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https://github.com/AuxXxilium/linux_dsm_epyc7002.git
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51bb38cb78
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>
259 lines
7.7 KiB
C
259 lines
7.7 KiB
C
// SPDX-License-Identifier: GPL-2.0
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// Copyright (C) 2018 Hangzhou C-SKY Microsystems co.,ltd.
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#include <linux/uaccess.h>
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#include <linux/types.h>
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unsigned long raw_copy_from_user(void *to, const void *from,
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unsigned long n)
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{
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___copy_from_user(to, from, n);
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return n;
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}
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EXPORT_SYMBOL(raw_copy_from_user);
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unsigned long raw_copy_to_user(void *to, const void *from,
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unsigned long n)
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{
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___copy_to_user(to, from, n);
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return n;
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}
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EXPORT_SYMBOL(raw_copy_to_user);
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/*
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* copy a null terminated string from userspace.
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*/
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#define __do_strncpy_from_user(dst, src, count, res) \
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do { \
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int tmp; \
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long faultres; \
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asm volatile( \
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" cmpnei %3, 0 \n" \
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" bf 4f \n" \
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"1: cmpnei %1, 0 \n" \
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" bf 5f \n" \
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"2: ldb %4, (%3, 0) \n" \
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" stb %4, (%2, 0) \n" \
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" cmpnei %4, 0 \n" \
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" bf 3f \n" \
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" addi %3, 1 \n" \
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" addi %2, 1 \n" \
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" subi %1, 1 \n" \
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" br 1b \n" \
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"3: subu %0, %1 \n" \
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" br 5f \n" \
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"4: mov %0, %5 \n" \
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" br 5f \n" \
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".section __ex_table, \"a\" \n" \
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".align 2 \n" \
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".long 2b, 4b \n" \
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".previous \n" \
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"5: \n" \
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: "=r"(res), "=r"(count), "=r"(dst), \
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"=r"(src), "=r"(tmp), "=r"(faultres) \
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: "5"(-EFAULT), "0"(count), "1"(count), \
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"2"(dst), "3"(src) \
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: "memory", "cc"); \
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} while (0)
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/*
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* __strncpy_from_user: - Copy a NUL terminated string from userspace,
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* with less checking.
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* @dst: Destination address, in kernel space. This buffer must be at
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* least @count bytes long.
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* @src: Source address, in user space.
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* @count: Maximum number of bytes to copy, including the trailing NUL.
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*
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* Copies a NUL-terminated string from userspace to kernel space.
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* Caller must check the specified block with access_ok() before calling
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* this function.
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*
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* On success, returns the length of the string (not including the trailing
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* NUL).
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*
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* If access to userspace fails, returns -EFAULT (some data may have been
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* copied).
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*
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* If @count is smaller than the length of the string, copies @count bytes
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* and returns @count.
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*/
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long __strncpy_from_user(char *dst, const char *src, long count)
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{
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long res;
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__do_strncpy_from_user(dst, src, count, res);
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return res;
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}
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EXPORT_SYMBOL(__strncpy_from_user);
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/*
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* strncpy_from_user: - Copy a NUL terminated string from userspace.
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* @dst: Destination address, in kernel space. This buffer must be at
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* least @count bytes long.
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* @src: Source address, in user space.
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* @count: Maximum number of bytes to copy, including the trailing NUL.
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*
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* Copies a NUL-terminated string from userspace to kernel space.
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*
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* On success, returns the length of the string (not including the trailing
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* NUL).
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*
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* If access to userspace fails, returns -EFAULT (some data may have been
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* copied).
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*
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* If @count is smaller than the length of the string, copies @count bytes
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* and returns @count.
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*/
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long strncpy_from_user(char *dst, const char *src, long count)
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{
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long res = -EFAULT;
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if (access_ok(src, 1))
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__do_strncpy_from_user(dst, src, count, res);
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return res;
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}
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EXPORT_SYMBOL(strncpy_from_user);
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/*
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* strlen_user: - Get the size of a string in user space.
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* @str: The string to measure.
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* @n: The maximum valid length
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*
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* Get the size of a NUL-terminated string in user space.
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*
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* Returns the size of the string INCLUDING the terminating NUL.
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* On exception, returns 0.
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* If the string is too long, returns a value greater than @n.
