From: Dave Hansen <[email protected]> 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 <[email protected]> Reviewed-by: Thomas Gleixner <[email protected]> --- b/arch/x86/Kconfig | 1 + b/include/linux/mm.h | 11 +++++++++++ b/mm/Kconfig | 3 +++ 3 files changed, 15 insertions(+) diff -puN arch/x86/Kconfig~pkeys-06-eat-high-vma-flags arch/x86/Kconfig --- a/arch/x86/Kconfig~pkeys-06-eat-high-vma-flags 2016-02-12 10:44:18.494350045 -0800 +++ b/arch/x86/Kconfig 2016-02-12 10:44:18.502350411 -0800 @@ -155,6 +155,7 @@ 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-06-eat-high-vma-flags include/linux/mm.h --- a/include/linux/mm.h~pkeys-06-eat-high-vma-flags 2016-02-12 10:44:18.496350136 -0800 +++ b/include/linux/mm.h 2016-02-12 10:44:18.503350456 -0800 @@ -170,6 +170,17 @@ 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_BIT_0 32 /* bit only usable on 64-bit architectures */ +#define VM_HIGH_ARCH_BIT_1 33 /* bit only usable on 64-bit architectures */ +#define VM_HIGH_ARCH_BIT_2 34 /* bit only usable on 64-bit architectures */ +#define VM_HIGH_ARCH_BIT_3 35 /* bit only usable on 64-bit architectures */ +#define VM_HIGH_ARCH_0 BIT(VM_HIGH_ARCH_BIT_0) +#define VM_HIGH_ARCH_1 BIT(VM_HIGH_ARCH_BIT_1) +#define VM_HIGH_ARCH_2 BIT(VM_HIGH_ARCH_BIT_2) +#define VM_HIGH_ARCH_3 BIT(VM_HIGH_ARCH_BIT_3) +#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-06-eat-high-vma-flags mm/Kconfig --- a/mm/Kconfig~pkeys-06-eat-high-vma-flags 2016-02-12 10:44:18.498350228 -0800 +++ b/mm/Kconfig 2016-02-12 10:44:18.503350456 -0800 @@ -669,3 +669,6 @@ config ZONE_DEVICE config FRAME_VECTOR bool + +config ARCH_USES_HIGH_VMA_FLAGS + bool _
