sw/device/silicon_creator/mask_rom/bootstrap.c - 3p/lowrisc/opentitan - Git at Google

 // Copyright lowRISC contributors.
 // Licensed under the Apache License, Version 2.0, see LICENSE for details.
 // SPDX-License-Identifier: Apache-2.0

 #include "sw/device/silicon_creator/mask_rom/bootstrap.h"

 #include <stdalign.h>

 #include "sw/device/lib/base/abs_mmio.h"
 #include "sw/device/lib/base/bitfield.h"
 #include "sw/device/lib/base/hardened.h"
 #include "sw/device/silicon_creator/lib/drivers/flash_ctrl.h"
 #include "sw/device/silicon_creator/lib/drivers/otp.h"
 #include "sw/device/silicon_creator/lib/drivers/rstmgr.h"
 #include "sw/device/silicon_creator/lib/drivers/spi_device.h"
 #include "sw/device/silicon_creator/lib/error.h"

 #include "flash_ctrl_regs.h"
 #include "gpio_regs.h"
 #include "hw/top_earlgrey/sw/autogen/top_earlgrey.h"
 #include "otp_ctrl_regs.h"

 enum {
   /*
    * Maximum flash address, exclusive.
    */
   kMaxAddress =
       FLASH_CTRL_PARAM_BYTES_PER_BANK * FLASH_CTRL_PARAM_REG_NUM_BANKS,
 };

 static_assert(FLASH_CTRL_PARAM_REG_NUM_BANKS == 2, "Flash must have 2 banks");

 /**
  * Bootstrap states.
  *
  * OpenTitan bootstrap consists of three states between which the chip
  * transitions sequentially.
  *
  * Encoding generated with
  * $ ./util/design/sparse-fsm-encode.py -d 5 -m 3 -n 32 \
  *     -s 375382971 --language=c
  *
  * Minimum Hamming distance: 17
  * Maximum Hamming distance: 19
  * Minimum Hamming weight: 16
  * Maximum Hamming weight: 19
  */
 typedef enum bootstrap_state {
   /**
    * Initial bootstrap state where the chip waits for a SECTOR_ERASE or
    * CHIP_ERASE command.
    */
   kBootstrapStateErase = 0xd4576543,
   /**
    * Second bootstrap state where the chip verifies that all data banks have
    * been erased.
    */
   kBootstrapStateEraseVerify = 0xf3c71bac,
   /**
    * Final bootstrap state. This is the main program loop where the chip handles
    * erase, program, and reset commands.
    */
   kBootstrapStateProgram = 0xbdd8ca60,
 } bootstrap_state_t;

 /**
  * Handles access permissions and erases both data banks of the embedded flash.
  *
  * @return Result of the operation.
  */
 static rom_error_t bootstrap_chip_erase(void) {
   flash_ctrl_bank_erase_perms_set(kHardenedBoolTrue);
   rom_error_t err_0 = flash_ctrl_data_erase(0, kFlashCtrlEraseTypeBank);
   rom_error_t err_1 = flash_ctrl_data_erase(FLASH_CTRL_PARAM_BYTES_PER_BANK,
                                             kFlashCtrlEraseTypeBank);
   flash_ctrl_bank_erase_perms_set(kHardenedBoolFalse);

   HARDENED_RETURN_IF_ERROR(err_0);
   return err_1;
 }

 /**
  * Handles access permissions and erases a 4 KiB region in the data partition of
  * the embedded flash.
  *
  * Since OpenTitan's flash page size is 2 KiB, this function erases two
  * consecutive pages.
  *
  * @param addr Address that falls within the 4 KiB region being deleted.
  * @return Result of the operation.
  */
 static rom_error_t bootstrap_sector_erase(uint32_t addr) {
   static_assert(FLASH_CTRL_PARAM_BYTES_PER_PAGE == 2048,
                 "Page size must be 2 KiB");
   enum {
     /**
      * Mask for truncating `addr` to the lower 4 KiB aligned address.
      */
     kPageAddrMask = ~UINT32_C(4096) + 1,
   };

   if (addr >= kMaxAddress) {
     return kErrorBootstrapEraseAddress;
   }
   addr &= kPageAddrMask;

   flash_ctrl_data_default_perms_set((flash_ctrl_perms_t){
       .read = kMultiBitBool4False,
       .write = kMultiBitBool4False,
       .erase = kMultiBitBool4True,
   });
   rom_error_t err_0 = flash_ctrl_data_erase(addr, kFlashCtrlEraseTypePage);
   rom_error_t err_1 = flash_ctrl_data_erase(
       addr + FLASH_CTRL_PARAM_BYTES_PER_PAGE, kFlashCtrlEraseTypePage);
   flash_ctrl_data_default_perms_set((flash_ctrl_perms_t){
       .read = kMultiBitBool4False,
       .write = kMultiBitBool4False,
       .erase = kMultiBitBool4False,
   });

