trezor-firmware/embed/extmod/modtrezorconfig/norcow.c

/*
 * This file is part of the TREZOR project, https://trezor.io/
 *
 * Copyright (c) SatoshiLabs
 *
 * 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, either version 3 of the License, or
 * (at your option) any later version.
 *
 * 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 <string.h>

#include "norcow.h"

#include "common.h"
#include "flash.h"

#ifndef NORCOW_SECTORS
#define NORCOW_SECTORS {FLASH_SECTOR_STORAGE_1, FLASH_SECTOR_STORAGE_2}
#endif

// NRCW = 4e524357
#define NORCOW_MAGIC      ((uint32_t)0x5743524e)
#define NORCOW_MAGIC_LEN  (sizeof(uint32_t))

static const uint8_t norcow_sectors[NORCOW_SECTOR_COUNT] = NORCOW_SECTORS;
static uint8_t norcow_active_sector = 0;
static uint32_t norcow_active_offset = NORCOW_MAGIC_LEN;

/*
 * Returns pointer to sector, starting with offset
 * Fails when there is not enough space for data of given size
 */
static const void *norcow_ptr(uint8_t sector, uint32_t offset, uint32_t size)
{
    ensure(sectrue * (sector <= NORCOW_SECTOR_COUNT), "invalid sector");
    return flash_get_address(norcow_sectors[sector], offset, size);
}

/*
 * Writes data to given sector, starting from offset
 */
static secbool norcow_write(uint8_t sector, uint32_t offset, uint32_t prefix, const uint8_t *data, uint16_t len)
{
    if (sector >= NORCOW_SECTOR_COUNT) {
        return secfalse;
    }
    ensure(flash_unlock(), NULL);

    // write prefix
    ensure(flash_write_word(norcow_sectors[sector], offset, prefix), NULL);

    if (len > 0) {
        offset += sizeof(uint32_t);
        // write data
        for (uint16_t i = 0; i < len; i++, offset++) {
            ensure(flash_write_byte(norcow_sectors[sector], offset, data[i]), NULL);
        }
        // pad with zeroes
        for (; offset % 4; offset++) {
            ensure(flash_write_byte(norcow_sectors[sector], offset, 0x00), NULL);
        }
    }
    ensure(flash_lock(), NULL);
    return sectrue;
}

/*
 * Erases sector (and sets a magic)
 */
static void norcow_erase(uint8_t sector, secbool set_magic)
{
    ensure(sectrue * (sector <= NORCOW_SECTOR_COUNT), "invalid sector");
    ensure(flash_erase_sector(norcow_sectors[sector]), "erase failed");
    if (sectrue == set_magic) {
        ensure(norcow_write(sector, 0, NORCOW_MAGIC, NULL, 0), "set magic failed");
    }
}

#define ALIGN4(X) (X) = ((X) + 3) & ~3

/*
 * Reads one item starting from offset
 */
static secbool read_item(uint8_t sector, uint32_t offset, uint16_t *key, const void **val, uint16_t *len, uint32_t *pos)
{
    *pos = offset;

    const void *k = norcow_ptr(sector, *pos, 2);
    if (k == NULL) return secfalse;
    *pos += 2;
    memcpy(key, k, sizeof(uint16_t));
    if (*key == 0xFFFF) {
        return secfalse;
    }

    const void *l = norcow_ptr(sector, *pos, 2);
    if (l == NULL) return secfalse;
    *pos += 2;
    memcpy(len, l, sizeof(uint16_t));

    *val = norcow_ptr(sector, *pos, *len);
    if (*val == NULL) return secfalse;
    *pos += *len;
    ALIGN4(*pos);
    return sectrue;
}

/*
 * Writes one item starting from offset
 */
static secbool write_item(uint8_t sector, uint32_t offset, uint16_t key, const void *val, uint16_t len, uint32_t *pos)
{
    uint32_t prefix = (len << 16) | key;
    *pos = offset + sizeof(uint32_t) + len;
    ALIGN4(*pos);
    return norcow_write(sector, offset, prefix, val, len);
}

/*
 * Finds item in given sector
 */
static secbool find_item(uint8_t sector, uint16_t key, const void **val, uint16_t *len)
{
    *val = 0;
    *len = 0;
    uint32_t offset = NORCOW_MAGIC_LEN;
    for (;;) {
        uint16_t k, l;
        const void *v;
        uint32_t pos;
        if (sectrue != read_item(sector, offset, &k, &v, &l, &pos)) {
            break;
        }
        if (key == k) {
            *val = v;
            *len = l;
        }
        offset = pos;
    }
    return sectrue * (*val != NULL);
}

