kaspar/RIOT
1
0
Fork 0
mirror of https://github.com/RIOT-OS/RIOT.git synced 2025-12-16 18:13:49 +01:00
Code Releases Activity

cpu/esp32/periph/hwrng: enable/disable bootloader RNG

Browse Source 
If the ADC SAR is used, the Bootloader RNG must not be enabled before the random numbers are actually required. The reason is that the Bootloader RNG uses the noise of the ADC SAR reference voltage as a non-RF entropy source. The calibration of the ADC SAR does not work correctly in this case. Therefore, the Bootloader RNG is only enabled if random numbers are really required.
This commit is contained in:
Gunar Schorcht 2025-04-29 12:23:21 +02:00
parent 47a8947720
commit 7adb50b901
1 changed files with 19 additions and 17 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

36
cpu/esp32/periph/hwrng.c
View File

@ -25,25 +25,15 @@
#include "bootloader_random.h"
#include "esp_random.h"
#include "soc/wdev_reg.h"
#define RNG_DATA_REG (*(volatile uint32_t *)RNG_DATA_REG_ADDR)
void hwrng_init(void)
{
if (!IS_USED(MODULE_WIFI_ANY)) {
/*
* The hardware RNG generates random numbers uses the noise in the
* RF system of the WiFi or the BT interface as entropy source.
* If both are disabled, the random number generator just returns
* pseudo-random numbers.
* However, the bootloader use an internal non-RF entropy source,
* the internal reference voltage noise. This can be re-enabled
* after startup as entropy source for applications that don't
* use the WiFi or the BT interface.
*/
bootloader_random_enable();
}
/* If the ADC SAR is used, the Bootloader RNG must not be enabled before
* the random numbers are actually required. The reason is that the
* Bootloader RNG uses the noise of the ADC SAR reference voltage as
* a non-RF entropy source. The calibration of the ADC SAR does not
* work correctly in this case. Therefore, the Bootloader RNG is only
* enabled if random numbers are really required. */
}
/**
@ -56,10 +46,22 @@ void hwrng_init(void)
*/
void hwrng_read(void *buf, unsigned int num)
{
if (!IS_USED(MODULE_ESP_WIFI_ANY) && !IS_USED(MODULE_ESP_BLE)) {
/* enable the Bootloader RNG if WiFi and BT are not used */
bootloader_random_enable();
}
esp_fill_random(buf, num);
if (!IS_USED(MODULE_ESP_WIFI_ANY) && !IS_USED(MODULE_ESP_BLE)) {
/* disable the Bootloader RNG to ensure that ADC SAR calibration works */
bootloader_random_disable();
}
}
uint32_t hwrand(void)
{
return esp_random();
uint32_t rand;
hwrng_read(&rand, 4);
return rand;
}