diff options
Diffstat (limited to 'arch/arm64/lib/strncmp.S')
| -rw-r--r-- | arch/arm64/lib/strncmp.S | 406 |
1 files changed, 184 insertions, 222 deletions
diff --git a/arch/arm64/lib/strncmp.S b/arch/arm64/lib/strncmp.S index 2a7ee949ed47..48d44f7fddb1 100644 --- a/arch/arm64/lib/strncmp.S +++ b/arch/arm64/lib/strncmp.S @@ -1,299 +1,261 @@ /* SPDX-License-Identifier: GPL-2.0-only */ /* - * Copyright (C) 2013 ARM Ltd. - * Copyright (C) 2013 Linaro. + * Copyright (c) 2013-2021, Arm Limited. * - * This code is based on glibc cortex strings work originally authored by Linaro - * be found @ - * - * http://bazaar.launchpad.net/~linaro-toolchain-dev/cortex-strings/trunk/ - * files/head:/src/aarch64/ + * Adapted from the original at: + * https://github.com/ARM-software/optimized-routines/blob/e823e3abf5f89ecb/string/aarch64/strncmp.S */ #include <linux/linkage.h> #include <asm/assembler.h> -/* - * compare two strings +/* Assumptions: * - * Parameters: - * x0 - const string 1 pointer - * x1 - const string 2 pointer - * x2 - the maximal length to be compared - * Returns: - * x0 - an integer less than, equal to, or greater than zero if s1 is found, - * respectively, to be less than, to match, or be greater than s2. + * ARMv8-a, AArch64 */ +#define L(label) .L ## label + #define REP8_01 0x0101010101010101 #define REP8_7f 0x7f7f7f7f7f7f7f7f #define REP8_80 0x8080808080808080 /* Parameters and result. */ -src1 .req x0 -src2 .req x1 -limit .req x2 -result .req x0 +#define src1 x0 +#define src2 x1 +#define limit x2 +#define result x0 /* Internal variables. */ -data1 .req x3 -data1w .req w3 -data2 .req x4 -data2w .req w4 -has_nul .req x5 -diff .req x6 -syndrome .req x7 -tmp1 .req x8 -tmp2 .req x9 -tmp3 .req x10 -zeroones .req x11 -pos .req x12 -limit_wd .req x13 -mask .req x14 -endloop .req x15 +#define data1 x3 +#define data1w w3 +#define data2 x4 +#define data2w w4 +#define has_nul x5 +#define diff x6 +#define syndrome x7 +#define tmp1 x8 +#define tmp2 x9 +#define tmp3 x10 +#define zeroones x11 +#define pos x12 +#define limit_wd x13 +#define mask x14 +#define endloop x15 +#define count mask SYM_FUNC_START_WEAK_PI(strncmp) - cbz limit, .Lret0 + cbz limit, L(ret0) eor tmp1, src1, src2 mov zeroones, #REP8_01 tst tmp1, #7 - b.ne .Lmisaligned8 - ands tmp1, src1, #7 - b.ne .Lmutual_align + and count, src1, #7 + b.ne L(misaligned8) + cbnz count, L(mutual_align) /* Calculate the number of full and partial words -1. */ - /* - * when limit is mulitply of 8, if not sub 1, - * the judgement of last dword will wrong. - */ - sub limit_wd, limit, #1 /* limit != 0, so no underflow. */ - lsr limit_wd, limit_wd, #3 /* Convert to Dwords. */ + 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 - * can be done in parallel across the entire word. - */ -.Lloop_aligned: + /* NUL detection works on the principle that (X - 1) & (~X) & 0x80 + (=> (X - 1) & ~(X | 0x7f)) is non-zero iff a byte is zero, and + can be done in parallel across the entire word. */ + .p2align 4 +L(loop_aligned): ldr data1, [src1], #8 ldr data2, [src2], #8 -.Lstart_realigned: +L(start_realigned): subs limit_wd, limit_wd, #1 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.*/ - bics has_nul, tmp1, tmp2 /* Non-zero if NUL terminator. */ + eor diff, data1, data2 /* Non-zero if differences found. */ + csinv endloop, diff, xzr, pl /* Last Dword or differences. */ + bics has_nul, tmp1, tmp2 /* Non-zero if NUL terminator. */ ccmp endloop, #0, #0, eq - b.eq .Lloop_aligned + 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, .Lnot_limit + /* 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 .Lnot_limit + b.eq L(not_limit) - lsl limit, limit, #3 /* Bits -> bytes. */ + lsl limit, limit, #3 /* Bits -> bytes. */ mov mask, #~0 -CPU_BE( lsr mask, mask, limit ) -CPU_LE( lsl mask, mask, limit ) +#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 -.Lnot_limit: +L(not_limit): orr syndrome, diff, has_nul - b .Lcal_cmpresult -.Lmutual_align: - /* - * Sources are mutually aligned, but are not currently at an - * alignment boundary. Round down the addresses and then mask off - * the bytes that precede the start point. - * We also need to adjust the limit calculations, but without - * overflowing if the limit is near ULONG_MAX. - */ +#ifndef __AARCH64EB__ + 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 + 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 + ret +#else + /* 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. */ + /* However, if there is no NUL byte in the dword, we can generate + the result directly. We can't just subtract the bytes as the + MSB might be significant. */ + cbnz has_nul, 1f + cmp data1, data2 + cset result, ne + cneg result, result, lo + ret +1: + /* Re-compute the NUL-byte detection, using a byte-reversed value. */ + rev tmp3, data1 + sub tmp1, tmp3, zeroones + orr tmp2, tmp3, #REP8_7f + bic has_nul, tmp1, tmp2 + 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. + Shifting left now will bring the critical information into the + top bits. */ + lsl data1, data1, pos + 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 + ret +#endif + +L(mutual_align): + /* Sources are mutually aligned, but are not currently at an + alignment boundary. Round down the addresses and then mask off + the bytes that precede the start point. + We also need to adjust the limit calculations, but without + overflowing if the limit is near ULONG_MAX. */ bic src1, src1, #7 bic src2, src2, #7 ldr data1, [src1], #8 - neg tmp3, tmp1, lsl #3 /* 64 - bits(bytes beyond 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. */ + sub limit_wd, limit, #1 /* limit != 0, so no underflow. */ +#ifdef __AARCH64EB__ /* Big-endian. Early bytes are at MSB. */ -CPU_BE( lsl tmp2, tmp2, tmp3 ) /* Shift (tmp1 & 63). */ + lsl tmp2, tmp2, tmp3 /* Shift (count & 63). */ +#else /* Little-endian. Early bytes are at LSB. */ -CPU_LE( lsr tmp2, tmp2, tmp3 ) /* Shift (tmp1 & 63). */ - + 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, tmp1 - add tmp3, tmp3, tmp1 + /* Adjust the limit. Only low 3 bits used, so overflow irrelevant. */ + add limit, limit, count + add tmp3, tmp3, count orr data1, data1, tmp2 orr data2, data2, tmp2 add limit_wd, limit_wd, tmp3, lsr #3 - b .Lstart_realigned + b L(start_realigned) + + .p2align 4 + /* Don't bother with dwords for up to 16 bytes. */ +L(misaligned8): + cmp limit, #16 + b.hs L(try_misaligned_words) -/*when src1 offset is not equal to src2 offset...*/ -.Lmisaligned8: - cmp limit, #8 - b.lo .Ltiny8proc /*limit < 8... */ - /* - * Get the align offset length to compare per byte first. - * After this process, one string's address will be aligned.*/ - and tmp1, src1, #7 - neg tmp1, tmp1 - add tmp1, tmp1, #8 - and tmp2, src2, #7 - neg tmp2, tmp2 - add tmp2, tmp2, #8 - subs tmp3, tmp1, tmp2 - csel pos, tmp1, tmp2, hi /*Choose the maximum. */ - /* - * Here, limit is not less than 8, so directly run .Ltinycmp - * without checking the limit.*/ - sub limit, limit, pos -.Ltinycmp: +L(byte_loop): + /* Perhaps we can do better than this. */ ldrb data1w, [src1], #1 ldrb data2w, [src2], #1 - subs pos, pos, #1 - ccmp data1w, #1, #0, ne /* NZCV = 0b0000. */ - ccmp data1w, data2w, #0, cs /* NZCV = 0b0000. */ - b.eq .Ltinycmp - cbnz pos, 1f /*find the null or unequal...*/ - cmp data1w, #1 - ccmp data1w, data2w, #0, cs - b.eq .Lstart_align /*the last bytes are equal....*/ -1: + subs limit, limit, #1 + ccmp data1w, #1, #0, hi /* NZCV = 0b0000. */ + ccmp data1w, data2w, #0, cs /* NZCV = 0b0000. */ + b.eq L(byte_loop) +L(done): sub result, data1, data2 ret - -.Lstart_align: + /* 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 limit_wd, .Lremain8 - /*process more leading bytes to make str1 aligned...