   HARDENED_RETURN_IF_ERROR(err_0);
   return err_1;
 }

 /**
  * Handles access permissions and programs up to 256 bytes of flash memory
  * starting at `addr`.
  *
  * If `byte_count` is not a multiple of flash word size, it's rounded up to next
  * flash word and missing bytes in `data` are set to `0xff`.
  *
  * @param addr Address to write to, must be flash word aligned.
  * @param byte_count Number of bytes to write. Rounded up to next flash word if
  * not a multiple of flash word size. Missing bytes in `data` are set to `0xff`.
  * @param data Data to write, must be word aligned. If `byte_count` is not a
  * multiple of flash word size, `data` must have enough space until the next
  * flash word.
  * @return Result of the operation.
  */
 static rom_error_t bootstrap_page_program(uint32_t addr, size_t byte_count,
                                           uint8_t *data) {
   static_assert(__builtin_popcount(FLASH_CTRL_PARAM_BYTES_PER_WORD) == 1,
                 "Bytes per flash word must be a power of two.");
   enum {
     /**
      * Mask for checking that `addr` is flash word aligned.
      */
     kFlashWordMask = FLASH_CTRL_PARAM_BYTES_PER_WORD - 1,
     /**
      * SPI flash programming page size in bytes.
      */
     kFlashProgPageSize = 256,
     /**
      * Mask for checking whether `addr` is flash programming page aligned.
      *
      * Flash programming page size is 256 bytes, writes that start at an `addr`
      * with a non-zero LSB wrap to the start of the 256 byte region.
      */
     kFlashProgPageMask = kFlashProgPageSize - 1,
   };

   if (addr & kFlashWordMask || addr >= kMaxAddress) {
     return kErrorBootstrapProgramAddress;
   }

   // Round up to next flash word and fill missing bytes with `0xff`.
   size_t flash_word_misalignment = byte_count & kFlashWordMask;
   if (flash_word_misalignment > 0) {
     size_t padding_byte_count =
         FLASH_CTRL_PARAM_BYTES_PER_WORD - flash_word_misalignment;
     for (size_t i = 0; i < padding_byte_count; ++i) {
       data[byte_count++] = 0xff;
     }
   }
   size_t rem_word_count = byte_count / sizeof(uint32_t);

   flash_ctrl_data_default_perms_set((flash_ctrl_perms_t){
       .read = kMultiBitBool4False,
       .write = kMultiBitBool4True,
       .erase = kMultiBitBool4False,
   });
   // Wrap to the start of the flash programming page if `addr` is not aligned.
   rom_error_t err_0 = kErrorOk;
   size_t prog_page_misalignment = addr & kFlashProgPageMask;
   if (prog_page_misalignment > 0) {
     size_t word_count =
         (kFlashProgPageSize - prog_page_misalignment) / sizeof(uint32_t);
     err_0 = flash_ctrl_data_write(addr, word_count, data);
     rem_word_count -= word_count;
     data += word_count * sizeof(uint32_t);
     addr &= ~kFlashProgPageMask;
   }
   rom_error_t err_1 = kErrorOk;
   if (rem_word_count > 0) {
     err_1 = flash_ctrl_data_write(addr, rem_word_count, data);
   }
   flash_ctrl_data_default_perms_set((flash_ctrl_perms_t){
       .read = kMultiBitBool4False,
       .write = kMultiBitBool4False,
       .erase = kMultiBitBool4False,
   });

