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Commit 41a69b50 authored by Linus Torvalds's avatar Linus Torvalds Committed by Alex Shi
Browse files

x86: remove more uaccess_32.h complexity 



I'm looking at trying to possibly merge the 32-bit and 64-bit versions
of the x86 uaccess.h implementation, but first this needs to be cleaned
up.

For example, the 32-bit version of "__copy_from_user_inatomic()" is
mostly the special cases for the constant size, and it's actually almost
never relevant.  Most users aren't actually using a constant size
anyway, and the few cases that do small constant copies are better off
just using __get_user() instead.

So get rid of the unnecessary complexity.

Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
(cherry picked from commit bd28b14591b98f696bc9f94c5ba2e598ca487dfd)
Signed-off-by: default avatarAlex Shi <alex.shi@linaro.org>
parent 30e3024b

arch/x86/include/asm/uaccess_32.h

+0 −26
Original line number Diff line number Diff line
@@ -65,32 +65,6 @@ __copy_to_user(void __user *to, const void *from, unsigned long n) 
static __always_inline unsigned long

__copy_from_user_inatomic(void *to, const void __user *from, unsigned long n)

{

	/* Avoid zeroing the tail if the copy fails..

	 * If 'n' is constant and 1, 2, or 4, we do still zero on a failure,

	 * but as the zeroing behaviour is only significant when n is not

	 * constant, that shouldn't be a problem.

	 */

	if (__builtin_constant_p(n)) {

		unsigned long ret;



		switch (n) {

		case 1:

			__uaccess_begin();

			__get_user_size(*(u8 *)to, from, 1, ret, 1);

			__uaccess_end();

			return ret;

		case 2:

			__uaccess_begin();

			__get_user_size(*(u16 *)to, from, 2, ret, 2);

			__uaccess_end();

			return ret;

		case 4:

			__uaccess_begin();

			__get_user_size(*(u32 *)to, from, 4, ret, 4);

			__uaccess_end();

			return ret;

		}

	}

	return __copy_from_user_ll_nozero(to, from, n);

}

kernel/events/uprobes.c

+1 −2
Original line number Diff line number Diff line
@@ -1692,8 +1692,7 @@ static int is_trap_at_addr(struct mm_struct *mm, unsigned long vaddr) 
	int result;



	pagefault_disable();

	result = __copy_from_user_inatomic(&opcode, (void __user*)vaddr,

							sizeof(opcode));

	result = __get_user(opcode, (uprobe_opcode_t __user *)vaddr);

	pagefault_enable();



	if (likely(result == 0))

kernel/futex.c

+1 −1
Original line number Diff line number Diff line
@@ -681,7 +681,7 @@ static int get_futex_value_locked(u32 *dest, u32 __user *from) 
	int ret;



	pagefault_disable();

	ret = __copy_from_user_inatomic(dest, from, sizeof(u32));

	ret = __get_user(*dest, from);

	pagefault_enable();



	return ret ? -EFAULT : 0;

mm/maccess.c

+1 −2
Original line number Diff line number Diff line
@@ -96,8 +96,7 @@ long strncpy_from_unsafe(char *dst, const void *unsafe_addr, long count) 
	pagefault_disable();



	do {

		ret = __copy_from_user_inatomic(dst++,

						(const void __user __force *)src++, 1);

		ret = __get_user(*dst++, (const char __user __force *)src++);

	} while (dst[-1] && ret == 0 && src - unsafe_addr < count);



	dst[-1] = '\0';