From: "George Spelvin" Subject: [PATCH 10/17] crypto: ansi_cprng - simplify get_prng_bytes Date: 2 Dec 2014 03:52:31 -0500 Message-ID: <20141202085231.19085.qmail@ns.horizon.com> References: <20141202083314.17647.qmail@ns.horizon.com> Cc: linux-crypto@vger.kernel.org, linux@horizon.com, smueller@chronox.de To: herbert@gondor.apana.org.au, nhorman@tuxdriver.com Return-path: Received: from ns.horizon.com ([71.41.210.147]:35977 "HELO ns.horizon.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1754589AbaLBIwc (ORCPT ); Tue, 2 Dec 2014 03:52:32 -0500 In-Reply-To: <20141202083314.17647.qmail@ns.horizon.com> Sender: linux-crypto-owner@vger.kernel.org List-ID: The crypto is so slow that there's no point unrolling this function. A simpler and clearer implementation will do just fine. Also move all modification of rand_read_pos out of _get_more_prng_bytes; that's variable belongs to the byte-at-a-time layer outside the block-oriented primitive. Signed-off-by: George Spelvin --- crypto/ansi_cprng.c | 67 ++++++++++++++--------------------------------------- 1 file changed, 18 insertions(+), 49 deletions(-) Friends don't let friends micro-optimize non-inner loops. diff --git a/crypto/ansi_cprng.c b/crypto/ansi_cprng.c index 6723a561..de13e741 100644 --- a/crypto/ansi_cprng.c +++ b/crypto/ansi_cprng.c @@ -166,7 +166,6 @@ static int _get_more_prng_bytes(struct prng_context *ctx, bool cont_test) } dbgprint("Returning new block for context %p\n", ctx); - ctx->rand_read_pos = 0; hexdump("Output DT: ", ctx->DT, DEFAULT_BLK_SZ); hexdump("Output V: ", ctx->V, DEFAULT_BLK_SZ); @@ -179,65 +178,36 @@ static int _get_more_prng_bytes(struct prng_context *ctx, bool cont_test) static int get_prng_bytes(unsigned char *buf, unsigned int nbytes, struct prng_context *ctx, bool do_cont_test) { - unsigned char *ptr = buf; - unsigned int byte_count = (unsigned int)nbytes; - int err; + unsigned int pos = 0; + unsigned int len; + int read_pos = ctx->rand_read_pos; + int err = -EINVAL; + + dbgprint(KERN_CRIT "getting %u random bytes for context %p\n", + nbytes, ctx); spin_lock_bh(&ctx->prng_lock); - err = -EINVAL; if (ctx->flags & PRNG_NEED_RESET) goto done; - err = byte_count; + while (nbytes - pos > DEFAULT_BLK_SZ - read_pos) { + len = DEFAULT_BLK_SZ - read_pos; - dbgprint(KERN_CRIT "getting %d random bytes for context %p\n", - byte_count, ctx); - -remainder: - if (ctx->rand_read_pos == DEFAULT_BLK_SZ) { + memcpy(buf + pos, ctx->rand_data + read_pos, len); if (_get_more_prng_bytes(ctx, do_cont_test) < 0) { memset(buf, 0, nbytes); - err = -EINVAL; goto done; } + pos += len; + read_pos = 0; } - /* - * Copy any data less than an entire block - */ - if (byte_count < DEFAULT_BLK_SZ) { -empty_rbuf: - while (ctx->rand_read_pos < DEFAULT_BLK_SZ) { - *ptr++ = ctx->rand_data[ctx->rand_read_pos++]; - if (--byte_count == 0) - goto done; - } - } - - /* - * Now copy whole blocks - */ - for (; byte_count >= DEFAULT_BLK_SZ; byte_count -= DEFAULT_BLK_SZ) { - if (ctx->rand_read_pos == DEFAULT_BLK_SZ) { - if (_get_more_prng_bytes(ctx, do_cont_test) < 0) { - memset(buf, 0, nbytes); - err = -EINVAL; - goto done; - } - } - if (ctx->rand_read_pos > 0) - goto empty_rbuf; - memcpy(ptr, ctx->rand_data, DEFAULT_BLK_SZ); - ctx->rand_read_pos += DEFAULT_BLK_SZ; - ptr += DEFAULT_BLK_SZ; - } - - /* - * Now go back and get any remaining partial block - */ - if (byte_count) - goto remainder; + /* The final partial block */ + len = nbytes - pos; + memcpy(buf + pos, ctx->rand_data + read_pos, len); + ctx->rand_read_pos = read_pos + len; + err = nbytes; done: spin_unlock_bh(&ctx->prng_lock); @@ -351,7 +321,6 @@ static int fips_cprng_get_random(struct crypto_rng *tfm, u8 *rdata, static int fips_cprng_reset(struct crypto_rng *tfm, u8 *seed, unsigned int slen) { - u8 rdata[DEFAULT_BLK_SZ]; u8 const *key = seed + DEFAULT_BLK_SZ; int rc; @@ -370,7 +339,7 @@ static int fips_cprng_reset(struct crypto_rng *tfm, u8 *seed, unsigned int slen) goto out; /* this primes our continuity test */ - rc = get_prng_bytes(rdata, DEFAULT_BLK_SZ, prng, 0); + rc = _get_more_prng_bytes(prng, false); prng->rand_read_pos = DEFAULT_BLK_SZ; out: -- 2.1.3