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/*
* Copyright (C) 2021 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include "libxbc.h"
#define BOOTCONFIG_MAGIC "#BOOTCONFIG\n"
#define BOOTCONFIG_MAGIC_SIZE 12
#define BOOTCONFIG_SIZE_SIZE 4
#define BOOTCONFIG_CHECKSUM_SIZE 4
#define BOOTCONFIG_TRAILER_SIZE BOOTCONFIG_MAGIC_SIZE + \
BOOTCONFIG_SIZE_SIZE + \
BOOTCONFIG_CHECKSUM_SIZE
/*
* Simple checksum for a buffer.
*
* @param addr pointer to the start of the buffer.
* @param size size of the buffer in bytes.
* @return check sum result.
*/
static uint32_t checksum(const unsigned char* const buffer, uint32_t size) {
uint32_t sum = 0;
for (uint32_t i = 0; i < size; i++) {
sum += buffer[i];
}
return sum;
}
/*
* Check if the bootconfig trailer is present within the bootconfig section.
*
* @param bootconfig_end_addr address of the end of the bootconfig section. If
* the trailer is present, it will be directly preceding this address.
* @return true if the trailer is present, false if not.
*/
static bool isTrailerPresent(uint64_t bootconfig_end_addr) {
return !strncmp((char*)(bootconfig_end_addr - BOOTCONFIG_MAGIC_SIZE),
BOOTCONFIG_MAGIC, BOOTCONFIG_MAGIC_SIZE);
}
/*
* Add a string of boot config parameters to memory appended by the trailer.
*/
int32_t addBootConfigParameters(char* params, uint32_t params_size,
uint64_t bootconfig_start_addr, uint32_t bootconfig_size) {
if (!params || !bootconfig_start_addr) {
return -1;
}
if (params_size == 0) {
return 0;
}
int32_t applied_bytes = 0;
int32_t new_size = 0;
uint64_t end = bootconfig_start_addr + bootconfig_size;
if (isTrailerPresent(end)) {
end -= BOOTCONFIG_TRAILER_SIZE;
applied_bytes -= BOOTCONFIG_TRAILER_SIZE;
memcpy(&new_size, (void *)end, BOOTCONFIG_SIZE_SIZE);
} else {
new_size = bootconfig_size;
}
// params
memcpy((void*)end, params, params_size);
applied_bytes += params_size;
applied_bytes += addBootConfigTrailer(bootconfig_start_addr,
bootconfig_size + applied_bytes);
return applied_bytes;
}
/*
* Add boot config trailer.
*/
int32_t addBootConfigTrailer(uint64_t bootconfig_start_addr,
uint32_t bootconfig_size) {
if (!bootconfig_start_addr) {
return -1;
}
if (bootconfig_size == 0) {
return 0;
}
uint64_t end = bootconfig_start_addr + bootconfig_size;
if (isTrailerPresent(end)) {
// no need to overwrite the current trailers
return 0;
}
// size
memcpy((void *)(end), &bootconfig_size, BOOTCONFIG_SIZE_SIZE);
// checksum
uint32_t sum =
checksum((unsigned char*)bootconfig_start_addr, bootconfig_size);
memcpy((void *)(end + BOOTCONFIG_SIZE_SIZE), &sum,
BOOTCONFIG_CHECKSUM_SIZE);
// magic
memcpy((void *)(end + BOOTCONFIG_SIZE_SIZE + BOOTCONFIG_CHECKSUM_SIZE),
BOOTCONFIG_MAGIC, BOOTCONFIG_MAGIC_SIZE);
return BOOTCONFIG_TRAILER_SIZE;
}
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