[PATCH] x86/efi: Fix 3DNow optimization build failure in EFI stub

[Matt Fleming]

From: Matt Fleming <matt.fleming@xxxxxxxxx>

Building a 32-bit kernel with CONFIG_X86_USE_3DNOW and CONFIG_EFI_STUB
leads to the following build error,

  drivers/firmware/efi/libstub/lib.a(efi-stub-helper.o): In function `efi_relocate_kernel':
  efi-stub-helper.c:(.text+0xda5): undefined reference to `_mmx_memcpy'

This is due to the fact that the EFI boot stub pulls in the 3DNow
optimized versions of the memcpy() prototype from
arch/x86/include/asm/string_32.h, even though the _mmx_memcpy()
implementation isn't available in the EFI stub.

For now, predicate CONFIG_EFI on !CONFIG_X86_USE_3DNOW. This is most
definitely a temporary fix. A complete solution will involve selectively
including kernel headers/symbols into the early-boot execution
environment of the EFI boot stub, i.e. something analogous to the way
that the _SETUP symbol is used.

Previous attempts have been made to fix this kind of problem, though
none seem to have ever been merged,

  http://lkml.kernel.org/r/20120329104822.GA17233@xxxxxxxxxxxxxxx

Clearly, this problem has been around for a long time.

Reported-by: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: H. Peter Anvin <hpa@xxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Matt Fleming <matt.fleming@xxxxxxxxx>

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 801ed36c2e49..fcad2e15e92a 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1520,7 +1520,7 @@ config X86_SMAP
 
 config EFI
 	bool "EFI runtime service support"
-	depends on ACPI
+	depends on ACPI && !X86_USE_3DNOW
 	select UCS2_STRING
 	select EFI_RUNTIME_WRAPPERS
 	---help---
-- 
1.9.0

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/