| /* |
| * Copyright (C) 2013 ARM Ltd. |
| * Copyright (C) 2013 Linaro. |
| * |
| * This code is based on glibc cortex strings work originally authored by Linaro |
| * and re-licensed under GPLv2 for the Linux kernel. The original code can |
| * be found @ |
| * |
| * http://bazaar.launchpad.net/~linaro-toolchain-dev/cortex-strings/trunk/ |
| * files/head:/src/aarch64/ |
| * |
| * This program is free software; you can redistribute it and/or modify |
| * it under the terms of the GNU General Public License version 2 as |
| * published by the Free Software Foundation. |
| * |
| * This program is distributed in the hope that it will be useful, |
| * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| * GNU General Public License for more details. |
| * |
| * You should have received a copy of the GNU General Public License |
| * along with this program. If not, see <http://www.gnu.org/licenses/>. |
| */ |
| |
| #include <linux/linkage.h> |
| #include <asm/assembler.h> |
| |
| /* |
| * compare two strings |
| * |
| * 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. |
| */ |
| |
| #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 |
| |
| /* 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 |
| |
| WEAK(strncmp) |
| cbz limit, .Lret0 |
| eor tmp1, src1, src2 |
| mov zeroones, #REP8_01 |
| tst tmp1, #7 |
| b.ne .Lmisaligned8 |
| ands tmp1, src1, #7 |
| b.ne .Lmutual_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. */ |
| |
| /* |
| * 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: |
| ldr data1, [src1], #8 |
| ldr data2, [src2], #8 |
| .Lstart_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. */ |
| ccmp endloop, #0, #0, eq |
| b.eq .Lloop_aligned |
| |
| /*Not reached the limit, must have found the end or a diff. */ |
| tbz limit_wd, #63, .Lnot_limit |
| |
| /* Limit % 8 == 0 => all bytes significant. */ |
| ands limit, limit, #7 |
| b.eq .Lnot_limit |
| |
| lsl limit, limit, #3 /* Bits -> bytes. */ |
| mov mask, #~0 |
| CPU_BE( lsr mask, mask, limit ) |
| CPU_LE( lsl 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 |
| |
| .Lnot_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. |
| */ |
| bic src1, src1, #7 |
| bic src2, src2, #7 |
| ldr data1, [src1], #8 |
| neg tmp3, tmp1, lsl #3 /* 64 - bits(bytes beyond align). */ |
| ldr data2, [src2], #8 |
| mov tmp2, #~0 |
| sub limit_wd, limit, #1 /* limit != 0, so no underflow. */ |
| /* Big-endian. Early bytes are at MSB. */ |
| CPU_BE( lsl tmp2, tmp2, tmp3 ) /* Shift (tmp1 & 63). */ |
| /* Little-endian. Early bytes are at LSB. */ |
| CPU_LE( lsr tmp2, tmp2, tmp3 ) /* Shift (tmp1 & 63). */ |
| |
| 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 |
| orr data1, data1, tmp2 |
| orr data2, data2, tmp2 |
| add limit_wd, limit_wd, tmp3, lsr #3 |
| b .Lstart_realigned |
| |
| /*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: |
| 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: |
| sub result, data1, data2 |
| ret |
| |
| .Lstart_align: |
| 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 |
| |
| sub limit, limit, tmp3 |
| 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 |
| |
| /*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 |
| |
| ccmp data1w, #1, #0, ne /* NZCV = 0b0000. */ |
| ccmp data1w, data2w, #0, cs /* NZCV = 0b0000. */ |
| b.eq .Ltiny8proc |
| sub result, data1, data2 |
| ret |
| |
| .Lret0: |
| mov result, #0 |
| ret |
| ENDPIPROC(strncmp) |
| EXPORT_SYMBOL_NOKASAN(strncmp) |
