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s390/uaccess: shorten strncpy_from_user/strnlen_user 

Always stay within page boundaries when copying from user within
strlen_user_mvcos()/strncpy_from_user_mvcos(). This allows to
shorten the code a bit and may prevent unnecessary faults, since
we copy quite large amounts of memory to kernel space.

Also directly call the mvcos variants of copy_from_user() to
avoid indirect branches.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
This commit is contained in:
Heiko Carstens 2013-02-20 13:59:26 +01:00 committed by Martin Schwidefsky
parent ea4da6eae3
commit d7b788cd06
1 changed files with 12 additions and 12 deletions
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24
arch/s390/lib/uaccess_mvcos.c
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@ -162,19 +162,19 @@ static size_t clear_user_mvcos(size_t size, void __user *to)
static size_t strnlen_user_mvcos(size_t count, const char __user *src)
{
size_t done, len, offset, len_str;
char buf[256];
int rc;
size_t done, len, len_str;
done = 0;
do {
len = min(count - done, (size_t) 256);
rc = uaccess.copy_from_user(len, src + done, buf);
if (unlikely(rc == len))
offset = (size_t)src & ~PAGE_MASK;
len = min(256UL, PAGE_SIZE - offset);
len = min(count - done, len);
if (copy_from_user_mvcos(len, src, buf))
return 0;
len -= rc;
len_str = strnlen(buf, len);
done += len_str;
src += len_str;
} while ((len_str == len) && (done < count));
return done + 1;
}
@ -182,18 +182,18 @@ static size_t strnlen_user_mvcos(size_t count, const char __user *src)
static size_t strncpy_from_user_mvcos(size_t count, const char __user *src,
char *dst)
{
int rc;
size_t done, len, len_str;
size_t done, len, offset, len_str;
done = 0;
do {
len = min(count - done, (size_t) 4096);
rc = uaccess.copy_from_user(len, src + done, dst);
if (unlikely(rc == len))
offset = (size_t)src & ~PAGE_MASK;
len = min(count - done, PAGE_SIZE - offset);
if (copy_from_user_mvcos(len, src, dst))
return -EFAULT;
len -= rc;
len_str = strnlen(dst, len);
done += len_str;
src += len_str;
dst += len_str;
} while ((len_str == len) && (done < count));
return done;
}