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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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55
firmware/common/multiboot.c
View file

@ -26,44 +26,57 @@
#include <string.h>
#include <stdio.h>
static void write_bootdata_v0(struct boot_data_t *data, unsigned int boot_volume)
{
memset(data->payload, data->length, 0);
data->boot_volume = boot_volume;
data->version = 0;
}
/* Write bootdata into location in FIRMWARE marked by magic header
* Assumes buffer is already loaded with the firmware image
* We just need to find the location and write data into the
* payload region along with the crc for later verification and use.
* Returns payload len on success,
* On error returns EKEY_NOT_FOUND
* On error returns false
*/
int write_bootdata(unsigned char* buf, int len, unsigned int boot_volume)
bool write_bootdata(unsigned char* buf, int len, unsigned int boot_volume)
{
struct boot_data_t bl_boot_data;
struct boot_data_t *fw_boot_data = NULL;
int search_len = MIN(len, BOOT_DATA_SEARCH_SIZE) - sizeof(struct boot_data_t);
int payload_len = EKEY_NOT_FOUND;
/* search for boot data header prior to search_len */
for(int i = 0; i < search_len; i++)
{
fw_boot_data = (struct boot_data_t*) &buf[i];
if (fw_boot_data->magic[0] != BOOT_DATA_MAGIC0 ||
fw_boot_data->magic[1] != BOOT_DATA_MAGIC1)
struct boot_data_t *data = (struct boot_data_t *)&buf[i];
if (data->magic[0] != BOOT_DATA_MAGIC0 ||
data->magic[1] != BOOT_DATA_MAGIC1)
continue;
memset(&bl_boot_data.payload, 0, BOOT_DATA_PAYLOAD_SIZE);
bl_boot_data.boot_volume = boot_volume;
/* Ignore it if the length extends past the end of the buffer. */
int data_len = offsetof(struct boot_data_t, payload) + data->length;
if (i + data_len > len)
continue;
memset(fw_boot_data->payload, 0, fw_boot_data->length);
/* determine maximum bytes we can write to firmware
BOOT_DATA_PAYLOAD_SIZE is the size the bootloader expects */
payload_len = MIN(BOOT_DATA_PAYLOAD_SIZE, fw_boot_data->length);
fw_boot_data->length = payload_len;
/* copy data to FIRMWARE bootdata struct */
memcpy(fw_boot_data->payload, &bl_boot_data.payload, payload_len);
/* crc will be used within the firmware to check validity of bootdata */
fw_boot_data->crc = crc_32(fw_boot_data->payload, payload_len, 0xffffffff);
break;
/* Determine the maximum supported boot protocol version.
* Version 0 firmware may use 0 or 0xff, all other versions
* declare the highest supported version in the version byte. */
int proto_version = 0;
if (data->version < 0xff)
proto_version = MIN(BOOT_DATA_VERSION, data->version);
/* Write boot data according to the selected protocol */
if (proto_version == 0)
write_bootdata_v0(data, boot_volume);
else
break;
/* Calculate payload CRC, used by all protocol versions. */
data->crc = crc_32(data->payload, data->length, 0xffffffff);
return true;
}
return payload_len;
return false;
}
#ifdef HAVE_MULTIBOOT