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[PATCH] selftests/bpf: ignore pointer types check with clang

Andrea Righi posted 1 patch 2 years, 10 months ago 
tools/testing/selftests/bpf/Makefile | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
[PATCH] selftests/bpf: ignore pointer types check with clang
Posted by Andrea Righi 2 years, 10 months ago 
Building bpf selftests with clang can trigger errors like the following:

  CLNG-BPF [test_maps] bpf_iter_netlink.bpf.o
progs/bpf_iter_netlink.c:32:4: error: incompatible pointer types assigning to 'struct sock *' from 'struct sock___17 *' [-Werror,-Wincompatible-pointer-types]
        s = &nlk->sk;
          ^ ~~~~~~~~
1 error generated.

This is due to the fact that bpftool emits duplicate data types with
different names in vmlinux.h (i.e., `struct sock` in this case) and
these types, despite having a different name, represent in fact the same
object.

Add -Wno-incompatible-pointer-types to CLANG_CLAGS to prevent these
errors.

Signed-off-by: Andrea Righi <andrea.righi@canonical.com>
---
 tools/testing/selftests/bpf/Makefile | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
index b677dcd0b77a..0d9ef819a065 100644
--- a/tools/testing/selftests/bpf/Makefile
+++ b/tools/testing/selftests/bpf/Makefile
@@ -356,7 +356,8 @@ BPF_CFLAGS = -g -Werror -D__TARGET_ARCH_$(SRCARCH) $(MENDIAN) 		\
 	     -I$(abspath $(OUTPUT)/../usr/include)
 
 CLANG_CFLAGS = $(CLANG_SYS_INCLUDES) \
-	       -Wno-compare-distinct-pointer-types
+	       -Wno-compare-distinct-pointer-types \
+	       -Wno-incompatible-pointer-types
 
 $(OUTPUT)/test_l4lb_noinline.o: BPF_CFLAGS += -fno-inline
 $(OUTPUT)/test_xdp_noinline.o: BPF_CFLAGS += -fno-inline
-- 
2.39.2
Re: [PATCH] selftests/bpf: ignore pointer types check with clang
Posted by Alexei Starovoitov 2 years, 10 months ago 
On Wed, Apr 12, 2023 at 2:59 AM Andrea Righi <andrea.righi@canonical.com> wrote:
>
> Building bpf selftests with clang can trigger errors like the following:
>
>   CLNG-BPF [test_maps] bpf_iter_netlink.bpf.o
> progs/bpf_iter_netlink.c:32:4: error: incompatible pointer types assigning to 'struct sock *' from 'struct sock___17 *' [-Werror,-Wincompatible-pointer-types]
>         s = &nlk->sk;
>           ^ ~~~~~~~~
> 1 error generated.

I cannot reproduce this and BPF CI doesn't complain about it either.
What kind of clang do you use?
Some special version and build flags?
Re: [PATCH] selftests/bpf: ignore pointer types check with clang
Posted by Andrea Righi 2 years, 10 months ago 
On Thu, Apr 13, 2023 at 09:56:00PM -0700, Alexei Starovoitov wrote:
> On Wed, Apr 12, 2023 at 2:59 AM Andrea Righi <andrea.righi@canonical.com> wrote:
> >
> > Building bpf selftests with clang can trigger errors like the following:
> >
> >   CLNG-BPF [test_maps] bpf_iter_netlink.bpf.o
> > progs/bpf_iter_netlink.c:32:4: error: incompatible pointer types assigning to 'struct sock *' from 'struct sock___17 *' [-Werror,-Wincompatible-pointer-types]
> >         s = &nlk->sk;
> >           ^ ~~~~~~~~
> > 1 error generated.
> 
> I cannot reproduce this and BPF CI doesn't complain about it either.
> What kind of clang do you use?
> Some special version and build flags?

I'm using Ubuntu clang version 15.0.7 (Ubuntu 23.04), no special build
flag (unless Ubuntu enables some different default flags, but it
shouldn't be the case... I'll double check).

