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Diffstat (limited to 'tools/testing/selftests/bpf/README.rst')
| -rw-r--r-- | tools/testing/selftests/bpf/README.rst | 71 |
1 files changed, 71 insertions, 0 deletions
diff --git a/tools/testing/selftests/bpf/README.rst b/tools/testing/selftests/bpf/README.rst index fd148b8410fa..3353778c30f8 100644 --- a/tools/testing/selftests/bpf/README.rst +++ b/tools/testing/selftests/bpf/README.rst @@ -111,6 +111,45 @@ available in 10.0.1. The patch is available in llvm 11.0.0 trunk. __ https://reviews.llvm.org/D78466 +bpf_verif_scale/loop6.o test failure with Clang 12 +================================================== + +With Clang 12, the following bpf_verif_scale test failed: + * ``bpf_verif_scale/loop6.o`` + +The verifier output looks like + +.. code-block:: c + + R1 type=ctx expected=fp + The sequence of 8193 jumps is too complex. + +The reason is compiler generating the following code + +.. code-block:: c + + ; for (i = 0; (i < VIRTIO_MAX_SGS) && (i < num); i++) { + 14: 16 05 40 00 00 00 00 00 if w5 == 0 goto +64 <LBB0_6> + 15: bc 51 00 00 00 00 00 00 w1 = w5 + 16: 04 01 00 00 ff ff ff ff w1 += -1 + 17: 67 05 00 00 20 00 00 00 r5 <<= 32 + 18: 77 05 00 00 20 00 00 00 r5 >>= 32 + 19: a6 01 01 00 05 00 00 00 if w1 < 5 goto +1 <LBB0_4> + 20: b7 05 00 00 06 00 00 00 r5 = 6 + 00000000000000a8 <LBB0_4>: + 21: b7 02 00 00 00 00 00 00 r2 = 0 + 22: b7 01 00 00 00 00 00 00 r1 = 0 + ; for (i = 0; (i < VIRTIO_MAX_SGS) && (i < num); i++) { + 23: 7b 1a e0 ff 00 00 00 00 *(u64 *)(r10 - 32) = r1 + 24: 7b 5a c0 ff 00 00 00 00 *(u64 *)(r10 - 64) = r5 + +Note that insn #15 has w1 = w5 and w1 is refined later but +r5(w5) is eventually saved on stack at insn #24 for later use. +This cause later verifier failure. The bug has been `fixed`__ in +Clang 13. + +__ https://reviews.llvm.org/D97479 + BPF CO-RE-based tests and Clang version ======================================= @@ -131,3 +170,35 @@ failures: .. _2: https://reviews.llvm.org/D85174 .. _3: https://reviews.llvm.org/D83878 .. _4: https://reviews.llvm.org/D83242 + +Floating-point tests and Clang version +====================================== + +Certain selftests, e.g. core_reloc, require support for the floating-point +types, which was introduced in `Clang 13`__. The older Clang versions will +either crash when compiling these tests, or generate an incorrect BTF. + +__ https://reviews.llvm.org/D83289 + +Kernel function call test and Clang version +=========================================== + +Some selftests (e.g. kfunc_call and bpf_tcp_ca) require a LLVM support +to generate extern function in BTF. It was introduced in `Clang 13`__. + +Without it, the error from compiling bpf selftests looks like: + +.. code-block:: console + + libbpf: failed to find BTF for extern 'tcp_slow_start' [25] section: -2 + +__ https://reviews.llvm.org/D93563 + +Clang dependencies for static linking tests +=========================================== + +linked_vars, linked_maps, and linked_funcs tests depend on `Clang fix`__ to +generate valid BTF information for weak variables. Please make sure you use +Clang that contains the fix. + +__ https://reviews.llvm.org/D100362 |