Commit f0df68d5 authored by Hans de Goede's avatar Hans de Goede Committed by Ard Biesheuvel
Browse files

efi: Add embedded peripheral firmware support 



Just like with PCI options ROMs, which we save in the setup_efi_pci*
functions from arch/x86/boot/compressed/eboot.c, the EFI code / ROM itself
sometimes may contain data which is useful/necessary for peripheral drivers
to have access to.

Specifically the EFI code may contain an embedded copy of firmware which
needs to be (re)loaded into the peripheral. Normally such firmware would be
part of linux-firmware, but in some cases this is not feasible, for 2
reasons:

1) The firmware is customized for a specific use-case of the chipset / use
with a specific hardware model, so we cannot have a single firmware file
for the chipset. E.g. touchscreen controller firmwares are compiled
specifically for the hardware model they are used with, as they are
calibrated for a specific model digitizer.

2) Despite repeated attempts we have failed to get permission to
redistribute the firmware. This is especially a problem with customized
firmwares, these get created by the chip vendor for a specific ODM and the
copyright may partially belong with the ODM, so the chip vendor cannot
give a blanket permission to distribute these.

This commit adds support for finding peripheral firmware embedded in the
EFI code and makes the found firmware available through the new
efi_get_embedded_fw() function.

Support for loading these firmwares through the standard firmware loading
mechanism is added in a follow-up commit in this patch-series.

Note we check the EFI_BOOT_SERVICES_CODE for embedded firmware near the end
of start_kernel(), just before calling rest_init(), this is on purpose
because the typical EFI_BOOT_SERVICES_CODE memory-segment is too large for
early_memremap(), so the check must be done after mm_init(). This relies
on EFI_BOOT_SERVICES_CODE not being free-ed until efi_free_boot_services()
is called, which means that this will only work on x86 for now.

Reported-by: default avatarDave Olsthoorn <dave@bewaar.me>
Suggested-by: default avatarPeter Jones <pjones@redhat.com>
Acked-by: default avatarArd Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: default avatarHans de Goede <hdegoede@redhat.com>
Link: https://lore.kernel.org/r/20200115163554.101315-3-hdegoede@redhat.com


Signed-off-by: default avatarArd Biesheuvel <ardb@kernel.org>
parent 0e72a6a3

arch/x86/platform/efi/efi.c

+1 −0
Original line number Diff line number Diff line
@@ -944,6 +944,7 @@ static void __init __efi_enter_virtual_mode(void) 
		goto err;

	}



	efi_check_for_embedded_firmwares();

	efi_free_boot_services();



	/*

drivers/firmware/efi/Kconfig

+5 −0
Original line number Diff line number Diff line
@@ -239,6 +239,11 @@ config EFI_DISABLE_PCI_DMA 


endmenu



config EFI_EMBEDDED_FIRMWARE

	bool

	depends on EFI

	select CRYPTO_LIB_SHA256



config UEFI_CPER

	bool

drivers/firmware/efi/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -26,6 +26,7 @@ obj-$(CONFIG_EFI_TEST) += test/ 
obj-$(CONFIG_EFI_DEV_PATH_PARSER)	+= dev-path-parser.o

obj-$(CONFIG_APPLE_PROPERTIES)		+= apple-properties.o

obj-$(CONFIG_EFI_RCI2_TABLE)		+= rci2-table.o

obj-$(CONFIG_EFI_EMBEDDED_FIRMWARE)	+= embedded-firmware.o



fake_map-y				+= fake_mem.o

fake_map-$(CONFIG_X86)			+= x86_fake_mem.o

drivers/firmware/efi/embedded-firmware.c

0 → 100644
+147 −0
Original line number Diff line number Diff line 
// SPDX-License-Identifier: GPL-2.0

/*

 * Support for extracting embedded firmware for peripherals from EFI code,

 *

 * Copyright (c) 2018 Hans de Goede <hdegoede@redhat.com>

 */



#include <linux/dmi.h>

#include <linux/efi.h>

#include <linux/efi_embedded_fw.h>

#include <linux/io.h>

#include <linux/slab.h>

#include <linux/types.h>

#include <linux/vmalloc.h>

#include <crypto/sha.h>



/* Exported for use by lib/test_firmware.c only */

LIST_HEAD(efi_embedded_fw_list);

