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authorArd Biesheuvel <ard.biesheuvel@linaro.org>2018-07-11 12:40:38 +0300
committerIngo Molnar <mingo@kernel.org>2018-07-16 01:43:12 +0300
commit3d7ee348aa4127a7893c11261da9b76371a970e6 (patch)
treeb3dee7e3ebdf9d4ddce9cd259031fce35ed145e5 /drivers/firmware/efi
parentf5dcc214aae29a68b37b2b4183f7171724e7b02d (diff)
downloadlinux-3d7ee348aa4127a7893c11261da9b76371a970e6.tar.xz
efi/libstub/arm: Add opt-in Kconfig option for the DTB loader
There are various ways a platform can provide a device tree binary to the kernel, with different levels of sophistication: - ideally, the UEFI firmware, which is tightly coupled with the platform, provides a device tree image directly as a UEFI configuration table, and typically permits the contents to be manipulated either via menu options or via UEFI environment variables that specify a replacement image, - GRUB for ARM has a 'devicetree' directive which allows a device tree image to be loaded from any location accessible to GRUB, and supersede the one provided by the firmware, - the EFI stub implements a dtb= command line option that allows a device tree image to be loaded from a file residing in the same file system as the one the kernel image was loaded from. The dtb= command line option was never intended to be more than a development feature, to allow the other options to be implemented in parallel. So let's make it an opt-in feature that is disabled by default, but can be re-enabled at will. Note that we already disable the dtb= command line option when we detect that we are running with UEFI Secure Boot enabled. Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> Reviewed-by: Alexander Graf <agraf@suse.de> Acked-by: Leif Lindholm <leif.lindholm@linaro.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: linux-efi@vger.kernel.org Link: http://lkml.kernel.org/r/20180711094040.12506-7-ard.biesheuvel@linaro.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'drivers/firmware/efi')
-rw-r--r--drivers/firmware/efi/Kconfig12
-rw-r--r--drivers/firmware/efi/libstub/arm-stub.c7
2 files changed, 16 insertions, 3 deletions
diff --git a/drivers/firmware/efi/Kconfig b/drivers/firmware/efi/Kconfig
index 781a4a337557..d8e159feb573 100644
--- a/drivers/firmware/efi/Kconfig
+++ b/drivers/firmware/efi/Kconfig
@@ -87,6 +87,18 @@ config EFI_RUNTIME_WRAPPERS
config EFI_ARMSTUB
bool
+config EFI_ARMSTUB_DTB_LOADER
+ bool "Enable the DTB loader"
+ depends on EFI_ARMSTUB
+ help
+ Select this config option to add support for the dtb= command
+ line parameter, allowing a device tree blob to be loaded into
+ memory from the EFI System Partition by the stub.
+
+ The device tree is typically provided by the platform or by
+ the bootloader, so this option is mostly for development
+ purposes only.
+
config EFI_BOOTLOADER_CONTROL
tristate "EFI Bootloader Control"
depends on EFI_VARS
diff --git a/drivers/firmware/efi/libstub/arm-stub.c b/drivers/firmware/efi/libstub/arm-stub.c
index 01a9d78ee415..c98b1856fc3d 100644
--- a/drivers/firmware/efi/libstub/arm-stub.c
+++ b/drivers/firmware/efi/libstub/arm-stub.c
@@ -202,9 +202,10 @@ unsigned long efi_entry(void *handle, efi_system_table_t *sys_table,
* 'dtb=' unless UEFI Secure Boot is disabled. We assume that secure
* boot is enabled if we can't determine its state.
*/
- if (secure_boot != efi_secureboot_mode_disabled &&
- strstr(cmdline_ptr, "dtb=")) {
- pr_efi(sys_table, "Ignoring DTB from command line.\n");
+ if (!IS_ENABLED(CONFIG_EFI_ARMSTUB_DTB_LOADER) ||
+ secure_boot != efi_secureboot_mode_disabled) {
+ if (strstr(cmdline_ptr, "dtb="))
+ pr_efi(sys_table, "Ignoring DTB from command line.\n");
} else {
status = handle_cmdline_files(sys_table, image, cmdline_ptr,
"dtb=",