korg/linux
0
0
Fork 0
mirror of https://mirrors.bfsu.edu.cn/git/linux.git synced 2024-11-24 20:54:10 +08:00
Code Issues Packages Projects Releases Wiki Activity
06f3f76441
linux/arch/csky/lib/usercopy.c
Al Viro 51bb38cb78 csky: Fixup raw_copy_from_user() 
If raw_copy_from_user(to, from, N) returns K, callers expect
the first N - K bytes starting at to to have been replaced with
the contents of corresponding area starting at from and the last
K bytes of destination *left* *unmodified*.

What arch/sky/lib/usercopy.c is doing is broken - it can lead to e.g.
data corruption on write(2).

raw_copy_to_user() is inaccurate about return value, which is a bug,
but consequences are less drastic than for raw_copy_from_user().
And just what are those access_ok() doing in there?  I mean, look into
linux/uaccess.h; that's where we do that check (as well as zero tail
on failure in the callers that need zeroing).

AFAICS, all of that shouldn't be hard to fix; something like a patch
below might make a useful starting point.

I would suggest moving these macros into usercopy.c (they are never
used anywhere else) and possibly expanding them there; if you leave
them alive, please at least rename __copy_user_zeroing(). Again,
it must not zero anything on failed read.

Said that, I'm not sure we won't be better off simply turning
usercopy.c into usercopy.S - all that is left there is a couple of
functions, each consisting only of inline asm.

Guo Ren reply:

Yes, raw_copy_from_user is wrong, it's no need zeroing code.

unsigned long _copy_from_user(void *to, const void __user *from,
unsigned long n)
{
        unsigned long res = n;
        might_fault();
        if (likely(access_ok(from, n))) {
                kasan_check_write(to, n);
                res = raw_copy_from_user(to, from, n);
        }
        if (unlikely(res))
                memset(to + (n - res), 0, res);
        return res;
}
EXPORT_SYMBOL(_copy_from_user);

You are right and access_ok() should be removed.

but, how about:
do {
...
        "2:     stw     %3, (%1, 0)     \n"             \
+       "       subi    %0, 4          \n"               \
        "9:     stw     %4, (%1, 4)     \n"             \
+       "       subi    %0, 4          \n"               \
        "10:    stw     %5, (%1, 8)     \n"             \
+       "       subi    %0, 4          \n"               \
        "11:    stw     %6, (%1, 12)    \n"             \
+       "       subi    %0, 4          \n"               \
        "       addi    %2, 16          \n"             \
        "       addi    %1, 16          \n"             \

Don't expand __ex_table

AI Viro reply:

Hey, I've no idea about the instruction scheduling on csky -
if that doesn't slow the things down, all the better.  It's just
that copy_to_user() and friends are on fairly hot codepaths,
and in quite a few situations they will dominate the speed of
e.g. read(2).  So I tried to keep the fast path unchanged.
Up to the architecture maintainers, obviously.  Which would be
you...

As for the fixups size increase (__ex_table size is unchanged)...
You have each of those macros expanded exactly once.
So the size is not a serious argument, IMO - useless complexity
would be, if it is, in fact, useless; the size... not really,
especially since those extra subi will at least offset it.

Again, up to you - asm optimizations of (essentially)
memcpy()-style loops are tricky and can depend upon the
fairly subtle details of architecture.  So even on something
I know reasonably well I would resort to direct experiments
if I can't pass the buck to architecture maintainers.

It *is* worth optimizing - this is where read() from a file
that is already in page cache spends most of the time, etc.

Guo Ren reply:

Thx, after fixup some typo “sub %0, 4”, apply the patch.

