Orange Pi5 kernel

^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300   1) /* SPDX-License-Identifier: GPL-2.0 */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300   2) /*
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300   3)  * arch/alpha/lib/ev6-clear_user.S
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300   4)  * 21264 version contributed by Rick Gorton <rick.gorton@alpha-processor.com>
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300   5)  *
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300   6)  * Zero user space, handling exceptions as we go.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300   7)  *
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300   8)  * We have to make sure that $0 is always up-to-date and contains the
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300   9)  * right "bytes left to zero" value (and that it is updated only _after_
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  10)  * a successful copy).  There is also some rather minor exception setup
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  11)  * stuff.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  12)  *
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  13)  * Much of the information about 21264 scheduling/coding comes from:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  14)  *	Compiler Writer's Guide for the Alpha 21264
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  15)  *	abbreviated as 'CWG' in other comments here
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  16)  *	ftp.digital.com/pub/Digital/info/semiconductor/literature/dsc-library.html
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  17)  * Scheduling notation:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  18)  *	E	- either cluster
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  19)  *	U	- upper subcluster; U0 - subcluster U0; U1 - subcluster U1
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  20)  *	L	- lower subcluster; L0 - subcluster L0; L1 - subcluster L1
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  21)  * Try not to change the actual algorithm if possible for consistency.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  22)  * Determining actual stalls (other than slotting) doesn't appear to be easy to do.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  23)  * From perusing the source code context where this routine is called, it is
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  24)  * a fair assumption that significant fractions of entire pages are zeroed, so
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  25)  * it's going to be worth the effort to hand-unroll a big loop, and use wh64.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  26)  * ASSUMPTION:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  27)  *	The believed purpose of only updating $0 after a store is that a signal
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  28)  *	may come along during the execution of this chunk of code, and we don't
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  29)  *	want to leave a hole (and we also want to avoid repeating lots of work)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  30)  */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  31) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  32) #include <asm/export.h>
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  33) /* Allow an exception for an insn; exit if we get one.  */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  34) #define EX(x,y...)			\
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  35) 	99: x,##y;			\
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  36) 	.section __ex_table,"a";	\
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  37) 	.long 99b - .;			\
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  38) 	lda $31, $exception-99b($31); 	\
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  39) 	.previous
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  40) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  41) 	.set noat
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  42) 	.set noreorder
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  43) 	.align 4
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  44) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  45) 	.globl __clear_user
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  46) 	.ent __clear_user
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  47) 	.frame	$30, 0, $26
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  48) 	.prologue 0
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  49) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  50) 				# Pipeline info : Slotting & Comments
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  51) __clear_user:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  52) 	and	$17, $17, $0
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  53) 	and	$16, 7, $4	# .. E  .. ..	: find dest head misalignment
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  54) 	beq	$0, $zerolength # U  .. .. ..	:  U L U L
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  55) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  56) 	addq	$0, $4, $1	# .. .. .. E	: bias counter
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  57) 	and	$1, 7, $2	# .. .. E  ..	: number of misaligned bytes in tail
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  58) # Note - we never actually use $2, so this is a moot computation
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  59) # and we can rewrite this later...
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  60) 	srl	$1, 3, $1	# .. E  .. ..	: number of quadwords to clear
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  61) 	beq	$4, $headalign	# U  .. .. ..	: U L U L
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  62) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  63) /*
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  64)  * Head is not aligned.  Write (8 - $4) bytes to head of destination
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  65)  * This means $16 is known to be misaligned
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  66)  */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  67) 	EX( ldq_u $5, 0($16) )	# .. .. .. L	: load dst word to mask back in
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  68) 	beq	$1, $onebyte	# .. .. U  ..	: sub-word store?
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  69) 	mskql	$5, $16, $5	# .. U  .. ..	: take care of misaligned head
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  70) 	addq	$16, 8, $16	# E  .. .. .. 	: L U U L
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  71) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  72) 	EX( stq_u $5, -8($16) )	# .. .. .. L	:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  73) 	subq	$1, 1, $1	# .. .. E  ..	:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  74) 	addq	$0, $4, $0	# .. E  .. ..	: bytes left -= 8 - misalignment
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  75) 	subq	$0, 8, $0	# E  .. .. ..	: U L U L
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  76) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  77) 	.align	4
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  78) /*
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  79)  * (The .align directive ought to be a moot point)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  80)  * values upon initial entry to the loop
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  81)  * $1 is number of quadwords to clear (zero is a valid value)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  82)  * $2 is number of trailing bytes (0..7) ($2 never used...)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  83)  * $16 is known to be aligned 0mod8
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  84)  */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  85) $headalign:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  86) 	subq	$1, 16, $4	# .. .. .. E	: If < 16, we can not use the huge loop
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  87) 	and	$16, 0x3f, $2	# .. .. E  ..	: Forward work for huge loop
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  88) 	subq	$2, 0x40, $3	# .. E  .. ..	: bias counter (huge loop)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  89) 	blt	$4, $trailquad	# U  .. .. ..	: U L U L
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  90) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  91) /*
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  92)  * We know that we're going to do at least 16 quads, which means we are
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  93)  * going to be able to use the large block clear loop at least once.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  94)  * Figure out how many quads we need to clear before we are 0mod64 aligned
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  95)  * so we can use the wh64 instruction.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  96)  */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  97) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  98) 	nop			# .. .. .. E
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  99) 	nop			# .. .. E  ..
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 100) 	nop			# .. E  .. ..
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 101) 	beq	$3, $bigalign	# U  .. .. ..	: U L U L : Aligned 0mod64
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 102) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 103) $alignmod64:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 104) 	EX( stq_u $31, 0($16) )	# .. .. .. L
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 105) 	addq	$3, 8, $3	# .. .. E  ..