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*/
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long strnlen_user(const char *s, long n)
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{
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unsigned long res, tmp;
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if (s == NULL)
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return 0;
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asm volatile(
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" cmpnei %1, 0 \n"
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" bf 3f \n"
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"1: cmpnei %0, 0 \n"
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" bf 3f \n"
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"2: ldb %3, (%1, 0) \n"
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" cmpnei %3, 0 \n"
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" bf 3f \n"
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" subi %0, 1 \n"
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" addi %1, 1 \n"
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" br 1b \n"
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"3: subu %2, %0 \n"
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" addi %2, 1 \n"
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" br 5f \n"
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"4: movi %0, 0 \n"
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" br 5f \n"
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".section __ex_table, \"a\" \n"
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".align 2 \n"
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".long 2b, 4b \n"
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".previous \n"
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"5: \n"
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: "=r"(n), "=r"(s), "=r"(res), "=r"(tmp)
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: "0"(n), "1"(s), "2"(n)
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: "memory", "cc");
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return res;
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}
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EXPORT_SYMBOL(strnlen_user);
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#define __do_clear_user(addr, size) \
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do { \
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int __d0, zvalue, tmp; \
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\
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asm volatile( \
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"0: cmpnei %1, 0 \n" \
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" bf 7f \n" \
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" mov %3, %1 \n" \
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" andi %3, 3 \n" \
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" cmpnei %3, 0 \n" \
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" bf 1f \n" \
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" br 5f \n" \
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"1: cmplti %0, 32 \n" /* 4W */ \
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" bt 3f \n" \
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"8: stw %2, (%1, 0) \n" \
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"10: stw %2, (%1, 4) \n" \
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"11: stw %2, (%1, 8) \n" \
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"12: stw %2, (%1, 12) \n" \
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"13: stw %2, (%1, 16) \n" \
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"14: stw %2, (%1, 20) \n" \
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"15: stw %2, (%1, 24) \n" \
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"16: stw %2, (%1, 28) \n" \
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" addi %1, 32 \n" \
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" subi %0, 32 \n" \
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" br 1b \n" \
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"3: cmplti %0, 4 \n" /* 1W */ \
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" bt 5f \n" \
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"4: stw %2, (%1, 0) \n" \
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" addi %1, 4 \n" \
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" subi %0, 4 \n" \
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" br 3b \n" \
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"5: cmpnei %0, 0 \n" /* 1B */ \
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"9: bf 7f \n" \
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"6: stb %2, (%1, 0) \n" \
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" addi %1, 1 \n" \
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" subi %0, 1 \n" \
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" br 5b \n" \
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".section __ex_table,\"a\" \n" \
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".align 2 \n" \
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".long 8b, 9b \n" \
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".long 10b, 9b \n" \
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".long 11b, 9b \n" \
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".long 12b, 9b \n" \
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".long 13b, 9b \n" \
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".long 14b, 9b \n" \
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".long 15b, 9b \n" \
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".long 16b, 9b \n" \
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".long 4b, 9b \n" \
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".long 6b, 9b \n" \
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".previous \n" \
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"7: \n" \
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: "=r"(size), "=r" (__d0), \
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"=r"(zvalue), "=r"(tmp) \
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: "0"(size), "1"(addr), "2"(0) \
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: "memory", "cc"); \
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} while (0)
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/*
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* clear_user: - Zero a block of memory in user space.
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* @to: Destination address, in user space.
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* @n: Number of bytes to zero.
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*
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* Zero a block of memory in user space.
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*
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* Returns number of bytes that could not be cleared.
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* On success, this will be zero.
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*/
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unsigned long
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clear_user(void __user *to, unsigned long n)
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{
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if (access_ok(to, n))
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__do_clear_user(to, n);
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return n;
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}
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EXPORT_SYMBOL(clear_user);
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/*
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* __clear_user: - Zero a block of memory in user space, with less checking.
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* @to: Destination address, in user space.
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* @n: Number of bytes to zero.
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*
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* Zero a block of memory in user space. Caller must check
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* the specified block with access_ok() before calling this function.
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*
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* Returns number of bytes that could not be cleared.
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* On success, this will be zero.
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*/
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unsigned long
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__clear_user(void __user *to, unsigned long n)
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{
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__do_clear_user(to, n);
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return n;
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}
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EXPORT_SYMBOL(__clear_user);
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