-Andrea
Re: [PATCH] selftests/bpf: ignore pointer types check with clang
Posted by Ilya Leoshkevich 2 years, 10 months ago 
On Fri, Apr 14, 2023 at 08:15:03AM +0200, Andrea Righi wrote:
> On Thu, Apr 13, 2023 at 09:56:00PM -0700, Alexei Starovoitov wrote:
> > On Wed, Apr 12, 2023 at 2:59 AM Andrea Righi <andrea.righi@canonical.com> wrote:
> > >
> > > Building bpf selftests with clang can trigger errors like the following:
> > >
> > >   CLNG-BPF [test_maps] bpf_iter_netlink.bpf.o
> > > progs/bpf_iter_netlink.c:32:4: error: incompatible pointer types assigning to 'struct sock *' from 'struct sock___17 *' [-Werror,-Wincompatible-pointer-types]
> > >         s = &nlk->sk;
> > >           ^ ~~~~~~~~
> > > 1 error generated.
> > 
> > I cannot reproduce this and BPF CI doesn't complain about it either.
> > What kind of clang do you use?
> > Some special version and build flags?
> 
> I'm using Ubuntu clang version 15.0.7 (Ubuntu 23.04), no special build
> flag (unless Ubuntu enables some different default flags, but it
> shouldn't be the case... I'll double check).
> 
> -Andrea

Hi,

FWIW, I see similar errors when I don't use recent pahole.

Best regards,
Ilya
Re: [PATCH] selftests/bpf: ignore pointer types check with clang
Posted by Andrea Righi 2 years, 10 months ago 
On Fri, Apr 14, 2023 at 06:15:38PM +0200, Ilya Leoshkevich wrote:
> On Fri, Apr 14, 2023 at 08:15:03AM +0200, Andrea Righi wrote:
> > On Thu, Apr 13, 2023 at 09:56:00PM -0700, Alexei Starovoitov wrote:
> > > On Wed, Apr 12, 2023 at 2:59 AM Andrea Righi <andrea.righi@canonical.com> wrote:
> > > >
> > > > Building bpf selftests with clang can trigger errors like the following:
> > > >
> > > >   CLNG-BPF [test_maps] bpf_iter_netlink.bpf.o
> > > > progs/bpf_iter_netlink.c:32:4: error: incompatible pointer types assigning to 'struct sock *' from 'struct sock___17 *' [-Werror,-Wincompatible-pointer-types]
> > > >         s = &nlk->sk;
> > > >           ^ ~~~~~~~~
> > > > 1 error generated.
> > > 
> > > I cannot reproduce this and BPF CI doesn't complain about it either.
> > > What kind of clang do you use?
> > > Some special version and build flags?
> > 
> > I'm using Ubuntu clang version 15.0.7 (Ubuntu 23.04), no special build
> > flag (unless Ubuntu enables some different default flags, but it
> > shouldn't be the case... I'll double check).
> > 
> > -Andrea
> 
> Hi,
> 
> FWIW, I see similar errors when I don't use recent pahole.

I'm using pahole v1.24.

