Re: [PATCH bpf-next v2 3/4] selftests/bpf: Exercise unsafe obj drops from tracing progs

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] The selftest `task_kfunc_obj_drop_nmi_with_kptr` uses the x86-only `nmi_handler` tracepoint, breaking the test suite on other architectures.
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commit 1282fb89cc1ac86a478ae0747dc71f01a3bfc729
Author: Kumar Kartikeya Dwivedi <memxor@gmail.com>

selftests/bpf: Exercise unsafe obj drops from tracing progs

This commit adds task_kfunc failure cases for bpf_obj_drop() on local
objects with referenced kptr fields. It introduces tests for tracing and
NMI tracing programs to ensure they are rejected by the verifier.

> diff --git a/tools/testing/selftests/bpf/progs/task_kfunc_failure.c b/tools/testing/selftests/bpf/progs/task_kfunc_failure.c
> --- a/tools/testing/selftests/bpf/progs/task_kfunc_failure.c
> +++ b/tools/testing/selftests/bpf/progs/task_kfunc_failure.c

[ ... ]

> +SEC("tp_btf/nmi_handler")
> +__failure __msg("bpf_obj_drop cannot be used in tracing programs on types with NMI unsafe fields")
> +int BPF_PROG(task_kfunc_obj_drop_nmi_with_kptr, void *handler, s64 delta_ns,
> +	     int handled)

[Severity: Medium]
Will this break the selftest suite on non-x86 architectures?

The nmi_handler tracepoint is only defined and instantiated on x86
architectures. On non-x86 architectures like ARM64 or RISC-V, libbpf will
fail to resolve the BTF ID for this tracepoint, and the BPF program load
will abort before the verifier is invoked.

Consequently, the test_loader framework will not find the expected verifier
failure message in the log, causing the test to incorrectly report as failed.
Is there an architecture-independent tracepoint that could be used instead,
or should this test be skipped on non-x86 platforms?

> +{
> +	struct __tasks_kfunc_map_value *local;
> +	struct task_struct *task, *acquired, *old;

[ ... ]

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Sashiko AI review · https://sashiko.dev/#/patchset/20260609093719.2858096-1-memxor@gmail.com?part=3