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crypto: skcipher - document skcipher_walk_done() and rename some vars

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skcipher_walk_done() has an unusual calling convention, and some of its
local variables have unclear names.  Document it and rename variables to
make it a bit clearer what is going on.  No change in behavior.

Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
This commit is contained in:
Eric Biggers 2025-01-05 11:34:09 -08:00 • committed by Herbert Xu
parent 42c5675c2f
commit e71778c95a
2 changed files with 35 additions and 17 deletions
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50
crypto/skcipher.c
View file

@ -89,17 +89,35 @@ static int skcipher_done_slow(struct skcipher_walk *walk, unsigned int bsize)
return 0;
}
int skcipher_walk_done(struct skcipher_walk *walk, int err)
/**
* skcipher_walk_done() - finish one step of a skcipher_walk
* @walk: the skcipher_walk
* @res: number of bytes *not* processed (>= 0) from walk->nbytes,
* or a -errno value to terminate the walk due to an error
*
* This function cleans up after one step of walking through the source and
* destination scatterlists, and advances to the next step if applicable.
* walk->nbytes is set to the number of bytes available in the next step,
* walk->total is set to the new total number of bytes remaining, and
* walk->{src,dst}.virt.addr is set to the next pair of data pointers. If there
* is no more data, or if an error occurred (i.e. -errno return), then
* walk->nbytes and walk->total are set to 0 and all resources owned by the
* skcipher_walk are freed.
*
* Return: 0 or a -errno value. If @res was a -errno value then it will be
* returned, but other errors may occur too.
*/
int skcipher_walk_done(struct skcipher_walk *walk, int res)
{
unsigned int n = walk->nbytes;
unsigned int nbytes = 0;
unsigned int n = walk->nbytes; /* num bytes processed this step */
unsigned int total = 0; /* new total remaining */
if (!n)
goto finish;
if (likely(err >= 0)) {
n -= err;
nbytes = walk->total - n;
if (likely(res >= 0)) {
n -= res; /* subtract num bytes *not* processed */
total = walk->total - n;
}
if (likely(!(walk->flags & (SKCIPHER_WALK_SLOW |
@ -115,31 +133,31 @@ unmap_src:
memcpy(walk->dst.virt.addr, walk->page, n);
skcipher_unmap_dst(walk);
} else if (unlikely(walk->flags & SKCIPHER_WALK_SLOW)) {
if (err > 0) {
if (res > 0) {
/*
* Didn't process all bytes. Either the algorithm is
* broken, or this was the last step and it turned out
* the message wasn't evenly divisible into blocks but
* the algorithm requires it.
*/
err = -EINVAL;
nbytes = 0;
res = -EINVAL;
total = 0;
} else
n = skcipher_done_slow(walk, n);
}
if (err > 0)
err = 0;
if (res > 0)
res = 0;
walk->total = nbytes;
walk->total = total;
walk->nbytes = 0;
scatterwalk_advance(&walk->in, n);
scatterwalk_advance(&walk->out, n);
scatterwalk_done(&walk->in, 0, nbytes);
scatterwalk_done(&walk->out, 1, nbytes);
scatterwalk_done(&walk->in, 0, total);
scatterwalk_done(&walk->out, 1, total);
if (nbytes) {
if (total) {
crypto_yield(walk->flags & SKCIPHER_WALK_SLEEP ?
CRYPTO_TFM_REQ_MAY_SLEEP : 0);
return skcipher_walk_next(walk);
@ -158,7 +176,7 @@ finish:
free_page((unsigned long)walk->page);
out:
return err;
return res;
}
EXPORT_SYMBOL_GPL(skcipher_walk_done);

2
include/crypto/internal/skcipher.h
View file

@ -196,7 +196,7 @@ void crypto_unregister_lskciphers(struct lskcipher_alg *algs, int count);
int lskcipher_register_instance(struct crypto_template *tmpl,
struct lskcipher_instance *inst);
int skcipher_walk_done(struct skcipher_walk *walk, int err);
int skcipher_walk_done(struct skcipher_walk *walk, int res);
int skcipher_walk_virt(struct skcipher_walk *walk,
struct skcipher_request *req,
bool atomic);