[PATCH AUTOSEL 4.18 66/88] efi/arm: preserve early mapping of UEFI memory map longer for BGRT

[Sasha Levin]

From: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>

[ Upstream commit 3ea86495aef2f6de26b7cb1599ba350dd6a0c521 ]

The BGRT code validates the contents of the table against the UEFI
memory map, and so it expects it to be mapped when the code runs.

On ARM, this is currently not the case, since we tear down the early
mapping after efi_init() completes, and only create the permanent
mapping in arm_enable_runtime_services(), which executes as an early
initcall, but still leaves a window where the UEFI memory map is not
mapped.

So move the call to efi_memmap_unmap() from efi_init() to
arm_enable_runtime_services().

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
[will: fold in EFI_MEMMAP attribute check from Ard]
Signed-off-by: Will Deacon <will.deacon@xxxxxxx>
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxxxx>
---
 drivers/firmware/efi/arm-init.c    | 1 -
 drivers/firmware/efi/arm-runtime.c | 4 +++-
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/firmware/efi/arm-init.c b/drivers/firmware/efi/arm-init.c
index b5214c143fee..388a929baf95 100644
--- a/drivers/firmware/efi/arm-init.c
+++ b/drivers/firmware/efi/arm-init.c
@@ -259,7 +259,6 @@ void __init efi_init(void)
 
 	reserve_regions();
 	efi_esrt_init();
-	efi_memmap_unmap();
 
 	memblock_reserve(params.mmap & PAGE_MASK,
 			 PAGE_ALIGN(params.mmap_size +
diff --git a/drivers/firmware/efi/arm-runtime.c b/drivers/firmware/efi/arm-runtime.c
index 5889cbea60b8..4712445c3213 100644
--- a/drivers/firmware/efi/arm-runtime.c
+++ b/drivers/firmware/efi/arm-runtime.c
@@ -110,11 +110,13 @@ static int __init arm_enable_runtime_services(void)
 {
 	u64 mapsize;
 
-	if (!efi_enabled(EFI_BOOT)) {
+	if (!efi_enabled(EFI_BOOT) || !efi_enabled(EFI_MEMMAP)) {
 		pr_info("EFI services will not be available.\n");
 		return 0;
 	}
 
+	efi_memmap_unmap();
+
 	if (efi_runtime_disabled()) {
 		pr_info("EFI runtime services will be disabled.\n");
 		return 0;
-- 
2.17.1