x86,efi: Implement efi_no_storage_paranoia parameter

commit 8c58bf3eec3b8fc8162fe557e9361891c20758f2 upstream.

Using this parameter one can disable the storage_size/2 check if
he is really sure that the UEFI does sane gc and fulfills the spec.

This parameter is useful if a devices uses more than 50% of the
storage by default.
The Intel DQSW67 desktop board is such a sucker for exmaple.

Signed-off-by: Richard Weinberger <richard@nod.at>
Signed-off-by: Matt Fleming <matt.fleming@intel.com>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

2 files changed, 19 insertions, 1 deletions

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 897f223dcf3e..2ba8272a4b82 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -734,6 +734,12 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
 	edd=		[EDD]
 			Format: {"off" | "on" | "skip[mbr]"}
 
+	efi_no_storage_paranoia [EFI; X86]
+			Using this parameter you can use more than 50% of
+			your efi variable storage. Use this parameter only if
+			you are really sure that your UEFI does sane gc and
+			fulfills the spec otherwise your board may brick.
+
 	eisa_irq_edge=	[PARISC,HW]
 			See header of drivers/parisc/eisa.c.
 
diff --git a/arch/x86/platform/efi/efi.c b/arch/x86/platform/efi/efi.c
index 3d7bb0535126..07ef7e8b2827 100644
--- a/arch/x86/platform/efi/efi.c
+++ b/arch/x86/platform/efi/efi.c
@@ -101,6 +101,15 @@ static int __init setup_add_efi_memmap(char *arg)
 }
 early_param("add_efi_memmap", setup_add_efi_memmap);
 
+static bool efi_no_storage_paranoia;
+
+static int __init setup_storage_paranoia(char *arg)
+{
+	efi_no_storage_paranoia = true;
+	return 0;
+}
+early_param("efi_no_storage_paranoia", setup_storage_paranoia);
+
 
 static efi_status_t virt_efi_get_time(efi_time_t *tm, efi_time_cap_t *tc)
 {
@@ -839,7 +848,10 @@ efi_status_t efi_query_variable_store(u32 attributes, unsigned long size)
 			    " is returning MaxVariableSize=0\n");
 
 	if (!storage_size || size > remaining_size ||
-	    (max_size && size > max_size) ||
+	    (max_size && size > max_size))
+		return EFI_OUT_OF_RESOURCES;
+
+	if (!efi_no_storage_paranoia &&
 	    (remaining_size - size) < (storage_size / 2))
 		return EFI_OUT_OF_RESOURCES;