR8
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 35ad8480c464..6a9ca938d9a9 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -1494,6 +1494,18 @@ static void validate_apic_and_package_id(struct cpuinfo_x86 *c)
#endif
}

+/*
+ * PKS is independent of PKU and either or both may be supported on a CPU.
+ * Configure PKS if the CPU supports the feature.
+ */
+static void setup_pks(void)
+{
+ if (!cpu_feature_enabled(X86_FEATURE_PKS))
+ return;
+
+ cr4_set_bits(X86_CR4_PKS);
+}
+
/*
* This does the hard work of actually picking apart the CPU stuff...
*/
@@ -1591,6 +1603,7 @@ static void identify_cpu(struct cpuinfo_x86 *c)

x86_init_rdrand(c);
setup_pku(c);
+ setup_pks();

/*
* Clear/Set all flags overridden by options, need do it
diff --git a/mm/Kconfig b/mm/Kconfig
index d42423f884a7..fc9ce7f65683 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -826,6 +826,8 @@ config ARCH_USES_HIGH_VMA_FLAGS
bool
config ARCH_HAS_PKEYS
bool
+config ARCH_HAS_SUPERVISOR_PKEYS
+ bool

config PERCPU_STATS
bool "Collect percpu memory statistics"
--
2.28.0.rc0.12.gb6a658bd00c9