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Subject: Re: Question about "asm/rwonce.h: No such file or directory"
To:     Masahiro Yamada <yamada.masahiro@socionext.com>,
        Daniel Borkmann <daniel@iogearbox.net>
Cc:     Will Deacon <will@kernel.org>,
        linux-arch <linux-arch@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Alexei Starovoitov <ast@kernel.org>
References: <1da2db04-da6a-cedb-e85a-6ded68dada82@163.com>
 <20191112123125.GD17835@willie-the-truck>
 <CAK7LNARA99UUTY2v6rS=Nb4Cg5pB4RsR0PogLqdT9uNLcH20ew@mail.gmail.com>
 <32a3b660-f4d2-268e-2206-d50073298c0c@iogearbox.net>
 <CAK7LNASR=R=gyuaMO=VzdXrY3gaQ_FVE4es60bzXf=9ASR2qUw@mail.gmail.com>
From:   Xiao Yang <ice_yangxiao@163.com>
Message-ID: <021e7b46-047e-d381-9dca-bd61db08e4f8@163.com>
Date:   Wed, 13 Nov 2019 13:51:34 +0800
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On 11/13/19 1:28 PM, Masahiro Yamada wrote:
> On Wed, Nov 13, 2019 at 12:13 AM Daniel Borkmann <daniel@iogearbox.net> wrote:
>> On 11/12/19 1:50 PM, Masahiro Yamada wrote:
>>> On Tue, Nov 12, 2019 at 9:31 PM Will Deacon <will@kernel.org> 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)

Hi Masahiro,

Is it correct for include/linux/compiler.h to include <asm/rwonce.h>?

On x86_64 arch, asm/rwonce.h is generated in 
./arch/x86/include/generated/ directory and compiler.h cannot find it.

Best Regards,

XIao Yang

>
>