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esp32: Enable flash encryption by setting FLASH_CRYPT_CNT to max

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Previous method was to write-protect this efuse, however on ECO3
the write protect field also covers the UART_DOWNLOAD_DIS efuse.

Doing it this way keeps the possibility of disabling UART download
mode, later.
This commit is contained in:
Angus Gratton 2020-03-30 17:59:33 +11:00 committed by Angus Gratton
parent 7c34711c07
commit c17d55eb9b
1 changed files with 8 additions and 5 deletions
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13
components/bootloader_support/src/esp32/flash_encrypt.c
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@ -221,16 +221,19 @@ static esp_err_t encrypt_flash_contents(uint32_t flash_crypt_cnt, bool flash_cry
ESP_LOGD(TAG, "All flash regions checked for encryption pass");
uint32_t new_flash_crypt_cnt;
#ifdef CONFIG_SECURE_FLASH_ENCRYPTION_MODE_RELEASE
// Go straight to max, permanently enabled
ESP_LOGI(TAG, "Setting FLASH_CRYPT_CNT for permanent encryption");
new_flash_crypt_cnt = EFUSE_FLASH_CRYPT_CNT;
#else
/* Set least significant 0-bit in flash_crypt_cnt */
int ffs_inv = __builtin_ffs((~flash_crypt_cnt) & EFUSE_RD_FLASH_CRYPT_CNT);
/* ffs_inv shouldn't be zero, as zero implies flash_crypt_cnt == EFUSE_RD_FLASH_CRYPT_CNT (0x7F) */
uint32_t new_flash_crypt_cnt = flash_crypt_cnt + (1 << (ffs_inv - 1));
new_flash_crypt_cnt = flash_crypt_cnt + (1 << (ffs_inv - 1));
#endif
ESP_LOGD(TAG, "FLASH_CRYPT_CNT 0x%x -> 0x%x", flash_crypt_cnt, new_flash_crypt_cnt);
uint32_t wdata0_reg = ((new_flash_crypt_cnt & EFUSE_FLASH_CRYPT_CNT) << EFUSE_FLASH_CRYPT_CNT_S);
#ifdef CONFIG_SECURE_FLASH_ENCRYPTION_MODE_RELEASE
ESP_LOGI(TAG, "Write protecting FLASH_CRYPT_CNT eFuse");
wdata0_reg |= EFUSE_WR_DIS_FLASH_CRYPT_CNT;
#endif
REG_WRITE(EFUSE_BLK0_WDATA0_REG, wdata0_reg);
esp_efuse_burn_new_values();