diff options
| -rw-r--r-- | Documentation/acpi/ssdt-overlays.txt | 67 | ||||
| -rw-r--r-- | Documentation/kernel-parameters.txt | 7 | ||||
| -rw-r--r-- | drivers/firmware/efi/efi.c | 96 |
3 files changed, 170 insertions, 0 deletions
diff --git a/Documentation/acpi/ssdt-overlays.txt b/Documentation/acpi/ssdt-overlays.txt index 8050259..c4b57ba 100644 --- a/Documentation/acpi/ssdt-overlays.txt +++ b/Documentation/acpi/ssdt-overlays.txt @@ -89,3 +89,70 @@ 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 diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt index 82b42c9..bbfb56f 100644 --- a/Documentation/kernel-parameters.txt +++ b/Documentation/kernel-parameters.txt @@ -1185,6 +1185,13 @@ 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. diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c index 05509f3..8730fd4 100644 --- a/drivers/firmware/efi/efi.c +++ b/drivers/firmware/efi/efi.c @@ -24,6 +24,9 @@ #include <linux/of_fdt.h> #include <linux/io.h> #include <linux/platform_device.h> +#include <linux/slab.h> +#include <linux/acpi.h> +#include <linux/ucs2_string.h> #include <asm/early_ioremap.h> @@ -195,6 +198,96 @@ 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] __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 * efivars subsystem with the efi subsystem, if the system was booted with @@ -218,6 +311,9 @@ 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", |
