Commit 475fb4e8 authored by Octavian Purdila's avatar Octavian Purdila Committed by Rafael J. Wysocki
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efi / ACPI: load SSTDs from EFI variables 



This patch allows SSDTs to be loaded from EFI variables. It works by
specifying the EFI variable name containing the SSDT to be loaded. All
variables with the same name (regardless of the vendor GUID) will be
loaded.

Note that we can't use acpi_install_table and we must rely on the
dynamic ACPI table loading and bus re-scanning mechanisms. That is
because I2C/SPI controllers are initialized earlier then the EFI
subsystems and all I2C/SPI ACPI devices are enumerated when the
I2C/SPI controllers are initialized.

Signed-off-by: default avatarOctavian Purdila <octavian.purdila@intel.com>
Reviewed-by: default avatarMatt Fleming <matt@codeblueprint.co.uk>
Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
parent 7f24467f

Documentation/acpi/ssdt-overlays.txt

+67 −0
Original line number Original line Diff line number Diff line
@@ -89,3 +89,70 @@ cp ssdt.aml kernel/firmware/acpi 
# on top:

# on top:

find kernel | cpio -H newc --create > /boot/instrumented_initrd

find kernel | cpio -H newc --create > /boot/instrumented_initrd

cat /boot/initrd >>/boot/instrumented_initrd

cat /boot/initrd >>/boot/instrumented_initrd



== Loading ACPI SSDTs from EFI variables ==



This is the preferred method, when EFI is supported on the platform, because it

allows a persistent, OS independent way of storing the user defined SSDTs. There

is also work underway to implement EFI support for loading user defined SSDTs

and using this method will make it easier to convert to the EFI loading

mechanism when that will arrive.



In order to load SSDTs from an EFI variable the efivar_ssdt kernel command line

parameter can be used. The argument for the option is the variable name to

use. If there are multiple variables with the same name but with different

vendor GUIDs, all of them will be loaded.



In order to store the AML code in an EFI variable the efivarfs filesystem can be

used. It is enabled and mounted by default in /sys/firmware/efi/efivars in all

recent distribution.



Creating a new file in /sys/firmware/efi/efivars will automatically create a new

EFI variable. Updating a file in /sys/firmware/efi/efivars will update the EFI

variable. Please note that the file name needs to be specially formatted as

"Name-GUID" and that the first 4 bytes in the file (little-endian format)

represent the attributes of the EFI variable (see EFI_VARIABLE_MASK in

include/linux/efi.h). Writing to the file must also be done with one write

operation.



For example, you can use the following bash script to create/update an EFI

variable with the content from a given file:



#!/bin/sh -e



while ! [ -z "$1" ]; do

        case "$1" in

        "-f") filename="$2"; shift;;

        "-g") guid="$2"; shift;;

        *) name="$1";;

        esac

        shift

done



usage()

{

        echo "Syntax: ${0##*/} -f filename [ -g guid ] name"

        exit 1

}



[ -n "$name" -a -f "$filename" ] || usage



EFIVARFS="/sys/firmware/efi/efivars"



[ -d "$EFIVARFS" ] || exit 2



if stat -tf $EFIVARFS | grep -q -v de5e81e4; then

        mount -t efivarfs none $EFIVARFS

fi



# try to pick up an existing GUID

[ -n "$guid" ] || guid=$(find "$EFIVARFS" -name "$name-*" | head -n1 | cut -f2- -d-)



# use a randomly generated GUID

[ -n "$guid" ] || guid="$(cat /proc/sys/kernel/random/uuid)"



# efivarfs expects all of the data in one write

tmp=$(mktemp)

/bin/echo -ne "\007\000\000\000" | cat - $filename > $tmp

dd if=$tmp of="$EFIVARFS/$name-$guid" bs=$(stat -c %s $tmp)

rm $tmp

Documentation/kernel-parameters.txt

+7 −0
Original line number Original line Diff line number Diff line
@@ -1185,6 +1185,13 @@ bytes respectively. Such letter suffixes can also be entirely omitted. 
			Address Range Mirroring feature even if your box

			Address Range Mirroring feature even if your box

			doesn't support it.

			doesn't support it.





	efivar_ssdt=	[EFI; X86] Name of an EFI variable that contains an SSDT

			that is to be dynamically loaded by Linux. If there are

			multiple variables with the same name but with different

			vendor GUIDs, all of them will be loaded. See

			Documentation/acpi/ssdt-overlays.txt for details.





	eisa_irq_edge=	[PARISC,HW]

	eisa_irq_edge=	[PARISC,HW]

			See header of drivers/parisc/eisa.c.