   HARDENED_RETURN_IF_ERROR(err_0);
   return err_1;
 }

 /**
  * Bootstrap state 1: Wait for an erase command and erase the data
  * partition.
  *
  * This function erases both data banks of the flash regardless of the type of
  * the erase command (CHIP_ERASE or SECTOR_ERASE).
  *
  * @param state Bootstrap state.
  * @return Result of the operation.
  */
 static rom_error_t bootstrap_handle_erase(bootstrap_state_t *state) {
   HARDENED_CHECK_EQ(*state, kBootstrapStateErase);

   spi_device_cmd_t cmd;
   RETURN_IF_ERROR(spi_device_cmd_get(&cmd));
   // Erase requires WREN, ignore if WEL is not set.
   if (!bitfield_bit32_read(spi_device_flash_status_get(), kSpiDeviceWelBit)) {
     return kErrorOk;
   }

   rom_error_t error = kErrorUnknown;
   switch (cmd.opcode) {
     case kSpiDeviceOpcodeChipErase:
     case kSpiDeviceOpcodeSectorErase:
       error = bootstrap_chip_erase();
       HARDENED_RETURN_IF_ERROR(error);
       *state = kBootstrapStateEraseVerify;
       break;
     default:
       // Ignore any other command, e.g. PAGE_PROGRAM, RESET.
       error = kErrorOk;
   }

   // Note: We clear WIP and WEN bits in `bootstrap_handle_erase_verify()` after
   // checking that both data banks have been erased.
   return error;
 }

 /**
  * Bootstrap state 2: Verify that all data banks have been erased.
  *
  * This function also clears the WIP and WEN bits of the flash status register.
  *
  * @param state Bootstrap state.
  * @return Result of the operation.
  */
 static rom_error_t bootstrap_handle_erase_verify(bootstrap_state_t *state) {
   HARDENED_CHECK_EQ(*state, kBootstrapStateEraseVerify);

   rom_error_t err_0 = flash_ctrl_data_erase_verify(0, kFlashCtrlEraseTypeBank);
   rom_error_t err_1 = flash_ctrl_data_erase_verify(
       FLASH_CTRL_PARAM_BYTES_PER_BANK, kFlashCtrlEraseTypeBank);
   HARDENED_RETURN_IF_ERROR(err_0);
   HARDENED_RETURN_IF_ERROR(err_1);

   *state = kBootstrapStateProgram;
   spi_device_flash_status_clear();
   return err_0;
 }

 /**
  * Bootstrap state 3: (Erase/)Program loop.
  *
  * @param state Bootstrap state.
  * @return Result of the operation.
  */
 static rom_error_t bootstrap_handle_program(bootstrap_state_t *state) {
   static_assert(alignof(spi_device_cmd_t) >= sizeof(uint32_t) &&
                     offsetof(spi_device_cmd_t, payload) >= sizeof(uint32_t),
                 "Payload must be word aligned.");
   static_assert(
       sizeof((spi_device_cmd_t){0}.payload) % FLASH_CTRL_PARAM_BYTES_PER_WORD ==
           0,
       "Payload size must be a multiple of flash word size.");

   HARDENED_CHECK_EQ(*state, kBootstrapStateProgram);

   spi_device_cmd_t cmd;
   RETURN_IF_ERROR(spi_device_cmd_get(&cmd));
   // Erase and program require WREN, ignore if WEL is not set.
   if (cmd.opcode != kSpiDeviceOpcodeReset &&
       !bitfield_bit32_read(spi_device_flash_status_get(), kSpiDeviceWelBit)) {
     return kErrorOk;
   }

   rom_error_t error = kErrorUnknown;
   switch (cmd.opcode) {
     case kSpiDeviceOpcodeChipErase:
       error = bootstrap_chip_erase();
       break;
     case kSpiDeviceOpcodeSectorErase:
       error = bootstrap_sector_erase(cmd.address);
       break;
     case kSpiDeviceOpcodePageProgram:
       error = bootstrap_page_program(cmd.address, cmd.payload_byte_count,
                                      cmd.payload);
       break;
     case kSpiDeviceOpcodeReset:
       rstmgr_reset();
 #ifdef OT_PLATFORM_RV32
       HARDENED_UNREACHABLE();
 #else
       // If this is an off-target test, return `kErrorUnknown` to be able to
       // test without requiring EXPECT_DEATH.
       error = kErrorUnknown;
 #endif
       break;
     default:
       // We don't expect any other commands but we can potentially end up
       // here with a 0x0 opcode due to glitches on SPI or strap lines (see
       // #11871).
       error = kErrorOk;
   }
   HARDENED_RETURN_IF_ERROR(error);

   spi_device_flash_status_clear();
   return error;
 }

 hardened_bool_t bootstrap_requested(void) {
   uint32_t res = otp_read32(OTP_CTRL_PARAM_ROM_BOOTSTRAP_EN_OFFSET);
   if (launder32(res) != kHardenedBoolTrue) {
     return kHardenedBoolFalse;
   }
   HARDENED_CHECK_EQ(res, kHardenedBoolTrue);

