@@ -88,3 +88,70 @@ cp ssdt.aml kernel/firmware/acpi
# on top:
find kernel | cpio -H newc --create > /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
@@ -1164,6 +1164,13 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
Address Range Mirroring feature even if your box
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]
See header of drivers/parisc/eisa.c.
@@ -24,6 +24,8 @@
#include <linux/of_fdt.h>
#include <linux/io.h>
#include <linux/platform_device.h>
+#include <linux/slab.h>
+#include <linux/acpi.h>
#include <asm/early_ioremap.h>
@@ -194,6 +196,110 @@ static void generic_ops_unregister(void)
efivars_unregister(&generic_efivars);
}
+#if IS_ENABLED(CONFIG_ACPI)
+#define EFIVAR_SSDT_NAME_MAX 16
+static char efivar_ssdt[EFIVAR_SSDT_NAME_MAX];
+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 LIST_HEAD(efivar_ssdts);
+
+static inline void pr_efivar_name(efi_char16_t *name16)
+{
+ char name[EFIVAR_SSDT_NAME_MAX];
+ int i;
+
+ for (i = 0; i < EFIVAR_SSDT_NAME_MAX - 1; i++)
+ name[i] = name16[i] & 0xFF;
+ name[i] = 0;
+ pr_cont("%s", name);
+}
+
+static __init int efivar_acpi_iter(efi_char16_t *name, efi_guid_t vendor,
+ unsigned long name_size, void *data)
+{
+ int i;
+ int str_len = name_size / sizeof(efi_char16_t);
+ struct efivar_entry *entry;
+
+ if (str_len != strlen(efivar_ssdt) + 1)
+ return 0;
+
+ for (i = 0; i < str_len; i++)
+ if ((name[i] & 0xFF) != efivar_ssdt[i])
+ return 0;
+
+ entry = kzalloc(sizeof(*entry), GFP_KERNEL);
+ if (!entry)
+ return -ENOMEM;
+
+ memcpy(entry->var.VariableName, name, name_size);
+ memcpy(&entry->var.VendorGuid, &vendor, sizeof(efi_guid_t));
+
+ efivar_entry_add(entry, &efivar_ssdts);
+
+ return 0;
+}
+
+static __init int efivar_ssdt_load(void)
+{
+ struct efivar_entry *i;
+ int err;
+
+ err = efivar_init(efivar_acpi_iter, NULL, false, false,
+ &efivar_ssdts);
+ if (err) {
+ pr_err("%s: efivar_init failed: %d\n", __func__, err);
+ return err;
+ }
+
+ list_for_each_entry(i, &efivar_ssdts, list) {
+ void *data;
+ unsigned long size;
+
+ pr_info("loading SSDT from EFI variable ");
+ pr_efivar_name(i->var.VariableName); pr_cont("\n");
+
+ err = efivar_entry_size(i, &size);
+ if (err) {
+ pr_err("failed to get size\n");
+ continue;
+ }
+
+ data = kmalloc(size, GFP_KERNEL);
+ if (!data)
+ continue;
+
+ err = efivar_entry_get(i, NULL, &size, data);
+ if (err) {
+ pr_err("failed to get data\n");
+ kfree(data);
+ continue;
+ }
+
+ err = acpi_load_table(data);
+ if (err) {
+ pr_err("failed to load table: %d\n", err);
+ kfree(data);
+ continue;
+ }
+
+ add_taint(TAINT_OVERLAY_ACPI_TABLE, LOCKDEP_STILL_OK);
+ }
+
+ return 0;
+}
+#else
+static inline int efivar_ssdt_load(void) {}
+#endif
+
/*
* We register the efi subsystem with the firmware subsystem and the
* efivars subsystem with the efi subsystem, if the system was booted with
@@ -217,6 +323,9 @@ static int __init efisubsys_init(void)
if (error)
goto err_put;
+ if (efi_enabled(EFI_RUNTIME_SERVICES))
+ efivar_ssdt_load();
+
error = sysfs_create_group(efi_kobj, &efi_subsys_attr_group);
if (error) {
pr_err("efi: Sysfs attribute export failed with error %d.\n",
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: Octavian Purdila <octavian.purdila@intel.com> --- Documentation/acpi/ssdt-overlays.txt | 67 +++++++++++++++++++++ Documentation/kernel-parameters.txt | 7 +++ drivers/firmware/efi/efi.c | 109 +++++++++++++++++++++++++++++++++++ 3 files changed, 183 insertions(+)