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efi: Make it possible to disable efivar_ssdt entirely

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commit 435d1a4715 upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Peter Jones 2020-06-15 16:24:08 -04:00 committed by Greg Kroah-Hartman
parent 89306f5ea3
commit d08e8347b7
2 changed files with 12 additions and 1 deletions
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11
drivers/firmware/efi/Kconfig
View file

@ -164,6 +164,17 @@ config RESET_ATTACK_MITIGATION
have been evicted, since otherwise it will trigger even on clean
reboots.
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.endmenu
endmenu
config UEFI_CPER

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

@ -221,7 +221,7 @@ static void generic_ops_unregister(void)
efivars_unregister(&generic_efivars);
}
#if IS_ENABLED(CONFIG_ACPI)
#ifdef CONFIG_EFI_CUSTOM_SSDT_OVERLAYS
#define EFIVAR_SSDT_NAME_MAX 16
static char efivar_ssdt[EFIVAR_SSDT_NAME_MAX] __initdata;
static int __init efivar_ssdt_setup(char *str)