netdev - Re: [PATCH 5/5] selftests/bpf: make cfi

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Message-Id: <e9a1bd633fb4bb3d2820f63f41a8dd60d8c9c5e3c699fa56057ae393ef2f31d0@mail.kernel.org>
Date: Wed, 31 Dec 2025 18:04:13 +0000 (UTC)
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Subject: Re: [PATCH 5/5] selftests/bpf: make cfi_stubs globals const

> diff --git a/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c b/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c
> index 90c4b1a51de6..5e460b1dbdb6 100644
> --- a/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c
> +++ b/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c

[ ... ]

> @@ -1275,7 +1275,7 @@ bpf_testmod_ops__test_return_ref_kptr(int dummy, struct task_struct *task__ref,
>  	return NULL;
>  }
>
> -static struct bpf_testmod_ops __bpf_testmod_ops = {
> +static const struct bpf_testmod_ops __bpf_testmod_ops = {
>  	.test_1 = bpf_testmod_test_1,
>  	.test_2 = bpf_testmod_test_2,

Is it safe to make __bpf_testmod_ops const here? In bpf_testmod_init(),
this struct is modified at runtime:

    tramp = (void **)&__bpf_testmod_ops.tramp_1;
    while (tramp <= (void **)&__bpf_testmod_ops.tramp_40)
        *tramp++ = bpf_testmod_tramp;

Writing to a const-qualified object is undefined behavior and may cause a
protection fault when the compiler places this in read-only memory. Would
the module fail to load on systems where .rodata is actually read-only?


---
AI reviewed your patch. Please fix the bug or email reply why it's not a bug.
See: https://github.com/kernel-patches/vmtest/blob/master/ci/claude/README.md

CI run summary: https://github.com/kernel-patches/bpf/actions/runs/20624206229