Lib changes and strnlen_user() changes

commit 5ecb0857043a8d4a115843c28e724ec781b84a91
Author: faux123 <reioux@gmail.com>
Date:   Thu May 31 14:41:40 2012 -0700

    ARM: use generic strnlen_user and strncpy_from_user
     functions

    This patch implements the word-at-a-time interface for ARM using the
    same algorithm as x86. Although we have a clz instruction from ARMv5,
    this only saves us one mov instruction when building with Thumb-2 and
    makes no difference when targetting ARM, so we use the magic 0x0ff0001
    constant for all CPUs. For big-endian configurations, we use the
    implementation from asm-generic.

    With this implemented, we can replace our byte-at-a-time strnlen_user
    and strncpy_from_user functions with the optimised generic versions.

    Signed-off-by: Will Deacon <will.deacon@arm.com>
    modified for Linux 3.0 from Linux 3.4+ by faux123

commit f4e3b35c79de1bfe205be4ca3e4fa8e383f045a9
Author: faux123 <reioux@gmail.com>
Date:   Thu May 31 14:28:46 2012 -0700

    kernel: Move REPEAT_BYTE definition into linux/kernel.h

    And make sure that everything using it explicitly includes
    that header file.

    Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
    modified for Linux 3.0 from Linux 3.4+ by faux123

commit 726fcc1ec7cb23aee40c03af4a474c4e88107a4d
Author: Paul Mackerras <paulus@samba.org>
Date:   Mon May 28 12:59:56 2012 +1000

    lib: Fix generic strnlen_user for 32-bit big-endian machines

    The aligned_byte_mask() definition is wrong for 32-bit big-endian
    machines: the "7-(n)" part of the definition assumes a long is 8
    bytes.  This fixes it by using BITS_PER_LONG - 8 instead of 8*7.
    Tested on 32-bit and 64-bit PowerPC.

    Signed-off-by: Paul Mackerras <paulus@samba.org>
    Acked-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

commit ec266a2e46347e3beba220703e03a09000874626
Author: Linus Torvalds <torvalds@linux-foundation.org>
Date:   Thu May 31 14:14:27 2012 -0700

    lib: add generic strnlen_user() function

    This adds a new generic optimized strnlen_user() function that uses the
    <asm/word-at-a-time.h> infrastructure to portably do efficient string
    handling.

    In many ways, strnlen is much simpler than strncpy, and in particular we
    can always pre-align the words we load from memory.  That means that all
    the worries about alignment etc are a non-issue, so this one can easily
    be used on any architecture.  You obviously do have to do the
    appropriate word-at-a-time.h macros.

    Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

commit 417b4dfec225fe11d7491bc54ab2831ef3d194b2
Author: faux123 <reioux@gmail.com>
Date:   Thu May 31 14:10:54 2012 -0700

    word-at-a-time: make the interfaces truly generic

    This changes the interfaces in <asm/word-at-a-time.h> to be a bit more
    complicated, but a lot more generic.

    In particular, it allows us to really do the operations efficiently on
    both little-endian and big-endian machines, pretty much regardless of
    machine details.  For example, if you can rely on a fast population
    count instruction on your architecture, this will allow you to make your
    optimized <asm/word-at-a-time.h> file with that.

    NOTE! The "generic" version in include/asm-generic/word-at-a-time.h is
    not truly generic, it actually only works on big-endian.  Why? Because
    on little-endian the generic algorithms are wasteful, since you can
    inevitably do better. The x86 implementation is an example of that.

    (The only truly non-generic part of the asm-generic implementation is
    the "find_zero()" function, and you could make a little-endian version
    of it.  And if the Kbuild infrastructure allowed us to pick a particular
    header file, that would be lovely)

    The <asm/word-at-a-time.h> functions are as follows:

     - WORD_AT_A_TIME_CONSTANTS: specific constants that the algorithm
       uses.

     - has_zero(): take a word, and determine if it has a zero byte in it.
       It gets the word, the pointer to the constant pool, and a pointer to
       an intermediate "data" field it can set.

       This is the "quick-and-dirty" zero tester: it's what is run inside
       the hot loops.

     - "prep_zero_mask()": take the word, the data that has_zero() produced,
       and the constant pool, and generate an *exact* mask of which byte had
       the first zero.  This is run directly *outside* the loop, and allows
       the "has_zero()" function to answer the "is there a zero byte"
       question without necessarily getting exactly *which* byte is the
       first one to contain a zero.

       If you do multiple byte lookups concurrently (eg "hash_name()", which
       looks for both NUL and '/' bytes), after you've done the prep_zero_mask()
       phase, the result of those can be or'ed together to get the "either
       or" case.

     - The result from "prep_zero_mask()" can then be fed into "find_zero()"
       (to find the byte offset of the first byte that was zero) or into
       "zero_bytemask()" (to find the bytemask of the bytes preceding the
       zero byte).

       The existence of zero_bytemask() is optional, and is not necessary
       for the normal string routines.  But dentry name hashing needs it, so
       if you enable DENTRY_WORD_AT_A_TIME you need to expose it.

    This changes the generic strncpy_from_user() function and the dentry
    hashing functions to use these modified word-at-a-time interfaces.  This
    gets us back to the optimized state of the x86 strncpy that we lost in
    the previous commit when moving over to the generic version.

    Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
    modified for Linux 3.0 from Linux 3.4+ by faux123

commit 04f69dbd478ddbc6c2fcdf77be19f1c78c4c6944
Author: faux123 <reioux@gmail.com>
Date:   Thu May 31 13:35:14 2012 -0700

    lib: Sparc's strncpy_from_user is generic enough, move under
     lib/

    To use this, an architecture simply needs to:

    1) Provide a user_addr_max() implementation via asm/uaccess.h

    2) Add "select GENERIC_STRNCPY_FROM_USER" to their arch Kcnfig

    3) Remove the existing strncpy_from_user() implementation and symbol
       exports their architecture had.

    Signed-off-by: David S. Miller <davem@davemloft.net>
    Acked-by: David Howells <dhowells@redhat.com>
    modified for Linux 3.0 Kernel from Linux 3.4+ by faux123