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diff --git a/tools/testing/selftests/bpf/README.rst b/tools/testing/selftests/bpf/README.rst new file mode 100644 index 000000000000..e885d351595f --- /dev/null +++ b/tools/testing/selftests/bpf/README.rst @@ -0,0 +1,45 @@ +================== +BPF Selftest Notes +================== +General instructions on running selftests can be found in +`Documentation/bpf/bpf_devel_QA.rst`_. + +Additional information about selftest failures are +documented here. + +bpf_iter test failures with clang/llvm 10.0.0 +============================================= + +With clang/llvm 10.0.0, the following two bpf_iter tests failed: + * ``bpf_iter/ipv6_route`` + * ``bpf_iter/netlink`` + +The symptom for ``bpf_iter/ipv6_route`` looks like + +.. code-block:: c + + 2: (79) r8 = *(u64 *)(r1 +8) + ... + 14: (bf) r2 = r8 + 15: (0f) r2 += r1 + ; BPF_SEQ_PRINTF(seq, "%pi6 %02x ", &rt->fib6_dst.addr, rt->fib6_dst.plen); + 16: (7b) *(u64 *)(r8 +64) = r2 + only read is supported + +The symptom for ``bpf_iter/netlink`` looks like + +.. code-block:: c + + ; struct netlink_sock *nlk = ctx->sk; + 2: (79) r7 = *(u64 *)(r1 +8) + ... + 15: (bf) r2 = r7 + 16: (0f) r2 += r1 + ; BPF_SEQ_PRINTF(seq, "%pK %-3d ", s, s->sk_protocol); + 17: (7b) *(u64 *)(r7 +0) = r2 + only read is supported + +This is due to a llvm BPF backend bug. The fix + https://reviews.llvm.org/D78466 +has been pushed to llvm 10.x release branch and will be +available in 10.0.1. The fix is available in llvm 11.0.0 trunk. |