[tip:mm/pkeys] mm/core, x86/mm/pkeys: Add arch_validate_pkey()

[tip-bot for Dave Hansen <tipbot@zytor.com>]

Commit-ID:  66d375709d2c891acc639538fd3179fa0cbb0daf
Gitweb:     http://git.kernel.org/tip/66d375709d2c891acc639538fd3179fa0cbb0daf
Author:     Dave Hansen <dave.hansen@linux.intel.com>
AuthorDate: Fri, 12 Feb 2016 13:02:32 -0800
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Thu, 18 Feb 2016 19:46:31 +0100

mm/core, x86/mm/pkeys: Add arch_validate_pkey()

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>
Reviewed-by: Thomas 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/20160212210232.774EEAAB@viggo.jf.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 arch/x86/Kconfig             |  1 +
 arch/x86/include/asm/pkeys.h |  6 ++++++
 include/linux/pkeys.h        | 25 +++++++++++++++++++++++++
 mm/Kconfig                   |  2 ++
 4 files changed, 34 insertions(+)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index b875434..eda18ce 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -156,6 +156,7 @@ 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 --git a/arch/x86/include/asm/pkeys.h b/arch/x86/include/asm/pkeys.h
new file mode 100644
index 0000000..04243c2
--- /dev/null
+++ b/arch/x86/include/asm/pkeys.h
@@ -0,0 +1,6 @@
+#ifndef _ASM_X86_PKEYS_H
+#define _ASM_X86_PKEYS_H
+
+#define arch_max_pkey() (boot_cpu_has(X86_FEATURE_OSPKE) ? 16 : 1)
+
+#endif /*_ASM_X86_PKEYS_H */
diff --git a/include/linux/pkeys.h b/include/linux/pkeys.h
new file mode 100644
index 0000000..55e465f
--- /dev/null
+++ b/include/linux/pkeys.h
@@ -0,0 +1,25 @@
+#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 */
+#define arch_max_pkey() (1)
+#endif /* ! CONFIG_ARCH_HAS_PKEYS */
+
+/*
+ * This is called from mprotect_pkey().
+ *
+ * Returns true if the protection keys is valid.
+ */
+static inline bool validate_pkey(int pkey)
+{
+	if (pkey < 0)
+		return false;
+	return (pkey < arch_max_pkey());
+}
+
+#endif /* _LINUX_PKEYS_H */
diff --git a/mm/Kconfig b/mm/Kconfig
index 6cf4399..2702bb6 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -672,3 +672,5 @@ config FRAME_VECTOR
 
 config ARCH_USES_HIGH_VMA_FLAGS
 	bool
+config ARCH_HAS_PKEYS
+	bool