leandrof/linux
1
0
Fork 0
forked from Minki/linux
Code Issues Pull Requests Packages Projects Releases Wiki Activity
8d11f21a73
linux/arch/csky/include/asm/uaccess.h
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

411 lines
12 KiB
C
Raw Blame History

/* SPDX-License-Identifier: GPL-2.0 */
// Copyright (C) 2018 Hangzhou C-SKY Microsystems co.,ltd.
#ifndef __ASM_CSKY_UACCESS_H
#define __ASM_CSKY_UACCESS_H
/*
* User space memory access functions
*/
#include <linux/compiler.h>
#include <linux/errno.h>
#include <linux/types.h>
#include <linux/sched.h>
#include <linux/string.h>
#include <linux/version.h>
#include <asm/segment.h>
static inline int access_ok(const void *addr, unsigned long size)
{
unsigned long limit = current_thread_info()->addr_limit.seg;
return (((unsigned long)addr < limit) &&
((unsigned long)(addr + size) < limit));
}
#define __addr_ok(addr) (access_ok(addr, 0))
extern int __put_user_bad(void);
/*
* Tell gcc we read from memory instead of writing: this is because
* we do not write to any memory gcc knows about, so there are no
* aliasing issues.
*/
/*
* These are the main single-value transfer routines. They automatically
* use the right size if we just have the right pointer type.
*
* This gets kind of ugly. We want to return _two_ values in "get_user()"
* and yet we don't want to do any pointers, because that is too much
* of a performance impact. Thus we have a few rather ugly macros here,
* and hide all the ugliness from the user.
*
* The "__xxx" versions of the user access functions are versions that
* do not verify the address space, that must have been done previously
* with a separate "access_ok()" call (this is used when we do multiple
* accesses to the same area of user memory).
*
* As we use the same address space for kernel and user data on
* Ckcore, we can just do these as direct assignments. (Of course, the
* exception handling means that it's no longer "just"...)
*/
#define put_user(x, ptr) \
__put_user_check((x), (ptr), sizeof(*(ptr)))
#define __put_user(x, ptr) \
__put_user_nocheck((x), (ptr), sizeof(*(ptr)))
#define __ptr(x) ((unsigned long *)(x))
#define get_user(x, ptr) \
__get_user_check((x), (ptr), sizeof(*(ptr)))
#define __get_user(x, ptr) \
__get_user_nocheck((x), (ptr), sizeof(*(ptr)))
#define __put_user_nocheck(x, ptr, size) \
({ \
long __pu_err = 0; \
typeof(*(ptr)) *__pu_addr = (ptr); \
typeof(*(ptr)) __pu_val = (typeof(*(ptr)))(x); \
if (__pu_addr) \
__put_user_size(__pu_val, (__pu_addr), (size), \
__pu_err); \
__pu_err; \
})
#define __put_user_check(x, ptr, size) \
({ \
long __pu_err = -EFAULT; \
typeof(*(ptr)) *__pu_addr = (ptr); \
typeof(*(ptr)) __pu_val = (typeof(*(ptr)))(x); \
if (access_ok(__pu_addr, size) && __pu_addr) \
__put_user_size(__pu_val, __pu_addr, (size), __pu_err); \
__pu_err; \
})
#define __put_user_size(x, ptr, size, retval) \
do { \
retval = 0; \
switch (size) { \
case 1: \
__put_user_asm_b(x, ptr, retval); \
break; \
case 2: \
__put_user_asm_h(x, ptr, retval); \
break; \
case 4: \
__put_user_asm_w(x, ptr, retval); \
break; \
case 8: \
__put_user_asm_64(x, ptr, retval); \
break; \
default: \
__put_user_bad(); \
} \
} while (0)
/*
* We don't tell gcc that we are accessing memory, but this is OK
* because we do not write to any memory gcc knows about, so there
* are no aliasing issues.
*
* Note that PC at a fault is the address *after* the faulting
* instruction.
