refactor(trng): cleanup the existing TRNG support
This patch adds the following changes to complete the existing
TRNG implementation:
1. Adds a feature specific scope for buildlog generation.
2. Updates the docs on the build flag "TRNG_SUPPORT" and its values.
3. Makefile update and improves the existing comments at few sections
for better understanding of the underlying logic.
Change-Id: I3f72f0ccd5c94005a2df87158cf23199d2160d37
Signed-off-by: Jayanth Dodderi Chidanand <jayanthdodderi.chidanand@arm.com>
diff --git a/services/std_svc/std_svc_setup.c b/services/std_svc/std_svc_setup.c
index 08d16e2..2884a3b 100644
--- a/services/std_svc/std_svc_setup.c
+++ b/services/std_svc/std_svc_setup.c
@@ -74,7 +74,10 @@
sdei_init();
#endif
+#if TRNG_SUPPORT
+ /* TRNG initialisation */
trng_setup();
+#endif /* TRNG_SUPPORT */
#if DRTM_SUPPORT
if (drtm_setup() != 0) {
@@ -172,7 +175,8 @@
return trng_smc_handler(smc_fid, x1, x2, x3, x4, cookie, handle,
flags);
}
-#endif
+#endif /* TRNG_SUPPORT */
+
#if ENABLE_RME
if (is_rmmd_el3_fid(smc_fid)) {
diff --git a/services/std_svc/trng/trng_entropy_pool.c b/services/std_svc/trng/trng_entropy_pool.c
index ac13b1d..30105b3 100644
--- a/services/std_svc/trng/trng_entropy_pool.c
+++ b/services/std_svc/trng/trng_entropy_pool.c
@@ -1,5 +1,5 @@
/*
- * Copyright (c) 2021, ARM Limited. All rights reserved.
+ * Copyright (c) 2021-2022, ARM Limited. All rights reserved.
*
* SPDX-License-Identifier: BSD-3-Clause
*/
@@ -18,7 +18,7 @@
* 192 bits of entropy, we don't have to throw out the leftover 1-63 bits of
* entropy.
*/
-#define WORDS_IN_POOL (4)
+#define WORDS_IN_POOL (4)
static uint64_t entropy[WORDS_IN_POOL];
/* index in bits of the first bit of usable entropy */
static uint32_t entropy_bit_index;
@@ -27,14 +27,14 @@
static spinlock_t trng_pool_lock;
-#define BITS_PER_WORD (sizeof(entropy[0]) * 8)
-#define BITS_IN_POOL (WORDS_IN_POOL * BITS_PER_WORD)
-#define ENTROPY_MIN_WORD (entropy_bit_index / BITS_PER_WORD)
-#define ENTROPY_FREE_BIT (entropy_bit_size + entropy_bit_index)
-#define _ENTROPY_FREE_WORD (ENTROPY_FREE_BIT / BITS_PER_WORD)
-#define ENTROPY_FREE_INDEX (_ENTROPY_FREE_WORD % WORDS_IN_POOL)
+#define BITS_PER_WORD (sizeof(entropy[0]) * 8)
+#define BITS_IN_POOL (WORDS_IN_POOL * BITS_PER_WORD)
+#define ENTROPY_MIN_WORD (entropy_bit_index / BITS_PER_WORD)
+#define ENTROPY_FREE_BIT (entropy_bit_size + entropy_bit_index)
+#define _ENTROPY_FREE_WORD (ENTROPY_FREE_BIT / BITS_PER_WORD)
+#define ENTROPY_FREE_INDEX (_ENTROPY_FREE_WORD % WORDS_IN_POOL)
/* ENTROPY_WORD_INDEX(0) includes leftover bits in the lower bits */
-#define ENTROPY_WORD_INDEX(i) ((ENTROPY_MIN_WORD + i) % WORDS_IN_POOL)
+#define ENTROPY_WORD_INDEX(i) ((ENTROPY_MIN_WORD + i) % WORDS_IN_POOL)
/*
* Fill the entropy pool until we have at least as many bits as requested.
