Commit 387d828a authored by Joey Gouly's avatar Joey Gouly Committed by Will Deacon
Browse files

arm64: lib: Import latest version of Arm Optimized Routines' strncmp 

Import the latest version of the Arm Optimized Routines strncmp function based
on the upstream code of string/aarch64/strncmp.S at commit 189dfefe37d5 from:
  https://github.com/ARM-software/optimized-routines



This latest version includes MTE support.

Note that for simplicity Arm have chosen to contribute this code to Linux under
GPLv2 rather than the original MIT OR Apache-2.0 WITH LLVM-exception license.
Arm is the sole copyright holder for this code.

Signed-off-by: default avatarJoey Gouly <joey.gouly@arm.com>
Cc: Robin Murphy <robin.murphy@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Acked-by: default avatarMark Rutland <mark.rutland@arm.com>
Acked-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
Link: https://lore.kernel.org/r/20220301101435.19327-3-joey.gouly@arm.com


Signed-off-by: default avatarWill Deacon <will@kernel.org>
parent 507f788d

arch/arm64/lib/strncmp.S

+141 −93
Original line number Diff line number Diff line 
/* SPDX-License-Identifier: GPL-2.0-only */

/*

 * Copyright (c) 2013-2021, Arm Limited.

 * Copyright (c) 2013-2022, Arm Limited.

 *

 * Adapted from the original at:

 * https://github.com/ARM-software/optimized-routines/blob/e823e3abf5f89ecb/string/aarch64/strncmp.S

 * https://github.com/ARM-software/optimized-routines/blob/189dfefe37d54c5b/string/aarch64/strncmp.S

 */



#include <linux/linkage.h>
@@ -11,14 +11,14 @@ 


/* Assumptions:

 *

 * ARMv8-a, AArch64

 * ARMv8-a, AArch64.

 * MTE compatible.

 */



#define L(label) .L ## label



#define REP8_01 0x0101010101010101

#define REP8_7f 0x7f7f7f7f7f7f7f7f

#define REP8_80 0x8080808080808080



/* Parameters and result.  */

#define src1		x0
@@ -39,10 +39,24 @@ 
#define tmp3		x10

#define zeroones	x11

#define pos		x12

#define limit_wd	x13

#define mask		x14

#define endloop		x15

#define mask		x13

#define endloop		x14

#define count		mask

#define offset		pos

#define neg_offset	x15



/* Define endian dependent shift operations.

   On big-endian early bytes are at MSB and on little-endian LSB.

   LS_FW means shifting towards early bytes.

   LS_BK means shifting towards later bytes.

   */

#ifdef __AARCH64EB__

#define LS_FW lsl

#define LS_BK lsr

#else

#define LS_FW lsr

#define LS_BK lsl

#endif



SYM_FUNC_START_WEAK_PI(strncmp)

	cbz	limit, L(ret0)
@@ -52,9 +66,6 @@ SYM_FUNC_START_WEAK_PI(strncmp) 
	and	count, src1, #7

	b.ne	L(misaligned8)

	cbnz	count, L(mutual_align)

	/* Calculate the number of full and partial words -1.  */

	sub	limit_wd, limit, #1	/* limit != 0, so no underflow.  */

	lsr	limit_wd, limit_wd, #3	/* Convert to Dwords.  */



	/* NUL detection works on the principle that (X - 1) & (~X) & 0x80

	   (=> (X - 1) & ~(X | 0x7f)) is non-zero iff a byte is zero, and
@@ -64,56 +75,52 @@ L(loop_aligned): 
	ldr	data1, [src1], #8

	ldr	data2, [src2], #8

L(start_realigned):

	subs	limit_wd, limit_wd, #1

	subs	limit, limit, #8

	sub	tmp1, data1, zeroones

	orr	tmp2, data1, #REP8_7f

	eor	diff, data1, data2	/* Non-zero if differences found.  */

	csinv	endloop, diff, xzr, pl	/* Last Dword or differences.  */

	csinv	endloop, diff, xzr, hi	/* Last Dword or differences.  */

	bics	has_nul, tmp1, tmp2	/* Non-zero if NUL terminator.  */

	ccmp	endloop, #0, #0, eq

	b.eq	L(loop_aligned)

	/* End of main loop */



	/* Not reached the limit, must have found the end or a diff.  */

	tbz	limit_wd, #63, L(not_limit)



	/* Limit % 8 == 0 => all bytes significant.  */

	ands	limit, limit, #7

	b.eq	L(not_limit)



	lsl	limit, limit, #3	/* Bits -> bytes.  */

	mov	mask, #~0

#ifdef __AARCH64EB__

	lsr	mask, mask, limit

#else

	lsl	mask, mask, limit

#endif

	bic	data1, data1, mask

	bic	data2, data2, mask



	/* Make sure that the NUL byte is marked in the syndrome.  */

	orr	has_nul, has_nul, mask



L(not_limit):

	orr	syndrome, diff, has_nul



L(full_check):

#ifndef __AARCH64EB__

	orr	syndrome, diff, has_nul

	add	limit, limit, 8	/* Rewind limit to before last subs. */

L(syndrome_check):

	/* Limit was reached. Check if the NUL byte or the difference

	   is before the limit. */

	rev	syndrome, syndrome

	rev	data1, data1

	/* The MS-non-zero bit of the syndrome marks either the first bit

	   that is different, or the top bit of the first zero byte.

