pico-keys-sdk/src/fs/flash.c

/*
 * This file is part of the Pico HSM SDK distribution (https://github.com/polhenarejos/pico-hsm-sdk).
 * Copyright (c) 2022 Pol Henarejos.
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, version 3.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program. If not, see <http://www.gnu.org/licenses/>.
 */


#include <stdint.h>
#include <string.h>

#include "pico/stdlib.h"
#include "hardware/flash.h"
#include "hsm.h"
#include "file.h"

/*
 * ------------------------------------------------------
 * |                                                    |
 * | next_addr | prev_addr | fid | data (len + payload) |
 * |                                                    |
 * ------------------------------------------------------
 */
#define FLASH_TARGET_OFFSET (PICO_FLASH_SIZE_BYTES >> 1) // DATA starts at the mid of flash
#define FLASH_DATA_HEADER_SIZE (sizeof(uintptr_t)+sizeof(uint32_t))
#define FLASH_PERMANENT_REGION (4*FLASH_SECTOR_SIZE) // 4 sectors (16kb) of permanent memory

//To avoid possible future allocations, data region starts at the end of flash and goes upwards to the center region

const uintptr_t start_data_pool = (XIP_BASE + FLASH_TARGET_OFFSET);
const uintptr_t end_data_pool = (XIP_BASE + PICO_FLASH_SIZE_BYTES)-FLASH_DATA_HEADER_SIZE-FLASH_PERMANENT_REGION-FLASH_DATA_HEADER_SIZE-4; //This is a fixed value. DO NOT CHANGE
const uintptr_t end_rom_pool = (XIP_BASE + PICO_FLASH_SIZE_BYTES)-FLASH_DATA_HEADER_SIZE-4; //This is a fixed value. DO NOT CHANGE
const uintptr_t start_rom_pool = (XIP_BASE + PICO_FLASH_SIZE_BYTES)-FLASH_DATA_HEADER_SIZE-FLASH_PERMANENT_REGION; //This is a fixed value. DO NOT CHANGE

extern int flash_program_block(uintptr_t addr, const uint8_t *data, size_t len);
extern int flash_program_halfword (uintptr_t addr, uint16_t data);
extern int flash_program_uintptr(uintptr_t, uintptr_t);
extern uintptr_t flash_read_uintptr(uintptr_t addr);
extern uint16_t flash_read_uint16(uintptr_t addr);

extern void low_flash_available();

uintptr_t allocate_free_addr(uint16_t size, bool persistent) {
    if (size > FLASH_SECTOR_SIZE)
        return 0x0; //ERROR
    size_t real_size = size+sizeof(uint16_t)+sizeof(uintptr_t)+sizeof(uint16_t)+sizeof(uintptr_t); //len+len size+next address+fid+prev_addr size
    uintptr_t next_base = 0x0, endp = end_data_pool, startp = start_data_pool;
    if (persistent) {
        endp = end_rom_pool;
        startp = start_rom_pool;
    }
    for (uintptr_t base = endp; base >= startp; base = next_base) {
        uintptr_t addr_alg = base & -FLASH_SECTOR_SIZE; //start address of sector
        uintptr_t potential_addr = base-real_size;
        next_base = flash_read_uintptr(base);
        //printf("nb %x %x %x %x\r\n",base,next_base,addr_alg,potential_addr);
        //printf("fid %x\r\n",flash_read_uint16(next_base+sizeof(uintptr_t)));
        if (next_base == 0x0) { //we are at the end
            //now we check if we fit in the current sector
            if (addr_alg <= potential_addr) //it fits in the current sector
            {
                flash_program_uintptr(potential_addr, 0x0);
                flash_program_uintptr(potential_addr+sizeof(uintptr_t), base);
                flash_program_uintptr(base, potential_addr);
                return potential_addr;
            }
            else if (addr_alg-FLASH_SECTOR_SIZE >= startp) { //check whether it fits in the next sector, so we take addr_aligned as the base
                potential_addr = addr_alg-real_size;
                flash_program_uintptr(potential_addr, 0x0);
                flash_program_uintptr(potential_addr+sizeof(uintptr_t), base);
                flash_program_uintptr(base, potential_addr);
                return potential_addr;
            }
            return 0x0;
        }
        //we check if |base-(next_addr+size_next_addr)| > |base-potential_addr| only if fid != 1xxx (not size blocked)
        else if (addr_alg <= potential_addr && base-(next_base+flash_read_uint16(next_base+sizeof(uintptr_t)+sizeof(uintptr_t)+sizeof(uint16_t))+2*sizeof(uint16_t)+2*sizeof(uintptr_t)) > base-potential_addr && (flash_read_uint16(next_base+sizeof(uintptr_t)) & 0x1000) != 0x1000) {
            flash_program_uintptr(potential_addr, next_base);
            flash_program_uintptr(potential_addr+sizeof(uintptr_t), base);
            flash_program_uintptr(base, potential_addr);
            return potential_addr;
        }
    }
    return 0x0; //probably never reached
}

