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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strchr.S (2019B)

      1/* SPDX-License-Identifier: GPL-2.0 */
      2/*
      3 * arch/alpha/lib/strchr.S
      4 * Contributed by Richard Henderson (rth@tamu.edu)
      5 *
      6 * Return the address of a given character within a null-terminated
      7 * string, or null if it is not found.
      8 */
      9#include <asm/export.h>
     10#include <asm/regdef.h>
     11
     12	.set noreorder
     13	.set noat
     14
     15	.align 3
     16	.globl strchr
     17	.ent strchr
     18strchr:
     19	.frame sp, 0, ra
     20	.prologue 0
     21
     22	zapnot	a1, 1, a1	# e0    : zero extend the search character
     23	ldq_u   t0, 0(a0)	# .. e1 : load first quadword
     24	sll	a1, 8, t5	# e0    : replicate the search character
     25	andnot  a0, 7, v0	# .. e1 : align our loop pointer
     26	or	t5, a1, a1	# e0    :
     27	lda	t4, -1		# .. e1 : build garbage mask
     28	sll	a1, 16, t5	# e0    :
     29	cmpbge  zero, t0, t2	# .. e1 : bits set iff byte == zero
     30	mskqh	t4, a0, t4	# e0    :
     31	or	t5, a1, a1	# .. e1 :
     32	sll	a1, 32, t5	# e0    :
     33	cmpbge	zero, t4, t4	# .. e1 : bits set iff byte is garbage
     34	or	t5, a1, a1	# e0    :
     35	xor	t0, a1, t1	# .. e1 : make bytes == c zero
     36	cmpbge  zero, t1, t3	# e0    : bits set iff byte == c
     37	or	t2, t3, t0	# e1    : bits set iff char match or zero match
     38	andnot	t0, t4, t0	# e0    : clear garbage bits
     39	bne	t0, $found	# .. e1 (zdb)
     40
     41$loop:	ldq	t0, 8(v0)	# e0    :
     42	addq	v0, 8, v0	# .. e1 :
     43	nop			# e0    :
     44	xor	t0, a1, t1	# .. e1 (ev5 data stall)
     45	cmpbge	zero, t0, t2	# e0    : bits set iff byte == 0
     46	cmpbge	zero, t1, t3	# .. e1 : bits set iff byte == c
     47	or	t2, t3, t0	# e0    :
     48	beq	t0, $loop	# .. e1 (zdb)
     49
     50$found:	negq    t0, t1		# e0    : clear all but least set bit
     51	and     t0, t1, t0	# e1 (stall)
     52
     53	and	t0, t3, t1	# e0    : bit set iff byte was the char
     54	beq	t1, $retnull	# .. e1 (zdb)
     55
     56	and     t0, 0xf0, t2	# e0    : binary search for that set bit
     57	and	t0, 0xcc, t3	# .. e1 :
     58	and	t0, 0xaa, t4	# e0    :
     59	cmovne	t2, 4, t2	# .. e1 :
     60	cmovne	t3, 2, t3	# e0    :
     61	cmovne	t4, 1, t4	# .. e1 :
     62	addq	t2, t3, t2	# e0    :
     63	addq	v0, t4, v0	# .. e1 :
     64	addq	v0, t2, v0	# e0    :
     65	ret			# .. e1 :
     66
     67$retnull:
     68	mov	zero, v0	# e0    :
     69	ret			# .. e1 :
     70
     71	.end strchr
     72	EXPORT_SYMBOL(strchr)