cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
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clear_user.S (2491B)

      1/* SPDX-License-Identifier: GPL-2.0 */
      2/*
      3 * arch/alpha/lib/clear_user.S
      4 * Contributed by Richard Henderson <rth@tamu.edu>
      5 *
      6 * Zero user space, handling exceptions as we go.
      7 *
      8 * We have to make sure that $0 is always up-to-date and contains the
      9 * right "bytes left to zero" value (and that it is updated only _after_
     10 * a successful copy).  There is also some rather minor exception setup
     11 * stuff.
     12 */
     13#include <asm/export.h>
     14
     15/* Allow an exception for an insn; exit if we get one.  */
     16#define EX(x,y...)			\
     17	99: x,##y;			\
     18	.section __ex_table,"a";	\
     19	.long 99b - .;			\
     20	lda $31, $exception-99b($31); 	\
     21	.previous
     22
     23	.set noat
     24	.set noreorder
     25	.align 4
     26
     27	.globl __clear_user
     28	.ent __clear_user
     29	.frame	$30, 0, $26
     30	.prologue 0
     31
     32$loop:
     33	and	$1, 3, $4	# e0    :
     34	beq	$4, 1f		# .. e1 :
     35
     360:	EX( stq_u $31, 0($16) )	# e0    : zero one word
     37	subq	$0, 8, $0	# .. e1 :
     38	subq	$4, 1, $4	# e0    :
     39	addq	$16, 8, $16	# .. e1 :
     40	bne	$4, 0b		# e1    :
     41	unop			#       :
     42
     431:	bic	$1, 3, $1	# e0    :
     44	beq	$1, $tail	# .. e1 :
     45
     462:	EX( stq_u $31, 0($16) )	# e0    : zero four words
     47	subq	$0, 8, $0	# .. e1 :
     48	EX( stq_u $31, 8($16) )	# e0    :
     49	subq	$0, 8, $0	# .. e1 :
     50	EX( stq_u $31, 16($16) )	# e0    :
     51	subq	$0, 8, $0	# .. e1 :
     52	EX( stq_u $31, 24($16) )	# e0    :
     53	subq	$0, 8, $0	# .. e1 :
     54	subq	$1, 4, $1	# e0    :
     55	addq	$16, 32, $16	# .. e1 :
     56	bne	$1, 2b		# e1    :
     57
     58$tail:
     59	bne	$2, 1f		# e1    : is there a tail to do?
     60	ret	$31, ($26), 1	# .. e1 :
     61
     621:	EX( ldq_u $5, 0($16) )	# e0    :
     63	clr	$0		# .. e1 :
     64	nop			# e1    :
     65	mskqh	$5, $0, $5	# e0    :
     66	EX( stq_u $5, 0($16) )	# e0    :
     67	ret	$31, ($26), 1	# .. e1 :
     68
     69__clear_user:
     70	and	$17, $17, $0
     71	and	$16, 7, $4	# e0    : find dest misalignment
     72	beq	$0, $zerolength # .. e1 :
     73	addq	$0, $4, $1	# e0    : bias counter
     74	and	$1, 7, $2	# e1    : number of bytes in tail
     75	srl	$1, 3, $1	# e0    :
     76	beq	$4, $loop	# .. e1 :
     77
     78	EX( ldq_u $5, 0($16) )	# e0    : load dst word to mask back in
     79	beq	$1, $oneword	# .. e1 : sub-word store?
     80
     81	mskql	$5, $16, $5	# e0    : take care of misaligned head
     82	addq	$16, 8, $16	# .. e1 :
     83	EX( stq_u $5, -8($16) )	# e0    :
     84	addq	$0, $4, $0	# .. e1 : bytes left -= 8 - misalignment
     85	subq	$1, 1, $1	# e0    :
     86	subq	$0, 8, $0	# .. e1 :
     87	br	$loop		# e1    :
     88	unop			#       :
     89
     90$oneword:
     91	mskql	$5, $16, $4	# e0    :
     92	mskqh	$5, $2, $5	# e0    :
     93	or	$5, $4, $5	# e1    :
     94	EX( stq_u $5, 0($16) )	# e0    :
     95	clr	$0		# .. e1 :
     96
     97$zerolength:
     98$exception:
     99	ret	$31, ($26), 1	# .. e1 :
    100
    101	.end __clear_user
    102	EXPORT_SYMBOL(__clear_user)