linux-kernel - Re: [PATCH bpf-next v10 0/7] Generalizing bpf_local

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Message-ID: <CACYkzJ7fM4KEhWh1ACkJbtc+VNnN1A0CESkn3k45L5Bywae21w@mail.gmail.com>
Date:   Wed, 26 Aug 2020 00:51:57 +0200
From:   KP Singh <kpsingh@...omium.org>
To:     Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc:     LKML <linux-kernel@...r.kernel.org>, bpf <bpf@...r.kernel.org>,
        LSM List <linux-security-module@...r.kernel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Martin KaFai Lau <kafai@...com>,
        Paul Turner <pjt@...gle.com>, Jann Horn <jannh@...gle.com>,
        Florent Revest <revest@...omium.org>
Subject: Re: [PATCH bpf-next v10 0/7] Generalizing bpf_local_storage

On Wed, Aug 26, 2020 at 12:13 AM Alexei Starovoitov
<alexei.starovoitov@...il.com> wrote:
>
> On Tue, Aug 25, 2020 at 2:05 PM Alexei Starovoitov
> <alexei.starovoitov@...il.com> wrote:
> >
> > On Tue, Aug 25, 2020 at 11:29 AM KP Singh <kpsingh@...omium.org> wrote:
> > >
> > > From: KP Singh <kpsingh@...gle.com>
> > >
> > > # v9 -> v10
> > >
> > > - Added NULL check for inode_storage_ptr before calling
> > >   bpf_local_storage_update
> > > - Removed an extraneous include
> > > - Rebased and added Acks / Signoff.
> >
> > Hmm. Though it looks good I cannot apply it, because
> > test_progs -t map_ptr
> > is broken:
> > 2225: (18) r2 = 0xffffc900004e5004
> > 2227: (b4) w1 = 58
> > 2228: (63) *(u32 *)(r2 +0) = r1
> >  R0=map_value(id=0,off=0,ks=4,vs=4,imm=0) R1_w=inv58
> > R2_w=map_value(id=0,off=4,ks=4,vs=8,imm=0) R3=inv49 R4=inv63
> > R5=inv(id=0,umax_value=4294967295,var_off=(0x0; 0xffffffff)) R6_w=inv0
> > R7=invP8 R8=map_ptr(id=0,off=0,ks=4,vs=4,imm=0) R10=?
> > ; VERIFY_TYPE(BPF_MAP_TYPE_SK_STORAGE, check_sk_storage);
> > 2229: (18) r1 = 0xffffc900004e5000
> > 2231: (b4) w3 = 24
> > 2232: (63) *(u32 *)(r1 +0) = r3
> >  R0=map_value(id=0,off=0,ks=4,vs=4,imm=0)
> > R1_w=map_value(id=0,off=0,ks=4,vs=8,imm=0)
> > R2_w=map_value(id=0,off=4,ks=4,vs=8,imm=0) R3_w=inv24 R4=inv63
> > R5=inv(id=0,umax_value=4294967295,var_off=(0x0; 0xffffffff)) R6_w=inv0
> > R7=invP8 R8=map_pt?
> > 2233: (18) r3 = 0xffff8881f03f7000
> > ; VERIFY(indirect->map_type == direct->map_type);
> > 2235: (85) call unknown#195896080
> > invalid func unknown#195896080
> > processed 4678 insns (limit 1000000) max_states_per_insn 9
> > total_states 240 peak_states 178 mark_read 11
> >
> > libbpf: -- END LOG --
> > libbpf: failed to load program 'cgroup_skb/egress'
> > libbpf: failed to load object 'map_ptr_kern'
> > libbpf: failed to load BPF skeleton 'map_ptr_kern': -4007
> > test_map_ptr:FAIL:skel_open_load open_load failed
> > #43 map_ptr:FAIL
> >
> > Above 'invalid func unknown#195896080' happens
> > when libbpf fails to do a relocation at runtime.
> > Please debug.
> > It's certainly caused by this set, but not sure why.
>
> So I've ended up bisecting and debugging it.
> It turned out that the patch 1 was responsible.
> I've added the following hunk to fix it:

Thanks for fixing and debugging it.

> diff --git a/tools/testing/selftests/bpf/progs/map_ptr_kern.c
> b/tools/testing/selftests/bpf/progs/map_ptr_kern.c
> index 473665cac67e..982a2d8aa844 100644
> --- a/tools/testing/selftests/bpf/progs/map_ptr_kern.c
> +++ b/tools/testing/selftests/bpf/progs/map_ptr_kern.c
> @@ -589,7 +589,7 @@ static inline int check_stack(void)
>         return 1;

[...]

> and pushed the whole set.
> In the future please always run test_progs and test_progs-no_alu32

Noted, I do run them but this test gave me a different error and I always
ended up ignoring this:

./test_progs -t map_ptr
libbpf: Error in bpf_create_map_xattr(m_array_of_maps):ERROR:
strerror_r(-524)=22(-524). Retrying without BTF.
libbpf: Error in bpf_create_map_xattr(m_hash_of_maps):ERROR:
strerror_r(-524)=22(-524). Retrying without BTF.
libbpf: Error in bpf_create_map_xattr(m_perf_event_array):ERROR:
strerror_r(-524)=22(-524). Retrying without BTF.
libbpf: Error in bpf_create_map_xattr(m_stack_trace):ERROR:
strerror_r(-524)=22(-524). Retrying without BTF.
libbpf: Error in bpf_create_map_xattr(m_cgroup_array):ERROR:
strerror_r(-524)=22(-524). Retrying without BTF.
libbpf: Error in bpf_create_map_xattr(m_devmap):ERROR:
strerror_r(-524)=22(-524). Retrying without BTF.
libbpf: Error in bpf_create_map_xattr(m_sockmap):Invalid
argument(-22). Retrying without BTF.
libbpf: map 'm_sockmap': failed to create: Invalid argument(-22)
libbpf: failed to load object 'map_ptr_kern'
libbpf: failed to load BPF skeleton 'map_ptr_kern': -22
test_map_ptr:FAIL:skel_open_load open_load failed

I now realized that I was not sourcing
tools/testing/selftests/bpf/config correctly
and CONFIG_BPF_STREAM_PARSER was not enabled in my configuration.

Nonetheless, no excuses and will ensure these tests pass in the future.

- KP

> for every patch and submit patches only if _all_ tests are passing.
> Do not assume that your change is not responsible for breakage.