TODO:
 - user copy/from codes are still need optimizing.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Guo Ren <guoren@linux.alibaba.com>
2020-05-15 00:16:30 +08:00

259 lines
7.7 KiB
C
Raw Blame History

// SPDX-License-Identifier: GPL-2.0
// Copyright (C) 2018 Hangzhou C-SKY Microsystems co.,ltd.
#include <linux/uaccess.h>
#include <linux/types.h>
unsigned long raw_copy_from_user(void *to, const void *from,
unsigned long n)
{
___copy_from_user(to, from, n);
return n;
}
EXPORT_SYMBOL(raw_copy_from_user);
unsigned long raw_copy_to_user(void *to, const void *from,
unsigned long n)
{
___copy_to_user(to, from, n);
return n;
}
EXPORT_SYMBOL(raw_copy_to_user);
/*
* copy a null terminated string from userspace.
*/
#define __do_strncpy_from_user(dst, src, count, res) \
do { \
int tmp; \
long faultres; \
asm volatile( \
" cmpnei %3, 0 \n" \
" bf 4f \n" \
"1: cmpnei %1, 0 \n" \
" bf 5f \n" \
"2: ldb %4, (%3, 0) \n" \
" stb %4, (%2, 0) \n" \
" cmpnei %4, 0 \n" \
" bf 3f \n" \
" addi %3, 1 \n" \
" addi %2, 1 \n" \
" subi %1, 1 \n" \
" br 1b \n" \
"3: subu %0, %1 \n" \
" br 5f \n" \
"4: mov %0, %5 \n" \
" br 5f \n" \
".section __ex_table, \"a\" \n" \
".align 2 \n" \
".long 2b, 4b \n" \
".previous \n" \
"5: \n" \
: "=r"(res), "=r"(count), "=r"(dst), \
"=r"(src), "=r"(tmp), "=r"(faultres) \
: "5"(-EFAULT), "0"(count), "1"(count), \
"2"(dst), "3"(src) \
: "memory", "cc"); \
} while (0)
/*
* __strncpy_from_user: - Copy a NUL terminated string from userspace,
* with less checking.
* @dst: Destination address, in kernel space. This buffer must be at
* least @count bytes long.
* @src: Source address, in user space.
* @count: Maximum number of bytes to copy, including the trailing NUL.
*
* Copies a NUL-terminated string from userspace to kernel space.
* Caller must check the specified block with access_ok() before calling
* this function.
*
* On success, returns the length of the string (not including the trailing
* NUL).
*
* If access to userspace fails, returns -EFAULT (some data may have been
* copied).
*
* If @count is smaller than the length of the string, copies @count bytes
* and returns @count.
*/
long __strncpy_from_user(char *dst, const char *src, long count)
{
long res;
__do_strncpy_from_user(dst, src, count, res);
return res;
}
EXPORT_SYMBOL(__strncpy_from_user);
/*
* strncpy_from_user: - Copy a NUL terminated string from userspace.
* @dst: Destination address, in kernel space. This buffer must be at
* least @count bytes long.
* @src: Source address, in user space.
* @count: Maximum number of bytes to copy, including the trailing NUL.
*
* Copies a NUL-terminated string from userspace to kernel space.
*
* On success, returns the length of the string (not including the trailing
* NUL).
*
* If access to userspace fails, returns -EFAULT (some data may have been
* copied).
*
* If @count is smaller than the length of the string, copies @count bytes
* and returns @count.
*/
long strncpy_from_user(char *dst, const char *src, long count)
{
long res = -EFAULT;
if (access_ok(src, 1))
__do_strncpy_from_user(dst, src, count, res);
return res;
}
