Re: umh build...
From: David Miller <davem@davemloft.net>
Date: 2018-06-05 23:51:53
From: Alexei Starovoitov <redacted> Date: Tue, 5 Jun 2018 15:29:34 -0700
On Tue, Jun 05, 2018 at 05:03:59PM -0400, David Miller wrote:quoted
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.
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quoted hunk ↗ jump to hunk
@@ -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.