int flash_clear_file(file_t *file) {
    uintptr_t base_addr = (uintptr_t)(file->data-sizeof(uintptr_t)-sizeof(uint16_t)-sizeof(uintptr_t));
    uintptr_t prev_addr = flash_read_uintptr(base_addr+sizeof(uintptr_t));
    uintptr_t next_addr = flash_read_uintptr(base_addr);
    //printf("nc %x->%x   %x->%x\r\n",prev_addr,flash_read_uintptr(prev_addr),base_addr,next_addr);
    flash_program_uintptr(prev_addr, next_addr);
    flash_program_halfword((uintptr_t)file->data, 0);
    if (next_addr > 0)
        flash_program_uintptr(next_addr+sizeof(uintptr_t), prev_addr);
    //printf("na %x->%x\r\n",prev_addr,flash_read_uintptr(prev_addr));
    return CCID_OK;
}

int flash_write_data_to_file_offset(file_t *file, const uint8_t *data, uint16_t len, uint16_t offset) {
    if (!file)
        return CCID_ERR_NULL_PARAM;
    uint16_t size_file_flash = file->data ? flash_read_uint16((uintptr_t)file->data) : 0;
    uint8_t *old_data = NULL;
    if (offset+len > FLASH_SECTOR_SIZE || offset > size_file_flash)
        return CCID_ERR_NO_MEMORY;
    if (file->data) { //already in flash
        if (offset+len <= size_file_flash) { //it fits, no need to move it
            flash_program_halfword((uintptr_t)file->data, offset+len);
            if (data)
                flash_program_block((uintptr_t)file->data+sizeof(uint16_t)+offset, data, len);
            return CCID_OK;
        }
        else { //we clear the old file
            flash_clear_file(file);
            if (offset > 0) {
                old_data = (uint8_t *)calloc(1, offset+len);
                memcpy(old_data, file->data+sizeof(uint16_t), offset);
                memcpy(old_data+offset, data, len);
                len = offset+len;
                data = old_data;
            }
        }
    }

    uintptr_t new_addr = allocate_free_addr(len, (file->type & FILE_PERSISTENT) == FILE_PERSISTENT);
    //printf("na %x\r\n",new_addr);
    if (new_addr == 0x0)
        return CCID_ERR_NO_MEMORY;
    file->data = (uint8_t *)new_addr+sizeof(uintptr_t)+sizeof(uint16_t)+sizeof(uintptr_t); //next addr+fid+prev addr
    flash_program_halfword(new_addr+sizeof(uintptr_t)+sizeof(uintptr_t), file->fid);
    flash_program_halfword((uintptr_t)file->data, len);
    if (data)
        flash_program_block((uintptr_t)file->data+sizeof(uint16_t), data, len);
    if (old_data)
        free(old_data);
    return CCID_OK;
}
int flash_write_data_to_file(file_t *file, const uint8_t *data, uint16_t len) {
    return flash_write_data_to_file_offset(file, data, len, 0);
}