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linux/arch/s390/lib/uaccess.c
Heiko Carstens f5c8b96010 s390/uaccess: use sane length for __strncpy_from_user() 
The average string that is copied from user space to kernel space is
rather short. E.g. booting a system involves about 50.000
strncpy_from_user() calls where the NULL terminated string has an
average size of 27 bytes.

By default our s390 specific strncpy_from_user() implementation
however copies up to 4096 bytes, which is a waste of cpu cycles and
cache lines. Therefore reduce the default length to L1_CACHE_BYTES
(256 bytes), which also reduces the average execution time of
strncpy_from_user() by 30-40%.

Alternatively we could have switched to the generic
strncpy_from_user() implementation, however it turned out that that
variant would be slower than the now optimized s390 variant.

Reported-by: Al Viro <viro@ZenIV.linux.org.uk>
Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Reviewed-by: Gerald Schaefer <gerald.schaefer@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
2017-05-09 10:43:24 +02:00

360 lines
9.3 KiB
C
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/*
* Standard user space access functions based on mvcp/mvcs and doing
* interesting things in the secondary space mode.
*
* Copyright IBM Corp. 2006,2014
* Author(s): Martin Schwidefsky (schwidefsky@de.ibm.com),
* Gerald Schaefer (gerald.schaefer@de.ibm.com)
*/
#include <linux/jump_label.h>
#include <linux/uaccess.h>
#include <linux/export.h>
#include <linux/errno.h>
#include <linux/mm.h>
#include <asm/mmu_context.h>
#include <asm/facility.h>
static DEFINE_STATIC_KEY_FALSE(have_mvcos);
static inline unsigned long copy_from_user_mvcos(void *x, const void __user *ptr,
unsigned long size)
{
register unsigned long reg0 asm("0") = 0x81UL;
unsigned long tmp1, tmp2;
tmp1 = -4096UL;
asm volatile(
"0: .insn ss,0xc80000000000,0(%0,%2),0(%1),0\n"
"6: jz 4f\n"
"1: algr %0,%3\n"
" slgr %1,%3\n"
" slgr %2,%3\n"
" j 0b\n"
"2: la %4,4095(%1)\n"/* %4 = ptr + 4095 */
" nr %4,%3\n" /* %4 = (ptr + 4095) & -4096 */
" slgr %4,%1\n"
" clgr %0,%4\n" /* copy crosses next page boundary? */
" jnh 5f\n"
"3: .insn ss,0xc80000000000,0(%4,%2),0(%1),0\n"
"7: slgr %0,%4\n"
" j 5f\n"
"4: slgr %0,%0\n"
"5:\n"
EX_TABLE(0b,2b) EX_TABLE(3b,5b) EX_TABLE(6b,2b) EX_TABLE(7b,5b)
: "+a" (size), "+a" (ptr), "+a" (x), "+a" (tmp1), "=a" (tmp2)
: "d" (reg0) : "cc", "memory");
return size;
}
static inline unsigned long copy_from_user_mvcp(void *x, const void __user *ptr,
unsigned long size)
{
unsigned long tmp1, tmp2;
load_kernel_asce();
tmp1 = -256UL;
asm volatile(
" sacf 0\n"
"0: mvcp 0(%0,%2),0(%1),%3\n"
"7: jz 5f\n"
"1: algr %0,%3\n"
" la %1,256(%1)\n"
" la %2,256(%2)\n"
"2: mvcp 0(%0,%2),0(%1),%3\n"
"8: jnz 1b\n"
" j 5f\n"
"3: la %4,255(%1)\n" /* %4 = ptr + 255 */
" lghi %3,-4096\n"
" nr %4,%3\n" /* %4 = (ptr + 255) & -4096 */
" slgr %4,%1\n"
" clgr %0,%4\n" /* copy crosses next page boundary? */
" jnh 6f\n"
"4: mvcp 0(%4,%2),0(%1),%3\n"
"9: slgr %0,%4\n"
" j 6f\n"
"5: slgr %0,%0\n"
"6: sacf 768\n"
EX_TABLE(0b,3b) EX_TABLE(2b,3b) EX_TABLE(4b,6b)
EX_TABLE(7b,3b) EX_TABLE(8b,3b) EX_TABLE(9b,6b)
: "+a" (size), "+a" (ptr), "+a" (x), "+a" (tmp1), "=a" (tmp2)
: : "cc", "memory");
return size;
}
