/****************************************************************************
* get_lbtable
*
* Find the coreboot table and set global variable lbtable to point to it.
****************************************************************************/
void get_lbtable(void)
{
int i, bad_header_count, bad_table_count, bad_headers, bad_tables;
if (lbtable != NULL)
return;
/* The coreboot table is located in low physical memory, which may be
* conveniently accessed by calling mmap() on /dev/mem.
*/
if ((fd = open("/dev/mem", O_RDONLY, 0)) < 0) {
fprintf(stderr, "%s: Can not open /dev/mem for reading: %s\n",
prog_name, strerror(errno));
exit(1);
}
if ((low_phys_mem =
mmap(NULL, BYTES_TO_MAP, PROT_READ, MAP_SHARED, fd, 0))
== MAP_FAILED) {
fprintf(stderr, "%s: Failed to mmap /dev/mem: %s\n", prog_name,
strerror(errno));
exit(1);
}
bad_header_count = 0;
bad_table_count = 0;
for (i = 0; i < NUM_MEM_RANGES; i++) {
lbtable = lbtable_scan(phystov(mem_ranges[i].start),
phystov(mem_ranges[i].end),
&bad_headers, &bad_tables);
if (lbtable != NULL)
return; /* success: we found it! */
bad_header_count += bad_headers;
bad_table_count += bad_tables;
}
fprintf(stderr,
"%s: coreboot table not found. coreboot does not appear to\n"
" be installed on this system. Scanning for the table "
"produced the\n"
" following results:\n\n"
" %d valid signatures were found with bad header "
"checksums.\n"
" %d valid headers were found with bad table "
"checksums.\n", prog_name, bad_header_count, bad_table_count);
exit(1);
}
/****************************************************************************
* lbtable_scan
*
* Scan the chunk of memory specified by 'start' and 'end' for a coreboot
* table. The first 4 bytes of the table are marked by the signature
* { 'L', 'B', 'I', 'O' }. 'start' and 'end' indicate the addresses of the
* first and last bytes of the chunk of memory to be scanned. For instance,
* values of 0x10000000 and 0x1000ffff for 'start' and 'end' specify a 64k
* chunk of memory starting at address 0x10000000. 'start' and 'end' are
* physical addresses.
*
* If a coreboot table is found, return a pointer to it. Otherwise return
* NULL. On return, *bad_header_count and *bad_table_count are set as
* follows:
*
* *bad_header_count:
* Indicates the number of times in which a valid signature was found
* but the header checksum was invalid.
*
* *bad_table_count:
* Indicates the number of times in which a header with a valid
* checksum was found but the table checksum was invalid.
****************************************************************************/
static const struct lb_header *lbtable_scan(unsigned long start,
unsigned long end,
int *bad_header_count,
int *bad_table_count)
{
static const char signature[4] = { 'L', 'B', 'I', 'O' };
const struct lb_header *table;
const struct lb_forward *forward;
unsigned long p;
uint32_t sig;
assert(end >= start);
memcpy(&sig, signature, sizeof(sig));
table = NULL;
*bad_header_count = 0;
*bad_table_count = 0;
/* Look for signature. Table is aligned on 16-byte boundary. Therefore
* only check every fourth 32-bit memory word. As the loop is coded below,
* this function will behave in a reasonable manner for ALL possible values
* for 'start' and 'end': even weird boundary cases like 0x00000000 and
* 0xffffffff on a 32-bit architecture.