   // A single read is sufficient since we expect strong pull-ups on the strap
   // pins.
   res ^= kBootstrapPinMask;
   res ^=
       abs_mmio_read32(TOP_EARLGREY_GPIO_BASE_ADDR + GPIO_DATA_IN_REG_OFFSET) &
       kBootstrapPinMask;
   if (launder32(res) != kHardenedBoolTrue) {
     return kHardenedBoolFalse;
   }
   HARDENED_CHECK_EQ(res, kHardenedBoolTrue);
   return res;
 }

 rom_error_t bootstrap(void) {
   hardened_bool_t requested = bootstrap_requested();
   if (launder32(requested) != kHardenedBoolTrue) {
     return kErrorBootstrapNotRequested;
   }
   HARDENED_CHECK_EQ(requested, kHardenedBoolTrue);

   spi_device_init();

   // Bootstrap event loop.
   bootstrap_state_t state = kBootstrapStateErase;
   rom_error_t error = kErrorUnknown;
   while (true) {
     switch (launder32(state)) {
       case kBootstrapStateErase:
         HARDENED_CHECK_EQ(state, kBootstrapStateErase);
         error = bootstrap_handle_erase(&state);
         break;
       case kBootstrapStateEraseVerify:
         HARDENED_CHECK_EQ(state, kBootstrapStateEraseVerify);
         error = bootstrap_handle_erase_verify(&state);
         break;
       case kBootstrapStateProgram:
         HARDENED_CHECK_EQ(state, kBootstrapStateProgram);
         error = bootstrap_handle_program(&state);
         break;
       default:
         error = kErrorBootstrapInvalidState;
     }
     HARDENED_RETURN_IF_ERROR(error);
   }
   HARDENED_UNREACHABLE();
 }
	// Copyright lowRISC contributors.
	// Licensed under the Apache License, Version 2.0, see LICENSE for details.
	// SPDX-License-Identifier: Apache-2.0

	#include "sw/device/silicon_creator/mask_rom/bootstrap.h"

	#include <stdalign.h>

	#include "sw/device/lib/base/abs_mmio.h"
	#include "sw/device/lib/base/bitfield.h"
	#include "sw/device/lib/base/hardened.h"
	#include "sw/device/silicon_creator/lib/drivers/flash_ctrl.h"
	#include "sw/device/silicon_creator/lib/drivers/otp.h"
	#include "sw/device/silicon_creator/lib/drivers/rstmgr.h"
	#include "sw/device/silicon_creator/lib/drivers/spi_device.h"
	#include "sw/device/silicon_creator/lib/error.h"

	#include "flash_ctrl_regs.h"
	#include "gpio_regs.h"
	#include "hw/top_earlgrey/sw/autogen/top_earlgrey.h"
	#include "otp_ctrl_regs.h"

	enum {
	/*
	* Maximum flash address, exclusive.
	*/
	kMaxAddress =
	FLASH_CTRL_PARAM_BYTES_PER_BANK * FLASH_CTRL_PARAM_REG_NUM_BANKS,
	};

	static_assert(FLASH_CTRL_PARAM_REG_NUM_BANKS == 2, "Flash must have 2 banks");

	/**
	* Bootstrap states.
	*
	* OpenTitan bootstrap consists of three states between which the chip
	* transitions sequentially.
	*
	* Encoding generated with
	* $ ./util/design/sparse-fsm-encode.py -d 5 -m 3 -n 32 \
	* -s 375382971 --language=c
	*
	* Minimum Hamming distance: 17
	* Maximum Hamming distance: 19
	* Minimum Hamming weight: 16
	* Maximum Hamming weight: 19
	*/
	typedef enum bootstrap_state {
	/**
	* Initial bootstrap state where the chip waits for a SECTOR_ERASE or
	* CHIP_ERASE command.
	*/
	kBootstrapStateErase = 0xd4576543,
	/**
	* Second bootstrap state where the chip verifies that all data banks have
	* been erased.
	*/
	kBootstrapStateEraseVerify = 0xf3c71bac,
	/**
	* Final bootstrap state. This is the main program loop where the chip handles
	* erase, program, and reset commands.
	*/
	kBootstrapStateProgram = 0xbdd8ca60,
	} bootstrap_state_t;