*/ - ands xzr, src1, #7 - b.eq .Lrecal_offset - add src1, src1, tmp3 /*tmp3 is positive in this branch.*/ - add src2, src2, tmp3 - ldr data1, [src1], #8 - ldr data2, [src2], #8 + cbz count, L(do_misaligned) - sub limit, limit, tmp3 + neg count, count + and count, count, #7 + sub limit, limit, count lsr limit_wd, limit, #3 - subs limit_wd, limit_wd, #1 - sub tmp1, data1, zeroones - orr tmp2, data1, #REP8_7f - eor diff, data1, data2 /* Non-zero if differences found. */ - csinv endloop, diff, xzr, ne/*if limit_wd is 0,will finish the cmp*/ - bics has_nul, tmp1, tmp2 - ccmp endloop, #0, #0, eq /*has_null is ZERO: no null byte*/ - b.ne .Lunequal_proc - /*How far is the current str2 from the alignment boundary...*/ - and tmp3, tmp3, #7 -.Lrecal_offset: - neg pos, tmp3 -.Lloopcmp_proc: - /* - * Divide the eight bytes into two parts. First,backwards the src2 - * to an alignment boundary,load eight bytes from the SRC2 alignment - * boundary,then compare with the relative bytes from SRC1. - * If all 8 bytes are equal,then start the second part's comparison. - * Otherwise finish the comparison. - * This special handle can garantee all the accesses are in the - * thread/task space in avoid to overrange access. - */ - ldr data1, [src1,pos] - ldr data2, [src2,pos] - sub tmp1, data1, zeroones - orr tmp2, data1, #REP8_7f - bics has_nul, tmp1, tmp2 /* Non-zero if NUL terminator. */ - eor diff, data1, data2 /* Non-zero if differences found. */ - csinv endloop, diff, xzr, eq - cbnz endloop, .Lunequal_proc +L(page_end_loop): + ldrb data1w, [src1], #1 + ldrb data2w, [src2], #1 + cmp data1w, #1 + ccmp data1w, data2w, #0, cs /* NZCV = 0b0000. */ + b.ne L(done) + 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 second part process*/ ldr data1, [src1], #8 ldr data2, [src2], #8 - subs limit_wd, limit_wd, #1 sub tmp1, data1, zeroones orr tmp2, data1, #REP8_7f - eor diff, data1, data2 /* Non-zero if differences found. */ - csinv endloop, diff, xzr, ne/*if limit_wd is 0,will finish the cmp*/ - bics has_nul, tmp1, tmp2 - ccmp endloop, #0, #0, eq /*has_null is ZERO: no null byte*/ - b.eq .Lloopcmp_proc - -.Lunequal_proc: - orr syndrome, diff, has_nul - cbz syndrome, .Lremain8 -.Lcal_cmpresult: - /* - * reversed the byte-order as big-endian,then CLZ can find the most - * significant zero bits. - */ -CPU_LE( rev syndrome, syndrome ) -CPU_LE( rev data1, data1 ) -CPU_LE( rev data2, data2 ) - /* - * 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. - * However, if there is no NUL byte in the dword, we can generate - * the result directly. We can't just subtract the bytes as the - * MSB might be significant. - */ -CPU_BE( cbnz has_nul, 1f ) -CPU_BE( cmp data1, data2 ) -CPU_BE( cset result, ne ) -CPU_BE( cneg result, result, lo ) -CPU_BE( ret ) -CPU_BE( 1: ) - /* Re-compute the NUL-byte detection, using a byte-reversed value.*/ -CPU_BE( rev tmp3, data1 ) -CPU_BE( sub tmp1, tmp3, zeroones ) -CPU_BE( orr tmp2, tmp3, #REP8_7f ) -CPU_BE( bic has_nul, tmp1, tmp2 ) -CPU_BE( rev has_nul, has_nul ) -CPU_BE( orr syndrome, diff, has_nul ) - /* - * 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 - lsl data1, data1, pos - 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 - ret - -.Lremain8: - /* Limit % 8 == 0 => all bytes significant. */ - ands limit, limit, #7 - b.eq .Lret0 -.Ltiny8proc: - ldrb data1w, [src1], #1 - ldrb data2w, [src2], #1 - subs limit, limit, #1 + 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) - ccmp data1w, #1, #0, ne /* NZCV = 0b0000. */ - ccmp data1w, data2w, #0, cs /* NZCV = 0b0000. */ - b.eq .Ltiny8proc - sub result, data1, data2 - ret +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 + 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) -.Lret0: +L(ret0): mov result, #0 ret + SYM_FUNC_END_PI(strncmp) EXPORT_SYMBOL_NOKASAN(strncmp) |