Messages in this thread | | | Subject | Re: [PATCH] perf test: Fix perf test 42 | From | Thomas Richter <> | Date | Wed, 24 Mar 2021 08:18:34 +0100 |
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On 3/23/21 7:06 PM, Arnaldo Carvalho de Melo wrote: > Em Mon, Mar 22, 2021 at 01:53:39PM +0100, Thomas Richter escreveu: >> For some time now the perf test 42: BPF filter returns an error >> on bpf relocation subtest, at least on x86 and s390. This is caused by >> >> commit d859900c4c56 ("bpf, libbpf: support global data/bss/rodata sections") >> >> which introduces support for global variables in eBPF programs. At least >> for global variables defined static. >> >> Perf test 42 checks that the eBPF relocation fails when the eBPF program >> contains a global variable. It returns OK when the eBPF program >> could not be loaded and FAILED otherwise. >> >> With above commit the test logic for the eBPF relocation need to change: >> 1. The function prepare_bpf() now always succeeds, the eBPF program >> compiled without errors and returns a valid object pointer instead of >> NULL. >> 2. There is no kprobe named sys_write, it now named ksys_write. >> 3. The function do_test() now returns TEST_FAIL because function >> parse_events_load_bpf_obj() can not execute the eBPF program. The >> eBPF verifier complains on an invalid map pointer: >> libbpf: load bpf program failed: Permission denied >> libbpf: -- BEGIN DUMP LOG --- >> libbpf: >> 0: (b7) r1 = 0 >> 1: (63) *(u32 *)(r10 -4) = r1 >> last_idx 1 first_idx 0 >> regs=2 stack=0 before 0: (b7) r1 = 0 >> 2: (63) *(u32 *)(r10 -8) = r1 >> 3: (bf) r2 = r10 >> 4: (07) r2 += -4 >> 5: (bf) r3 = r10 >> 6: (07) r3 += -8 >> 7: (18) r1 = 0x380006ce000 >> 9: (b7) r4 = 0 >> 10: (85) call bpf_map_update_elem#2 >> R1 type=map_value expected=map_ptr >> >> Fix this by added logic to handle the kernel verifier return code: >> 1. Add function myksys_write() to cope with successful compile. >> 2. Use kprobe ksys_write >> 3. Handle eBPF verifier error. >> >> Output after: >> 42: BPF filter : >> 42.1: Basic BPF filtering : Ok >> 42.2: BPF pinning : Ok >> 42.3: BPF prologue generation : Ok >> 42.4: BPF relocation checker : Failed >> # >> >> Output after: >> # ./perf test -F 42 >> 42: BPF filter : >> 42.1: Basic BPF filtering : Ok >> 42.2: BPF pinning : Ok >> 42.3: BPF prologue generation : Ok >> 42.4: BPF relocation checker : Ok >> # >> >> Signed-off-by: Thomas Richter <tmricht@linux.ibm.com> >> --- >> tools/perf/tests/bpf-script-test-relocation.c | 4 ++-- >> tools/perf/tests/bpf.c | 11 +++++++++++ >> 2 files changed, 13 insertions(+), 2 deletions(-) >> >> diff --git a/tools/perf/tests/bpf-script-test-relocation.c b/tools/perf/tests/bpf-script-test-relocation.c >> index 74006e4b2d24..f8f8176ad4d1 100644 >> --- a/tools/perf/tests/bpf-script-test-relocation.c >> +++ b/tools/perf/tests/bpf-script-test-relocation.c >> @@ -34,8 +34,8 @@ struct bpf_map_def SEC("maps") my_table = { >> >> int this_is_a_global_val; >> >> -SEC("func=sys_write") >> -int bpf_func__sys_write(void *ctx) >> +SEC("func=ksys_write") >> +int bpf_func__ksys_write(void *ctx) >> { >> int key = 0; >> int value = 0; >> diff --git a/tools/perf/tests/bpf.c b/tools/perf/tests/bpf.c >> index f57e075b0ed2..d60ef9472d3d 100644 >> --- a/tools/perf/tests/bpf.c >> +++ b/tools/perf/tests/bpf.c >> @@ -59,6 +59,11 @@ static int llseek_loop(void) >> >> #endif >> >> +static int myksys_write(void) >> +{ >> + return 0; >> +} >> + >> static struct { >> enum test_llvm__testcase prog_id; >> const char *desc; >> @@ -105,6 +110,7 @@ static struct { >> .name = "[bpf_relocation_test]", >> .msg_compile_fail = "fix 'perf test LLVM' first", >> .msg_load_fail = "libbpf error when dealing with relocation", >> + .target_func = &myksys_write, >> }, >> }; >> >> @@ -258,6 +264,11 @@ static int __test__bpf(int idx) >> ret = do_test(obj, >> bpf_testcase_table[idx].target_func, >> bpf_testcase_table[idx].expect_result); >> + if (bpf_testcase_table[idx].prog_id == LLVM_TESTCASE_BPF_RELOCATION >> + && ret == TEST_FAIL) { >> + ret = TEST_OK; >> + goto out; >> + } > > At this point, if it doesn't matter if it fails or succeeds, just drop > this test case? > > - Arnaldo >
Arnaldo,
dropping this test case is fine with me. Support for eBPF global variables is now part of the linux kernel and there are test programs in the .../testing/selftests/bpf directory. File prog_tests/global_data.c for example.
If you agree, I will provide a patch to remove the test case 42.4.
-- Thomas Richter, Dept 3303, IBM s390 Linux Development, Boeblingen, Germany -- Vorsitzender des Aufsichtsrats: Gregor Pillen Geschäftsführung: Dirk Wittkopp Sitz der Gesellschaft: Böblingen / Registergericht: Amtsgericht Stuttgart, HRB 243294
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