On Thu, Dec 17, 2020 at 1:54 AM Christophe Leroy <christophe.leroy@xxxxxxxxxx> wrote: > > > > Le 17/12/2020 à 07:11, Alexei Starovoitov a écrit : > > On Wed, Dec 16, 2020 at 10:07:37AM +0000, Christophe Leroy wrote: > >> Implement Extended Berkeley Packet Filter on Powerpc 32 > >> > >> Test result with test_bpf module: > >> > >> test_bpf: Summary: 378 PASSED, 0 FAILED, [354/366 JIT'ed] > > > > nice! > > > >> Registers mapping: > >> > >> [BPF_REG_0] = r11-r12 > >> /* function arguments */ > >> [BPF_REG_1] = r3-r4 > >> [BPF_REG_2] = r5-r6 > >> [BPF_REG_3] = r7-r8 > >> [BPF_REG_4] = r9-r10 > >> [BPF_REG_5] = r21-r22 (Args 9 and 10 come in via the stack) > >> /* non volatile registers */ > >> [BPF_REG_6] = r23-r24 > >> [BPF_REG_7] = r25-r26 > >> [BPF_REG_8] = r27-r28 > >> [BPF_REG_9] = r29-r30 > >> /* frame pointer aka BPF_REG_10 */ > >> [BPF_REG_FP] = r31 > >> /* eBPF jit internal registers */ > >> [BPF_REG_AX] = r19-r20 > >> [TMP_REG] = r18 > >> > >> As PPC32 doesn't have a redzone in the stack, > >> use r17 as tail call counter. > >> > >> r0 is used as temporary register as much as possible. It is referenced > >> directly in the code in order to avoid misuse of it, because some > >> instructions interpret it as value 0 instead of register r0 > >> (ex: addi, addis, stw, lwz, ...) > >> > >> 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 */ > > > > Those are sensible limitations. MOD and DIV are rare, but XADD is common. > > Please consider doing it as a cmpxchg loop in the future. > > > > Also please run test_progs. It will give a lot better coverage than test_bpf.ko > > > > I'm having hard time cross building test_progs: > > ~/linux-powerpc/tools/testing/selftests/bpf/$ make CROSS_COMPILE=ppc-linux- > ... > GEN > /home/chr/linux-powerpc/tools/testing/selftests/bpf/tools/build/bpftool/Documentation/bpf-helpers.7 > INSTALL eBPF_helpers-manpage > INSTALL Documentation-man > GEN vmlinux.h > /bin/sh: /home/chr/linux-powerpc/tools/testing/selftests/bpf/tools/sbin/bpftool: cannot execute > binary file > make: *** [/home/chr/linux-powerpc/tools/testing/selftests/bpf/tools/include/vmlinux.h] Error 126 > make: *** Deleting file `/home/chr/linux-powerpc/tools/testing/selftests/bpf/tools/include/vmlinux.h' > > Looks like it builds bpftool for powerpc and tries to run it on my x86. > How should I proceed ? The best way would be to fix whatever needs to be fixed in selftests/bpf and/or bpftool Makefiles to support cross-compilation. There was some work already for bpftool to support that (with building bpftool-bootstrap separately for a host architecture, etc). Please check what's broken and let's try to fix it. > > Thanks > Christophe
