esp-idf/components/bootloader_support/src/bootloader_random.c
Angus Gratton 420aef1ffe Updates for riscv support
* Target components pull in xtensa component directly
* Use CPU HAL where applicable
* Remove unnecessary xtensa headers
* Compilation changes necessary to support non-xtensa gcc types (ie int32_t/uint32_t is no
  longer signed/unsigned int).

Changes come from internal branch commit a6723fc
2020-11-13 07:49:11 +11:00

58 lines
1.9 KiB
C

// Copyright 2010-2020 Espressif Systems (Shanghai) PTE LTD
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
#include "sdkconfig.h"
#include "bootloader_random.h"
#include "hal/cpu_hal.h"
#include "soc/wdev_reg.h"
#ifndef BOOTLOADER_BUILD
#include "esp_system.h"
#include "driver/periph_ctrl.h"
__attribute__((weak)) void bootloader_fill_random(void *buffer, size_t length)
{
return esp_fill_random(buffer, length);
}
#else
__attribute__((weak)) void bootloader_fill_random(void *buffer, size_t length)
{
uint8_t *buffer_bytes = (uint8_t *)buffer;
uint32_t random;
uint32_t start, now;
assert(buffer != NULL);
for (int i = 0; i < length; i++) {
if (i == 0 || i % 4 == 0) { /* redundant check is for a compiler warning */
/* in bootloader with ADC feeding HWRNG, we accumulate 1
bit of entropy per 40 APB cycles (==80 CPU cycles.)
To avoid reading the entire RNG hardware state out
as-is, we repeatedly read the RNG register and XOR all
values.
*/
random = REG_READ(WDEV_RND_REG);
start = cpu_hal_get_cycle_count();
do {
random ^= REG_READ(WDEV_RND_REG);
now = cpu_hal_get_cycle_count();
} while (now - start < 80 * 32 * 2); /* extra factor of 2 is precautionary */
}
buffer_bytes[i] = random >> ((i % 4) * 8);
}
}
#endif // BOOTLOADER_BUILD