2018-05-31 0:17 GMT+09:00 Alexei Starovoitov <alexei.starovoitov@xxxxxxxxx>: > On Mon, May 28, 2018 at 05:31:01PM +0200, Arnd Bergmann wrote: >> When build testing across architectures, I run into a build error on >> all targets other than X86: >> >> gcc-8.1.0-nolibc/arm-linux-gnueabi/bin/arm-linux-gnueabi-objdump: net/bpfilter/bpfilter_umh: File format not recognized >> gcc-8.1.0-nolibc/arm-linux-gnueabi/bin/arm-linux-gnueabi-objcopy:net/bpfilter/bpfilter_umh.o: Invalid bfd target >> >> The problem is that 'hostprogs' get built with 'gcc' rather than >> '$(CROSS_COMPILE)gcc', and my default gcc (as most people's) targets x86. >> >> To work around it, adding an X86 dependency gets randconfigs building >> again on my box. >> >> Clearly, this is not a good solution, since it should actually work fine >> when building native kernels on other architectures but that is now >> disabled, while cross building an x86 kernel on another host is still >> broken after my patch. >> >> What we probably want here is to try out if the compiler is able to build >> executables for the target architecture and not build the helper otherwise, >> at least when compile-testing. No idea how to do that though. >> >> Link: http://www.kernel.org/pub/tools/crosstool/ >> Cc: Masahiro Yamada <yamada.masahiro@xxxxxxxxxxxxx> >> Cc: linux-kbuild@xxxxxxxxxxxxxxx >> Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx> >> --- >> net/bpfilter/Kconfig | 1 + >> 1 file changed, 1 insertion(+) >> >> diff --git a/net/bpfilter/Kconfig b/net/bpfilter/Kconfig >> index 60725c5f79db..61cc4fcbb4d0 100644 >> --- a/net/bpfilter/Kconfig >> +++ b/net/bpfilter/Kconfig >> @@ -9,6 +9,7 @@ menuconfig BPFILTER >> if BPFILTER >> config BPFILTER_UMH >> tristate "bpfilter kernel module with user mode helper" >> + depends on X86 # actually depends on native builds > > depends on X86 will break it on arm. > I think the better short term fix would be to test that HOSTCC == CC > It doesn't have to be the same compiler. HOSTCC's arch == kernel ARCH > Not sure how to hack makefile to do that. > Long term we need to get rid of HOSTCC dependency. > -- > To unsubscribe from this list: send the line "unsubscribe linux-kbuild" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html Hmm. For cross-compiling, we set 'ARCH' via the environment variable or the command line. ARCH is not explicitly set, the top-level Makefile sets it to $(SUBARCH) ARCH ?= $(SUBARCH) Maybe, we can assume the native build if $(ARCH) and $(SUBARCH) are the same? -- Best Regards Masahiro Yamada -- To unsubscribe from this list: send the line "unsubscribe linux-kbuild" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
