From: Matteo Croce <mcroce@linux.microsoft.com>
To: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Cc: davem@davemloft.net, daniel@iogearbox.net, andrii@kernel.org,
john.fastabend@gmail.com, lmb@cloudflare.com,
mcroce@microsoft.com, bpf@vger.kernel.org, kernel-team@fb.com
Subject: Re: [PATCH RFC bpf-next 01/10] bpf: Prepare relo_core.c for kernel duty.
Date: Tue, 28 Sep 2021 19:11:03 +0200 [thread overview]
Message-ID: <20210928191103.193a9c62@linux.microsoft.com> (raw)
In-Reply-To: <20210928163730.7v7ovjhk7kxputny@ast-mbp.dhcp.thefacebook.com>
On Tue, 28 Sep 2021 09:37:30 -0700
Alexei Starovoitov <alexei.starovoitov@gmail.com> wrote:
> On Tue, Sep 28, 2021 at 04:45:15PM +0200, Matteo Croce wrote:
> > On Fri, 17 Sep 2021 14:57:12 -0700
> > Alexei Starovoitov <alexei.starovoitov@gmail.com> wrote:
> >
> > > From: Alexei Starovoitov <ast@kernel.org>
> > >
> > > Make relo_core.c to be compiled with kernel and with libbpf.
> > >
> > > Signed-off-by: Alexei Starovoitov <ast@kernel.org>
> > > ---
> >
> > I give it a try with a sample co-re program.
>
> Thanks for testing!
>
I just found an error during the relocations.
It was hiding because of bpf_core_apply_relo() always returning
success[1].
I have a BPF with the following programs:
#if 0
SEC("tp_btf/xdp_devmap_xmit")
int BPF_PROG(tp_xdp_devmap_xmit_multi, const struct net_device *from_dev,
const struct net_device *to_dev, int sent, int drops, int err)
{
randmap(from_dev->ifindex);
return 0;
}
#endif
SEC("fentry/eth_type_trans")
int BPF_PROG(fentry_eth_type_trans, struct sk_buff *skb,
struct net_device *dev, unsigned short protocol)
{
randmap(dev->ifindex + skb->len);
return 0;
}
SEC("fexit/eth_type_trans")
int BPF_PROG(fexit_eth_type_trans, struct sk_buff *skb,
struct net_device *dev, unsigned short protocol)
{
randmap(dev->ifindex + skb->len);
return 0;
}
randmap() just writes the value into a random map. If I keep #if 0
everything works, if I remove it so to build tp_btf/xdp_devmap_xmit
too, I get this:
[ 3619.229378] libbpf: prog 'prog_name': relo #0: kind <byte_off> (0), spec is [24] STRUCT net_device.ifindex (0:17 @ offset 208)
[ 3619.229384] libbpf: prog 'prog_name': relo #0: matching candidate #0 [2617] STRUCT net_device.ifindex (0:17 @ offset 208)
[ 3619.229538] libbpf: prog 'prog_name': relo #0: patched insn #0 (LDX/ST/STX) off 208 -> 208
[ 3619.230278] libbpf: prog 'prog_name': relo #0: kind <byte_off> (0), spec is [87] STRUCT sk_buff.len (0:5 @ offset 104)
[ 3619.230282] libbpf: prog 'prog_name': relo #0: matching candidate #0 [2660] STRUCT sk_buff.len (0:5 @ offset 104)
[ 3619.230393] libbpf: prog 'prog_name': relo #0: trying to relocate unrecognized insn #0, code:0x85, src:0x0, dst:0x0, off:0x0, imm:0x7
[ 3619.230562] libbpf: prog 'prog_name': relo #0: failed to patch insn #0: -22
The program in tp_btf/xdp_devmap_xmit makes the relocations into
another section fail, note that sk_buff.len is used in the fentry
program.
Ideas?
[1] https://lore.kernel.org/bpf/20210927200410.460e014f@linux.microsoft.com/
Regards,
--
per aspera ad upstream
next prev parent reply other threads:[~2021-09-28 17:11 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-17 21:57 [PATCH RFC bpf-next 00/10] bpf: CO-RE support in the kernel Alexei Starovoitov
2021-09-17 21:57 ` [PATCH RFC bpf-next 01/10] bpf: Prepare relo_core.c for kernel duty Alexei Starovoitov
2021-09-21 21:25 ` Andrii Nakryiko
2021-09-28 14:45 ` Matteo Croce
2021-09-28 16:37 ` Alexei Starovoitov
2021-09-28 17:11 ` Matteo Croce [this message]
2021-09-28 20:34 ` Alexei Starovoitov
2021-09-29 12:32 ` Matteo Croce
2021-09-29 17:38 ` Matteo Croce
2021-09-29 23:00 ` Alexei Starovoitov
2021-09-29 23:49 ` Matteo Croce
2021-10-22 0:48 ` Matteo Croce
2021-10-22 0:51 ` Alexei Starovoitov
2021-09-17 21:57 ` [PATCH RFC bpf-next 02/10] bpf: Define enum bpf_core_relo_kind as uapi Alexei Starovoitov
2021-09-21 21:27 ` Andrii Nakryiko
2021-09-17 21:57 ` [PATCH RFC bpf-next 03/10] bpf: Add proto of bpf_core_apply_relo() Alexei Starovoitov
2021-09-23 11:21 ` Lorenz Bauer
2021-09-23 18:48 ` Andrii Nakryiko
2021-09-17 21:57 ` [PATCH RFC bpf-next 04/10] bpf: Add bpf_core_add_cands() and wire it into bpf_core_apply_relo_insn() Alexei Starovoitov
2021-09-21 21:34 ` Andrii Nakryiko
2021-09-27 18:04 ` Matteo Croce
2021-09-17 21:57 ` [PATCH RFC bpf-next 05/10] libbpf: Use CO-RE in the kernel in light skeleton Alexei Starovoitov
2021-09-17 21:57 ` [PATCH RFC bpf-next 06/10] libbpf: Make gen_loader data aligned Alexei Starovoitov
2021-09-17 21:57 ` [PATCH RFC bpf-next 07/10] libbpf: Support init of inner maps in light skeleton Alexei Starovoitov
2021-09-17 21:57 ` [PATCH RFC bpf-next 08/10] selftests/bpf: Convert kfunc test with CO-RE to lskel Alexei Starovoitov
2021-09-17 21:57 ` [PATCH RFC bpf-next 09/10] selftests/bpf: Improve inner_map test coverage Alexei Starovoitov
2021-09-17 21:57 ` [PATCH RFC bpf-next 10/10] selftests/bpf: Convert map_ptr_kern test to use light skeleton Alexei Starovoitov
2021-09-23 11:33 ` [PATCH RFC bpf-next 00/10] bpf: CO-RE support in the kernel Lorenz Bauer
2021-09-23 18:52 ` Andrii Nakryiko
2021-09-24 23:13 ` Alexei Starovoitov
2021-09-27 16:12 ` Lorenz Bauer
2021-09-27 16:50 ` Alexei Starovoitov
2021-09-28 8:30 ` Lorenz Bauer
2021-09-28 16:35 ` Alexei Starovoitov
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