EXPORT_SYMBOL(strncpy_from_user);
/*
* strlen_user: - Get the size of a string in user space.
* @str: The string to measure.
* @n: The maximum valid length
*
* Get the size of a NUL-terminated string in user space.
*
* Returns the size of the string INCLUDING the terminating NUL.
* On exception, returns 0.
* If the string is too long, returns a value greater than @n.
*/
long strnlen_user(const char *s, long n)
{
unsigned long res, tmp;
if (s == NULL)
return 0;
asm volatile(
" cmpnei %1, 0 \n"
" bf 3f \n"
"1: cmpnei %0, 0 \n"
" bf 3f \n"
"2: ldb %3, (%1, 0) \n"
" cmpnei %3, 0 \n"
" bf 3f \n"
" subi %0, 1 \n"
" addi %1, 1 \n"
" br 1b \n"
"3: subu %2, %0 \n"
" addi %2, 1 \n"
" br 5f \n"
"4: movi %0, 0 \n"
" br 5f \n"
".section __ex_table, \"a\" \n"
".align 2 \n"
".long 2b, 4b \n"
".previous \n"
"5: \n"
: "=r"(n), "=r"(s), "=r"(res), "=r"(tmp)
: "0"(n), "1"(s), "2"(n)
: "memory", "cc");
return res;
}
EXPORT_SYMBOL(strnlen_user);
#define __do_clear_user(addr, size) \
do { \
int __d0, zvalue, tmp; \
\
asm volatile( \
"0: cmpnei %1, 0 \n" \
" bf 7f \n" \
" mov %3, %1 \n" \
" andi %3, 3 \n" \
" cmpnei %3, 0 \n" \
" bf 1f \n" \
" br 5f \n" \
"1: cmplti %0, 32 \n" /* 4W */ \
" bt 3f \n" \
"8: stw %2, (%1, 0) \n" \
"10: stw %2, (%1, 4) \n" \
"11: stw %2, (%1, 8) \n" \
"12: stw %2, (%1, 12) \n" \
"13: stw %2, (%1, 16) \n" \
"14: stw %2, (%1, 20) \n" \
"15: stw %2, (%1, 24) \n" \
"16: stw %2, (%1, 28) \n" \
" addi %1, 32 \n" \
" subi %0, 32 \n" \
" br 1b \n" \
"3: cmplti %0, 4 \n" /* 1W */ \
" bt 5f \n" \
"4: stw %2, (%1, 0) \n" \
" addi %1, 4 \n" \
" subi %0, 4 \n" \
" br 3b \n" \
"5: cmpnei %0, 0 \n" /* 1B */ \
"9: bf 7f \n" \
"6: stb %2, (%1, 0) \n" \
" addi %1, 1 \n" \
" subi %0, 1 \n" \
" br 5b \n" \
".section __ex_table,\"a\" \n" \
".align 2 \n" \
".long 8b, 9b \n" \
".long 10b, 9b \n" \
".long 11b, 9b \n" \
".long 12b, 9b \n" \
".long 13b, 9b \n" \
".long 14b, 9b \n" \
".long 15b, 9b \n" \
".long 16b, 9b \n" \
".long 4b, 9b \n" \
".long 6b, 9b \n" \
".previous \n" \
"7: \n" \
: "=r"(size), "=r" (__d0), \
"=r"(zvalue), "=r"(tmp) \
: "0"(size), "1"(addr), "2"(0) \
: "memory", "cc"); \
} while (0)
/*
* clear_user: - Zero a block of memory in user space.
* @to: Destination address, in user space.
* @n: Number of bytes to zero.
*
* Zero a block of memory in user space.
*
* Returns number of bytes that could not be cleared.
* On success, this will be zero.
*/
unsigned long
clear_user(void __user *to, unsigned long n)
{
if (access_ok(to, n))
__do_clear_user(to, n);
return n;
}
EXPORT_SYMBOL(clear_user);
/*
* __clear_user: - Zero a block of memory in user space, with less checking.
* @to: Destination address, in user space.
* @n: Number of bytes to zero.
*
* Zero a block of memory in user space. Caller must check
* the specified block with access_ok() before calling this function.
*
* Returns number of bytes that could not be cleared.
* On success, this will be zero.
*/
unsigned long
__clear_user(void __user *to, unsigned long n)
{
__do_clear_user(to, n);
return n;
}
EXPORT_SYMBOL(__clear_user);
Reference in New Issue View Git Blame Copy Permalink