Re: [PATCH] [net-next, wrong] make BPFILTER_UMH depend on X86

From: Geert Uytterhoeven
Date: Fri Jun 08 2018 - 05:41:01 EST

Hi Daniel,

On Fri, Jun 8, 2018 at 11:33 AM, Daniel Borkmann <daniel@xxxxxxxxxxxxx> wrote:
> On 06/08/2018 10:57 AM, Geert Uytterhoeven wrote:
>> 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
>>> 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:
>> with CONFIG_OUTPUT_FORMAT being defined on X86 only...
> That hard dependency should have been fixed with the following patch in -net tree:

Thanks, confirmed.



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