linux-kernel - [PATCH v2] x86/efi: Fix 3DNow optimization build failure in EFI stub

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Date:	Tue,  5 Aug 2014 00:12:19 +0100
From:	Matt Fleming <matt@...sole-pimps.org>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Ingo Molnar <mingo@...nel.org>, linux-efi@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Matt Fleming <matt.fleming@...el.com>,
	Borislav Petkov <bp@...e.de>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: [PATCH v2] x86/efi: Fix 3DNow optimization build failure in EFI stub

From: Matt Fleming <matt.fleming@...el.com>

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_STUB 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@x1.osrc.amd.com

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

Reported-by: Ingo Molnar <mingo@...nel.org>
Cc: H. Peter Anvin <hpa@...or.com>
Cc: Borislav Petkov <bp@...e.de>
Cc: Thomas Gleixner <tglx@...utronix.de>
Signed-off-by: Matt Fleming <matt.fleming@...el.com>

---

v2: Only disallow CONFIG_X86_USE_3DNOW for EFI_STUB, not for the EFI
runtime services.

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 801ed36c2e49..7ea8aaaab7fc 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1536,7 +1536,7 @@ config EFI

 config EFI_STUB
        bool "EFI stub support"
-       depends on EFI
+       depends on EFI && !X86_USE_3DNOW
        ---help---
           This kernel feature allows a bzImage to be loaded directly
 	  by EFI firmware without the use of a bootloader.
-- 
1.9.0

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