@@ -65,12 +65,12 @@
*/
bool trng_pack_entropy(uint32_t nbits, uint64_t *out)
{
- bool success = true;
+ bool ret = true;
spin_lock(&trng_pool_lock);
if (!trng_fill_entropy(nbits)) {
- success = false;
+ ret = false;
goto out;
}
@@ -82,9 +82,8 @@
for (word_i = 0; word_i < to_fill; word_i++) {
/*
* Repack the entropy from the pool into the passed in out
- * buffer. This takes the lower bits from the valid upper bits
- * of word_i and the upper bits from the lower bits of
- * (word_i + 1).
+ * buffer. This takes lesser bits from the valid upper bits
+ * of word_i and more bits from the lower bits of (word_i + 1).
*
* I found the following diagram useful. note: `e` represents
* valid entropy, ` ` represents invalid bits (not entropy) and
@@ -136,7 +135,7 @@
out:
spin_unlock(&trng_pool_lock);
- return success;
+ return ret;
}
void trng_entropy_pool_setup(void)
diff --git a/services/std_svc/trng/trng_main.c b/services/std_svc/trng/trng_main.c
index 38aa649..90098a8 100644
--- a/services/std_svc/trng/trng_main.c
+++ b/services/std_svc/trng/trng_main.c
@@ -1,5 +1,5 @@
/*
- * Copyright (c) 2021, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2021-2022, ARM Limited and Contributors. All rights reserved.
*
* SPDX-License-Identifier: BSD-3-Clause
*/
@@ -23,9 +23,9 @@
static uintptr_t trng_rnd32(uint32_t nbits, void *handle)
{
uint32_t mask = ~0U;
- uint64_t ent[2];
+ uint64_t ent[2] = {0};
- if (nbits == 0U || nbits > 96U) {
+ if (nbits == 0U || nbits > TRNG_RND32_ENTROPY_MAXBITS) {
SMC_RET1(handle, TRNG_E_INVALID_PARAMS);
}
@@ -59,9 +59,9 @@
static uintptr_t trng_rnd64(uint32_t nbits, void *handle)
{
uint64_t mask = ~0ULL;
- uint64_t ent[3];
+ uint64_t ent[3] = {0};
- if (nbits == 0U || nbits > 192U) {
+ if (nbits == 0U || nbits > TRNG_RND64_ENTROPY_MAXBITS) {
SMC_RET1(handle, TRNG_E_INVALID_PARAMS);
}
@@ -117,9 +117,9 @@
switch (smc_fid) {
case ARM_TRNG_VERSION:
SMC_RET1(handle, MAKE_SMCCC_VERSION(
- TRNG_VERSION_MAJOR, TRNG_VERSION_MINOR
- ));
+ TRNG_VERSION_MAJOR, TRNG_VERSION_MINOR));
break; /* unreachable */
+
case ARM_TRNG_FEATURES:
if (is_trng_fid((uint32_t)x1)) {
SMC_RET1(handle, TRNG_E_SUCCESS);
@@ -127,16 +127,19 @@
SMC_RET1(handle, TRNG_E_NOT_SUPPORTED);
}
break; /* unreachable */
+
case ARM_TRNG_GET_UUID:
SMC_UUID_RET(handle, plat_trng_uuid);
break; /* unreachable */
+
case ARM_TRNG_RND32:
return trng_rnd32((uint32_t)x1, handle);
+
case ARM_TRNG_RND64:
return trng_rnd64((uint32_t)x1, handle);
+
default:
- WARN("Unimplemented TRNG Service Call: 0x%x\n",
- smc_fid);
+ WARN("Unimplemented TRNG Service Call: 0x%x\n", smc_fid);
SMC_RET1(handle, TRNG_E_NOT_IMPLEMENTED);
break; /* unreachable */
}