Commit fd9d0ca2 authored by Nathan Chancellor's avatar Nathan Chancellor Committed by Thomas Bogendoerfer

MIPS: Unconditionally specify '-EB' or '-EL'

This was all done to work around a GCC bug that has been fixed after
4.2. The kernel requires GCC 4.6 or newer so remove all of these hacks
and just use the traditional flags.

 $ mips64-linux-gcc --version | head -n1
 mips64-linux-gcc (GCC) 4.6.3

 $ mips64-linux-gcc -EB -dM -E -C -x c /dev/null | grep MIPSE
 #define MIPSEB 1
 #define __MIPSEB__ 1
 #define _MIPSEB 1
 #define __MIPSEB 1

 $ mips64-linux-gcc -EL -dM -E -C -x c /dev/null | grep MIPSE
 #define __MIPSEL__ 1
 #define MIPSEL 1
 #define _MIPSEL 1
 #define __MIPSEL 1

This is necessary when converting the MIPS VDSO to use $(LD) instead of
$(CC) to link because the OUTPUT_FORMAT is defaulted to little endian
and only flips to big endian when '-EB' is set on the command line.
There is no issue currently because the compiler explicitly passes
'-EB' or '-EL' to the linker regardless of whether or not it was
provided by the user. Passing '-v' to VDSO_LDFLAGS shows:

<gcc_prefix>/libexec/gcc/mips64-linux/9.3.0/collect2 ... -EB ...

even though '-EB' is nowhere to be found in KBUILD_CFLAGS. The VDSO
Makefile already supports getting '-EB' or '-EL' from KBUILD_CFLAGS
through a filter directive but '-EB' or '-EL' is not always present.

If we do not do this, we will see the following error when compiling
for big endian:

$ make -j$(nproc) ARCH=mips CROSS_COMPILE=mips64-linux- \
  64r2el_defconfig arch/mips/vdso/
...
mips64-linux-ld: arch/mips/vdso/elf.o: compiled for a big endian system
and target is little endian
mips64-linux-ld: arch/mips/vdso/elf.o: endianness incompatible with that
of the selected emulation
mips64-linux-ld: failed to merge target specific data of file
arch/mips/vdso/elf.o
...

Remove this legacy hack and just use '-EB' and '-EL' unconditionally.
Reported-by: default avatarThomas Bogendoerfer <tsbogend@alpha.franken.de>
Signed-off-by: default avatarNathan Chancellor <natechancellor@gmail.com>
Signed-off-by: default avatarThomas Bogendoerfer <tsbogend@alpha.franken.de>
parent e91946d6
......@@ -116,33 +116,8 @@ endif
cflags-y += -ffreestanding
#
# We explicitly add the endianness specifier if needed, this allows
# to compile kernels with a toolchain for the other endianness. We
# carefully avoid to add it redundantly because gcc 3.3/3.4 complains
# when fed the toolchain default!
#
# Certain gcc versions up to gcc 4.1.1 (probably 4.2-subversion as of
# 2006-10-10 don't properly change the predefined symbols if -EB / -EL
# are used, so we kludge that here. A bug has been filed at
# http://gcc.gnu.org/bugzilla/show_bug.cgi?id=29413.
#
# clang doesn't suffer from these issues and our checks against -dumpmachine
# don't work so well when cross compiling, since without providing --target
# clang's output will be based upon the build machine. So for clang we simply
# unconditionally specify -EB or -EL as appropriate.
#
ifdef CONFIG_CC_IS_CLANG
cflags-$(CONFIG_CPU_BIG_ENDIAN) += -EB
cflags-$(CONFIG_CPU_LITTLE_ENDIAN) += -EL
else
undef-all += -UMIPSEB -U_MIPSEB -U__MIPSEB -U__MIPSEB__
undef-all += -UMIPSEL -U_MIPSEL -U__MIPSEL -U__MIPSEL__
predef-be += -DMIPSEB -D_MIPSEB -D__MIPSEB -D__MIPSEB__
predef-le += -DMIPSEL -D_MIPSEL -D__MIPSEL -D__MIPSEL__
cflags-$(CONFIG_CPU_BIG_ENDIAN) += $(shell $(CC) -dumpmachine |grep -q 'mips.*el-.*' && echo -EB $(undef-all) $(predef-be))
cflags-$(CONFIG_CPU_LITTLE_ENDIAN) += $(shell $(CC) -dumpmachine |grep -q 'mips.*el-.*' || echo -EL $(undef-all) $(predef-le))
endif
cflags-$(CONFIG_SB1XXX_CORELIS) += $(call cc-option,-mno-sched-prolog) \
-fno-omit-frame-pointer
......
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