Re: Question about "asm/rwonce.h: No such file or directory"

[Masahiro Yamada]

On Wed, Nov 13, 2019 at 12:13 AM Daniel Borkmann <daniel@xxxxxxxxxxxxx> wrote:
>
> On 11/12/19 1:50 PM, Masahiro Yamada wrote:
> > On Tue, Nov 12, 2019 at 9:31 PM Will Deacon <will@xxxxxxxxxx> wrote:
> >>
> >> [+lkml, Masahiro, Alexei and Daniel]
> >>
> >> On Tue, Nov 12, 2019 at 04:56:39PM +0800, Xiao Yang wrote:
> >>> With your patch[1], I alway get the following error when building
> >>> tools/bpf:
> >>
> >> In case people want to reproduce this, my branch is here:
> >>
> >> https://git.kernel.org/pub/scm/linux/kernel/git/will/linux.git/log/?h=lto
> >>
> >>> ----------------------------------------------------------------------------------
> >>>
> >>> make -C tools/bpf/
> >>> make: Entering directory
> >>> '/usr/src/perf_selftests-x86_64-rhel-7.6-642a312d47ceb54603630d9d04f5052f3b46d9a3/tools/bpf'
> >>>
> >>> Auto-detecting system features:
> >>> ... libbfd: [ on ]
> >>> ... disassembler-four-args: [ OFF ]
> >>>
> >>> CC bpf_jit_disasm.o
> >>> CC bpf_dbg.o
> >>> In file included from
> >>> /usr/src/perf_selftests-x86_64-rhel-7.6-642a312d47ceb54603630d9d04f5052f3b46d9a3/include/uapi/linux/filter.h:9:0,
> >>> from
> >>> /usr/src/perf_selftests-x86_64-rhel-7.6-642a312d47ceb54603630d9d04f5052f3b46d9a3/tools/bpf/bpf_dbg.c:41:
> >>> /usr/src/perf_selftests-x86_64-rhel-7.6-642a312d47ceb54603630d9d04f5052f3b46d9a3/include/linux/compiler.h:247:24:
> >>> fatal error: asm/rwonce.h: No such file or directory
> >>> #include <asm/rwonce.h>
> >>> ^
> >>> compilation terminated.
> >>> Makefile:61: recipe for target 'bpf_dbg.o' failed
> >>> make: *** [bpf_dbg.o] Error 1
> >>> make: *** Waiting for unfinished jobs....
> >>> make: Leaving directory
> >>>
> >>> ----------------------------------------------------------------------------------
> >>>
> >>> [1] https://git.kernel.org/pub/scm/linux/kernel/git/will/linux.git/commit/?h=lto&id=642a312d47ceb54603630d9d04f5052f3b46d9a3
> >>>
> >>> It seems that include/linux/compiler.h cannot find the asm/rwonce.h because
> >>> tools/bpf/Makefile doesn't include arch/*/include/generated/asm/rwonce.h.
> >>
> >> The problem with referring to the generated files is that they don't exist
> >> unless you've configured the main source directory. The real problem here
> >> seems to be that tools/bpf/ refers directly to header files in the kernel
> >> sources without any understanding of kbuild, and therefore mandatory-y
> >> headers simply don't exist when it goes looking for them.
>
> Hmm, I am puzzled why that is. :/ I think there are two options, i) remove it
> from CFLAGS like below (at least this doesn't let the build fail in my case
> but requires linux headers to be installed) or ii) add a copy of filter.h to
> tools/include/uapi/linux/filter.h so the few tools can just reuse it. We do have
> bpf_common.h and bpf.h there already.
>
> diff --git a/tools/bpf/Makefile b/tools/bpf/Makefile
> index 5d1995fd369c..08dfd289174c 100644
> --- a/tools/bpf/Makefile
> +++ b/tools/bpf/Makefile
> @@ -10,7 +10,6 @@ MAKE = make
>   INSTALL ?= install
>
>   CFLAGS += -Wall -O2
> -CFLAGS += -D__EXPORTED_HEADERS__ -I$(srctree)/include/uapi -I$(srctree)/include
>
>   # This will work when bpf is built in tools env. where srctree
>   # isn't set and when invoked from selftests build, where srctree
>


I think this is the most sane fix
to include the linux/filter.h in the system.

(probably, it is located in /usr/include/linux/filter.h)


-- 
Best Regards
Masahiro Yamada