On Sun, Apr 26, 2020 at 06:27:37PM +0200, Thomas Bogendoerfer wrote: > On Thu, Apr 23, 2020 at 10:18:06AM -0700, Nathan Chancellor wrote: > > Currently, the VDSO is being linked through $(CC). This does not match > > how the rest of the kernel links objects, which is through the $(LD) > > variable. > > this causes build errors for me when (cross) compiling a big endian target: > > target is little endian > mips64-linux-gnu-ld: arch/mips/vdso/elf.o: endianness incompatible with that of the selected emulation > mips64-linux-gnu-ld: failed to merge target specific data of file arch/mips/vdso/elf.o > > Thomas. > Thanks for reporting this, I figured it out. This is the solution that I came up with, I'll send out a v4 tomorrow once I do some more testing. Cheers, Nathan >From 256e3b6c8fff7a66aa29961ebefc0fe653ec34b6 Mon Sep 17 00:00:00 2001 From: Nathan Chancellor <natechancellor@xxxxxxxxx> Date: Mon, 27 Apr 2020 17:02:55 -0700 Subject: [PATCH] MIPS: Unconditionally specify '-EL' or '-EB' 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, which is inherited from KBUILD_CFLAGS. Without this, we will see the following error when compiling for big endian (64r2_defconfig): $ make -j$(nproc) ARCH=mips CROSS_COMPILE=mips64-linux- \ 64r2el_defconfig arch/mips/vdso/ ... mips64-linux-ld: arch/mips/vdso/elf.o: compiled for a big endian system and target is little endian mips64-linux-ld: arch/mips/vdso/elf.o: endianness incompatible with that of the selected emulation mips64-linux-ld: failed to merge target specific data of file arch/mips/vdso/elf.o ... Reported-by: Thomas Bogendoerfer <tsbogend@xxxxxxxxxxxxxxxx> Signed-off-by: Nathan Chancellor <natechancellor@xxxxxxxxx> --- arch/mips/Makefile | 25 ------------------------- 1 file changed, 25 deletions(-) diff --git a/arch/mips/Makefile b/arch/mips/Makefile index e1c44aed81565..301efb90b51ed 100644 --- a/arch/mips/Makefile +++ b/arch/mips/Makefile @@ -116,33 +116,8 @@ endif cflags-y += -ffreestanding -# -# We explicitly add the endianness specifier if needed, this allows -# to compile kernels with a toolchain for the other endianness. We -# carefully avoid to add it redundantly because gcc 3.3/3.4 complains -# when fed the toolchain default! -# -# Certain gcc versions up to gcc 4.1.1 (probably 4.2-subversion as of -# 2006-10-10 don't properly change the predefined symbols if -EB / -EL -# are used, so we kludge that here. A bug has been filed at -# http://gcc.gnu.org/bugzilla/show_bug.cgi?id=29413. -# -# clang doesn't suffer from these issues and our checks against -dumpmachine -# don't work so well when cross compiling, since without providing --target -# clang's output will be based upon the build machine. So for clang we simply -# unconditionally specify -EB or -EL as appropriate. -# -ifdef CONFIG_CC_IS_CLANG cflags-$(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 -- 2.26.2