	   Shifting left now will bring the critical information into the

	   top bits.  */

	clz	pos, syndrome

	rev	data2, data2

	lsl	data1, data1, pos

	cmp	limit, pos, lsr #3

	lsl	data2, data2, pos

	/* But we need to zero-extend (char is unsigned) the value and then

	   perform a signed 32-bit subtraction.  */

	lsr	data1, data1, #56

	sub	result, data1, data2, lsr #56

	csel result, result, xzr, hi

	ret

#else

	/* Not reached the limit, must have found the end or a diff.  */

	tbz	limit, #63, L(not_limit)

	add	tmp1, limit, 8

	cbz	limit, L(not_limit)



	lsl	limit, tmp1, #3	/* Bits -> bytes.  */

	mov	mask, #~0

	lsr	mask, mask, limit

	bic	data1, data1, mask

	bic	data2, data2, mask



	/* Make sure that the NUL byte is marked in the syndrome.  */

	orr	has_nul, has_nul, mask



L(not_limit):

	/* For big-endian we cannot use the trick with the syndrome value

	   as carry-propagation can corrupt the upper bits if the trailing

	   bytes in the string contain 0x01.  */
@@ -134,10 +141,11 @@ L(not_limit): 
	rev	has_nul, has_nul

	orr	syndrome, diff, has_nul

	clz	pos, syndrome

	/* The MS-non-zero bit of the syndrome marks either the first bit

	   that is different, or the top bit of the first zero byte.

	/* The most-significant-non-zero bit of the syndrome marks either the

	   first bit that is different, or the top bit of the first zero byte.

	   Shifting left now will bring the critical information into the

	   top bits.  */

L(end_quick):

	lsl	data1, data1, pos

	lsl	data2, data2, pos

	/* But we need to zero-extend (char is unsigned) the value and then
@@ -159,22 +167,12 @@ L(mutual_align): 
	neg	tmp3, count, lsl #3	/* 64 - bits(bytes beyond align). */

	ldr	data2, [src2], #8

	mov	tmp2, #~0

	sub	limit_wd, limit, #1	/* limit != 0, so no underflow.  */

#ifdef __AARCH64EB__

	/* Big-endian.  Early bytes are at MSB.  */

	lsl	tmp2, tmp2, tmp3	/* Shift (count & 63).  */

#else

	/* Little-endian.  Early bytes are at LSB.  */

	lsr	tmp2, tmp2, tmp3	/* Shift (count & 63).  */

#endif

	and	tmp3, limit_wd, #7

	lsr	limit_wd, limit_wd, #3

	/* Adjust the limit. Only low 3 bits used, so overflow irrelevant.  */

	add	limit, limit, count

	add	tmp3, tmp3, count

	LS_FW	tmp2, tmp2, tmp3	/* Shift (count & 63).  */

	/* Adjust the limit and ensure it doesn't overflow.  */

	adds	limit, limit, count

	csinv	limit, limit, xzr, lo

	orr	data1, data1, tmp2

	orr	data2, data2, tmp2

	add	limit_wd, limit_wd, tmp3, lsr #3

	b	L(start_realigned)



	.p2align 4
@@ -197,13 +195,11 @@ L(done): 
	/* Align the SRC1 to a dword by doing a bytewise compare and then do

	   the dword loop.  */

L(try_misaligned_words):

	lsr	limit_wd, limit, #3

	cbz	count, L(do_misaligned)

	cbz	count, L(src1_aligned)



	neg	count, count

	and	count, count, #7

	sub	limit, limit, count

	lsr	limit_wd, limit, #3



L(page_end_loop):

	ldrb	data1w, [src1], #1
@@ -214,48 +210,100 @@ L(page_end_loop): 
	subs	count, count, #1

	b.hi	L(page_end_loop)



L(do_misaligned):

	/* Prepare ourselves for the next page crossing.  Unlike the aligned

	   loop, we fetch 1 less dword because we risk crossing bounds on

	   SRC2.  */

	mov	count, #8

	subs	limit_wd, limit_wd, #1

	b.lo	L(done_loop)

L(loop_misaligned):

	and	tmp2, src2, #0xff8

	eor	tmp2, tmp2, #0xff8

	cbz	tmp2, L(page_end_loop)

	/* The following diagram explains the comparison of misaligned strings.

	   The bytes are shown in natural order. For little-endian, it is

	   reversed in the registers. The "x" bytes are before the string.

	   The "|" separates data that is loaded at one time.

	   src1     | a a a a a a a a | b b b c c c c c | . . .

	   src2     | x x x x x a a a   a a a a a b b b | c c c c c . . .



