linux/arch/xtensa/lib/strnlen_user.S
Max Filippov d6d5f19e21 xtensa: abstract 'entry' and 'retw' in assembly code
Provide abi_entry, abi_entry_default, abi_ret and abi_ret_default macros
that allocate aligned stack frame in windowed and call0 ABIs.
Provide XTENSA_SPILL_STACK_RESERVE macro that specifies required stack
frame size when register spilling is involved.
Replace all uses of 'entry' and 'retw' with the above macros.
This makes most of the xtensa assembly code ready for XEA3 and call0 ABI.

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
2019-07-08 10:04:48 -07:00

142 lines
3.6 KiB
ArmAsm

/*
* 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 <linux/linkage.h>
#include <asm/asmmacro.h>
#include <asm/core.h>
/*
* 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
ENTRY(__strnlen_user)
abi_entry_default
# 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(10f) l32i a9, a4, 4 # 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(10f) l32i a9, a4, 4 # 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
abi_ret_default
# 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
abi_ret_default
.Lz1: # byte 1 is zero
addi a4, a4, 1+1 # point just beyond zero byte
sub a2, a4, a2 # subtract to get length
abi_ret_default
.Lz2: # byte 2 is zero
addi a4, a4, 2+1 # point just beyond zero byte
sub a2, a4, a2 # subtract to get length
abi_ret_default
.L1mod2: # address is odd
EX(10f) l8ui a9, a4, 4 # 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(10f) l32i a9, a4, 0 # 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
abi_ret_default
ENDPROC(__strnlen_user)
.section .fixup, "ax"
.align 4
10:
movi a2, 0
abi_ret_default