	/**
	* Handles access permissions and erases both data banks of the embedded flash.
	*
	* @return Result of the operation.
	*/
	static rom_error_t bootstrap_chip_erase(void) {
	flash_ctrl_bank_erase_perms_set(kHardenedBoolTrue);
	rom_error_t err_0 = flash_ctrl_data_erase(0, kFlashCtrlEraseTypeBank);
	rom_error_t err_1 = flash_ctrl_data_erase(FLASH_CTRL_PARAM_BYTES_PER_BANK,
	kFlashCtrlEraseTypeBank);
	flash_ctrl_bank_erase_perms_set(kHardenedBoolFalse);

	HARDENED_RETURN_IF_ERROR(err_0);
	return err_1;
	}

	/**
	* Handles access permissions and erases a 4 KiB region in the data partition of
	* the embedded flash.
	*
	* Since OpenTitan's flash page size is 2 KiB, this function erases two
	* consecutive pages.
	*
	* @param addr Address that falls within the 4 KiB region being deleted.
	* @return Result of the operation.
	*/
	static rom_error_t bootstrap_sector_erase(uint32_t addr) {
	static_assert(FLASH_CTRL_PARAM_BYTES_PER_PAGE == 2048,
	"Page size must be 2 KiB");
	enum {
	/**
	* Mask for truncating `addr` to the lower 4 KiB aligned address.
	*/
	kPageAddrMask = ~UINT32_C(4096) + 1,
	};

	if (addr >= kMaxAddress) {
	return kErrorBootstrapEraseAddress;
	}
	addr &= kPageAddrMask;

	flash_ctrl_data_default_perms_set((flash_ctrl_perms_t){
	.read = kMultiBitBool4False,
	.write = kMultiBitBool4False,
	.erase = kMultiBitBool4True,
	});
	rom_error_t err_0 = flash_ctrl_data_erase(addr, kFlashCtrlEraseTypePage);
	rom_error_t err_1 = flash_ctrl_data_erase(
	addr + FLASH_CTRL_PARAM_BYTES_PER_PAGE, kFlashCtrlEraseTypePage);
	flash_ctrl_data_default_perms_set((flash_ctrl_perms_t){
	.read = kMultiBitBool4False,
	.write = kMultiBitBool4False,
	.erase = kMultiBitBool4False,
	});

	HARDENED_RETURN_IF_ERROR(err_0);
	return err_1;
	}

	/**
	* Handles access permissions and programs up to 256 bytes of flash memory
	* starting at `addr`.
	*
	* If `byte_count` is not a multiple of flash word size, it's rounded up to next
	* flash word and missing bytes in `data` are set to `0xff`.
	*
	* @param addr Address to write to, must be flash word aligned.
	* @param byte_count Number of bytes to write. Rounded up to next flash word if
	* not a multiple of flash word size. Missing bytes in `data` are set to `0xff`.
	* @param data Data to write, must be word aligned. If `byte_count` is not a
	* multiple of flash word size, `data` must have enough space until the next
	* flash word.
	* @return Result of the operation.
	*/
	static rom_error_t bootstrap_page_program(uint32_t addr, size_t byte_count,
	uint8_t *data) {
	static_assert(__builtin_popcount(FLASH_CTRL_PARAM_BYTES_PER_WORD) == 1,
	"Bytes per flash word must be a power of two.");
	enum {
	/**
	* Mask for checking that `addr` is flash word aligned.
	*/
	kFlashWordMask = FLASH_CTRL_PARAM_BYTES_PER_WORD - 1,
	/**
	* SPI flash programming page size in bytes.
	*/
	kFlashProgPageSize = 256,
	/**
	* Mask for checking whether `addr` is flash programming page aligned.
	*
	* Flash programming page size is 256 bytes, writes that start at an `addr`
	* with a non-zero LSB wrap to the start of the 256 byte region.
	*/
	kFlashProgPageMask = kFlashProgPageSize - 1,
	};

	if (addr & kFlashWordMask \|\| addr >= kMaxAddress) {
	return kErrorBootstrapProgramAddress;
	}

