Hi Arnd, Alexei, On Mon, May 28, 2018 at 5:31 PM, Arnd Bergmann <arnd@xxxxxxxx> 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. So that was done in commit 819dd92b9c0bc7bc ("bpfilter: switch to CC from HOSTCC"), but it is not sufficient: GEN net/bpfilter/bpfilter_umh.o Usage: m68k-linux-gnu-objcopy [option(s)] in-file [out-file] Copies a binary file, possibly transforming it in the process The options are: [...] net/bpfilter/Makefile:29: recipe for target 'net/bpfilter/bpfilter_umh.o' failed make[5]: *** [net/bpfilter/bpfilter_umh.o] Error 1 > --- 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 No, (currently) it does depend on X86, due to its use of: $(OBJCOPY) -I binary -O $(CONFIG_OUTPUT_FORMAT) with CONFIG_OUTPUT_FORMAT being defined on X86 only... > default m > help > This builds bpfilter kernel module with embedded user mode helper Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds -- 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