linux-kernel - Re: [PATCH v2 0/8] Implement EBPF on powerpc32

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Message-ID: <86028d25-c3fe-3765-f7c3-12448523405a@csgroup.eu>
Date:   Fri, 26 Mar 2021 15:41:59 +0100
From:   Christophe Leroy <christophe.leroy@...roup.eu>
To:     Andrii Nakryiko <andrii.nakryiko@...il.com>
Cc:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>, Martin Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        john fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...omium.org>, naveen.n.rao@...ux.ibm.com,
        sandipan@...ux.ibm.com, open list <linux-kernel@...r.kernel.org>,
        linuxppc-dev@...ts.ozlabs.org, Networking <netdev@...r.kernel.org>,
        bpf <bpf@...r.kernel.org>
Subject: Re: [PATCH v2 0/8] Implement EBPF on powerpc32



Le 22/03/2021 à 18:53, Andrii Nakryiko a écrit :
> On Mon, Mar 22, 2021 at 9:37 AM Christophe Leroy
> <christophe.leroy@...roup.eu> wrote:
>>
>> This series implements extended BPF on powerpc32. For the implementation
>> details, see the patch before the last.
>>
>> The following operations are not implemented:
>>
>>                  case BPF_ALU64 | BPF_DIV | BPF_X: /* dst /= src */
>>                  case BPF_ALU64 | BPF_MOD | BPF_X: /* dst %= src */
>>                  case BPF_STX | BPF_XADD | BPF_DW: /* *(u64 *)(dst + off) += src */
>>
>> The following operations are only implemented for power of two constants:
>>
>>                  case BPF_ALU64 | BPF_MOD | BPF_K: /* dst %= imm */
>>                  case BPF_ALU64 | BPF_DIV | BPF_K: /* dst /= imm */
>>
>> Below are the results on a powerpc 885:
>> - with the patch, with and without bpf_jit_enable
>> - without the patch, with bpf_jit_enable (ie with CBPF)
>>
>> With the patch, with bpf_jit_enable = 1 :
>>
>> [   60.826529] test_bpf: Summary: 378 PASSED, 0 FAILED, [354/366 JIT'ed]
>> [   60.832505] test_bpf: test_skb_segment: Summary: 2 PASSED, 0 FAILED
>>
>> With the patch, with bpf_jit_enable = 0 :
>>
>> [   75.186337] test_bpf: Summary: 378 PASSED, 0 FAILED, [0/366 JIT'ed]
>> [   75.192325] test_bpf: test_skb_segment: Summary: 2 PASSED, 0 FAILED
>>
>> Without the patch, with bpf_jit_enable = 1 :
>>
>> [  186.112429] test_bpf: Summary: 371 PASSED, 7 FAILED, [119/366 JIT'ed]
>>
>> Couldn't run test_progs because it doesn't build (clang 11 crashes during the build).
> 
> Can you please try checking out the latest clang from sources and use
> that one instead?

The crash is fixed, it builds one step more, then fails at:

[root@...server-ldb bpf]# make CROSS_COMPILE=ppc-linux- ARCH=powerpc V=1
/root/gen_ldb/linux-powerpc/tools/testing/selftests/bpf/host-tools/sbin/bpftool gen skeleton 
/root/gen_ldb/linux-powerpc/tools/testing/selftests/bpf/atomic_bounds.o > 
/root/gen_ldb/linux-powerpc/tools/testing/selftests/bpf/atomic_bounds.skel.h
libbpf: elf: endianness mismatch in atomic_bounds.
Error: failed to open BPF object file: Endian mismatch

I'm cross-building on x86 for powerpc/32

[root@...server-ldb bpf]# file atomic_bounds.o
atomic_bounds.o: ELF 64-bit MSB relocatable, eBPF, version 1 (SYSV), with debug_info, not stripped

Christophe