	// Round up to next flash word and fill missing bytes with `0xff`.
	size_t flash_word_misalignment = byte_count & kFlashWordMask;
	if (flash_word_misalignment > 0) {
	size_t padding_byte_count =
	FLASH_CTRL_PARAM_BYTES_PER_WORD - flash_word_misalignment;
	for (size_t i = 0; i < padding_byte_count; ++i) {
	data[byte_count++] = 0xff;
	}
	}
	size_t rem_word_count = byte_count / sizeof(uint32_t);

	flash_ctrl_data_default_perms_set((flash_ctrl_perms_t){
	.read = kMultiBitBool4False,
	.write = kMultiBitBool4True,
	.erase = kMultiBitBool4False,
	});
	// Wrap to the start of the flash programming page if `addr` is not aligned.
	rom_error_t err_0 = kErrorOk;
	size_t prog_page_misalignment = addr & kFlashProgPageMask;
	if (prog_page_misalignment > 0) {
	size_t word_count =
	(kFlashProgPageSize - prog_page_misalignment) / sizeof(uint32_t);
	err_0 = flash_ctrl_data_write(addr, word_count, data);
	rem_word_count -= word_count;
	data += word_count * sizeof(uint32_t);
	addr &= ~kFlashProgPageMask;
	}
	rom_error_t err_1 = kErrorOk;
	if (rem_word_count > 0) {
	err_1 = flash_ctrl_data_write(addr, rem_word_count, data);
	}
	flash_ctrl_data_default_perms_set((flash_ctrl_perms_t){
	.read = kMultiBitBool4False,
	.write = kMultiBitBool4False,
	.erase = kMultiBitBool4False,
	});

	HARDENED_RETURN_IF_ERROR(err_0);
	return err_1;
	}

	/**
	* Bootstrap state 1: Wait for an erase command and erase the data
	* partition.
	*
	* This function erases both data banks of the flash regardless of the type of
	* the erase command (CHIP_ERASE or SECTOR_ERASE).
	*
	* @param state Bootstrap state.
	* @return Result of the operation.
	*/
	static rom_error_t bootstrap_handle_erase(bootstrap_state_t *state) {
	HARDENED_CHECK_EQ(*state, kBootstrapStateErase);

	spi_device_cmd_t cmd;
	RETURN_IF_ERROR(spi_device_cmd_get(&cmd));
	// Erase requires WREN, ignore if WEL is not set.
	if (!bitfield_bit32_read(spi_device_flash_status_get(), kSpiDeviceWelBit)) {
	return kErrorOk;
	}

	rom_error_t error = kErrorUnknown;
	switch (cmd.opcode) {
	case kSpiDeviceOpcodeChipErase:
	case kSpiDeviceOpcodeSectorErase:
	error = bootstrap_chip_erase();
	HARDENED_RETURN_IF_ERROR(error);
	*state = kBootstrapStateEraseVerify;
	break;
	default:
	// Ignore any other command, e.g. PAGE_PROGRAM, RESET.
	error = kErrorOk;
	}

	// Note: We clear WIP and WEN bits in `bootstrap_handle_erase_verify()` after
	// checking that both data banks have been erased.
	return error;
	}

	/**
	* Bootstrap state 2: Verify that all data banks have been erased.
	*
	* This function also clears the WIP and WEN bits of the flash status register.
	*
	* @param state Bootstrap state.
	* @return Result of the operation.
	*/
	static rom_error_t bootstrap_handle_erase_verify(bootstrap_state_t *state) {
	HARDENED_CHECK_EQ(*state, kBootstrapStateEraseVerify);

	rom_error_t err_0 = flash_ctrl_data_erase_verify(0, kFlashCtrlEraseTypeBank);
	rom_error_t err_1 = flash_ctrl_data_erase_verify(
	FLASH_CTRL_PARAM_BYTES_PER_BANK, kFlashCtrlEraseTypeBank);
	HARDENED_RETURN_IF_ERROR(err_0);
	HARDENED_RETURN_IF_ERROR(err_1);

	*state = kBootstrapStateProgram;
	spi_device_flash_status_clear();
	return err_0;
	}

