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										 |  |  | # User exported sparc header files | 
					
						
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											2011-08-04 01:35:12 -07:00
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											2012-09-05 12:04:14 +08:00
										 |  |  | generic-y += clkdev.h | 
					
						
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											2013-03-30 11:44:22 +00:00
										 |  |  | generic-y += cputime.h | 
					
						
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											2011-08-04 01:35:12 -07:00
										 |  |  | generic-y += div64.h | 
					
						
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											2013-03-30 11:44:22 +00:00
										 |  |  | generic-y += emergency-restart.h | 
					
						
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											2012-08-03 12:12:38 +04:00
										 |  |  | generic-y += exec.h | 
					
						
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											2013-05-07 11:55:55 +02:00
										 |  |  | generic-y += linkage.h | 
					
						
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											2011-08-04 01:35:12 -07:00
										 |  |  | generic-y += local64.h | 
					
						
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											2013-03-30 11:44:22 +00:00
										 |  |  | generic-y += mutex.h | 
					
						
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											2011-08-04 01:35:12 -07:00
										 |  |  | generic-y += irq_regs.h | 
					
						
							|  |  |  | generic-y += local.h | 
					
						
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											2012-09-28 14:31:03 +09:30
										 |  |  | generic-y += module.h | 
					
						
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											2013-03-30 11:44:22 +00:00
										 |  |  | generic-y += serial.h | 
					
						
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											2012-11-13 12:18:21 -08:00
										 |  |  | generic-y += trace_clock.h | 
					
						
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											2013-03-31 07:01:47 +00:00
										 |  |  | generic-y += types.h | 
					
						
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												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>
											
										 
											2012-05-26 10:43:17 -07:00
										 |  |  | generic-y += word-at-a-time.h | 
					
						
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											2013-08-14 14:55:40 +02:00
										 |  |  | generic-y += preempt.h |