Commit b16d8c23 authored by Matt Fleming's avatar Matt Fleming Committed by H. Peter Anvin

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

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: default avatarIngo Molnar <mingo@kernel.org>
Cc: Borislav Petkov <bp@suse.de>
Signed-off-by: default avatarMatt Fleming <matt.fleming@intel.com>
Link: http://lkml.kernel.org/r/1407193939-27813-1-git-send-email-matt@console-pimps.orgSigned-off-by: default avatarH. Peter Anvin <hpa@linux.intel.com>
parent 99a5603e
......@@ -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.
......
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