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saner calling conventions for csum_and_copy_..._user()

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All callers of these primitives will
	* discard anything we might've copied in case of error
	* ignore the csum value in case of error
	* always pass 0xffffffff as the initial sum, so the
resulting csum value (in case of success, that is) will never be 0.

That suggest the following calling conventions:
	* don't pass err_ptr - just return 0 on error.
	* don't bother with zeroing destination, etc. in case of error
	* don't pass the initial sum - just use 0xffffffff.

This commit does the minimal conversion in the instances of csum_and_copy_...();
the changes of actual asm code behind them are done later in the series.
Note that this asm code is often shared with csum_partial_copy_nocheck();
the difference is that csum_partial_copy_nocheck() passes 0 for initial
sum while csum_and_copy_..._user() pass 0xffffffff.  Fortunately, we are
free to pass 0xffffffff in all cases and subsequent patches will use that
freedom without any special comments.

A part that could be split off: parisc and uml/i386 claimed to have
csum_and_copy_to_user() instances of their own, but those were identical
to the generic one, so we simply drop them.  Not sure if it's worth
a separate commit...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro
2020-07-11 00:27:49 -04:00
parent 99a2c96d52
commit c693cc4676
19 changed files with 183 additions and 287 deletions
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34
arch/sh/include/asm/checksum_32.h
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@@ -50,15 +50,16 @@ __wsum csum_partial_copy_nocheck(const void *src, void *dst, int len)
#define _HAVE_ARCH_COPY_AND_CSUM_FROM_USER
static inline
__wsum csum_and_copy_from_user(const void __user *src, void *dst,
int len, __wsum sum, int *err_ptr)
__wsum csum_and_copy_from_user(const void __user *src, void *dst, int len)
{
if (access_ok(src, len))
return csum_partial_copy_generic((__force const void *)src, dst,
len, sum, err_ptr, NULL);
if (len)
*err_ptr = -EFAULT;
return sum;
int err = 0;
__wsum sum = ~0U;
if (!access_ok(src, len))
return 0;
sum = csum_partial_copy_generic((__force const void *)src, dst,
len, sum, &err, NULL);
return err ? 0 : sum;
}
/*
@@ -199,16 +200,15 @@ static inline __sum16 csum_ipv6_magic(const struct in6_addr *saddr,
#define HAVE_CSUM_COPY_USER
static inline __wsum csum_and_copy_to_user(const void *src,
void __user *dst,
int len, __wsum sum,
int *err_ptr)
int len)
{
if (access_ok(dst, len))
return csum_partial_copy_generic((__force const void *)src,
dst, len, sum, NULL, err_ptr);
int err = 0;
__wsum sum = ~0U;
if (len)
*err_ptr = -EFAULT;
return (__force __wsum)-1; /* invalid checksum */
if (!access_ok(dst, len))
return 0;
sum = csum_partial_copy_generic((__force const void *)src,
dst, len, sum, NULL, &err);
return err ? 0 : sum;
}
#endif /* __ASM_SH_CHECKSUM_H */