Re: [PATCH bpf-next v8 10/10] selftests/bpf: test case for register_bpf_struct_ops().

[Kui-Feng Lee <sinquersw@gmail.com>]

On 10/30/23 23:59, Martin KaFai Lau wrote:
> On 10/30/23 12:28 PM, thinker.li@gmail.com wrote:
>> diff --git 
>> a/tools/testing/selftests/bpf/prog_tests/test_struct_ops_module.c 
>> b/tools/testing/selftests/bpf/prog_tests/test_struct_ops_module.c
>> new file mode 100644
>> index 000000000000..3a00dc294583
>> --- /dev/null
>> +++ b/tools/testing/selftests/bpf/prog_tests/test_struct_ops_module.c
>> @@ -0,0 +1,39 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +/* Copyright (c) 2023 Meta Platforms, Inc. and affiliates. */
>> +#include <test_progs.h>
>> +#include <time.h>
>> +
>> +#include "rcu_tasks_trace_gp.skel.h"
>> +#include "struct_ops_module.skel.h"
>> +
>> +static void test_regular_load(void)
>> +{
>> +    struct struct_ops_module *skel;
>> +    struct bpf_link *link;
>> +    DECLARE_LIBBPF_OPTS(bpf_object_open_opts, opts);
>> +    int err;
>> +
>> +    skel = struct_ops_module__open_opts(&opts);
>> +    if (!ASSERT_OK_PTR(skel, "struct_ops_module_open"))
>> +        return;
>> +    err = struct_ops_module__load(skel);
>> +    if (!ASSERT_OK(err, "struct_ops_module_load"))
>> +        return;
>> +
>> +    link = bpf_map__attach_struct_ops(skel->maps.testmod_1);
>> +    ASSERT_OK_PTR(link, "attach_test_mod_1");
>> +
>> +    /* test_2() will be called from bpf_dummy_reg() in bpf_testmod.c */
>> +    ASSERT_EQ(skel->bss->test_2_result, 7, "test_2_result");
>> +
>> +    bpf_link__destroy(link);
>> +
>> +    struct_ops_module__destroy(skel);
>> +}
>> +
>> +void serial_test_struct_ops_module(void)
>> +{
>> +    if (test__start_subtest("regular_load"))
>> +        test_regular_load();
> 
> Could it also add some negative tests, e.g. missing 'struct 
> bpf_struct_ops_common_value', reg() when the module is gone...etc.
> 
> [ ... ]
> 
>> +/* This function will trigger call_rcu_tasks_trace() in the kernel */
>> +static int kern_sync_rcu_tasks_trace(void)
> 
> With patch 4, is it still needed?

Patch 4 shortens time of holding the module, but it still can happen
since bpf_link_put() is performed asynchronously.

> 
>> +{
>> +    struct rcu_tasks_trace_gp *rcu;
>> +    time_t start;
>> +    long gp_seq;
>> +    LIBBPF_OPTS(bpf_test_run_opts, opts);
>> +
>> +    rcu = rcu_tasks_trace_gp__open_and_load();
>> +    if (IS_ERR(rcu))
>> +        return -EFAULT;
>> +    if (rcu_tasks_trace_gp__attach(rcu))
>> +        return -EFAULT;
>> +
>> +    gp_seq = READ_ONCE(rcu->bss->gp_seq);
>> +
>> +    if 
>> (bpf_prog_test_run_opts(bpf_program__fd(rcu->progs.do_call_rcu_tasks_trace),
>> +                   &opts))
>> +        return -EFAULT;
>> +    if (opts.retval != 0)
>> +        return -EFAULT;
>> +
>> +    start = time(NULL);
>> +    while ((start + 2) > time(NULL) &&
>> +           gp_seq == READ_ONCE(rcu->bss->gp_seq))
>> +        sched_yield();
>> +
>> +    rcu_tasks_trace_gp__destroy(rcu);
>> +
>> +    return 0;
>> +}
>> +
>>   /*
>>    * Trigger synchronize_rcu() in kernel.
>>    */
>>   int kern_sync_rcu(void)
>>   {
>> +    if (kern_sync_rcu_tasks_trace())
>> +        return -EFAULT;
>>       return syscall(__NR_membarrier, MEMBARRIER_CMD_SHARED, 0, 0);
>>   }
>