From b484296f6fda23ab2c996892826ebcc12cbd2303 Mon Sep 17 00:00:00 2001
From: AKASHI Takahiro <takahiro.akashi@linaro.org>
Date: Wed, 11 Mar 2020 15:18:18 +0900
Subject: [PATCH] efi_loader: get_memory_map: return parameters whenever
 possible

Currently, if GetMemoryMap API returns EFI_BUFFER_TOO_SMALL, it doesn't
set valid values to other parameters, descriptor_size and
descriptor_version, except memory_map_size.
Some efi applications, however, may use those value; in particular,
xen uses descriptor_size to calculate a size of buffer to be allocated.

While UEFI specification is ambiguous in this point, it would be better
to address this issue proactively to maximize the compatibility with
existing efi applications.

With this patch, for example, xen.efi (and hence linux kernel) can be
started via bootefi without modification.

Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
Reviewed-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
---
 lib/efi_loader/efi_memory.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/lib/efi_loader/efi_memory.c b/lib/efi_loader/efi_memory.c
index 89adf20310..97d90f069a 100644
--- a/lib/efi_loader/efi_memory.c
+++ b/lib/efi_loader/efi_memory.c
@@ -627,18 +627,18 @@ efi_status_t efi_get_memory_map(efi_uintn_t *memory_map_size,
 
 	*memory_map_size = map_size;
 
-	if (provided_map_size < map_size)
-		return EFI_BUFFER_TOO_SMALL;
-
-	if (!memory_map)
-		return EFI_INVALID_PARAMETER;
-
 	if (descriptor_size)
 		*descriptor_size = sizeof(struct efi_mem_desc);
 
 	if (descriptor_version)
 		*descriptor_version = EFI_MEMORY_DESCRIPTOR_VERSION;
 
+	if (provided_map_size < map_size)
+		return EFI_BUFFER_TOO_SMALL;
+
+	if (!memory_map)
+		return EFI_INVALID_PARAMETER;
+
 	/* Copy list into array */
 	/* Return the list in ascending order */
 	memory_map = &memory_map[map_entries - 1];
-- 
2.39.5