unsigned long raw_copy_from_user(void *to, const void __user *from, unsigned long n)
{
if (static_branch_likely(&have_mvcos))
return copy_from_user_mvcos(to, from, n);
return copy_from_user_mvcp(to, from, n);
}
EXPORT_SYMBOL(raw_copy_from_user);
static inline unsigned long copy_to_user_mvcos(void __user *ptr, const void *x,
unsigned long size)
{
register unsigned long reg0 asm("0") = 0x810000UL;
unsigned long tmp1, tmp2;
tmp1 = -4096UL;
asm volatile(
"0: .insn ss,0xc80000000000,0(%0,%1),0(%2),0\n"
"6: jz 4f\n"
"1: algr %0,%3\n"
" slgr %1,%3\n"
" slgr %2,%3\n"
" j 0b\n"
"2: la %4,4095(%1)\n"/* %4 = ptr + 4095 */
" nr %4,%3\n" /* %4 = (ptr + 4095) & -4096 */
" slgr %4,%1\n"
" clgr %0,%4\n" /* copy crosses next page boundary? */
" jnh 5f\n"
"3: .insn ss,0xc80000000000,0(%4,%1),0(%2),0\n"
"7: slgr %0,%4\n"
" j 5f\n"
"4: slgr %0,%0\n"
"5:\n"
EX_TABLE(0b,2b) EX_TABLE(3b,5b) EX_TABLE(6b,2b) EX_TABLE(7b,5b)
: "+a" (size), "+a" (ptr), "+a" (x), "+a" (tmp1), "=a" (tmp2)
: "d" (reg0) : "cc", "memory");
return size;
}
static inline unsigned long copy_to_user_mvcs(void __user *ptr, const void *x,
unsigned long size)
{
unsigned long tmp1, tmp2;
load_kernel_asce();
tmp1 = -256UL;
asm volatile(
" sacf 0\n"
"0: mvcs 0(%0,%1),0(%2),%3\n"
"7: jz 5f\n"
"1: algr %0,%3\n"
" la %1,256(%1)\n"
" la %2,256(%2)\n"
"2: mvcs 0(%0,%1),0(%2),%3\n"
"8: jnz 1b\n"
" j 5f\n"
"3: la %4,255(%1)\n" /* %4 = ptr + 255 */
" lghi %3,-4096\n"
" nr %4,%3\n" /* %4 = (ptr + 255) & -4096 */
" slgr %4,%1\n"
" clgr %0,%4\n" /* copy crosses next page boundary? */
" jnh 6f\n"
"4: mvcs 0(%4,%1),0(%2),%3\n"
"9: slgr %0,%4\n"
" j 6f\n"
"5: slgr %0,%0\n"
"6: sacf 768\n"
EX_TABLE(0b,3b) EX_TABLE(2b,3b) EX_TABLE(4b,6b)
EX_TABLE(7b,3b) EX_TABLE(8b,3b) EX_TABLE(9b,6b)
: "+a" (size), "+a" (ptr), "+a" (x), "+a" (tmp1), "=a" (tmp2)
: : "cc", "memory");
return size;
}
unsigned long raw_copy_to_user(void __user *to, const void *from, unsigned long n)
{
if (static_branch_likely(&have_mvcos))
return copy_to_user_mvcos(to, from, n);
return copy_to_user_mvcs(to, from, n);
}
EXPORT_SYMBOL(raw_copy_to_user);
static inline unsigned long copy_in_user_mvcos(void __user *to, const void __user *from,
unsigned long size)
{
register unsigned long reg0 asm("0") = 0x810081UL;
unsigned long tmp1, tmp2;
tmp1 = -4096UL;
/* FIXME: copy with reduced length. */
asm volatile(
"0: .insn ss,0xc80000000000,0(%0,%1),0(%2),0\n"
" jz 2f\n"
"1: algr %0,%3\n"
" slgr %1,%3\n"
" slgr %2,%3\n"
" j 0b\n"
"2:slgr %0,%0\n"
"3: \n"
EX_TABLE(0b,3b)
: "+a" (size), "+a" (to), "+a" (from), "+a" (tmp1), "=a" (tmp2)
: "d" (reg0) : "cc", "memory");
return size;
}
static inline unsigned long copy_in_user_mvc(void __user *to, const void __user *from,
unsigned long size)
{
unsigned long tmp1;
load_kernel_asce();
asm volatile(
" sacf 256\n"
" aghi %0,-1\n"
" jo 5f\n"
" bras %3,3f\n"
"0: aghi %0,257\n"
"1: mvc 0(1,%1),0(%2)\n"
" la %1,1(%1)\n"
" la %2,1(%2)\n"
" aghi %0,-1\n"
" jnz 1b\n"
" j 5f\n"
"2: mvc 0(256,%1),0(%2)\n"
" la %1,256(%1)\n"
" la %2,256(%2)\n"
"3: aghi %0,-256\n"
" jnm 2b\n"
"4: ex %0,1b-0b(%3)\n"
"5: slgr %0,%0\n"
"6: sacf 768\n"
EX_TABLE(1b,6b) EX_TABLE(2b,0b) EX_TABLE(4b,0b)
: "+a" (size), "+a" (to), "+a" (from), "=a" (tmp1)
: : "cc", "memory");
return size;
}