EXPORT_SYMBOL_GPL(efi_embedded_fw_list);



static bool checked_for_fw;



static const struct dmi_system_id * const embedded_fw_table[] = {

	NULL

};



/*

 * Note the efi_check_for_embedded_firmwares() code currently makes the

 * following 2 assumptions. This may needs to be revisited if embedded firmware

 * is found where this is not true:

 * 1) The firmware is only found in EFI_BOOT_SERVICES_CODE memory segments

 * 2) The firmware always starts at an offset which is a multiple of 8 bytes

 */

static int __init efi_check_md_for_embedded_firmware(

	efi_memory_desc_t *md, const struct efi_embedded_fw_desc *desc)

{

	struct sha256_state sctx;

	struct efi_embedded_fw *fw;

	u8 sha256[32];

	u64 i, size;

	u8 *map;



	size = md->num_pages << EFI_PAGE_SHIFT;

	map = memremap(md->phys_addr, size, MEMREMAP_WB);

	if (!map) {

		pr_err("Error mapping EFI mem at %#llx\n", md->phys_addr);

		return -ENOMEM;

	}



	for (i = 0; (i + desc->length) <= size; i += 8) {

		if (memcmp(map + i, desc->prefix, EFI_EMBEDDED_FW_PREFIX_LEN))

			continue;



		sha256_init(&sctx);

		sha256_update(&sctx, map + i, desc->length);

		sha256_final(&sctx, sha256);

		if (memcmp(sha256, desc->sha256, 32) == 0)

			break;

	}

	if ((i + desc->length) > size) {

		memunmap(map);

		return -ENOENT;

	}



	pr_info("Found EFI embedded fw '%s'\n", desc->name);



	fw = kmalloc(sizeof(*fw), GFP_KERNEL);

	if (!fw) {

		memunmap(map);

		return -ENOMEM;

	}



	fw->data = kmemdup(map + i, desc->length, GFP_KERNEL);

	memunmap(map);

	if (!fw->data) {

		kfree(fw);

		return -ENOMEM;

	}



	fw->name = desc->name;

	fw->length = desc->length;

	list_add(&fw->list, &efi_embedded_fw_list);



	return 0;

}



void __init efi_check_for_embedded_firmwares(void)

{

	const struct efi_embedded_fw_desc *fw_desc;

	const struct dmi_system_id *dmi_id;

	efi_memory_desc_t *md;

	int i, r;



	for (i = 0; embedded_fw_table[i]; i++) {

		dmi_id = dmi_first_match(embedded_fw_table[i]);

		if (!dmi_id)

			continue;



		fw_desc = dmi_id->driver_data;



		/*

		 * In some drivers the struct driver_data contains may contain

		 * other driver specific data after the fw_desc struct; and

		 * the fw_desc struct itself may be empty, skip these.

		 */

		if (!fw_desc->name)

			continue;



		for_each_efi_memory_desc(md) {

			if (md->type != EFI_BOOT_SERVICES_CODE)

				continue;



			r = efi_check_md_for_embedded_firmware(md, fw_desc);

			if (r == 0)

				break;

		}

	}



	checked_for_fw = true;

}



int efi_get_embedded_fw(const char *name, const u8 **data, size_t *size)

{

	struct efi_embedded_fw *iter, *fw = NULL;



	if (!checked_for_fw) {

		pr_warn("Warning %s called while we did not check for embedded fw\n",

			__func__);

		return -ENOENT;

	}



	list_for_each_entry(iter, &efi_embedded_fw_list, list) {

		if (strcmp(name, iter->name) == 0) {

			fw = iter;

			break;

		}

	}



	if (!fw)

		return -ENOENT;



	*data = fw->data;

	*size = fw->length;



	return 0;

}

EXPORT_SYMBOL_GPL(efi_get_embedded_fw);

include/linux/efi.h

+6 −0
Original line number Diff line number Diff line
@@ -1554,6 +1554,12 @@ static inline void 
efi_enable_reset_attack_mitigation(void) { }

#endif



#ifdef CONFIG_EFI_EMBEDDED_FIRMWARE

void efi_check_for_embedded_firmwares(void);

#else

static inline void efi_check_for_embedded_firmwares(void) { }

#endif



efi_status_t efi_random_get_seed(void);



void efi_retrieve_tpm2_eventlog(void);

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