Messages in this thread Patch in this message | | | Subject | [PATCH] i386: Add a temporary to make put_user more type safe. | From | (Eric W. Biederman) | Date | Sat, 28 Jan 2006 23:26:18 -0700 |
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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>
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include/asm-i386/uaccess.h | 11 ++++++----- 1 files changed, 6 insertions(+), 5 deletions(-)
dd1215e541bfe2ed94a902f7fb263ca44b7e8afa diff --git a/include/asm-i386/uaccess.h b/include/asm-i386/uaccess.h index 3f1337c..1641613 100644 --- a/include/asm-i386/uaccess.h +++ b/include/asm-i386/uaccess.h @@ -198,12 +198,13 @@ extern void __put_user_8(void); #define put_user(x,ptr) \ ({ int __ret_pu; \ __chk_user_ptr(ptr); \ + __typeof__(*(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; \ }) -- 1.1.5.g3480 - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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