unsigned long raw_copy_in_user(void __user *to, const void __user *from, unsigned long n)
{
if (static_branch_likely(&have_mvcos))
return copy_in_user_mvcos(to, from, n);
return copy_in_user_mvc(to, from, n);
}
EXPORT_SYMBOL(raw_copy_in_user);
static inline unsigned long clear_user_mvcos(void __user *to, unsigned long size)
{
register unsigned long reg0 asm("0") = 0x810000UL;
unsigned long tmp1, tmp2;
tmp1 = -4096UL;
asm volatile(
"0: .insn ss,0xc80000000000,0(%0,%1),0(%4),0\n"
" jz 4f\n"
"1: algr %0,%2\n"
" slgr %1,%2\n"
" j 0b\n"
"2: la %3,4095(%1)\n"/* %4 = to + 4095 */
" nr %3,%2\n" /* %4 = (to + 4095) & -4096 */
" slgr %3,%1\n"
" clgr %0,%3\n" /* copy crosses next page boundary? */
" jnh 5f\n"
"3: .insn ss,0xc80000000000,0(%3,%1),0(%4),0\n"
" slgr %0,%3\n"
" j 5f\n"
"4: slgr %0,%0\n"
"5:\n"
EX_TABLE(0b,2b) EX_TABLE(3b,5b)
: "+a" (size), "+a" (to), "+a" (tmp1), "=a" (tmp2)
: "a" (empty_zero_page), "d" (reg0) : "cc", "memory");
return size;
}
static inline unsigned long clear_user_xc(void __user *to, unsigned long size)
{
unsigned long tmp1, tmp2;
load_kernel_asce();
asm volatile(
" sacf 256\n"
" aghi %0,-1\n"
" jo 5f\n"
" bras %3,3f\n"
" xc 0(1,%1),0(%1)\n"
"0: aghi %0,257\n"
" la %2,255(%1)\n" /* %2 = ptr + 255 */
" srl %2,12\n"
" sll %2,12\n" /* %2 = (ptr + 255) & -4096 */
" slgr %2,%1\n"
" clgr %0,%2\n" /* clear crosses next page boundary? */
" jnh 5f\n"
" aghi %2,-1\n"
"1: ex %2,0(%3)\n"
" aghi %2,1\n"
" slgr %0,%2\n"
" j 5f\n"
"2: xc 0(256,%1),0(%1)\n"
" la %1,256(%1)\n"
"3: aghi %0,-256\n"
" jnm 2b\n"
"4: ex %0,0(%3)\n"
"5: slgr %0,%0\n"
"6: sacf 768\n"
EX_TABLE(1b,6b) EX_TABLE(2b,0b) EX_TABLE(4b,0b)
: "+a" (size), "+a" (to), "=a" (tmp1), "=a" (tmp2)
: : "cc", "memory");
return size;
}
unsigned long __clear_user(void __user *to, unsigned long size)
{
if (static_branch_likely(&have_mvcos))
return clear_user_mvcos(to, size);
return clear_user_xc(to, size);
}
EXPORT_SYMBOL(__clear_user);
static inline unsigned long strnlen_user_srst(const char __user *src,
unsigned long size)
{
register unsigned long reg0 asm("0") = 0;
unsigned long tmp1, tmp2;
asm volatile(
" la %2,0(%1)\n"
" la %3,0(%0,%1)\n"
" slgr %0,%0\n"
" sacf 256\n"
"0: srst %3,%2\n"
" jo 0b\n"
" la %0,1(%3)\n" /* strnlen_user results includes \0 */
" slgr %0,%1\n"
"1: sacf 768\n"
EX_TABLE(0b,1b)
: "+a" (size), "+a" (src), "=a" (tmp1), "=a" (tmp2)
: "d" (reg0) : "cc", "memory");
return size;
}
unsigned long __strnlen_user(const char __user *src, unsigned long size)
{
if (unlikely(!size))
return 0;
load_kernel_asce();
return strnlen_user_srst(src, size);
}
EXPORT_SYMBOL(__strnlen_user);
long __strncpy_from_user(char *dst, const char __user *src, long size)
{
size_t done, len, offset, len_str;
if (unlikely(size <= 0))
return 0;
done = 0;
do {
offset = (size_t)src & (L1_CACHE_BYTES - 1);
len = min(size - done, L1_CACHE_BYTES - offset);
if (copy_from_user(dst, src, len))
return -EFAULT;
len_str = strnlen(dst, len);
done += len_str;
src += len_str;
dst += len_str;
} while ((len_str == len) && (done < size));
return done;
}
EXPORT_SYMBOL(__strncpy_from_user);
static int __init uaccess_init(void)
{
if (test_facility(27))
static_branch_enable(&have_mvcos);
return 0;
}
early_initcall(uaccess_init);
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