			See header of drivers/parisc/eisa.c.

drivers/firmware/efi/efi.c

+96 −0
Original line number Original line Diff line number Diff line
@@ -24,6 +24,9 @@ 
#include <linux/of_fdt.h>

#include <linux/of_fdt.h>

#include <linux/io.h>

#include <linux/io.h>

#include <linux/platform_device.h>

#include <linux/platform_device.h>

#include <linux/slab.h>

#include <linux/acpi.h>

#include <linux/ucs2_string.h>





#include <asm/early_ioremap.h>

#include <asm/early_ioremap.h>
@@ -195,6 +198,96 @@ static void generic_ops_unregister(void) 
	efivars_unregister(&generic_efivars);

	efivars_unregister(&generic_efivars);

}

}





#if IS_ENABLED(CONFIG_ACPI)

#define EFIVAR_SSDT_NAME_MAX	16

static char efivar_ssdt[EFIVAR_SSDT_NAME_MAX] __initdata;

static int __init efivar_ssdt_setup(char *str)

{

	if (strlen(str) < sizeof(efivar_ssdt))

		memcpy(efivar_ssdt, str, strlen(str));

	else

		pr_warn("efivar_ssdt: name too long: %s\n", str);

	return 0;

}

__setup("efivar_ssdt=", efivar_ssdt_setup);



static __init int efivar_ssdt_iter(efi_char16_t *name, efi_guid_t vendor,

				   unsigned long name_size, void *data)

{

	struct efivar_entry *entry;

	struct list_head *list = data;

	char utf8_name[EFIVAR_SSDT_NAME_MAX];

	int limit = min_t(unsigned long, EFIVAR_SSDT_NAME_MAX, name_size);



	ucs2_as_utf8(utf8_name, name, limit - 1);

	if (strncmp(utf8_name, efivar_ssdt, limit) != 0)

		return 0;



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

	if (!entry)

		return 0;



	memcpy(entry->var.VariableName, name, name_size);

	memcpy(&entry->var.VendorGuid, &vendor, sizeof(efi_guid_t));



	efivar_entry_add(entry, list);



	return 0;

}



static __init int efivar_ssdt_load(void)

{

	LIST_HEAD(entries);

	struct efivar_entry *entry, *aux;

	unsigned long size;

	void *data;

	int ret;



	ret = efivar_init(efivar_ssdt_iter, &entries, true, &entries);



	list_for_each_entry_safe(entry, aux, &entries, list) {

		pr_info("loading SSDT from variable %s-%pUl\n", efivar_ssdt,

			&entry->var.VendorGuid);



		list_del(&entry->list);



		ret = efivar_entry_size(entry, &size);

		if (ret) {

			pr_err("failed to get var size\n");

			goto free_entry;

		}



		data = kmalloc(size, GFP_KERNEL);

		if (!data)

			goto free_entry;



		ret = efivar_entry_get(entry, NULL, &size, data);

		if (ret) {

			pr_err("failed to get var data\n");

			goto free_data;

		}



		ret = acpi_load_table(data);

		if (ret) {

			pr_err("failed to load table: %d\n", ret);

			goto free_data;

		}



		goto free_entry;



free_data:

		kfree(data);



free_entry:

		kfree(entry);

	}



	return ret;

}

#else

static inline int efivar_ssdt_load(void) { return 0; }

#endif



/*

/*

 * We register the efi subsystem with the firmware subsystem and the

 * We register the efi subsystem with the firmware subsystem and the

 * efivars subsystem with the efi subsystem, if the system was booted with

 * efivars subsystem with the efi subsystem, if the system was booted with
@@ -218,6 +311,9 @@ static int __init efisubsys_init(void) 
	if (error)

	if (error)

		goto err_put;

		goto err_put;





	if (efi_enabled(EFI_RUNTIME_SERVICES))

		efivar_ssdt_load();



	error = sysfs_create_group(efi_kobj, &efi_subsys_attr_group);

	error = sysfs_create_group(efi_kobj, &efi_subsys_attr_group);

	if (error) {

	if (error) {

		pr_err("efi: Sysfs attribute export failed with error %d.\n",

		pr_err("efi: Sysfs attribute export failed with error %d.\n",

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