	   After shifting in each step, the data looks like this:

	                STEP_A              STEP_B              STEP_C

	   data1    a a a a a a a a     b b b c c c c c     b b b c c c c c

	   data2    a a a a a a a a     b b b 0 0 0 0 0     0 0 0 c c c c c



	   The bytes with "0" are eliminated from the syndrome via mask.



	   Align SRC2 down to 16 bytes. This way we can read 16 bytes at a

	   time from SRC2. The comparison happens in 3 steps. After each step

	   the loop can exit, or read from SRC1 or SRC2. */

L(src1_aligned):

	/* Calculate offset from 8 byte alignment to string start in bits. No

	   need to mask offset since shifts are ignoring upper bits. */

	lsl	offset, src2, #3

	bic	src2, src2, #0xf

	mov	mask, -1

	neg	neg_offset, offset

	ldr	data1, [src1], #8

	ldr	data2, [src2], #8

	sub	tmp1, data1, zeroones

	orr	tmp2, data1, #REP8_7f

	eor	diff, data1, data2	/* Non-zero if differences found.  */

	bics	has_nul, tmp1, tmp2	/* Non-zero if NUL terminator.  */

	ccmp	diff, #0, #0, eq

	b.ne	L(not_limit)

	subs	limit_wd, limit_wd, #1

	b.pl	L(loop_misaligned)

	ldp	tmp1, tmp2, [src2], #16

	LS_BK	mask, mask, neg_offset

	and	neg_offset, neg_offset, #63	/* Need actual value for cmp later. */

	/* Skip the first compare if data in tmp1 is irrelevant. */

	tbnz	offset, 6, L(misaligned_mid_loop)



L(done_loop):

	/* We found a difference or a NULL before the limit was reached.  */

	and	limit, limit, #7

	cbz	limit, L(not_limit)

	/* Read the last word.  */

	sub	src1, src1, 8

	sub	src2, src2, 8

	ldr	data1, [src1, limit]

	ldr	data2, [src2, limit]

	sub	tmp1, data1, zeroones

	orr	tmp2, data1, #REP8_7f

L(loop_misaligned):

	/* STEP_A: Compare full 8 bytes when there is enough data from SRC2.*/

	LS_FW	data2, tmp1, offset

	LS_BK	tmp1, tmp2, neg_offset

	subs	limit, limit, #8

	orr	data2, data2, tmp1	/* 8 bytes from SRC2 combined from two regs.*/

	sub	has_nul, data1, zeroones

	eor	diff, data1, data2	/* Non-zero if differences found.  */

	bics	has_nul, tmp1, tmp2	/* Non-zero if NUL terminator.  */

	ccmp	diff, #0, #0, eq

	b.ne	L(not_limit)

	orr	tmp3, data1, #REP8_7f

	csinv	endloop, diff, xzr, hi	/* If limit, set to all ones. */

	bic	has_nul, has_nul, tmp3	/* Non-zero if NUL byte found in SRC1. */

	orr	tmp3, endloop, has_nul

	cbnz	tmp3, L(full_check)



	ldr	data1, [src1], #8

L(misaligned_mid_loop):

	/* STEP_B: Compare first part of data1 to second part of tmp2. */

	LS_FW	data2, tmp2, offset

#ifdef __AARCH64EB__

	/* For big-endian we do a byte reverse to avoid carry-propagation

	problem described above. This way we can reuse the has_nul in the

	next step and also use syndrome value trick at the end. */

	rev	tmp3, data1

	#define data1_fixed tmp3

#else

	#define data1_fixed data1

#endif

	sub	has_nul, data1_fixed, zeroones

	orr	tmp3, data1_fixed, #REP8_7f

	eor	diff, data2, data1	/* Non-zero if differences found.  */

	bic	has_nul, has_nul, tmp3	/* Non-zero if NUL terminator.  */

#ifdef __AARCH64EB__

	rev	has_nul, has_nul

#endif

	cmp	limit, neg_offset, lsr #3

	orr	syndrome, diff, has_nul

	bic	syndrome, syndrome, mask	/* Ignore later bytes. */

	csinv	tmp3, syndrome, xzr, hi	/* If limit, set to all ones. */

	cbnz	tmp3, L(syndrome_check)



	/* STEP_C: Compare second part of data1 to first part of tmp1. */

	ldp	tmp1, tmp2, [src2], #16

	cmp	limit, #8

	LS_BK	data2, tmp1, neg_offset

	eor	diff, data2, data1	/* Non-zero if differences found.  */

	orr	syndrome, diff, has_nul

	and	syndrome, syndrome, mask	/* Ignore earlier bytes. */

	csinv	tmp3, syndrome, xzr, hi	/* If limit, set to all ones. */

	cbnz	tmp3, L(syndrome_check)



	ldr	data1, [src1], #8

	sub	limit, limit, #8

	b	L(loop_misaligned)



#ifdef	__AARCH64EB__

L(syndrome_check):

	clz	pos, syndrome

	cmp	pos, limit, lsl #3

	b.lo	L(end_quick)

#endif



L(ret0):

	mov	result, #0

	ret



SYM_FUNC_END_PI(strncmp)

EXPORT_SYMBOL_NOHWKASAN(strncmp)