-Andrea
Re: [PATCH] selftests/bpf: ignore pointer types check with clang
Posted by Alexei Starovoitov 2 years, 10 months ago 
On Fri, Apr 14, 2023 at 9:28 AM Andrea Righi <andrea.righi@canonical.com> wrote:
>
> On Fri, Apr 14, 2023 at 06:15:38PM +0200, Ilya Leoshkevich wrote:
> > On Fri, Apr 14, 2023 at 08:15:03AM +0200, Andrea Righi wrote:
> > > On Thu, Apr 13, 2023 at 09:56:00PM -0700, Alexei Starovoitov wrote:
> > > > On Wed, Apr 12, 2023 at 2:59 AM Andrea Righi <andrea.righi@canonical.com> wrote:
> > > > >
> > > > > Building bpf selftests with clang can trigger errors like the following:
> > > > >
> > > > >   CLNG-BPF [test_maps] bpf_iter_netlink.bpf.o
> > > > > progs/bpf_iter_netlink.c:32:4: error: incompatible pointer types assigning to 'struct sock *' from 'struct sock___17 *' [-Werror,-Wincompatible-pointer-types]
> > > > >         s = &nlk->sk;
> > > > >           ^ ~~~~~~~~
> > > > > 1 error generated.
> > > >
> > > > I cannot reproduce this and BPF CI doesn't complain about it either.
> > > > What kind of clang do you use?
> > > > Some special version and build flags?
> > >
> > > I'm using Ubuntu clang version 15.0.7 (Ubuntu 23.04), no special build
> > > flag (unless Ubuntu enables some different default flags, but it
> > > shouldn't be the case... I'll double check).
> > >
> > > -Andrea
> >
> > Hi,
> >
> > FWIW, I see similar errors when I don't use recent pahole.
>
> I'm using pahole v1.24.

I believe Ilya is correct.

struct sock___17 is likely coming from vmlinux.h
Which means that there were errors due vmlinux build which
caused multiple structs to be present in BTF
and therefore bpftool generated such broken vmlinux.h

The BTF section in such vmlinux is likely much larger than normal.
Let's get to the bottom of it instead of masking build error.

Please try pahole 1.25.
Re: [PATCH] selftests/bpf: ignore pointer types check with clang
Posted by Andrea Righi 2 years, 10 months ago 
On Fri, Apr 14, 2023 at 06:15:41PM -0700, Alexei Starovoitov wrote:
> On Fri, Apr 14, 2023 at 9:28 AM Andrea Righi <andrea.righi@canonical.com> wrote:
> >
> > On Fri, Apr 14, 2023 at 06:15:38PM +0200, Ilya Leoshkevich wrote:
> > > On Fri, Apr 14, 2023 at 08:15:03AM +0200, Andrea Righi wrote:
> > > > On Thu, Apr 13, 2023 at 09:56:00PM -0700, Alexei Starovoitov wrote:
> > > > > On Wed, Apr 12, 2023 at 2:59 AM Andrea Righi <andrea.righi@canonical.com> wrote:
> > > > > >
> > > > > > Building bpf selftests with clang can trigger errors like the following:
> > > > > >
> > > > > >   CLNG-BPF [test_maps] bpf_iter_netlink.bpf.o
> > > > > > progs/bpf_iter_netlink.c:32:4: error: incompatible pointer types assigning to 'struct sock *' from 'struct sock___17 *' [-Werror,-Wincompatible-pointer-types]
> > > > > >         s = &nlk->sk;
> > > > > >           ^ ~~~~~~~~
> > > > > > 1 error generated.
> > > > >
> > > > > I cannot reproduce this and BPF CI doesn't complain about it either.
> > > > > What kind of clang do you use?
> > > > > Some special version and build flags?
> > > >
> > > > I'm using Ubuntu clang version 15.0.7 (Ubuntu 23.04), no special build
> > > > flag (unless Ubuntu enables some different default flags, but it
> > > > shouldn't be the case... I'll double check).
> > > >
> > > > -Andrea
> > >
> > > Hi,
> > >
> > > FWIW, I see similar errors when I don't use recent pahole.
> >
> > I'm using pahole v1.24.
> 
> I believe Ilya is correct.
> 
> struct sock___17 is likely coming from vmlinux.h
> Which means that there were errors due vmlinux build which
> caused multiple structs to be present in BTF
> and therefore bpftool generated such broken vmlinux.h
> 
> The BTF section in such vmlinux is likely much larger than normal.
> Let's get to the bottom of it instead of masking build error.
> 
> Please try pahole 1.25.

Yay! Success. Everything is working fine with pahole 1.25. Please ignore
my patch, the fix is to simply upgrade pahole.

Thanks!
-Andrea

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