*/
#define __put_user_asm_b(x, ptr, err) \
do { \
int errcode; \
asm volatile( \
"1: stb %1, (%2,0) \n" \
" br 3f \n" \
"2: mov %0, %3 \n" \
" br 3f \n" \
".section __ex_table, \"a\" \n" \
".align 2 \n" \
".long 1b,2b \n" \
".previous \n" \
"3: \n" \
: "=r"(err), "=r"(x), "=r"(ptr), "=r"(errcode) \
: "0"(err), "1"(x), "2"(ptr), "3"(-EFAULT) \
: "memory"); \
} while (0)
#define __put_user_asm_h(x, ptr, err) \
do { \
int errcode; \
asm volatile( \
"1: sth %1, (%2,0) \n" \
" br 3f \n" \
"2: mov %0, %3 \n" \
" br 3f \n" \
".section __ex_table, \"a\" \n" \
".align 2 \n" \
".long 1b,2b \n" \
".previous \n" \
"3: \n" \
: "=r"(err), "=r"(x), "=r"(ptr), "=r"(errcode) \
: "0"(err), "1"(x), "2"(ptr), "3"(-EFAULT) \
: "memory"); \
} while (0)
#define __put_user_asm_w(x, ptr, err) \
do { \
int errcode; \
asm volatile( \
"1: stw %1, (%2,0) \n" \
" br 3f \n" \
"2: mov %0, %3 \n" \
" br 3f \n" \
".section __ex_table,\"a\" \n" \
".align 2 \n" \
".long 1b, 2b \n" \
".previous \n" \
"3: \n" \
: "=r"(err), "=r"(x), "=r"(ptr), "=r"(errcode) \
: "0"(err), "1"(x), "2"(ptr), "3"(-EFAULT) \
: "memory"); \
} while (0)
#define __put_user_asm_64(x, ptr, err) \
do { \
int tmp; \
int errcode; \
typeof(*(ptr))src = (typeof(*(ptr)))x; \
typeof(*(ptr))*psrc = &src; \
\
asm volatile( \
" ldw %3, (%1, 0) \n" \
"1: stw %3, (%2, 0) \n" \
" ldw %3, (%1, 4) \n" \
"2: stw %3, (%2, 4) \n" \
" br 4f \n" \
"3: mov %0, %4 \n" \
" br 4f \n" \
".section __ex_table, \"a\" \n" \
".align 2 \n" \
".long 1b, 3b \n" \
".long 2b, 3b \n" \
".previous \n" \
"4: \n" \
: "=r"(err), "=r"(psrc), "=r"(ptr), \
"=r"(tmp), "=r"(errcode) \
: "0"(err), "1"(psrc), "2"(ptr), "3"(0), "4"(-EFAULT) \
: "memory"); \
} while (0)
#define __get_user_nocheck(x, ptr, size) \
({ \
long __gu_err; \
__get_user_size(x, (ptr), (size), __gu_err); \
__gu_err; \
})
#define __get_user_check(x, ptr, size) \
({ \
int __gu_err = -EFAULT; \
const __typeof__(*(ptr)) __user *__gu_ptr = (ptr); \
if (access_ok(__gu_ptr, size) && __gu_ptr) \
__get_user_size(x, __gu_ptr, size, __gu_err); \
__gu_err; \
})
#define __get_user_size(x, ptr, size, retval) \
do { \
switch (size) { \
case 1: \
__get_user_asm_common((x), ptr, "ldb", retval); \
break; \
case 2: \
__get_user_asm_common((x), ptr, "ldh", retval); \
break; \
case 4: \
__get_user_asm_common((x), ptr, "ldw", retval); \
break; \
default: \
x = 0; \
(retval) = __get_user_bad(); \
} \
} while (0)
#define __get_user_asm_common(x, ptr, ins, err) \
do { \
int errcode; \
asm volatile( \
"1: " ins " %1, (%4,0) \n" \
" br 3f \n" \
/* Fix up codes */ \
"2: mov %0, %2 \n" \
" movi %1, 0 \n" \
" br 3f \n" \
".section __ex_table,\"a\" \n" \
".align 2 \n" \
".long 1b, 2b \n" \
".previous \n" \
"3: \n" \
: "=r"(err), "=r"(x), "=r"(errcode) \
: "0"(0), "r"(ptr), "2"(-EFAULT) \
: "memory"); \
} while (0)
extern int __get_user_bad(void);
#define ___copy_to_user(to, from, n) \
do { \
int w0, w1, w2, w3; \
asm volatile( \
"0: cmpnei %1, 0 \n" \
" bf 8f \n" \
" mov %3, %1 \n" \
" or %3, %2 \n" \
" andi %3, 3 \n" \
" cmpnei %3, 0 \n" \
" bf 1f \n" \
" br 5f \n" \
"1: cmplti %0, 16 \n" /* 4W */ \
" bt 3f \n" \
" ldw %3, (%2, 0) \n" \
" ldw %4, (%2, 4) \n" \
