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efi: Make it possible to disable efivar_ssdt entirely

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In most cases, such as CONFIG_ACPI_CUSTOM_DSDT and
CONFIG_ACPI_TABLE_UPGRADE, boot-time modifications to firmware tables
are tied to specific Kconfig options.  Currently this is not the case
for modifying the ACPI SSDT via the efivar_ssdt kernel command line
option and associated EFI variable.

This patch adds CONFIG_EFI_CUSTOM_SSDT_OVERLAYS, which defaults
disabled, in order to allow enabling or disabling that feature during
the build.

Cc: <stable@vger.kernel.org>
Signed-off-by: Peter Jones <pjones@redhat.com>
Link: https://lore.kernel.org/r/20200615202408.2242614-1-pjones@redhat.com
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
This commit is contained in:
Peter Jones 2020-06-15 16:24:08 -04:00 committed by Ard Biesheuvel
parent 8c0a839c2b
commit 435d1a4715
2 changed files with 12 additions and 1 deletions
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11
drivers/firmware/efi/Kconfig
View File

@ -278,3 +278,14 @@ config EFI_EARLYCON
depends on SERIAL_EARLYCON && !ARM && !IA64 depends on SERIAL_EARLYCON && !ARM && !IA64
select FONT_SUPPORT select FONT_SUPPORT
select ARCH_USE_MEMREMAP_PROT select ARCH_USE_MEMREMAP_PROT
config EFI_CUSTOM_SSDT_OVERLAYS
bool "Load custom ACPI SSDT overlay from an EFI variable"
depends on EFI_VARS && ACPI
default ACPI_TABLE_UPGRADE
help
Allow loading of an ACPI SSDT overlay from an EFI variable specified
by a kernel command line option.
See Documentation/admin-guide/acpi/ssdt-overlays.rst for more
information.

2
drivers/firmware/efi/efi.c
View File

@ -189,7 +189,7 @@ static void generic_ops_unregister(void)
efivars_unregister(&generic_efivars); efivars_unregister(&generic_efivars);
} }
#if IS_ENABLED(CONFIG_ACPI) #ifdef CONFIG_EFI_CUSTOM_SSDT_OVERLAYS
#define EFIVAR_SSDT_NAME_MAX 16 #define EFIVAR_SSDT_NAME_MAX 16
static char efivar_ssdt[EFIVAR_SSDT_NAME_MAX] __initdata; static char efivar_ssdt[EFIVAR_SSDT_NAME_MAX] __initdata;
static int __init efivar_ssdt_setup(char *str) static int __init efivar_ssdt_setup(char *str)