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 106) 	subq	$0, 8, $0	# .. E  .. ..
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 107) 	nop			# E  .. .. ..	: U L U L
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 108) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 109) 	nop			# .. .. .. E
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 110) 	subq	$1, 1, $1	# .. .. E  ..
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 111) 	addq	$16, 8, $16	# .. E  .. ..
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 112) 	blt	$3, $alignmod64	# U  .. .. ..	: U L U L
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 113) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 114) $bigalign:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 115) /*
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 116)  * $0 is the number of bytes left
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 117)  * $1 is the number of quads left
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 118)  * $16 is aligned 0mod64
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 119)  * we know that we'll be taking a minimum of one trip through
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 120)  * CWG Section 3.7.6: do not expect a sustained store rate of > 1/cycle
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 121)  * We are _not_ going to update $0 after every single store.  That
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 122)  * would be silly, because there will be cross-cluster dependencies
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 123)  * no matter how the code is scheduled.  By doing it in slightly
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 124)  * staggered fashion, we can still do this loop in 5 fetches
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 125)  * The worse case will be doing two extra quads in some future execution,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 126)  * in the event of an interrupted clear.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 127)  * Assumes the wh64 needs to be for 2 trips through the loop in the future
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 128)  * The wh64 is issued on for the starting destination address for trip +2
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 129)  * through the loop, and if there are less than two trips left, the target
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 130)  * address will be for the current trip.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 131)  */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 132) 	nop			# E :
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 133) 	nop			# E :
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 134) 	nop			# E :
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 135) 	bis	$16,$16,$3	# E : U L U L : Initial wh64 address is dest
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 136) 	/* This might actually help for the current trip... */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 137) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 138) $do_wh64:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 139) 	wh64	($3)		# .. .. .. L1	: memory subsystem hint
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 140) 	subq	$1, 16, $4	# .. .. E  ..	: Forward calculation - repeat the loop?
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 141) 	EX( stq_u $31, 0($16) )	# .. L  .. ..
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 142) 	subq	$0, 8, $0	# E  .. .. ..	: U L U L
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 143) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 144) 	addq	$16, 128, $3	# E : Target address of wh64
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 145) 	EX( stq_u $31, 8($16) )	# L :
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 146) 	EX( stq_u $31, 16($16) )	# L :
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 147) 	subq	$0, 16, $0	# E : U L L U
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 148) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 149) 	nop			# E :
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 150) 	EX( stq_u $31, 24($16) )	# L :
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 151) 	EX( stq_u $31, 32($16) )	# L :
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 152) 	subq	$0, 168, $5	# E : U L L U : two trips through the loop left?
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 153) 	/* 168 = 192 - 24, since we've already completed some stores */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 154) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 155) 	subq	$0, 16, $0	# E :
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 156) 	EX( stq_u $31, 40($16) )	# L :
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 157) 	EX( stq_u $31, 48($16) )	# L :
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 158) 	cmovlt	$5, $16, $3	# E : U L L U : Latency 2, extra mapping cycle
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 159) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 160) 	subq	$1, 8, $1	# E :
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 161) 	subq	$0, 16, $0	# E :
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 162) 	EX( stq_u $31, 56($16) )	# L :
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 163) 	nop			# E : U L U L
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 164) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 165) 	nop			# E :
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 166) 	subq	$0, 8, $0	# E :
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 167) 	addq	$16, 64, $16	# E :
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 168) 	bge	$4, $do_wh64	# U : U L U L
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 169) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 170) $trailquad:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 171) 	# zero to 16 quadwords left to store, plus any trailing bytes
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 172) 	# $1 is the number of quadwords left to go.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 173) 	# 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 174) 	nop			# .. .. .. E
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 175) 	nop			# .. .. E  ..
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 176) 	nop			# .. E  .. ..
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 177) 	beq	$1, $trailbytes	# U  .. .. ..	: U L U L : Only 0..7 bytes to go
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 178) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 179) $onequad:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 180) 	EX( stq_u $31, 0($16) )	# .. .. .. L
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 181) 	subq	$1, 1, $1	# .. .. E  ..
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 182) 	subq	$0, 8, $0	# .. E  .. ..
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 183) 	nop			# E  .. .. ..	: U L U L
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 184) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 185) 	nop			# .. .. .. E
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 186) 	nop			# .. .. E  ..
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 187) 	addq	$16, 8, $16	# .. E  .. ..
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 188) 	bgt	$1, $onequad	# U  .. .. ..	: U L U L
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 189) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 190) 	# We have an unknown number of bytes left to go.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 191) $trailbytes:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 192) 	nop			# .. .. .. E
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 193) 	nop			# .. .. E  ..
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 194) 	nop			# .. E  .. ..
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 195) 	beq	$0, $zerolength	# U  .. .. ..	: U L U L
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 196) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 197) 	# $0 contains the number of bytes left to copy (0..31)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 198) 	# so we will use $0 as the loop counter
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 199) 	# We know for a fact that $0 > 0 zero due to previous context
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 200) $onebyte:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 201) 	EX( stb $31, 0($16) )	# .. .. .. L
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 202) 	subq	$0, 1, $0	# .. .. E  ..	:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 203) 	addq	$16, 1, $16	# .. E  .. ..	:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 204) 	bgt	$0, $onebyte	# U  .. .. ..	: U L U L
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 205) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 206) $zerolength:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 207) $exception:			# Destination for exception recovery(?)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 208) 	nop			# .. .. .. E	:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 209) 	nop			# .. .. E  ..	:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 210) 	nop			# .. E  .. ..	:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 211) 	ret	$31, ($26), 1	# L0 .. .. ..	: L U L U
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 212) 	.end __clear_user
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 213) 	EXPORT_SYMBOL(__clear_user)