Re: [RFC PATCH v1 10/10] selftests/bpf: add file dynptr tests

[Mykyta Yatsenko <mykyta.yatsenko5@gmail.com>]

On 10/3/25 23:24, Eduard Zingerman wrote:
> On Fri, 2025-10-03 at 17:04 +0100, Mykyta Yatsenko wrote:
>
> [...]
>
>> diff --git a/tools/testing/selftests/bpf/progs/file_reader.c b/tools/testing/selftests/bpf/progs/file_reader.c
>> new file mode 100644
>> index 000000000000..9dd9a68f3563
>> --- /dev/null
>> +++ b/tools/testing/selftests/bpf/progs/file_reader.c
> Do we really need an example of ELF parsing in selftests?
> Maybe just stick to smaller test cases, exercising specific behaviors?
This may be a good idea, I implemented ELF parsing as a proof of concept,
to make sure we reach the goal.
For the selftests, maybe just verifying that the contents of the
file seen in BPF is the same as userspace is good enough.
>
> [...]
>
>> diff --git a/tools/testing/selftests/bpf/progs/file_reader_fail.c b/tools/testing/selftests/bpf/progs/file_reader_fail.c
>> new file mode 100644
>> index 000000000000..449c4f9a1c74
>> --- /dev/null
>> +++ b/tools/testing/selftests/bpf/progs/file_reader_fail.c
> [...]
>
>> +static long process_vma_unreleased_ref(struct task_struct *task, struct vm_area_struct *vma,
>> +				       void *data)
>> +{
>> +	struct bpf_dynptr dynptr;
>> +
>> +	if (!vma->vm_file)
>> +		return 1;
>> +
>> +	err = bpf_dynptr_from_file(vma->vm_file, 0, &dynptr);
>> +	return err ? 1 : 0;
>> +}
>> +
>> +SEC("fentry.s/" SYS_PREFIX "sys_nanosleep")
>> +__failure __msg("Unreleased reference id=") int on_nanosleep_unreleased_ref(void *ctx)
>> +{
>> +	struct task_struct *task = bpf_get_current_task_btf();
>> +
>> +	bpf_find_vma(task, (unsigned long)user_ptr, process_vma_unreleased_ref, NULL, 0);
> Why testing this via callback?
>
>> +	return 0;
>> +}
> [...]