[PATCH 13/37] x86, pkeys: store protection in high VMA flags

[Dave Hansen]

From: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>

vma->vm_flags is an 'unsigned long', so has space for 32 flags
on 32-bit architectures.  The high 32 bits are unused on 64-bit
platforms.  We've steered away from using the unused high VMA
bits for things because we would have difficulty supporting it
on 32-bit.

Protection Keys are not available in 32-bit mode, so there is
no concern about supporting this feature in 32-bit mode or on
32-bit CPUs.

This patch carves out 4 bits from the high half of
vma->vm_flags and allows architectures to set config option
to make them available.

Sparse complains about these constants unless we explicitly
call them "UL".

Signed-off-by: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
---

 b/arch/x86/Kconfig   |    1 +
 b/include/linux/mm.h |    7 +++++++
 b/mm/Kconfig         |    3 +++
 3 files changed, 11 insertions(+)

diff -puN arch/x86/Kconfig~pkeys-07-eat-high-vma-flags arch/x86/Kconfig
--- a/arch/x86/Kconfig~pkeys-07-eat-high-vma-flags	2015-11-16 12:35:40.938426022 -0800
+++ b/arch/x86/Kconfig	2015-11-16 12:35:40.945426340 -0800
@@ -152,6 +152,7 @@ config X86
 	select VIRT_TO_BUS
 	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
 
 config INSTRUCTION_DECODER
 	def_bool y
diff -puN include/linux/mm.h~pkeys-07-eat-high-vma-flags include/linux/mm.h
--- a/include/linux/mm.h~pkeys-07-eat-high-vma-flags	2015-11-16 12:35:40.940426113 -0800
+++ b/include/linux/mm.h	2015-11-16 12:35:40.946426385 -0800
@@ -158,6 +158,13 @@ extern unsigned int kobjsize(const void
 #define VM_NOHUGEPAGE	0x40000000	/* MADV_NOHUGEPAGE marked this vma */
 #define VM_MERGEABLE	0x80000000	/* KSM may merge identical pages */
 
+#ifdef CONFIG_ARCH_USES_HIGH_VMA_FLAGS
+#define VM_HIGH_ARCH_0  0x100000000UL	/* bit only usable on 64-bit architectures */
+#define VM_HIGH_ARCH_1  0x200000000UL	/* bit only usable on 64-bit architectures */
+#define VM_HIGH_ARCH_2  0x400000000UL	/* bit only usable on 64-bit architectures */
+#define VM_HIGH_ARCH_3  0x800000000UL	/* bit only usable on 64-bit architectures */
+#endif /* CONFIG_ARCH_USES_HIGH_VMA_FLAGS */
+
 #if defined(CONFIG_X86)
 # define VM_PAT		VM_ARCH_1	/* PAT reserves whole VMA at once (x86) */
 #elif defined(CONFIG_PPC)
diff -puN mm/Kconfig~pkeys-07-eat-high-vma-flags mm/Kconfig
--- a/mm/Kconfig~pkeys-07-eat-high-vma-flags	2015-11-16 12:35:40.942426204 -0800
+++ b/mm/Kconfig	2015-11-16 12:35:40.947426431 -0800
@@ -668,3 +668,6 @@ config ZONE_DEVICE
 
 config FRAME_VECTOR
 	bool
+
+config ARCH_USES_HIGH_VMA_FLAGS
+	bool
_
--
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