*/
map_pages(start, end - start);
for (p = start;
(p <= end) &&
(end - p >= (sizeof(uint32_t) - 1)); p += 4) {
if (*(uint32_t*)phystov(p) != sig)
continue;
/* We found a valid signature. */
table = (const struct lb_header *)phystov(p);
/* validate header checksum */
if (compute_ip_checksum((void *)table, sizeof(*table))) {
(*bad_header_count)++;
continue;
}
map_pages(p, table->table_bytes + sizeof(*table));
/* validate table checksum */
if (table->table_checksum !=
compute_ip_checksum(((char *)table) + sizeof(*table),
table->table_bytes)) {
(*bad_table_count)++;
continue;
}
/* checksums are ok: we found it! */
/* But it may just be a forwarding table, so look if there's a forwarder */
lbtable = table;
forward = (struct lb_forward *)find_lbrec(LB_TAG_FORWARD);
lbtable = NULL;
if (forward) {
uint64_t new_phys = forward->forward;
table = lbtable_scan(new_phys, new_phys + getpagesize(),
bad_header_count, bad_table_count);
}
return table;
}
return NULL;
}
/****************************************************************************
* lbtable_scan
*
* Scan the chunk of memory specified by 'start' and 'end' for a coreboot
* table. The first 4 bytes of the table are marked by the signature
* { 'L', 'B', 'I', 'O' }. 'start' and 'end' indicate the addresses of the
* first and last bytes of the chunk of memory to be scanned. For instance,
* values of 0x10000000 and 0x1000ffff for 'start' and 'end' specify a 64k
* chunk of memory starting at address 0x10000000. 'start' and 'end' are
* virtual addresses in the address space of the current process. They
* represent a chunk of memory obtained by calling mmap() on /dev/mem.
*
* If a coreboot table is found, return a pointer to it. Otherwise return
* NULL. On return, *bad_header_count and *bad_table_count are set as
* follows:
*
* *bad_header_count:
* Indicates the number of times in which a valid signature was found
* but the header checksum was invalid.
*
* *bad_table_count:
* Indicates the number of times in which a header with a valid
* checksum was found but the table checksum was invalid.
****************************************************************************/
static const struct lb_header *lbtable_scan(unsigned long start,
unsigned long end,
int *bad_header_count,
int *bad_table_count)
{
static const char signature[] = { 'L', 'B', 'I', 'O' };
const struct lb_header *table;
const struct lb_forward *forward;
const uint32_t *p;
uint32_t sig;
assert(end >= start);
sig = (*((const uint32_t *)signature));
table = NULL;
*bad_header_count = 0;
*bad_table_count = 0;
/* Look for signature. Table is aligned on 16-byte boundary. Therefore
* only check every fourth 32-bit memory word. As the loop is coded below,
* this function will behave in a reasonable manner for ALL possible values
* for 'start' and 'end': even weird boundary cases like 0x00000000 and
* 0xffffffff on a 32-bit architecture.
*/
for (p = (const uint32_t *)start;
(((unsigned long)p) <= end) &&
((end - (unsigned long)p) >= (sizeof(uint32_t) - 1)); p += 4) {
if (*p != sig)
continue;
/* We found a valid signature. */
table = (const struct lb_header *)p;
/* validate header checksum */
if (compute_ip_checksum((void *)table, sizeof(*table))) {
(*bad_header_count)++;
continue;
}
/* validate table checksum */
if (table->table_checksum !=
compute_ip_checksum(((char *)table) + sizeof(*table),
table->table_bytes)) {
(*bad_table_count)++;
continue;
}
/* checksums are ok: we found it! */
/* But it may just be a forwarding table, so look if there's a forwarder */
lbtable = table;
forward = (struct lb_forward *)find_lbrec(LB_TAG_FORWARD);
lbtable = NULL;
if (forward) {
uint64_t new_phys = forward->forward;
new_phys &= ~(getpagesize() - 1);
munmap((void *)low_phys_mem, BYTES_TO_MAP);
if ((low_phys_mem =
mmap(NULL, BYTES_TO_MAP, PROT_READ, MAP_SHARED, fd,
(off_t) new_phys)) == MAP_FAILED) {
fprintf(stderr,
"%s: Failed to mmap /dev/mem: %s\n",
prog_name, strerror(errno));
exit(1);
}
low_phys_base = new_phys;
table =
lbtable_scan(phystov(low_phys_base),
phystov(low_phys_base + BYTES_TO_MAP),
bad_header_count, bad_table_count);
}
return table;
}
return NULL;
}