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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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19
lib/iov_iter.c
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@@ -1449,15 +1449,14 @@ size_t csum_and_copy_from_iter(void *addr, size_t bytes, __wsum *csum,
return 0;
}
iterate_and_advance(i, bytes, v, ({
int err = 0;
next = csum_and_copy_from_user(v.iov_base,
(to += v.iov_len) - v.iov_len,
v.iov_len, ~0U, &err);
if (!err) {
v.iov_len);
if (next) {
sum = csum_block_add(sum, next, off);
off += v.iov_len;
}
err ? v.iov_len : 0;
next ? 0 : v.iov_len;
}), ({
char *p = kmap_atomic(v.bv_page);
sum = csum_and_memcpy((to += v.bv_len) - v.bv_len,
@@ -1491,11 +1490,10 @@ bool csum_and_copy_from_iter_full(void *addr, size_t bytes, __wsum *csum,
if (unlikely(i->count < bytes))
return false;
iterate_all_kinds(i, bytes, v, ({
int err = 0;
next = csum_and_copy_from_user(v.iov_base,
(to += v.iov_len) - v.iov_len,
v.iov_len, ~0U, &err);
if (err)
v.iov_len);
if (!next)
return false;
sum = csum_block_add(sum, next, off);
off += v.iov_len;
@@ -1537,15 +1535,14 @@ size_t csum_and_copy_to_iter(const void *addr, size_t bytes, void *csump,
return 0;
}
iterate_and_advance(i, bytes, v, ({
int err = 0;
next = csum_and_copy_to_user((from += v.iov_len) - v.iov_len,
v.iov_base,
v.iov_len, ~0U, &err);
if (!err) {
v.iov_len);
if (next) {
sum = csum_block_add(sum, next, off);
off += v.iov_len;
}
err ? v.iov_len : 0;
next ? 0 : v.iov_len;
}), ({
char *p = kmap_atomic(v.bv_page);
sum = csum_and_memcpy(p + v.bv_offset,