diff options
Diffstat (limited to 'kernel/arch/xtensa/lib/strnlen_user.S')
| -rw-r--r-- | kernel/arch/xtensa/lib/strnlen_user.S | 147 |
1 files changed, 147 insertions, 0 deletions
diff --git a/kernel/arch/xtensa/lib/strnlen_user.S b/kernel/arch/xtensa/lib/strnlen_user.S new file mode 100644 index 000000000..4c03b1e58 --- /dev/null +++ b/kernel/arch/xtensa/lib/strnlen_user.S @@ -0,0 +1,147 @@ +/* + * arch/xtensa/lib/strnlen_user.S + * + * This file is subject to the terms and conditions of the GNU General + * Public License. See the file "COPYING" in the main directory of + * this archive for more details. + * + * Returns strnlen, including trailing zero terminator. + * Zero indicates error. + * + * Copyright (C) 2002 Tensilica Inc. + */ + +#include <variant/core.h> + +/* Load or store instructions that may cause exceptions use the EX macro. */ + +#define EX(insn,reg1,reg2,offset,handler) \ +9: insn reg1, reg2, offset; \ + .section __ex_table, "a"; \ + .word 9b, handler; \ + .previous + +/* + * size_t __strnlen_user(const char *s, size_t len) + */ + +#ifdef __XTENSA_EB__ +# define MASK0 0xff000000 +# define MASK1 0x00ff0000 +# define MASK2 0x0000ff00 +# define MASK3 0x000000ff +#else +# define MASK0 0x000000ff +# define MASK1 0x0000ff00 +# define MASK2 0x00ff0000 +# define MASK3 0xff000000 +#endif + +# Register use: +# a2/ src +# a3/ len +# a4/ tmp +# a5/ mask0 +# a6/ mask1 +# a7/ mask2 +# a8/ mask3 +# a9/ tmp +# a10/ tmp + +.text +.align 4 +.global __strnlen_user +.type __strnlen_user,@function +__strnlen_user: + entry sp, 16 # minimal stack frame + # a2/ s, a3/ len + addi a4, a2, -4 # because we overincrement at the end; + # we compensate with load offsets of 4 + movi a5, MASK0 # mask for byte 0 + movi a6, MASK1 # mask for byte 1 + movi a7, MASK2 # mask for byte 2 + movi a8, MASK3 # mask for byte 3 + bbsi.l a2, 0, .L1mod2 # if only 8-bit aligned + bbsi.l a2, 1, .L2mod4 # if only 16-bit aligned + +/* + * String is word-aligned. + */ +.Laligned: + srli a10, a3, 2 # number of loop iterations with 4B per loop +#if XCHAL_HAVE_LOOPS + loopnez a10, .Ldone +#else + beqz a10, .Ldone + slli a10, a10, 2 + add a10, a10, a4 # a10 = end of last 4B chunk +#endif /* XCHAL_HAVE_LOOPS */ +.Loop: + EX(l32i, a9, a4, 4, lenfixup) # get next word of string + addi a4, a4, 4 # advance string pointer + bnone a9, a5, .Lz0 # if byte 0 is zero + bnone a9, a6, .Lz1 # if byte 1 is zero + bnone a9, a7, .Lz2 # if byte 2 is zero + bnone a9, a8, .Lz3 # if byte 3 is zero +#if !XCHAL_HAVE_LOOPS + blt a4, a10, .Loop +#endif + +.Ldone: + EX(l32i, a9, a4, 4, lenfixup) # load 4 bytes for remaining checks + + bbci.l a3, 1, .L100 + # check two more bytes (bytes 0, 1 of word) + addi a4, a4, 2 # advance string pointer + bnone a9, a5, .Lz0 # if byte 0 is zero + bnone a9, a6, .Lz1 # if byte 1 is zero +.L100: + bbci.l a3, 0, .L101 + # check one more byte (byte 2 of word) + # Actually, we don't need to check. Zero or nonzero, we'll add one. + # Do not add an extra one for the NULL terminator since we have + # exhausted the original len parameter. + addi a4, a4, 1 # advance string pointer +.L101: + sub a2, a4, a2 # compute length + retw + +# NOTE that in several places below, we point to the byte just after +# the zero byte in order to include the NULL terminator in the count. + +.Lz3: # byte 3 is zero + addi a4, a4, 3 # point to zero byte +.Lz0: # byte 0 is zero + addi a4, a4, 1 # point just beyond zero byte + sub a2, a4, a2 # subtract to get length + retw +.Lz1: # byte 1 is zero + addi a4, a4, 1+1 # point just beyond zero byte + sub a2, a4, a2 # subtract to get length + retw +.Lz2: # byte 2 is zero + addi a4, a4, 2+1 # point just beyond zero byte + sub a2, a4, a2 # subtract to get length + retw + +.L1mod2: # address is odd + EX(l8ui, a9, a4, 4, lenfixup) # get byte 0 + addi a4, a4, 1 # advance string pointer + beqz a9, .Lz3 # if byte 0 is zero + bbci.l a4, 1, .Laligned # if string pointer is now word-aligned + +.L2mod4: # address is 2 mod 4 + addi a4, a4, 2 # advance ptr for aligned access + EX(l32i, a9, a4, 0, lenfixup) # get word with first two bytes of string + bnone a9, a7, .Lz2 # if byte 2 (of word, not string) is zero + bany a9, a8, .Laligned # if byte 3 (of word, not string) is nonzero + # byte 3 is zero + addi a4, a4, 3+1 # point just beyond zero byte + sub a2, a4, a2 # subtract to get length + retw + + .section .fixup, "ax" + .align 4 +lenfixup: + movi a2, 0 + retw |