// (c) Copyright 2018 by Coinkite Inc. This file is part of Coldcard <coldcardwallet.com>
// and is covered by GPLv3 license found in COPYING.
//
#pragma once
#include <stdint.h>

// Our simple firmware header.
//
// Although called a header, this data is placed into the middle of the binary.
// It is located at start of firmware + 16k - sizeof(heaer). This is a gap unused in normal
// micropython layout. Exactly the last 64 bytes (signature) should be left out of
// the checksum. We do checksum areas beyond the end of the last byte of firmware (up to length)
// and expect those regions to be unprogrammed flash (ones).
//
// - timestamp must increase with each upgrade (downgrade protection)
// - version_string is for humans only
// - pubkey_num indicates which pubkey was used for signature
// - firmware_length, must be:
//      - bigger than minimum length, less than max
//      - 512-byte aligned
//  - bootloader assumes the flash filesystem (FAT FS) follows the firmware.
//  - this C header file is somewhat parsed and used by python signature-adding code
//  - timestamp is YYMMDDHHMMSS0000 in BCD
//

typedef struct {
    uint32_t    magic_value;            // fixed magic value
    uint8_t     timestamp[8];           // for downgrade protection, this must increase
    uint8_t     version_string[8];      // zero-terminated string: "1.0.0ab7" for humans
    uint32_t    pubkey_num;             // which pubkey was used to sign binary
    uint32_t    firmware_length;        // must be 512-aligned, and marks start of flash filesystem
    uint32_t    install_flags;          // flags about this release
    uint32_t    future[8];              // reserved words
    uint8_t     signature[64];          // signature over secp256k1
} coldcardFirmwareHeader_t;

#define FW_HEADER_SIZE       128
#define FW_HEADER_OFFSET     (0x4000-FW_HEADER_SIZE)

#define FW_HEADER_MAGIC      0xCC001234

// Firmware Image Size

// arbitrary min size
#define FW_MIN_LENGTH        (256*1024)

// absolute max size: 1MB flash - 32k for bootloader
// practical limit for our-protocol USB upgrades: 786432 (or else settings damaged)
#define FW_MAX_LENGTH        (0x100000 - 0x8000)

// Arguments to be used w/ python's struct module.
#define FWH_PY_FORMAT      "<I8s8sIII32s64s"
#define FWH_PY_VALUES      "magic_value timestamp version_string pubkey_num firmware_length install_flags future signature"
#define FWH_NUM_FUTURE      8
#define FWH_PK_NUM_OFFSET   20

// Bits in install_flags
#define FWHIF_HIGH_WATER        0x01

// There is a copy of the header at this location in RAM, copied by bootloader
// **after** it has been verified. If you write to this memory area, you will be reset!
#define RAM_HEADER_BASE          0x10007c20

// Original copy of header, as recorded in flash/firmware file.
#define FLASH_HEADER_BASE        0x0800bf80

// One 32-bit word of flags from bootloader about how we got here (in protected RAM)
#define RAM_BOOT_FLAGS           (RAM_HEADER_BASE+FW_HEADER_SIZE)

// Bitmask for RAM_BOOT_FLAGS
// - just did the SPI->flash copy on this bootup?
#define RBF_FRESH_VERSION      0x01
// - factory mode: flash not yet locked-down
#define RBF_FACTORY_MODE       0x02