Re: [RFC PATCH bpf-next v3 3/3] libbpf: Auto-upgrade kprobes to multi-kprobes when supported

[bot+bpf-ci]

> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> index bc749b9c291e..f566527d95f3 100644
> --- a/tools/lib/bpf/libbpf.c
> +++ b/tools/lib/bpf/libbpf.c

[ ... ]

> @@ -11841,6 +11867,30 @@ bpf_program__attach_kprobe_opts(const struct bpf_program *prog,
>  	offset = OPTS_GET(opts, offset, 0);
>  	pe_opts.bpf_cookie = OPTS_GET(opts, bpf_cookie, 0);
>
> +	/* This provides backwards compatibility to programs using kprobe, but
> +	 * have been auto-upgraded to multi kprobe.
> +	 */
> +	if (prog->expected_attach_type == BPF_TRACE_KPROBE_MULTI &&
> +	    offset == 0 && attach_mode == PROBE_ATTACH_MODE_DEFAULT) {

[ ... ]

> +	if (prog->expected_attach_type == BPF_TRACE_KPROBE_MULTI) {
> +		pr_warn("prog '%s': multi-kprobe upgrade failed (off=%lu, mode=%d); use SEC(\"kprobe.single\")\n",
> +			prog->name, offset, attach_mode);

Should this use %zu instead of %lu for offset?  It is declared as
size_t in this function, and the existing pr_warn() calls further
down use %zx for the same variable.

> +		return libbpf_err_ptr(-ENOTSUP);
> +	}

[ ... ]

> @@ -12297,14 +12347,24 @@ static int attach_kprobe(const struct bpf_program *prog, long cookie, struct bpf
>  	*link = NULL;
>
>  	/* no auto-attach for SEC("kprobe") and SEC("kretprobe") */
> -	if (strcmp(prog->sec_name, "kprobe") == 0 || strcmp(prog->sec_name, "kretprobe") == 0)
> +	if (strcmp(prog->sec_name, "kprobe") == 0 ||
> +	    strcmp(prog->sec_name, "kretprobe") == 0 ||
> +	    strcmp(prog->sec_name, "kprobe.single") == 0 ||
> +	    strcmp(prog->sec_name, "kretprobe.single") == 0)
>  		return 0;

The comment above still only mentions SEC("kprobe") and
SEC("kretprobe").  Could it be updated to also mention the .single
variants that are now handled here?


---
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