/*
 * Finds first unused offset in given sector
 */
static uint32_t find_free_offset(uint8_t sector)
{
    uint32_t offset = NORCOW_MAGIC_LEN;
    for (;;) {
        uint16_t key, len;
        const void *val;
        uint32_t pos;
        if (sectrue != read_item(sector, offset, &key, &val, &len, &pos)) {
            break;
        }
        offset = pos;
    }
    return offset;
}

/*
 * Compacts active sector and sets new active sector
 */
static void compact()
{
    uint8_t norcow_next_sector = (norcow_active_sector + 1) % NORCOW_SECTOR_COUNT;
    norcow_erase(norcow_next_sector, sectrue);

    uint32_t offset = NORCOW_MAGIC_LEN, offsetw = NORCOW_MAGIC_LEN;

    for (;;) {
        // read item
        uint16_t k, l;
        const void *v;
        uint32_t pos;
        secbool r = read_item(norcow_active_sector, offset, &k, &v, &l, &pos);
        if (sectrue != r) {
            break;
        }
        offset = pos;

        // check if not already saved
        const void *v2;
        uint16_t l2;
        r = find_item(norcow_next_sector, k, &v2, &l2);
        if (sectrue == r) {
            continue;
        }

        // scan for latest instance
        uint32_t offsetr = offset;
        for (;;) {
            uint16_t k2;
            uint32_t posr;
            r = read_item(norcow_active_sector, offsetr, &k2, &v2, &l2, &posr);
            if (sectrue != r) {
                break;
            }
            if (k == k2) {
                v = v2;
                l = l2;
            }
            offsetr = posr;
        }

        // copy the last item
        uint32_t posw;
        ensure(write_item(norcow_next_sector, offsetw, k, v, l, &posw), "compaction write failed");
        offsetw = posw;
    }

    norcow_erase(norcow_active_sector, secfalse);
    norcow_active_sector = norcow_next_sector;
    norcow_active_offset = find_free_offset(norcow_active_sector);
}

/*
 * Initializes storage
 */
void norcow_init(void)
{
    secbool found = secfalse;
    // detect active sector - starts with magic
    for (uint8_t i = 0; i < NORCOW_SECTOR_COUNT; i++) {
        const uint32_t *magic = norcow_ptr(i, 0, NORCOW_MAGIC_LEN);
        if (magic != NULL && *magic == NORCOW_MAGIC) {
            found = sectrue;
            norcow_active_sector = i;
            break;
        }
    }
    // no active sectors found - let's erase
    if (sectrue == found) {
        norcow_active_offset = find_free_offset(norcow_active_sector);
    } else {
        norcow_wipe();
    }
}

/*
 * Wipe the storage
 */
void norcow_wipe(void)
{
    norcow_erase(0, sectrue);
    for (uint8_t i = 1; i < NORCOW_SECTOR_COUNT; i++) {
        norcow_erase(i, secfalse);
    }
    norcow_active_sector = 0;
    norcow_active_offset = NORCOW_MAGIC_LEN;
}

/*
 * Looks for the given key, returns status of the operation
 */
secbool norcow_get(uint16_t key, const void **val, uint16_t *len)
{
    return find_item(norcow_active_sector, key, val, len);
}

/*
 * Sets the given key, returns status of the operation
 */
secbool norcow_set(uint16_t key, const void *val, uint16_t len)
{
    // check whether there is enough free space
    // and compact if full
    if (norcow_active_offset + sizeof(uint32_t) + len > NORCOW_SECTOR_SIZE) {
        compact();
    }
    // write item
    uint32_t pos;
    secbool r = write_item(norcow_active_sector, norcow_active_offset, key, val, len, &pos);
    if (sectrue == r) {
        norcow_active_offset = pos;
    }
    return r;
}

/*
 * Update a word in flash at the given pointer.  The pointer must point
 * into the NORCOW area.
 */
secbool norcow_update(uint16_t key, uint16_t offset, uint32_t value)
{
    const void *ptr;
    uint16_t len;
    if (sectrue != find_item(norcow_active_sector, key, &ptr, &len)) {
        return secfalse;
    }
    if ((offset & 3) != 0 || offset >= len) {
        return secfalse;
    }
    uint32_t sector_offset = (const uint8_t*) ptr - (const uint8_t *)norcow_ptr(norcow_active_sector, 0, NORCOW_SECTOR_SIZE) + offset;
    ensure(flash_unlock(), NULL);
    ensure(flash_write_word(norcow_sectors[norcow_active_sector], sector_offset, value), NULL);
    ensure(flash_lock(), NULL);
    return sectrue;
}