From: Alexei Starovoitov <alexei.starovoi...@gmail.com> Date: Tue, 5 Jun 2018 15:29:34 -0700
> On Tue, Jun 05, 2018 at 05:03:59PM -0400, David Miller wrote: >> >> Alexei, I tried to build bpfilter on sparc64 and it shows that >> CONFIG_OUTPUT_FORMAT is an x86 specific Kconfig value. >> >> And, even if I added it, it's not clear what it should even be set to. >> >> Right now, for example, my userland builds default to 32-bit sparc >> even though I'm building a 64-bit kernel. >> >> I think what ends up happening has to be in some way in response to >> what kind of "native" binaries HOSTCC is actually building. > > I guess you mean native-ness not of HOSTCC, but what target rootfs will be. Target rootfs is where I am building the kernel in this case. Kernel running is 64-bit, most of userland is 32-bit. Kernel is built explicitly with "-m64" but gcc by default is building 32-bit. > I guess it's probably equal to 32 or 64-bitness of the kernel from > CC. Nope, they are and can be different, even natively. > I completely forgot that I need to fix CONFIG_OUTPUT_FORMAT. > On my arm64 I just did > export CONFIG_OUTPUT_FORMAT=elf64-littleaarch64 > before doing 'make'. > I can do a hack to extract it from objdump > similar to the hack I do for '-B ...' > Like the patch below... > and it works on x64 too, but I'm not sure about sparc. ... > @@ -21,7 +21,7 @@ endif > # which bpfilter_kern.c passes further into umh blob loader at run-time > quiet_cmd_copy_umh = GEN $@ > cmd_copy_umh = echo ':' > $(obj)/.bpfilter_umh.o.cmd; \ > - $(OBJCOPY) -I binary -O $(CONFIG_OUTPUT_FORMAT) \ > + $(OBJCOPY) -I binary -O `$(OBJDUMP) -f $<|grep format|cut -d' ' -f8` \ > -B `$(OBJDUMP) -f $<|grep architecture|cut -d, -f1|cut -d' ' -f2` \ > --rename-section .data=.init.rodata $< $@ Yeah this doesn't do it in the 64-bit kernel 32-bit userspace scenerio. We build UMH which ends up being a 32-bit ELF binary, then we later try to link it: ld -m elf64_sparc -r -o net/bpfilter/bpfilter.o net/bpfilter/bpfilter_kern.o net/bpfilter/bpfilter_umh.o ; scripts/mod/modpost net/bpfilter/bpfilter.o ld: sparc:v8plusb architecture of input file `net/bpfilter/bpfilter_umh.o' is incompatible with sparc:v9 output But your patch is a step in the right direction because it gets us away from depending upon CONFIG_OUTPUT_FORMAT.
