Commit 84624087 authored by Will Deacon's avatar Will Deacon Committed by Catalin Marinas
Browse files

arm64: uaccess: Don't bother eliding access_ok checks in __{get, put}_user 



access_ok isn't an expensive operation once the addr_limit for the current
thread has been loaded into the cache. Given that the initial access_ok
check preceding a sequence of __{get,put}_user operations will take
the brunt of the miss, we can make the __* variants identical to the
full-fat versions, which brings with it the benefits of address masking.

The likely cost in these sequences will be from toggling PAN/UAO, which
we can address later by implementing the *_unsafe versions.

Reviewed-by: default avatarRobin Murphy <robin.murphy@arm.com>
Signed-off-by: default avatarWill Deacon <will.deacon@arm.com>
Signed-off-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
parent c2f0ad4f

arch/arm64/include/asm/uaccess.h

+32 −22
Original line number Diff line number Diff line
@@ -306,28 +306,33 @@ do { \ 
	(x) = (__force __typeof__(*(ptr)))__gu_val;			\

} while (0)



#define __get_user(x, ptr)						\

#define __get_user_check(x, ptr, err)					\

({									\

	int __gu_err = 0;						\

	__get_user_err((x), (ptr), __gu_err);				\

	__gu_err;							\

	__typeof__(*(ptr)) __user *__p = (ptr);				\

	might_fault();							\

	if (access_ok(VERIFY_READ, __p, sizeof(*__p))) {		\

		__p = uaccess_mask_ptr(__p);				\

		__get_user_err((x), __p, (err));			\

	} else {							\

		(x) = 0; (err) = -EFAULT;				\

	}								\

})



#define __get_user_error(x, ptr, err)					\

({									\

	__get_user_err((x), (ptr), (err));				\

	__get_user_check((x), (ptr), (err));				\

	(void)0;							\

})



#define get_user(x, ptr)						\

#define __get_user(x, ptr)						\

({									\

	__typeof__(*(ptr)) __user *__p = (ptr);				\

	might_fault();							\

	access_ok(VERIFY_READ, __p, sizeof(*__p)) ?			\

		__p = uaccess_mask_ptr(__p), __get_user((x), __p) :	\

		((x) = 0, -EFAULT);					\

	int __gu_err = 0;						\

	__get_user_check((x), (ptr), __gu_err);				\

	__gu_err;							\

})



#define get_user	__get_user



#define __put_user_asm(instr, alt_instr, reg, x, addr, err, feature)	\

	asm volatile(							\

	"1:"ALTERNATIVE(instr "     " reg "1, [%2]\n",			\
@@ -370,28 +375,33 @@ do { \ 
	uaccess_disable_not_uao();					\

} while (0)



#define __put_user(x, ptr)						\

#define __put_user_check(x, ptr, err)					\

({									\

	int __pu_err = 0;						\

	__put_user_err((x), (ptr), __pu_err);				\

	__pu_err;							\

	__typeof__(*(ptr)) __user *__p = (ptr);				\

	might_fault();							\

	if (access_ok(VERIFY_WRITE, __p, sizeof(*__p))) {		\

		__p = uaccess_mask_ptr(__p);				\

		__put_user_err((x), __p, (err));			\

	} else	{							\

		(err) = -EFAULT;					\

	}								\

})



#define __put_user_error(x, ptr, err)					\

({									\

	__put_user_err((x), (ptr), (err));				\

	__put_user_check((x), (ptr), (err));				\

	(void)0;							\

})



#define put_user(x, ptr)						\

#define __put_user(x, ptr)						\

({									\

	__typeof__(*(ptr)) __user *__p = (ptr);				\

	might_fault();							\

	access_ok(VERIFY_WRITE, __p, sizeof(*__p)) ?			\

		__p = uaccess_mask_ptr(__p), __put_user((x), __p) :	\

		-EFAULT;						\

	int __pu_err = 0;						\

	__put_user_check((x), (ptr), __pu_err);				\

	__pu_err;							\

})



#define put_user	__put_user



extern unsigned long __must_check __arch_copy_from_user(void *to, const void __user *from, unsigned long n);

#define raw_copy_from_user __arch_copy_from_user

extern unsigned long __must_check __arch_copy_to_user(void __user *to, const void *from, unsigned long n);

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