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ARM: 7449/1: use generic strnlen_user and strncpy_from_user functions
This patch implements the word-at-a-time interface for ARM using the same algorithm as x86. We use the fls macro from ARMv5 onwards, where we have a clz instruction available which saves us a mov instruction when targetting Thumb-2. For older CPUs, we use the magic 0x0ff0001 constant. Big-endian configurations make use of the implementation from asm-generic. With this implemented, we can replace our byte-at-a-time strnlen_user and strncpy_from_user functions with the optimised generic versions. Reviewed-by: Nicolas Pitre <nico@linaro.org> Signed-off-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
This commit is contained in:
Will Deacon
Russell King
parent
4295b898f5
commit
8c56cc8be5
7 changed files with 63 additions and 109 deletions
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@ -46,6 +46,8 @@ config ARM
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select GENERIC_SMP_IDLE_THREAD
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select KTIME_SCALAR
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select GENERIC_CLOCKEVENTS_BROADCAST if SMP
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select GENERIC_STRNCPY_FROM_USER
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select GENERIC_STRNLEN_USER
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help
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The ARM series is a line of low-power-consumption RISC chip designs
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licensed by ARM Ltd and targeted at embedded applications and
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@ -189,6 +189,9 @@ static inline void set_fs(mm_segment_t fs)
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#define access_ok(type,addr,size) (__range_ok(addr,size) == 0)
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#define user_addr_max() \
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(segment_eq(get_fs(), USER_DS) ? TASK_SIZE : ~0UL)
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/*
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* The "__xxx" versions of the user access functions do not verify the
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* address space - it must have been done previously with a separate
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@ -398,9 +401,6 @@ extern unsigned long __must_check __clear_user_std(void __user *addr, unsigned l
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#define __clear_user(addr,n) (memset((void __force *)addr, 0, n), 0)
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#endif
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extern unsigned long __must_check __strncpy_from_user(char *to, const char __user *from, unsigned long count);
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extern unsigned long __must_check __strnlen_user(const char __user *s, long n);
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static inline unsigned long __must_check copy_from_user(void *to, const void __user *from, unsigned long n)
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{
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if (access_ok(VERIFY_READ, from, n))
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@ -427,24 +427,9 @@ static inline unsigned long __must_check clear_user(void __user *to, unsigned lo
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return n;
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}
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static inline long __must_check strncpy_from_user(char *dst, const char __user *src, long count)
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{
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long res = -EFAULT;
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if (access_ok(VERIFY_READ, src, 1))
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res = __strncpy_from_user(dst, src, count);
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return res;
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}
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extern long strncpy_from_user(char *dest, const char __user *src, long count);
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#define strlen_user(s) strnlen_user(s, ~0UL >> 1)
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static inline long __must_check strnlen_user(const char __user *s, long n)
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{
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unsigned long res = 0;
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if (__addr_ok(s))
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res = __strnlen_user(s, n);
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return res;
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}
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extern __must_check long strlen_user(const char __user *str);
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extern __must_check long strnlen_user(const char __user *str, long n);
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#endif /* _ASMARM_UACCESS_H */
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55
arch/arm/include/asm/word-at-a-time.h
Normal file
55
arch/arm/include/asm/word-at-a-time.h
Normal file
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@ -0,0 +1,55 @@
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#ifndef __ASM_ARM_WORD_AT_A_TIME_H
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#define __ASM_ARM_WORD_AT_A_TIME_H
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#ifndef __ARMEB__
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/*
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* Little-endian word-at-a-time zero byte handling.
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* Heavily based on the x86 algorithm.
