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

[Andrii Nakryiko]

On Fri, Mar 26, 2021 at 7:42 AM Christophe Leroy
<christophe.leroy@xxxxxxxxxx> wrote:
>
>
>
> Le 22/03/2021 à 18:53, Andrii Nakryiko a écrit :
> > On Mon, Mar 22, 2021 at 9:37 AM Christophe Leroy
> > <christophe.leroy@xxxxxxxxxx> 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@PC-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

yeah, I'm not sure selftests/bpf supports cross-compiling. bpftool got
some patches recently to enable cross-compiling, but probably not
selftests/bpf.

>
> [root@PC-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