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multiboot: Refactor boot data validation, add version numbers

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Instead of verifying the CRC before every access of the boot data,
verify the CRC once at startup and set a flag to indicate the boot
data is valid.

Also add a framework to support multiple boot protocol versions.
Firmware declares the maximum supported protocol version using a
version byte in the boot data header. The bootloader chooses the
highest version supported by it and the firmware when deciding
what boot protocol to use.

Change-Id: I810194625dc0833f026d2a23b8d64ed467fa6aca
This commit is contained in:
Aidan MacDonald 2022-12-22 19:23:29 +00:00
parent af644e02a1
commit 6ffd42548b
11 changed files with 150 additions and 59 deletions
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74
firmware/common/bootdata.c Normal file
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@ -0,0 +1,74 @@
/***************************************************************************
* __________ __ ___.
* Open \______ \ ____ ____ | | _\_ |__ _______ ___
* Source | _// _ \_/ ___\| |/ /| __ \ / _ \ \/ /
* Jukebox | | ( <_> ) \___| < | \_\ ( <_> > < <
* Firmware |____|_ /\____/ \___ >__|_ \|___ /\____/__/\_ \
* \/ \/ \/ \/ \/
*
* Copyright (C) 2022 by Aidan MacDonald
*
* 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 2
* of the License, or (at your option) any later version.
*
* This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
* KIND, either express or implied.
*
****************************************************************************/
#include "bootdata.h"
#include "crc32.h"
#include <stddef.h>
#ifdef BOOTLOADER
# error "not to be included in bootloader builds"
#endif
bool boot_data_valid;
static bool verify_boot_data_v0(void) INIT_ATTR;
static bool verify_boot_data_v0(void)
{
/* validate protocol version */
if (boot_data.version != 0)
return false;
/* validate length */
if (boot_data.length != 4)
return false;
return true;
}
struct verify_bd_entry
{
int version;
bool (*verify) (void);
};
static const struct verify_bd_entry verify_bd[] INITDATA_ATTR = {
{ 0, verify_boot_data_v0 },
};
void verify_boot_data(void)
{
/* verify payload with checksum - all protocol versions */
uint32_t crc = crc_32(boot_data.payload, boot_data.length, 0xffffffff);
if (crc != boot_data.crc)
return;
/* apply verification specific to the protocol version */
for (size_t i = 0; i < ARRAYLEN(verify_bd); ++i)
{
const struct verify_bd_entry *e = &verify_bd[i];
if (e->version == boot_data.version)
{
if (e->verify())
boot_data_valid = true;
return;
}
}
}