[PATCH 28/37] x86, pkeys: add arch_validate_pkey()

[Dave Hansen <dave@sr71.net>]

From: Dave Hansen <dave.hansen@linux.intel.com>

The syscall-level code is passed a protection key and need to
return an appropriate error code if the protection key is bogus.
We will be using this in subsequent patches.

Note that this also begins a series of arch-specific calls that
we need to expose in otherwise arch-independent code.  We create
a linux/pkeys.h header where we will put *all* the stubs for
these functions.

Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
---

 b/arch/x86/Kconfig             |    1 +
 b/arch/x86/include/asm/pkeys.h |   10 ++++++++++
 b/include/linux/pkeys.h        |   22 ++++++++++++++++++++++
 b/mm/Kconfig                   |    2 ++
 4 files changed, 35 insertions(+)

diff -puN /dev/null arch/x86/include/asm/pkeys.h
--- /dev/null	2015-07-13 14:24:11.435656502 -0700
+++ b/arch/x86/include/asm/pkeys.h	2015-11-16 19:22:05.258547128 -0800
@@ -0,0 +1,10 @@
+#ifndef _ASM_X86_PKEYS_H
+#define _ASM_X86_PKEYS_H
+
+#define arch_max_pkey() (boot_cpu_has(X86_FEATURE_OSPKE) ?      \
+				CONFIG_NR_PROTECTION_KEYS : 1)
+#define arch_validate_pkey(pkey) (((pkey) >= 0) && ((pkey) < arch_max_pkey()))
+
+#endif /*_ASM_X86_PKEYS_H */
+
+
diff -puN arch/x86/Kconfig~pkeys-15-arch_validate_peky arch/x86/Kconfig
--- a/arch/x86/Kconfig~pkeys-15-arch_validate_peky	2015-11-16 12:36:27.802553114 -0800
+++ b/arch/x86/Kconfig	2015-11-16 12:36:27.808553386 -0800
@@ -153,6 +153,7 @@ config X86
 	select X86_DEV_DMA_OPS			if X86_64
 	select X86_FEATURE_NAMES		if PROC_FS
 	select ARCH_USES_HIGH_VMA_FLAGS		if X86_INTEL_MEMORY_PROTECTION_KEYS
+	select ARCH_HAS_PKEYS			if X86_INTEL_MEMORY_PROTECTION_KEYS
 
 config INSTRUCTION_DECODER
 	def_bool y
diff -puN /dev/null include/linux/pkeys.h
--- /dev/null	2015-07-13 14:24:11.435656502 -0700
+++ b/include/linux/pkeys.h	2015-11-16 19:22:07.781660707 -0800
@@ -0,0 +1,22 @@
+#ifndef _LINUX_PKEYS_H
+#define _LINUX_PKEYS_H
+
+#include <linux/mm_types.h>
+#include <asm/mmu_context.h>
+
+#ifdef CONFIG_ARCH_HAS_PKEYS
+#include <asm/pkeys.h>
+#else /* ! CONFIG_ARCH_HAS_PKEYS */
+
+/*
+ * This is called from mprotect_pkey().
+ *
+ * Returns true if the protection keys is valid.
+ */
+static inline bool arch_validate_pkey(int key)
+{
+	return true;
+}
+#endif /* ! CONFIG_ARCH_HAS_PKEYS */
+
+#endif /* _LINUX_PKEYS_H */
diff -puN mm/Kconfig~pkeys-15-arch_validate_peky mm/Kconfig
--- a/mm/Kconfig~pkeys-15-arch_validate_peky	2015-11-16 12:36:27.804553205 -0800
+++ b/mm/Kconfig	2015-11-16 19:22:07.781660707 -0800
@@ -671,3 +671,5 @@ config FRAME_VECTOR
 
 config ARCH_USES_HIGH_VMA_FLAGS
 	bool
+config ARCH_HAS_PKEYS
+	bool
_