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crypto: drbg - eliminate constant reinitialization of SGL 

The CTR DRBG requires two SGLs pointing to input/output buffers for the
CTR AES operation. The used SGLs always have only one entry. Thus, the
SGL can be initialized during allocation time, preventing a
re-initialization of the SGLs during each call.

The performance is increased by about 1 to 3 percent depending on the
size of the requested buffer size.

Signed-off-by: Stephan Mueller <smueller@chronox.de>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
This commit is contained in:
Stephan Mueller 2018-07-10 17:56:33 +02:00 committed by Herbert Xu
parent 3fd8093b41
commit cf862cbc83
2 changed files with 8 additions and 4 deletions
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11
crypto/drbg.c
View File

@ -1715,6 +1715,9 @@ static int drbg_init_sym_kernel(struct drbg_state *drbg)
drbg->outscratchpad = (u8 *)PTR_ALIGN(drbg->outscratchpadbuf,
alignmask + 1);
sg_init_table(&drbg->sg_in, 1);
sg_init_table(&drbg->sg_out, 1);
return alignmask;
}
@ -1743,17 +1746,17 @@ static int drbg_kcapi_sym_ctr(struct drbg_state *drbg,
u8 *inbuf, u32 inlen,
u8 *outbuf, u32 outlen)
{
struct scatterlist sg_in, sg_out;
struct scatterlist *sg_in = &drbg->sg_in, *sg_out = &drbg->sg_out;
int ret;
sg_init_one(&sg_in, inbuf, inlen);
sg_init_one(&sg_out, drbg->outscratchpad, DRBG_OUTSCRATCHLEN);
sg_set_buf(sg_in, inbuf, inlen);
sg_set_buf(sg_out, drbg->outscratchpad, DRBG_OUTSCRATCHLEN);
while (outlen) {
u32 cryptlen = min3(inlen, outlen, (u32)DRBG_OUTSCRATCHLEN);
/* Output buffer may not be valid for SGL, use scratchpad */
skcipher_request_set_crypt(drbg->ctr_req, &sg_in, &sg_out,
skcipher_request_set_crypt(drbg->ctr_req, sg_in, sg_out,
cryptlen, drbg->V);
ret = crypto_wait_req(crypto_skcipher_encrypt(drbg->ctr_req),
&drbg->ctr_wait);

1
include/crypto/drbg.h
View File

@ -127,6 +127,7 @@ struct drbg_state {
__u8 *outscratchpadbuf; /* CTR mode output scratchpad */
__u8 *outscratchpad; /* CTR mode aligned outbuf */
struct crypto_wait ctr_wait; /* CTR mode async wait obj */
struct scatterlist sg_in, sg_out; /* CTR mode SGLs */
bool seeded; /* DRBG fully seeded? */
bool pr; /* Prediction resistance enabled? */