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| author |   Ard Biesheuvel <ardb@kernel.org> | 2021-03-10 08:33:19 +0100 |
|---|---|---|
| committer | Ard Biesheuvel <ardb@kernel.org> | 2021-03-19 07:44:28 +0100 |
| commit | fb98cc0b3af2ba4d87301dff2b381b12eee35d7d (patch) | |
| tree | fe3f4a920ad0314863b5d42169170eb576c80820 /include | |
| parent | firmware/efi: Fix a use after bug in efi_mem_reserve_persistent (diff) | |
| download | linux-dev-fb98cc0b3af2ba4d87301dff2b381b12eee35d7d.tar.xz linux-dev-fb98cc0b3af2ba4d87301dff2b381b12eee35d7d.zip | |
efi: use 32-bit alignment for efi_guid_t literals
Commit 494c704f9af0 ("efi: Use 32-bit alignment for efi_guid_t") updated
the type definition of efi_guid_t to ensure that it always appears
sufficiently aligned (the UEFI spec is ambiguous about this, but given
the fact that its EFI_GUID type is defined in terms of a struct carrying
a uint32_t, the natural alignment is definitely >= 32 bits).
However, we missed the EFI_GUID() macro which is used to instantiate
efi_guid_t literals: that macro is still based on the guid_t type,
which does not have a minimum alignment at all. This results in warnings
such as
In file included from drivers/firmware/efi/mokvar-table.c:35:
include/linux/efi.h:1093:34: warning: passing 1-byte aligned argument to
4-byte aligned parameter 2 of 'get_var' may result in an unaligned pointer
access [-Walign-mismatch]
status = get_var(L"SecureBoot", &EFI_GLOBAL_VARIABLE_GUID, NULL, &size,
^
include/linux/efi.h:1101:24: warning: passing 1-byte aligned argument to
4-byte aligned parameter 2 of 'get_var' may result in an unaligned pointer
access [-Walign-mismatch]
get_var(L"SetupMode", &EFI_GLOBAL_VARIABLE_GUID, NULL, &size, &setupmode);
The distinction only matters on CPUs that do not support misaligned loads
fully, but 32-bit ARM's load-multiple instructions fall into that category,
and these are likely to be emitted by the compiler that built the firmware
for loading word-aligned 128-bit GUIDs from memory
So re-implement the initializer in terms of our own efi_guid_t type, so that
the alignment becomes a property of the literal's type.
Fixes: 494c704f9af0 ("efi: Use 32-bit alignment for efi_guid_t")
Reported-by: Nathan Chancellor <nathan@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Tested-by: Nathan Chancellor <nathan@kernel.org>
Link: https://github.com/ClangBuiltLinux/linux/issues/1327
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Diffstat (limited to 'include')
| -rw-r--r-- | include/linux/efi.h | 6 |
1 files changed, 4 insertions, 2 deletions
diff --git a/include/linux/efi.h b/include/linux/efi.h index 8710f5710c1d..6b5d36babfcc 100644 --- a/include/linux/efi.h +++ b/include/linux/efi.h @@ -72,8 +72,10 @@ typedef void *efi_handle_t; */ 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) +#define EFI_GUID(a, b, c, d...) (efi_guid_t){ { \ + (a) & 0xff, ((a) >> 8) & 0xff, ((a) >> 16) & 0xff, ((a) >> 24) & 0xff, \ + (b) & 0xff, ((b) >> 8) & 0xff, \ + (c) & 0xff, ((c) >> 8) & 0xff, d } } /* * Generic EFI table header |