Re: [RFC bpf-next 09/12] kbuild: Header guards for types from include/uapi/*.h in kernel BTF

[Eduard Zingerman <eddyz87@gmail.com>]

On Thu, 2022-10-27 at 15:44 -0700, Yonghong Song wrote:
> 
> On 10/27/22 11:55 AM, Yonghong Song wrote:
> > 
> > 
> > On 10/27/22 11:43 AM, Yonghong Song wrote:
> > > 
> > > 
> > > On 10/25/22 3:27 PM, Eduard Zingerman wrote:
> > > > Use pahole --header_guards_db flag to enable encoding of header guard
> > > > information in kernel BTF. The actual correspondence between header
> > > > file and guard string is computed by the scripts/infer_header_guards.pl.
> > > > 
> > > > The encoded header guard information could be used to restore the
> > > > original guards in the vmlinux.h, e.g.:
> > > > 
> > > >      include/uapi/linux/tcp.h:
> > > > 
> > > >        #ifndef _UAPI_LINUX_TCP_H
> > > >        #define _UAPI_LINUX_TCP_H
> > > >        ...
> > > >        union tcp_word_hdr {
> > > >          struct tcphdr hdr;
> > > >          __be32        words[5];
> > > >        };
> > > >        ...
> > > >        #endif /* _UAPI_LINUX_TCP_H */
> > > > 
> > > >      vmlinux.h:
> > > > 
> > > >        ...
> > > >        #ifndef _UAPI_LINUX_TCP_H
> > > > 
> > > >        union tcp_word_hdr {
> > > >          struct tcphdr hdr;
> > > >          __be32 words[5];
> > > >        };
> > > > 
> > > >        #endif /* _UAPI_LINUX_TCP_H */
> > > >        ...
> > > > 
> > > > Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
> > > > ---
> > > >   scripts/link-vmlinux.sh | 13 ++++++++++++-
> > > >   1 file changed, 12 insertions(+), 1 deletion(-)
> > > > 
> > > > diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh
> > > > index 918470d768e9..f57f621eda1f 100755
> > > > --- a/scripts/link-vmlinux.sh
> > > > +++ b/scripts/link-vmlinux.sh
> > > > @@ -110,6 +110,7 @@ vmlinux_link()
> > > >   gen_btf()
> > > >   {
> > > >       local pahole_ver
> > > > +    local extra_flags
> > > >       if ! [ -x "$(command -v ${PAHOLE})" ]; then
> > > >           echo >&2 "BTF: ${1}: pahole (${PAHOLE}) is not available"
> > > > @@ -122,10 +123,20 @@ gen_btf()
> > > >           return 1
> > > >       fi
> > > > +    if [ "${pahole_ver}" -ge "124" ]; then
> > > > +        scripts/infer_header_guards.pl \
> > > 
> > > We should have full path like
> > >      ${srctree}/scripts/infer_header_guards.pl
> > > so it can work if build directory is different from source directory.
> > 
> > handling arguments for infer_header_guards.pl should also take
> > care of full file path.
> > 
> > + /home/yhs/work/bpf-next/scripts/infer_header_guards.pl include/uapi 
> > include/generated/uapi arch/x86/include/uapi 
> > arch/x86/include/generated/uapi
> > + return 1
> 
> Also, please pay attention to bpf selftest result. I see quite a
> few selftest failures with this patch set.

Hi Yonghong,

Could you please copy-paste some of the error reports? I just re-run
the selftests locally and have test_maps, test_verifier, test_progs
and test_progs-no_alu32 passing.

Thanks,
Eduard

> 
> > > 
> > > > +            include/uapi \
> > > > +            include/generated/uapi \
> > > > +            arch/${SRCARCH}/include/uapi \
> > > > +            arch/${SRCARCH}/include/generated/uapi \
> > > > +            > .btf.uapi_header_guards || return 1;
> > > > +        extra_flags="--header_guards_db .btf.uapi_header_guards"
> > > > +    fi
> > > > +
> > > >       vmlinux_link ${1}
> > > >       info "BTF" ${2}
> > > > -    LLVM_OBJCOPY="${OBJCOPY}" ${PAHOLE} -J ${PAHOLE_FLAGS} ${1}
> > > > +    LLVM_OBJCOPY="${OBJCOPY}" ${PAHOLE} -J ${PAHOLE_FLAGS} 
> > > > ${extra_flags} ${1}
> > > >       # Create ${2} which contains just .BTF section but no symbols. Add
> > > >       # SHF_ALLOC because .BTF will be part of the vmlinux image. 
> > > > --strip-all