Commit 30e931d4 authored Mar 23, 2006 by Eric W. Biederman Committed by Linus Torvalds Mar 23, 2006

[PATCH] i386: Add a temporary to make put_user more type safe



In some code I am developing I had occasion to change the type of a
variable.  This made the value put_user was putting to user space wrong.
But the code continued to build cleanly without errors.

Introducing a temporary fixes this problem and at least with gcc-3.3.5 does
not cause gcc any problems with optimizing out the temporary.  gcc-4.x
using SSA internally ought to be even better at optimizing out temporaries,
so I don't expect a temporary to become a problem.  Especially because in
all correct cases the types on both sides of the assignment to the
temporary are the same.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

parent 4f886511

include/asm-i386/uaccess.h

+7 −5

Original line number	Diff line number	Diff line
		@@ -197,13 +197,15 @@ extern void __put_user_8(void);

		#define put_user(x,ptr) \
		({ int __ret_pu; \
		__typeof__(*(ptr)) __pu_val; \
		__chk_user_ptr(ptr); \
		__pu_val = x; \
		switch(sizeof(*(ptr))) { \
		case 1: __put_user_1(x, ptr); break; \
		case 2: __put_user_2(x, ptr); break; \
		case 4: __put_user_4(x, ptr); break; \
		case 8: __put_user_8(x, ptr); break; \
		default:__put_user_X(x, ptr); break; \
		case 1: __put_user_1(__pu_val, ptr); break; \
		case 2: __put_user_2(__pu_val, ptr); break; \
		case 4: __put_user_4(__pu_val, ptr); break; \
		case 8: __put_user_8(__pu_val, ptr); break; \
		default:__put_user_X(__pu_val, ptr); break; \
		} \
		__ret_pu; \
		})