• Linus Torvalds's avatar
    x86: merge 32/64-bit versions of 'strncpy_from_user()' and speed it up · 92ae03f2
    Linus Torvalds authored
    This merges the 32- and 64-bit versions of the x86 strncpy_from_user()
    by just rewriting it in C rather than the ancient inline asm versions
    that used lodsb/stosb and had been duplicated for (trivial) differences
    between the 32-bit and 64-bit versions.
    
    While doing that, it also speeds them up by doing the accesses a word at
    a time.  Finally, the new routines also properly handle the case of
    hitting the end of the address space, which we have never done correctly
    before (fs/namei.c has a hack around it for that reason).
    
    Despite all these improvements, it actually removes more lines than it
    adds, due to the de-duplication.  Also, we no longer export (or define)
    the legacy __strncpy_from_user() function (that was defined to not do
    the user permission checks), since it's not actually used anywhere, and
    the user address space checks are built in to the new code.
    
    Other architecture maintainers have been notified that the old hack in
    fs/namei.c will be going away in the 3.5 merge window, in case they
    copied the x86 approach of being a bit cavalier about the end of the
    address space.
    
    Cc: linux-arch@vger.kernel.org
    Cc: Ingo Molnar <mingo@kernel.org>
    Cc: Peter Anvin" <hpa@zytor.com>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    92ae03f2
uaccess_32.h 6.81 KB