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

[Xiao Yang]

On 11/13/19 1:28 PM, Masahiro Yamada wrote:
> 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)

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

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