" ldw %5, (%2, 8) \n" \
" ldw %6, (%2, 12) \n" \
"2: stw %3, (%1, 0) \n" \
"9: stw %4, (%1, 4) \n" \
"10: stw %5, (%1, 8) \n" \
"11: stw %6, (%1, 12) \n" \
" addi %2, 16 \n" \
" addi %1, 16 \n" \
" subi %0, 16 \n" \
" br 1b \n" \
"3: cmplti %0, 4 \n" /* 1W */ \
" bt 5f \n" \
" ldw %3, (%2, 0) \n" \
"4: stw %3, (%1, 0) \n" \
" addi %2, 4 \n" \
" addi %1, 4 \n" \
" subi %0, 4 \n" \
" br 3b \n" \
"5: cmpnei %0, 0 \n" /* 1B */ \
" bf 13f \n" \
" ldb %3, (%2, 0) \n" \
"6: stb %3, (%1, 0) \n" \
" addi %2, 1 \n" \
" addi %1, 1 \n" \
" subi %0, 1 \n" \
" br 5b \n" \
"7: subi %0, 4 \n" \
"8: subi %0, 4 \n" \
"12: subi %0, 4 \n" \
" br 13f \n" \
".section __ex_table, \"a\" \n" \
".align 2 \n" \
".long 2b, 13f \n" \
".long 4b, 13f \n" \
".long 6b, 13f \n" \
".long 9b, 12b \n" \
".long 10b, 8b \n" \
".long 11b, 7b \n" \
".previous \n" \
"13: \n" \
: "=r"(n), "=r"(to), "=r"(from), "=r"(w0), \
"=r"(w1), "=r"(w2), "=r"(w3) \
: "0"(n), "1"(to), "2"(from) \
: "memory"); \
} while (0)
#define ___copy_from_user(to, from, n) \
do { \
int tmp; \
int nsave; \
asm volatile( \
"0: cmpnei %1, 0 \n" \
" bf 7f \n" \
" mov %3, %1 \n" \
" or %3, %2 \n" \
" andi %3, 3 \n" \
" cmpnei %3, 0 \n" \
" bf 1f \n" \
" br 5f \n" \
"1: cmplti %0, 16 \n" \
" bt 3f \n" \
"2: ldw %3, (%2, 0) \n" \
"10: ldw %4, (%2, 4) \n" \
" stw %3, (%1, 0) \n" \
" stw %4, (%1, 4) \n" \
"11: ldw %3, (%2, 8) \n" \
"12: ldw %4, (%2, 12) \n" \
" stw %3, (%1, 8) \n" \
" stw %4, (%1, 12) \n" \
" addi %2, 16 \n" \
" addi %1, 16 \n" \
" subi %0, 16 \n" \
" br 1b \n" \
"3: cmplti %0, 4 \n" \
" bt 5f \n" \
"4: ldw %3, (%2, 0) \n" \
" stw %3, (%1, 0) \n" \
" addi %2, 4 \n" \
" addi %1, 4 \n" \
" subi %0, 4 \n" \
" br 3b \n" \
"5: cmpnei %0, 0 \n" \
" bf 7f \n" \
"6: ldb %3, (%2, 0) \n" \
" stb %3, (%1, 0) \n" \
" addi %2, 1 \n" \
" addi %1, 1 \n" \
" subi %0, 1 \n" \
" br 5b \n" \
"8: stw %3, (%1, 0) \n" \
" subi %0, 4 \n" \
" bf 7f \n" \
"9: subi %0, 8 \n" \
" bf 7f \n" \
"13: stw %3, (%1, 8) \n" \
" subi %0, 12 \n" \
" bf 7f \n" \
".section __ex_table, \"a\" \n" \
".align 2 \n" \
".long 2b, 7f \n" \
".long 4b, 7f \n" \
".long 6b, 7f \n" \
".long 10b, 8b \n" \
".long 11b, 9b \n" \
".long 12b,13b \n" \
".previous \n" \
"7: \n" \
: "=r"(n), "=r"(to), "=r"(from), "=r"(nsave), \
"=r"(tmp) \
: "0"(n), "1"(to), "2"(from) \
: "memory"); \
} while (0)
unsigned long raw_copy_from_user(void *to, const void *from, unsigned long n);
unsigned long raw_copy_to_user(void *to, const void *from, unsigned long n);
unsigned long clear_user(void *to, unsigned long n);
unsigned long __clear_user(void __user *to, unsigned long n);
long strncpy_from_user(char *dst, const char *src, long count);
long __strncpy_from_user(char *dst, const char *src, long count);
/*
* Return the size of a string (including the ending 0)
*
* Return 0 on exception, a value greater than N if too long
*/
long strnlen_user(const char *src, long n);
#define strlen_user(str) strnlen_user(str, 32767)
struct exception_table_entry {
unsigned long insn;
unsigned long nextinsn;
};
extern int fixup_exception(struct pt_regs *regs);
#endif /* __ASM_CSKY_UACCESS_H */
Reference in New Issue View Git Blame Copy Permalink