Commit 8c56cc8b authored by Will Deacon's avatar Will Deacon Committed by Russell King
Browse files

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: default avatarNicolas Pitre <nico@linaro.org>
Signed-off-by: default avatarWill Deacon <will.deacon@arm.com>
Signed-off-by: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
parent 4295b898

arch/arm/Kconfig

+2 −0
Original line number Diff line number Diff line
@@ -46,6 +46,8 @@ config ARM 
	select GENERIC_SMP_IDLE_THREAD

	select KTIME_SCALAR

	select GENERIC_CLOCKEVENTS_BROADCAST if SMP

	select GENERIC_STRNCPY_FROM_USER

	select GENERIC_STRNLEN_USER

	help

	  The ARM series is a line of low-power-consumption RISC chip designs

	  licensed by ARM Ltd and targeted at embedded applications and

arch/arm/include/asm/uaccess.h

+6 −21
Original line number Diff line number Diff line
@@ -189,6 +189,9 @@ static inline void set_fs(mm_segment_t fs) 


#define access_ok(type,addr,size)	(__range_ok(addr,size) == 0)



#define user_addr_max() \

	(segment_eq(get_fs(), USER_DS) ? TASK_SIZE : ~0UL)



/*

 * The "__xxx" versions of the user access functions do not verify the

 * address space - it must have been done previously with a separate
@@ -398,9 +401,6 @@ extern unsigned long __must_check __clear_user_std(void __user *addr, unsigned l 
#define __clear_user(addr,n)		(memset((void __force *)addr, 0, n), 0)

#endif



extern unsigned long __must_check __strncpy_from_user(char *to, const char __user *from, unsigned long count);

extern unsigned long __must_check __strnlen_user(const char __user *s, long n);



static inline unsigned long __must_check copy_from_user(void *to, const void __user *from, unsigned long n)

{

	if (access_ok(VERIFY_READ, from, n))
@@ -427,24 +427,9 @@ static inline unsigned long __must_check clear_user(void __user *to, unsigned lo 
	return n;

}



static inline long __must_check strncpy_from_user(char *dst, const char __user *src, long count)

{

	long res = -EFAULT;

	if (access_ok(VERIFY_READ, src, 1))

		res = __strncpy_from_user(dst, src, count);

	return res;

}



#define strlen_user(s)	strnlen_user(s, ~0UL >> 1)

extern long strncpy_from_user(char *dest, const char __user *src, long count);



static inline long __must_check strnlen_user(const char __user *s, long n)

{

	unsigned long res = 0;



	if (__addr_ok(s))

		res = __strnlen_user(s, n);



	return res;

}

extern __must_check long strlen_user(const char __user *str);

extern __must_check long strnlen_user(const char __user *str, long n);



#endif /* _ASMARM_UACCESS_H */

arch/arm/include/asm/word-at-a-time.h

0 → 100644
+55 −0
Original line number Diff line number Diff line 
#ifndef __ASM_ARM_WORD_AT_A_TIME_H

#define __ASM_ARM_WORD_AT_A_TIME_H



#ifndef __ARMEB__



/*

 * Little-endian word-at-a-time zero byte handling.

 * Heavily based on the x86 algorithm.

 */

#include <linux/kernel.h>



struct word_at_a_time {

	const unsigned long one_bits, high_bits;

};



#define WORD_AT_A_TIME_CONSTANTS { REPEAT_BYTE(0x01), REPEAT_BYTE(0x80) }



static inline unsigned long has_zero(unsigned long a, unsigned long *bits,

				     const struct word_at_a_time *c)

{

	unsigned long mask = ((a - c->one_bits) & ~a) & c->high_bits;

	*bits = mask;

	return mask;

}



#define prep_zero_mask(a, bits, c) (bits)



static inline unsigned long create_zero_mask(unsigned long bits)

{

	bits = (bits - 1) & ~bits;

	return bits >> 7;

}



static inline unsigned long find_zero(unsigned long mask)

{

	unsigned long ret;



#if __LINUX_ARM_ARCH__ >= 5

	/* We have clz available. */

	ret = fls(mask) >> 3;

#else

	/* (000000 0000ff 00ffff ffffff) -> ( 1 1 2 3 ) */

	ret = (0x0ff0001 + mask) >> 23;

	/* Fix the 1 for 00 case */

	ret &= mask;

#endif



	return ret;

}



#else	/* __ARMEB__ */

#include <asm-generic/word-at-a-time.h>

#endif



#endif /* __ASM_ARM_WORD_AT_A_TIME_H */

arch/arm/kernel/armksyms.c

+0 −4
Original line number Diff line number Diff line
@@ -87,10 +87,6 @@ EXPORT_SYMBOL(memmove); 
EXPORT_SYMBOL(memchr);

EXPORT_SYMBOL(__memzero);



	/* user mem (segment) */

EXPORT_SYMBOL(__strnlen_user);

EXPORT_SYMBOL(__strncpy_from_user);



#ifdef CONFIG_MMU

EXPORT_SYMBOL(copy_page);

arch/arm/lib/Makefile

+0 −1
Original line number Diff line number Diff line
@@ -8,7 +8,6 @@ lib-y := backtrace.o changebit.o csumipv6.o csumpartial.o \ 
		   csumpartialcopy.o csumpartialcopyuser.o clearbit.o \

		   delay.o findbit.o memchr.o memcpy.o		      \

		   memmove.o memset.o memzero.o setbit.o              \

		   strncpy_from_user.o strnlen_user.o                 \

		   strchr.o strrchr.o                                 \

		   testchangebit.o testclearbit.o testsetbit.o        \

		   ashldi3.o ashrdi3.o lshrdi3.o muldi3.o             \

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