Commit 12a0ef7b authored by Will Deacon's avatar Will Deacon Committed by Catalin Marinas
Browse files

arm64: use generic strnlen_user and strncpy_from_user functions 



This patch implements the word-at-a-time interface for arm64 using the
same algorithm as ARM. We use the fls64 macro, which expands to a clz
instruction via a compiler builtin. 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.

Signed-off-by: default avatarWill Deacon <will.deacon@arm.com>
Signed-off-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
parent 71586276

arch/arm64/Kconfig

+2 −0
Original line number Diff line number Diff line
@@ -17,6 +17,8 @@ config ARM64 
	select GENERIC_IRQ_SHOW

	select GENERIC_SCHED_CLOCK

	select GENERIC_SMP_IDLE_THREAD

	select GENERIC_STRNCPY_FROM_USER

	select GENERIC_STRNLEN_USER

	select GENERIC_TIME_VSYSCALL

	select HARDIRQS_SW_RESEND

	select HAVE_ARCH_TRACEHOOK

arch/arm64/include/asm/uaccess.h

+4 −21
Original line number Diff line number Diff line
@@ -100,6 +100,7 @@ static inline void set_fs(mm_segment_t fs) 
})



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

#define user_addr_max			get_fs



/*

 * The "__xxx" versions of the user access functions do not verify the address
@@ -240,9 +241,6 @@ extern unsigned long __must_check __copy_to_user(void __user *to, const void *fr 
extern unsigned long __must_check __copy_in_user(void __user *to, const void __user *from, unsigned long n);

extern unsigned long __must_check __clear_user(void __user *addr, unsigned long n);



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))
@@ -276,24 +274,9 @@ 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 /* __ASM_UACCESS_H */

arch/arm64/lib/strncpy_from_user.S→arch/arm64/include/asm/word-at-a-time.h

+54 −0
Original line number Diff line number Diff line 
/*

 * Based on arch/arm/lib/strncpy_from_user.S

 *

 * Copyright (C) 1995-2000 Russell King

 * Copyright (C) 2012 ARM Ltd.

 * Copyright (C) 2013 ARM Ltd.

 *

 * 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
@@ -16,35 +13,42 @@ 
 * You should have received a copy of the GNU General Public License

 * along with this program.  If not, see <http://www.gnu.org/licenses/>.

 */

#ifndef __ASM_WORD_AT_A_TIME_H

#define __ASM_WORD_AT_A_TIME_H



#include <linux/linkage.h>

#include <asm/assembler.h>

#include <asm/errno.h>

#ifndef __AARCH64EB__



	.text

	.align	5

#include <linux/kernel.h>



/*

 * Copy a string from user space to kernel space.

 *  x0 = dst, x1 = src, x2 = byte length

 * returns the number of characters copied (strlen of copied string),

 *  -EFAULT on exception, or "len" if we fill the whole buffer

 */

ENTRY(__strncpy_from_user)

	mov	x4, x1

1:	subs	x2, x2, #1

	bmi	2f

USER(9f, ldrb	w3, [x1], #1	)

	strb	w3, [x0], #1

	cbnz	w3, 1b

	sub	x1, x1, #1	// take NUL character out of count

2:	sub	x0, x1, x4

	ret

ENDPROC(__strncpy_from_user)



	.section .fixup,"ax"

	.align	0

9:	strb	wzr, [x0]	// null terminate

	mov	x0, #-EFAULT

	ret

	.previous
 
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)

{

	return fls64(mask) >> 3;

}



#else	/* __AARCH64EB__ */

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

#endif



#endif /* __ASM_WORD_AT_A_TIME_H */

arch/arm64/kernel/arm64ksyms.c

+1 −4
Original line number Diff line number Diff line
@@ -29,13 +29,10 @@ 


#include <asm/checksum.h>



	/* user mem (segment) */

EXPORT_SYMBOL(__strnlen_user);

EXPORT_SYMBOL(__strncpy_from_user);



EXPORT_SYMBOL(copy_page);

EXPORT_SYMBOL(clear_page);



	/* user mem (segment) */

EXPORT_SYMBOL(__copy_from_user);

EXPORT_SYMBOL(__copy_to_user);

EXPORT_SYMBOL(__clear_user);

arch/arm64/lib/Makefile

+3 −5
Original line number Diff line number Diff line 
lib-y		:= bitops.o delay.o					\

		   strncpy_from_user.o strnlen_user.o clear_user.o	\

		   copy_from_user.o copy_to_user.o copy_in_user.o	\

		   copy_page.o clear_page.o				\

		   memchr.o memcpy.o memmove.o memset.o			\

lib-y		:= bitops.o clear_user.o delay.o copy_from_user.o	\

		   copy_to_user.o copy_in_user.o copy_page.o		\

		   clear_page.o memchr.o memcpy.o memmove.o memset.o	\

		   strchr.o strrchr.o

CRA Git | Maintained and supported by SUSTech CRA and CCSE