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-rw-r--r--include/linux/efi.h15
1 files changed, 14 insertions, 1 deletions
diff --git a/include/linux/efi.h b/include/linux/efi.h
index 45ff763fba76..be08518c2553 100644
--- a/include/linux/efi.h
+++ b/include/linux/efi.h
@@ -48,7 +48,20 @@ typedef u16 efi_char16_t; /* UNICODE character */
typedef u64 efi_physical_addr_t;
typedef void *efi_handle_t;
-typedef guid_t efi_guid_t;
+/*
+ * The UEFI spec and EDK2 reference implementation both define EFI_GUID as
+ * struct { u32 a; u16; b; u16 c; u8 d[8]; }; and so the implied alignment
+ * is 32 bits not 8 bits like our guid_t. In some cases (i.e., on 32-bit ARM),
+ * this means that firmware services invoked by the kernel may assume that
+ * efi_guid_t* arguments are 32-bit aligned, and use memory accessors that
+ * do not tolerate misalignment. So let's set the minimum alignment to 32 bits.
+ *
+ * Note that the UEFI spec as well as some comments in the EDK2 code base
+ * suggest that EFI_GUID should be 64-bit aligned, but this appears to be
+ * a mistake, given that no code seems to exist that actually enforces that
+ * or relies on it.
+ */
+typedef guid_t efi_guid_t __aligned(__alignof__(u32));
#define EFI_GUID(a,b,c,d0,d1,d2,d3,d4,d5,d6,d7) \
GUID_INIT(a, b, c, d0, d1, d2, d3, d4, d5, d6, d7)