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

[Xiao Yang]

On 11/12/19 11:13 PM, Daniel Borkmann 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.

Hi Daniel,


Thanks for your suggestions.

Did you mean that building bpf uses the filter.h from installed linux 
header rather than include/uapi/linux/filter.h in kernel?

It seems that you just try to workaround the issue by using 
linux/filter.h from linux header.

The root casue is that include/linux/compiler.h cannot find the location 
of <asm/rwonce.h>.


Thanks,

Xiao Yang

> 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
> ÂINSTALL ?= install
>
> ÂCFLAGS += -Wall -O2
> -CFLAGS += -D__EXPORTED_HEADERS__ -I$(srctree)/include/uapi 
> -I$(srctree)/include
>
> Â# This will work when bpf is built in tools env. where srctree
> Â# isn't set and when invoked from selftests build, where srctree
>
> Thanks,
> Daniel