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authorCatalin Marinas <catalin.marinas@arm.com>2016-08-11 19:44:50 +0200
committerWill Deacon <will.deacon@arm.com>2016-08-25 19:00:29 +0200
commitcab15ce604e550020bb7115b779013b91bcdbc21 (patch)
tree0ba025b8ad16505532aaa6e1b4cc665473f026fa /arch/arm64/include/asm/Kbuild
parentarm64: kprobe: Always clear pstate.D in breakpoint exception handler (diff)
downloadlinux-cab15ce604e550020bb7115b779013b91bcdbc21.tar.xz
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arm64: Introduce execute-only page access permissions
The ARMv8 architecture allows execute-only user permissions by clearing the PTE_UXN and PTE_USER bits. However, the kernel running on a CPU implementation without User Access Override (ARMv8.2 onwards) can still access such page, so execute-only page permission does not protect against read(2)/write(2) etc. accesses. Systems requiring such protection must enable features like SECCOMP. This patch changes the arm64 __P100 and __S100 protection_map[] macros to the new __PAGE_EXECONLY attributes. A side effect is that pte_user() no longer triggers for __PAGE_EXECONLY since PTE_USER isn't set. To work around this, the check is done on the PTE_NG bit via the pte_ng() macro. VM_READ is also checked now for page faults. Reviewed-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com> Signed-off-by: Will Deacon <will.deacon@arm.com>
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