[PATCH 0/2] efi/arm regression fixes

[PATCH 0/2] efi/arm regression fixes

[Ard Biesheuvel]

A couple of fixes for ef/arm issues that were introduced before the
merge window.

Ard Biesheuvel (2):
  efi: arm: revert deferred unmap of early memmap mapping
  efi/arm: libstub: pack FDT after populating it

 drivers/firmware/efi/arm-init.c    | 4 ++++
 drivers/firmware/efi/arm-runtime.c | 2 +-
 drivers/firmware/efi/libstub/fdt.c | 4 ++++
 drivers/firmware/efi/memmap.c      | 3 +++
 4 files changed, 12 insertions(+), 1 deletion(-)

-- 
2.19.1

[PATCH 1/2] efi: arm: revert deferred unmap of early memmap mapping

[Ard Biesheuvel]

Commit 3ea86495aef2 ("efi/arm: preserve early mapping of UEFI memory
map longer for BGRT") deferred the unmap of the early mapping of the
UEFI to accommodate the ACPI BGRT code, which looks up the memory
type that backs the BGRT table to validate it against the requirements
of the UEFI spec.

Unfortunately, this causes problems on ARM, which does not permit
early mappings to persist after paging_init() is called, resulting
in a WARN() splat. Since we don't support the BGRT table on ARM anway,
let's revert ARM to the old behaviour, which is to take down the
early mapping at the end of efi_init().

Fixes: 3ea86495aef2 ("efi/arm: preserve early mapping of UEFI memory ...")
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
---
 drivers/firmware/efi/arm-init.c    | 4 ++++
 drivers/firmware/efi/arm-runtime.c | 2 +-
 drivers/firmware/efi/memmap.c      | 3 +++
 3 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/firmware/efi/arm-init.c b/drivers/firmware/efi/arm-init.c
index 388a929baf95..1a6a77df8a5e 100644
--- a/drivers/firmware/efi/arm-init.c
+++ b/drivers/firmware/efi/arm-init.c
@@ -265,6 +265,10 @@ void __init efi_init(void)
 				    (params.mmap & ~PAGE_MASK)));
 
 	init_screen_info();
+
+	/* ARM does not permit early mappings to persist across paging_init() */
+	if (IS_ENABLED(CONFIG_ARM))
+		efi_memmap_unmap();
 }
 
 static int __init register_gop_device(void)
diff --git a/drivers/firmware/efi/arm-runtime.c b/drivers/firmware/efi/arm-runtime.c
index 922cfb813109..a00934d263c5 100644
--- a/drivers/firmware/efi/arm-runtime.c
+++ b/drivers/firmware/efi/arm-runtime.c
@@ -110,7 +110,7 @@ static int __init arm_enable_runtime_services(void)
 {
 	u64 mapsize;
 
-	if (!efi_enabled(EFI_BOOT) || !efi_enabled(EFI_MEMMAP)) {
+	if (!efi_enabled(EFI_BOOT)) {
 		pr_info("EFI services will not be available.\n");
 		return 0;
 	}
diff --git a/drivers/firmware/efi/memmap.c b/drivers/firmware/efi/memmap.c
index fa2904fb841f..38b686c67b17 100644
--- a/drivers/firmware/efi/memmap.c
+++ b/drivers/firmware/efi/memmap.c
@@ -118,6 +118,9 @@ int __init efi_memmap_init_early(struct efi_memory_map_data *data)
 
 void __init efi_memmap_unmap(void)
 {
+	if (!efi_enabled(EFI_MEMMAP))
+		return;
+
 	if (!efi.memmap.late) {
 		unsigned long size;
 
-- 
2.19.1

[PATCH 2/2] efi/arm: libstub: pack FDT after populating it

[Ard Biesheuvel]

Commit 24d7c494ce46 ("efi/arm-stub: Round up FDT allocation to mapping
size") increased the allocation size for the FDT image created by the
stub to a fixed value of 2 MB, to simplify the former code that made
several attempts with increasing values for the size. This is reasonable
given that the allocation is of type EFI_LOADER_DATA, which is released
to the kernel unless it is explicitly memblock_reserve()d by the early
boot code.

However, this allocation size leaked into the 'size' field of the FDT
header metadata, and so the entire allocation remains occupied by the
device tree binary, even if most of it is not used to store device tree
information.

So call fdt_pack() to shrink the FDT data structure to its minimum size
after populating all the fields, so that the remaining memory is no
longer wasted.

Cc: <stable@vger.kernel.org> # v4.12+
Fixes: 24d7c494ce46 ("efi/arm-stub: Round up FDT allocation to mapping size")
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
---
 drivers/firmware/efi/libstub/fdt.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/firmware/efi/libstub/fdt.c b/drivers/firmware/efi/libstub/fdt.c
index 8830fa601e45..0c0d2312f4a8 100644
--- a/drivers/firmware/efi/libstub/fdt.c
+++ b/drivers/firmware/efi/libstub/fdt.c
@@ -158,6 +158,10 @@ static efi_status_t update_fdt(efi_system_table_t *sys_table, void *orig_fdt,
 			return efi_status;
 		}
 	}
+
+	/* shrink the FDT back to its minimum size */
+	fdt_pack(fdt);
+
 	return EFI_SUCCESS;
 
 fdt_set_fail:
-- 
2.19.1