	/**
	* Bootstrap state 3: (Erase/)Program loop.
	*
	* @param state Bootstrap state.
	* @return Result of the operation.
	*/
	static rom_error_t bootstrap_handle_program(bootstrap_state_t *state) {
	static_assert(alignof(spi_device_cmd_t) >= sizeof(uint32_t) &&
	offsetof(spi_device_cmd_t, payload) >= sizeof(uint32_t),
	"Payload must be word aligned.");
	static_assert(
	sizeof((spi_device_cmd_t){0}.payload) % FLASH_CTRL_PARAM_BYTES_PER_WORD ==
	0,
	"Payload size must be a multiple of flash word size.");

	HARDENED_CHECK_EQ(*state, kBootstrapStateProgram);

	spi_device_cmd_t cmd;
	RETURN_IF_ERROR(spi_device_cmd_get(&cmd));
	// Erase and program require WREN, ignore if WEL is not set.
	if (cmd.opcode != kSpiDeviceOpcodeReset &&
	!bitfield_bit32_read(spi_device_flash_status_get(), kSpiDeviceWelBit)) {
	return kErrorOk;
	}

	rom_error_t error = kErrorUnknown;
	switch (cmd.opcode) {
	case kSpiDeviceOpcodeChipErase:
	error = bootstrap_chip_erase();
	break;
	case kSpiDeviceOpcodeSectorErase:
	error = bootstrap_sector_erase(cmd.address);
	break;
	case kSpiDeviceOpcodePageProgram:
	error = bootstrap_page_program(cmd.address, cmd.payload_byte_count,
	cmd.payload);
	break;
	case kSpiDeviceOpcodeReset:
	rstmgr_reset();
	#ifdef OT_PLATFORM_RV32
	HARDENED_UNREACHABLE();
	#else
	// If this is an off-target test, return `kErrorUnknown` to be able to
	// test without requiring EXPECT_DEATH.
	error = kErrorUnknown;
	#endif
	break;
	default:
	// We don't expect any other commands but we can potentially end up
	// here with a 0x0 opcode due to glitches on SPI or strap lines (see
	// #11871).
	error = kErrorOk;
	}
	HARDENED_RETURN_IF_ERROR(error);

	spi_device_flash_status_clear();
	return error;
	}

	hardened_bool_t bootstrap_requested(void) {
	uint32_t res = otp_read32(OTP_CTRL_PARAM_ROM_BOOTSTRAP_EN_OFFSET);
	if (launder32(res) != kHardenedBoolTrue) {
	return kHardenedBoolFalse;
	}
	HARDENED_CHECK_EQ(res, kHardenedBoolTrue);

	// A single read is sufficient since we expect strong pull-ups on the strap
	// pins.
	res ^= kBootstrapPinMask;
	res ^=
	abs_mmio_read32(TOP_EARLGREY_GPIO_BASE_ADDR + GPIO_DATA_IN_REG_OFFSET) &
	kBootstrapPinMask;
	if (launder32(res) != kHardenedBoolTrue) {
	return kHardenedBoolFalse;
	}
	HARDENED_CHECK_EQ(res, kHardenedBoolTrue);
	return res;
	}

	rom_error_t bootstrap(void) {
	hardened_bool_t requested = bootstrap_requested();
	if (launder32(requested) != kHardenedBoolTrue) {
	return kErrorBootstrapNotRequested;
	}
	HARDENED_CHECK_EQ(requested, kHardenedBoolTrue);

	spi_device_init();

	// Bootstrap event loop.
	bootstrap_state_t state = kBootstrapStateErase;
	rom_error_t error = kErrorUnknown;
	while (true) {
	switch (launder32(state)) {
	case kBootstrapStateErase:
	HARDENED_CHECK_EQ(state, kBootstrapStateErase);
	error = bootstrap_handle_erase(&state);
	break;
	case kBootstrapStateEraseVerify:
	HARDENED_CHECK_EQ(state, kBootstrapStateEraseVerify);
	error = bootstrap_handle_erase_verify(&state);
	break;
	case kBootstrapStateProgram:
	HARDENED_CHECK_EQ(state, kBootstrapStateProgram);
	error = bootstrap_handle_program(&state);
	break;
	default:
	error = kErrorBootstrapInvalidState;
	}
	HARDENED_RETURN_IF_ERROR(error);
	}
	HARDENED_UNREACHABLE();
	}