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*/
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#include <linux/kernel.h>
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struct word_at_a_time {
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const unsigned long one_bits, high_bits;
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};
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#define WORD_AT_A_TIME_CONSTANTS { REPEAT_BYTE(0x01), REPEAT_BYTE(0x80) }
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static inline unsigned long has_zero(unsigned long a, unsigned long *bits,
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const struct word_at_a_time *c)
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{
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unsigned long mask = ((a - c->one_bits) & ~a) & c->high_bits;
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*bits = mask;
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return mask;
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}
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#define prep_zero_mask(a, bits, c) (bits)
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static inline unsigned long create_zero_mask(unsigned long bits)
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{
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bits = (bits - 1) & ~bits;
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return bits >> 7;
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}
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static inline unsigned long find_zero(unsigned long mask)
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{
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unsigned long ret;
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#if __LINUX_ARM_ARCH__ >= 5
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/* We have clz available. */
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ret = fls(mask) >> 3;
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#else
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/* (000000 0000ff 00ffff ffffff) -> ( 1 1 2 3 ) */
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ret = (0x0ff0001 + mask) >> 23;
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/* Fix the 1 for 00 case */
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ret &= mask;
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#endif
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return ret;
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}
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#else /* __ARMEB__ */
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#include <asm-generic/word-at-a-time.h>
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#endif
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#endif /* __ASM_ARM_WORD_AT_A_TIME_H */
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@ -87,10 +87,6 @@ EXPORT_SYMBOL(memmove);
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EXPORT_SYMBOL(memchr);
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EXPORT_SYMBOL(__memzero);
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/* user mem (segment) */
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EXPORT_SYMBOL(__strnlen_user);
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EXPORT_SYMBOL(__strncpy_from_user);
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#ifdef CONFIG_MMU
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EXPORT_SYMBOL(copy_page);
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@ -8,7 +8,6 @@ lib-y := backtrace.o changebit.o csumipv6.o csumpartial.o \
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csumpartialcopy.o csumpartialcopyuser.o clearbit.o \
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delay.o findbit.o memchr.o memcpy.o \
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memmove.o memset.o memzero.o setbit.o \
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strncpy_from_user.o strnlen_user.o \
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strchr.o strrchr.o \
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testchangebit.o testclearbit.o testsetbit.o \
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ashldi3.o ashrdi3.o lshrdi3.o muldi3.o \
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@ -1,43 +0,0 @@
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/*
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* linux/arch/arm/lib/strncpy_from_user.S
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*
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* Copyright (C) 1995-2000 Russell King
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*/
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#include <linux/linkage.h>
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#include <asm/assembler.h>
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#include <asm/errno.h>
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.text
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.align 5
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/*
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* Copy a string from user space to kernel space.
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* r0 = dst, r1 = src, r2 = byte length
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* returns the number of characters copied (strlen of copied string),
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* -EFAULT on exception, or "len" if we fill the whole buffer
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*/
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ENTRY(__strncpy_from_user)
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mov ip, r1
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1: subs r2, r2, #1
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ldrusr r3, r1, 1, pl
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bmi 2f
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strb r3, [r0], #1
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teq r3, #0
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bne 1b
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sub r1, r1, #1 @ take NUL character out of count
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2: sub r0, r1, ip
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mov pc, lr
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ENDPROC(__strncpy_from_user)
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.pushsection .fixup,"ax"
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.align 0
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9001: mov r3, #0
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strb r3, [r0, #0] @ null terminate
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mov r0, #-EFAULT
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mov pc, lr
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.popsection
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@ -1,40 +0,0 @@
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/*
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* linux/arch/arm/lib/strnlen_user.S
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*
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* Copyright (C) 1995-2000 Russell King
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*/
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#include <linux/linkage.h>
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#include <asm/assembler.h>
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#include <asm/errno.h>
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.text
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.align 5
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/* Prototype: unsigned long __strnlen_user(const char *str, long n)
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* Purpose : get length of a string in user memory
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* Params : str - address of string in user memory
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* Returns : length of string *including terminator*
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* or zero on exception, or n + 1 if too long
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*/
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ENTRY(__strnlen_user)
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mov r2, r0
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1:
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ldrusr r3, r0, 1
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teq r3, #0
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beq 2f
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subs r1, r1, #1
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bne 1b
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add r0, r0, #1
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2: sub r0, r0, r2
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mov pc, lr
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ENDPROC(__strnlen_user)
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.pushsection .fixup,"ax"
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.align 0
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9001: mov r0, #0
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mov pc, lr
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.popsection
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