Re: [RFC PATCH bpf-next 2/2] selftests/bpf: Add tests for duplicate kprobe symbol handling

[Jiri Olsa <olsajiri@gmail.com>]

On Wed, Feb 18, 2026 at 05:56:17PM -0500, Andrey Grodzovsky wrote:

SNIP

> diff --git a/tools/testing/selftests/bpf/test_kmods/bpf_testmod_dup_sym.c b/tools/testing/selftests/bpf/test_kmods/bpf_testmod_dup_sym.c
> new file mode 100644
> index 000000000000..98b3e085ae90
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/test_kmods/bpf_testmod_dup_sym.c
> @@ -0,0 +1,45 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/* Copyright (c) 2025 CrowdStrike */
> +/* Test module for duplicate kprobe symbol handling */
> +#include <linux/init.h>
> +#include <linux/module.h>
> +#include <linux/kernel.h>
> +
> +/* Duplicate symbol to test kprobe attachment with duplicate symbols.
> + * This creates a duplicate of the syscall wrapper used in attach_probe tests.
> + * The libbpf fix should handle this by preferring the vmlinux symbol.
> + * This function should NEVER be called - kprobes should attach to vmlinux version.
> + */
> +#ifdef __x86_64__
> +noinline int __x64_sys_nanosleep(void)
> +#elif defined(__s390x__)
> +noinline int __s390x_sys_nanosleep(void)
> +#elif defined(__aarch64__)
> +noinline int __arm64_sys_nanosleep(void)
> +#elif defined(__riscv)
> +noinline int __riscv_sys_nanosleep(void)
> +#else
> +noinline int sys_nanosleep(void)
> +#endif
> +{
> +	WARN_ONCE(1, "bpf_testmod_dup_sym: dummy nanosleep symbol called - this should never execute!\n");
> +	return -EINVAL;
> +}

hi,
this fails to build for me:

  CC [M]  bpf_testmod_dup_sym.o
bpf_testmod_dup_sym.c:14:14: error: no previous prototype for ‘__x64_sys_nanosleep’ [-Werror=missing-prototypes]
   14 | noinline int __x64_sys_nanosleep(void)
      |              ^~~~~~~~~~~~~~~~~~~

jirka

> +
> +static int __init bpf_testmod_dup_sym_init(void)
> +{
> +	pr_info("bpf_testmod_dup_sym: loaded (duplicate symbol test module)\n");
> +	return 0;
> +}
> +
> +static void __exit bpf_testmod_dup_sym_exit(void)
> +{
> +	pr_info("bpf_testmod_dup_sym: unloaded\n");
> +}
> +
> +module_init(bpf_testmod_dup_sym_init);
> +module_exit(bpf_testmod_dup_sym_exit);
> +
> +MODULE_AUTHOR("Andrey Grodzovsky");
> +MODULE_DESCRIPTION("BPF selftest duplicate symbol module");
> +MODULE_LICENSE("GPL");
> -- 
> 2.34.1
>