5 files changed, 138 insertions, 2 deletions
diff --git a/arch/x86/include/asm/pkeys.h b/arch/x86/include/asm/pkeys.h
index 5061aec2ed5e..7b84565c916c 100644
--- a/arch/x86/include/asm/pkeys.h
+++ b/arch/x86/include/asm/pkeys.h
@@ -6,4 +6,29 @@
 extern int arch_set_user_pkey_access(struct task_struct *tsk, int pkey,
 		unsigned long init_val);
 
+/*
+ * Try to dedicate one of the protection keys to be used as an
+ * execute-only protection key.
+ */
+#define PKEY_DEDICATED_EXECUTE_ONLY 15
+extern int __execute_only_pkey(struct mm_struct *mm);
+static inline int execute_only_pkey(struct mm_struct *mm)
+{
+	if (!boot_cpu_has(X86_FEATURE_OSPKE))
+		return 0;
+
+	return __execute_only_pkey(mm);
+}
+
+extern int __arch_override_mprotect_pkey(struct vm_area_struct *vma,
+		int prot, int pkey);
+static inline int arch_override_mprotect_pkey(struct vm_area_struct *vma,
+		int prot, int pkey)
+{
+	if (!boot_cpu_has(X86_FEATURE_OSPKE))
+		return 0;
+
+	return __arch_override_mprotect_pkey(vma, prot, pkey);
+}
+
 #endif /*_ASM_X86_PKEYS_H */
diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c
index 50813c35e9d9..1b1981812bb6 100644
--- a/arch/x86/kernel/fpu/xstate.c
+++ b/arch/x86/kernel/fpu/xstate.c
@@ -877,8 +877,6 @@ int arch_set_user_pkey_access(struct task_struct *tsk, int pkey,
 	int pkey_shift = (pkey * PKRU_BITS_PER_PKEY);
 	u32 new_pkru_bits = 0;
 
-	if (!validate_pkey(pkey))
-		return -EINVAL;
 	/*
 	 * This check implies XSAVE support.  OSPKE only gets
 	 * set if we enable XSAVE and we enable PKU in XCR0.
diff --git a/arch/x86/mm/Makefile b/arch/x86/mm/Makefile
index f9d38a48e3c8..67cf2e1e557b 100644
--- a/arch/x86/mm/Makefile
+++ b/arch/x86/mm/Makefile
@@ -34,3 +34,5 @@ obj-$(CONFIG_ACPI_NUMA)		+= srat.o
 obj-$(CONFIG_NUMA_EMU)		+= numa_emulation.o
 
 obj-$(CONFIG_X86_INTEL_MPX)	+= mpx.o
+obj-$(CONFIG_X86_INTEL_MEMORY_PROTECTION_KEYS) += pkeys.o
+
diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index d81744e6f39f..5877b92ab6f1 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -1108,6 +1108,16 @@ access_error(unsigned long error_code, struct vm_area_struct *vma)
 	 */
 	if (error_code & PF_PK)
 		return 1;
+
+	if (!(error_code & PF_INSTR)) {
+		/*
+		 * Assume all accesses require either read or execute
+		 * permissions.  This is not an instruction access, so
+		 * it requires read permissions.
+		 */
+		if (!(vma->vm_flags & VM_READ))
+			return 1;
+	}
 	/*
 	 * Make sure to check the VMA so that we do not perform
 	 * faults just to hit a PF_PK as soon as we fill in a
diff --git a/arch/x86/mm/pkeys.c b/arch/x86/mm/pkeys.c
new file mode 100644
index 000000000000..e8c474451928
--- /dev/null
+++ b/arch/x86/mm/pkeys.c
@@ -0,0 +1,101 @@
+/*
+ * Intel Memory Protection Keys management
+ * Copyright (c) 2015, Intel Corporation.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ */
+#include <linux/mm_types.h>             /* mm_struct, vma, etc...       */
+#include <linux/pkeys.h>                /* PKEY_*                       */
+#include <uapi/asm-generic/mman-common.h>
+
+#include <asm/cpufeature.h>             /* boot_cpu_has, ...            */
+#include <asm/mmu_context.h>            /* vma_pkey()                   */
+#include <asm/fpu/internal.h>           /* fpregs_active()              */
+
+int __execute_only_pkey(struct mm_struct *mm)
+{
+	int ret;
+
+	/*
+	 * We do not want to go through the relatively costly
+	 * dance to set PKRU if we do not need to.  Check it
+	 * first and assume that if the execute-only pkey is
+	 * write-disabled that we do not have to set it
+	 * ourselves.  We need preempt off so that nobody
+	 * can make fpregs inactive.
+	 */
+	preempt_disable();
+	if (fpregs_active() &&
+	    !__pkru_allows_read(read_pkru(), PKEY_DEDICATED_EXECUTE_ONLY)) {
+		preempt_enable();
+		return PKEY_DEDICATED_EXECUTE_ONLY;
+	}
+	preempt_enable();
+	ret = arch_set_user_pkey_access(current, PKEY_DEDICATED_EXECUTE_ONLY,
+			PKEY_DISABLE_ACCESS);
+	/*
+	 * If the PKRU-set operation failed somehow, just return
+	 * 0 and effectively disable execute-only support.
+	 */
+	if (ret)
+		return 0;
+
+	return PKEY_DEDICATED_EXECUTE_ONLY;
+}
+
+static inline bool vma_is_pkey_exec_only(struct vm_area_struct *vma)
+{
+	/* Do this check first since the vm_flags should be hot */
+	if ((vma->vm_flags & (VM_READ | VM_WRITE | VM_EXEC)) != VM_EXEC)
+		return false;
+	if (vma_pkey(vma) != PKEY_DEDICATED_EXECUTE_ONLY)
+		return false;
+
+	return true;
+}
+
+/*
+ * This is only called for *plain* mprotect calls.
+ */
+int __arch_override_mprotect_pkey(struct vm_area_struct *vma, int prot, int pkey)
+{
+	/*
+	 * Is this an mprotect_pkey() call?  If so, never
+	 * override the value that came from the user.
+	 */
+	if (pkey != -1)
+		return pkey;
+	/*
+	 * Look for a protection-key-drive execute-only mapping
+	 * which is now being given permissions that are not
+	 * execute-only.  Move it back to the default pkey.
+	 */
+	if (vma_is_pkey_exec_only(vma) &&
+	    (prot & (PROT_READ|PROT_WRITE))) {
+		return 0;
+	}
+	/*
+	 * The mapping is execute-only.  Go try to get the
+	 * execute-only protection key.  If we fail to do that,
+	 * fall through as if we do not have execute-only
+	 * support.
+	 */
+	if (prot == PROT_EXEC) {
+		pkey = execute_only_pkey(vma->vm_mm);
+		if (pkey > 0)
+			return pkey;
+	}
+	/*
+	 * This is a vanilla, non-pkey mprotect (or we failed to
+	 * setup execute-only), inherit the pkey from the VMA we
+	 * are working on.
+	 */
+	return vma_pkey(vma);
+}