cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
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embedded-firmware.c (3449B)

      1// SPDX-License-Identifier: GPL-2.0
      2/*
      3 * Support for extracting embedded firmware for peripherals from EFI code,
      4 *
      5 * Copyright (c) 2018 Hans de Goede <hdegoede@redhat.com>
      6 */
      7
      8#include <linux/dmi.h>
      9#include <linux/efi.h>
     10#include <linux/efi_embedded_fw.h>
     11#include <linux/io.h>
     12#include <linux/slab.h>
     13#include <linux/types.h>
     14#include <linux/vmalloc.h>
     15#include <crypto/sha2.h>
     16
     17/* Exported for use by lib/test_firmware.c only */
     18LIST_HEAD(efi_embedded_fw_list);
     19EXPORT_SYMBOL_NS_GPL(efi_embedded_fw_list, TEST_FIRMWARE);
     20bool efi_embedded_fw_checked;
     21EXPORT_SYMBOL_NS_GPL(efi_embedded_fw_checked, TEST_FIRMWARE);
     22
     23static const struct dmi_system_id * const embedded_fw_table[] = {
     24#ifdef CONFIG_TOUCHSCREEN_DMI
     25	touchscreen_dmi_table,
     26#endif
     27	NULL
     28};
     29
     30/*
     31 * Note the efi_check_for_embedded_firmwares() code currently makes the
     32 * following 2 assumptions. This may needs to be revisited if embedded firmware
     33 * is found where this is not true:
     34 * 1) The firmware is only found in EFI_BOOT_SERVICES_CODE memory segments
     35 * 2) The firmware always starts at an offset which is a multiple of 8 bytes
     36 */
     37static int __init efi_check_md_for_embedded_firmware(
     38	efi_memory_desc_t *md, const struct efi_embedded_fw_desc *desc)
     39{
     40	struct efi_embedded_fw *fw;
     41	u8 hash[32];
     42	u64 i, size;
     43	u8 *map;
     44
     45	size = md->num_pages << EFI_PAGE_SHIFT;
     46	map = memremap(md->phys_addr, size, MEMREMAP_WB);
     47	if (!map) {
     48		pr_err("Error mapping EFI mem at %#llx\n", md->phys_addr);
     49		return -ENOMEM;
     50	}
     51
     52	for (i = 0; (i + desc->length) <= size; i += 8) {
     53		if (memcmp(map + i, desc->prefix, EFI_EMBEDDED_FW_PREFIX_LEN))
     54			continue;
     55
     56		sha256(map + i, desc->length, hash);
     57		if (memcmp(hash, desc->sha256, 32) == 0)
     58			break;
     59	}
     60	if ((i + desc->length) > size) {
     61		memunmap(map);
     62		return -ENOENT;
     63	}
     64
     65	pr_info("Found EFI embedded fw '%s'\n", desc->name);
     66
     67	fw = kmalloc(sizeof(*fw), GFP_KERNEL);
     68	if (!fw) {
     69		memunmap(map);
     70		return -ENOMEM;
     71	}
     72
     73	fw->data = kmemdup(map + i, desc->length, GFP_KERNEL);
     74	memunmap(map);
     75	if (!fw->data) {
     76		kfree(fw);
     77		return -ENOMEM;
     78	}
     79
     80	fw->name = desc->name;
     81	fw->length = desc->length;
     82	list_add(&fw->list, &efi_embedded_fw_list);
     83
     84	return 0;
     85}
     86
     87void __init efi_check_for_embedded_firmwares(void)
     88{
     89	const struct efi_embedded_fw_desc *fw_desc;
     90	const struct dmi_system_id *dmi_id;
     91	efi_memory_desc_t *md;
     92	int i, r;
     93
     94	for (i = 0; embedded_fw_table[i]; i++) {
     95		dmi_id = dmi_first_match(embedded_fw_table[i]);
     96		if (!dmi_id)
     97			continue;
     98
     99		fw_desc = dmi_id->driver_data;
    100
    101		/*
    102		 * In some drivers the struct driver_data contains may contain
    103		 * other driver specific data after the fw_desc struct; and
    104		 * the fw_desc struct itself may be empty, skip these.
    105		 */
    106		if (!fw_desc->name)
    107			continue;
    108
    109		for_each_efi_memory_desc(md) {
    110			if (md->type != EFI_BOOT_SERVICES_CODE)
    111				continue;
    112
    113			r = efi_check_md_for_embedded_firmware(md, fw_desc);
    114			if (r == 0)
    115				break;
    116		}
    117	}
    118
    119	efi_embedded_fw_checked = true;
    120}
    121
    122int efi_get_embedded_fw(const char *name, const u8 **data, size_t *size)
    123{
    124	struct efi_embedded_fw *iter, *fw = NULL;
    125
    126	if (!efi_embedded_fw_checked) {
    127		pr_warn("Warning %s called while we did not check for embedded fw\n",
    128			__func__);
    129		return -ENOENT;
    130	}
    131
    132	list_for_each_entry(iter, &efi_embedded_fw_list, list) {
    133		if (strcmp(name, iter->name) == 0) {
    134			fw = iter;
    135			break;
    136		}
    137	}
    138
    139	if (!fw)
    140		return -ENOENT;
    141
    142	*data = fw->data;
    143	*size = fw->length;
    144
    145	return 0;
    146}
    147EXPORT_SYMBOL_GPL(efi_get_embedded_fw);