Commit f2db633d authored by Michael Cree's avatar Michael Cree Committed by Linus Torvalds
Browse files

alpha: Use new generic strncpy_from_user() and strnlen_user() 



Similar to x86/sparc/powerpc implementations except:
1) we implement an extremely efficient has_zero()/find_zero()
   sequence with both prep_zero_mask() and create_zero_mask()
   no-operations.
2) Our output from prep_zero_mask() differs in that only the
   lowest eight bits are used to represent the zero bytes
   nevertheless it can be safely ORed with other similar masks
   from prep_zero_mask() and forms input to create_zero_mask(),
   the two fundamental properties prep_zero_mask() must satisfy.

Tests on EV67 and EV68 CPUs revealed that the generic code is
essentially as fast (to within 0.5% of CPU cycles) of the old
Alpha specific code for large quadword-aligned strings, despite
the 30% extra CPU instructions executed.  In contrast, the
generic code for unaligned strings is substantially slower (by
more than a factor of 3) than the old Alpha specific code.

Signed-off-by: default avatarMichael Cree <mcree@orcon.net.nz>
Acked-by: default avatarMatt Turner <mattst88@gmail.com>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent d8d5da12

arch/alpha/Kconfig

+2 −0
Original line number Diff line number Diff line
@@ -18,6 +18,8 @@ config ALPHA 
	select ARCH_HAVE_NMI_SAFE_CMPXCHG

	select GENERIC_SMP_IDLE_THREAD

	select GENERIC_CMOS_UPDATE

	select GENERIC_STRNCPY_FROM_USER

	select GENERIC_STRNLEN_USER

	help

	  The Alpha is a 64-bit general-purpose processor designed and

	  marketed by the Digital Equipment Corporation of blessed memory,

arch/alpha/include/asm/uaccess.h

+5 −29
Original line number Diff line number Diff line
@@ -433,36 +433,12 @@ clear_user(void __user *to, long len) 
#undef __module_address

#undef __module_call



/* Returns: -EFAULT if exception before terminator, N if the entire

   buffer filled, else strlen.  */

#define user_addr_max() \

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



extern long __strncpy_from_user(char *__to, const char __user *__from, long __to_len);



extern inline long

strncpy_from_user(char *to, const char __user *from, long n)

{

	long ret = -EFAULT;

	if (__access_ok((unsigned long)from, 0, get_fs()))

		ret = __strncpy_from_user(to, from, n);

	return ret;

}



/* Returns: 0 if bad, string length+1 (memory size) of string if ok */

extern long __strlen_user(const char __user *);



extern inline long strlen_user(const char __user *str)

{

	return access_ok(VERIFY_READ,str,0) ? __strlen_user(str) : 0;

}



/* Returns: 0 if exception before NUL or reaching the supplied limit (N),

 * a value greater than N if the limit would be exceeded, else strlen.  */

extern long __strnlen_user(const char __user *, long);



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

{

	return access_ok(VERIFY_READ,str,0) ? __strnlen_user(str, n) : 0;

}

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

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

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



/*

 * About the exception table:

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

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

#define _ASM_WORD_AT_A_TIME_H



#include <asm/compiler.h>



/*

 * word-at-a-time interface for Alpha.

 */



/*

 * We do not use the word_at_a_time struct on Alpha, but it needs to be

 * implemented to humour the generic code.

 */

struct word_at_a_time {

	const unsigned long unused;

};



#define WORD_AT_A_TIME_CONSTANTS { 0 }



/* Return nonzero if val has a zero */

static inline unsigned long has_zero(unsigned long val, unsigned long *bits, const struct word_at_a_time *c)

{

	unsigned long zero_locations = __kernel_cmpbge(0, val);

	*bits = zero_locations;

	return zero_locations;

}



static inline unsigned long prep_zero_mask(unsigned long val, unsigned long bits, const struct word_at_a_time *c)

{

	return bits;

}



#define create_zero_mask(bits) (bits)



static inline unsigned long find_zero(unsigned long bits)

{

#if defined(CONFIG_ALPHA_EV6) && defined(CONFIG_ALPHA_EV67)

	/* Simple if have CIX instructions */

	return __kernel_cttz(bits);

#else

	unsigned long t1, t2, t3;

	/* Retain lowest set bit only */

	bits &= -bits;

	/* Binary search for lowest set bit */

	t1 = bits & 0xf0;

	t2 = bits & 0xcc;

	t3 = bits & 0xaa;

	if (t1) t1 = 4;

	if (t2) t2 = 2;

	if (t3) t3 = 1;

	return t1 + t2 + t3;

#endif

}



#endif /* _ASM_WORD_AT_A_TIME_H */

arch/alpha/kernel/alpha_ksyms.c

+0 −2
Original line number Diff line number Diff line
@@ -74,8 +74,6 @@ EXPORT_SYMBOL(alpha_fp_emul); 
 */

EXPORT_SYMBOL(__copy_user);

EXPORT_SYMBOL(__do_clear_user);

EXPORT_SYMBOL(__strncpy_from_user);

EXPORT_SYMBOL(__strnlen_user);



/* 

 * SMP-specific symbols.

arch/alpha/lib/Makefile

+0 −2
Original line number Diff line number Diff line
@@ -31,8 +31,6 @@ lib-y = __divqu.o __remqu.o __divlu.o __remlu.o \ 
	$(ev6-y)memchr.o \

	$(ev6-y)copy_user.o \

	$(ev6-y)clear_user.o \

	$(ev6-y)strncpy_from_user.o \

	$(ev67-y)strlen_user.o \

	$(ev6-y)csum_ipv6_magic.o \

	$(ev6-y)clear_page.o \

	$(ev6-y)copy_page.o \

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