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coreboot_table.c 2 KB
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Julius Werner's avatar
Add platform-independent coreboot support library    
Julius Werner committed
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/*
 * Copyright (c) 2017, ARM Limited and Contributors. All rights reserved.
 *
 * SPDX-License-Identifier: BSD-3-Clause
 */

#include <coreboot.h>
#include <debug.h>
#include <mmio.h>
#include <string.h>

/*
 * Structures describing coreboot's in-memory descriptor tables. See
 * <coreboot>/src/commonlib/include/commonlib/coreboot_tables.h for
 * canonical implementation.
 */

typedef struct {
	char signature[4];
	uint32_t header_bytes;
	uint32_t header_checksum;
	uint32_t table_bytes;
	uint32_t table_checksum;
	uint32_t table_entries;
} cb_header_t;

typedef enum {
	CB_TAG_SERIAL = 0xf,
} cb_tag_t;

typedef struct {
	uint32_t tag;
	uint32_t size;
	union {
		coreboot_serial_t serial;
	};
} cb_entry_t;

coreboot_serial_t coreboot_serial;

/*
 * The coreboot table is parsed before the MMU is enabled (i.e. with strongly
 * ordered memory), so we cannot make unaligned accesses. The table entries
 * immediately follow one another without padding, so nothing after the header
 * is guaranteed to be naturally aligned. Therefore, we need to define safety
 * functions that can read unaligned integers.
 */
static uint32_t read_le32(uint32_t *p)
{
	uintptr_t addr = (uintptr_t)p;
	return mmio_read_8(addr)		|
	       mmio_read_8(addr + 1) << 8	|
	       mmio_read_8(addr + 2) << 16	|
	       mmio_read_8(addr + 3) << 24;
}

void coreboot_table_setup(void *base)
{
	cb_header_t *header = base;
	void *ptr;
	int i;

	if (strncmp(header->signature, "LBIO", 4)) {
		ERROR("coreboot table signature corrupt!\n");
		return;
	}

	ptr = base + header->header_bytes;
	for (i = 0; i < header->table_entries; i++) {
		cb_entry_t *entry = ptr;

		if (ptr - base >= header->header_bytes + header->table_bytes) {
			ERROR("coreboot table exceeds its bounds!\n");
			break;
		}

		switch (read_le32(&entry->tag)) {
		case CB_TAG_SERIAL:
			memcpy(&coreboot_serial, &entry->serial,
			       sizeof(coreboot_serial));
			break;
		default:
			/* There are many tags TF doesn't need to care about. */
			break;
		}

		ptr += read_le32(&entry->size);
	}
}