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libbpf: Clarify raw-address single kprobe attach behavior

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bpf_program__attach_kprobe_opts() documents single-kprobe attach
through func_name, with an optional offset. For the PMU-based path,
func_name = NULL with an absolute address in offset already works as
well, but that is not described in the API.

This commit clarifies this existing non-legacy behavior. For PMU-based
attach, callers can use func_name = NULL with an absolute address in
offset as the raw-address form. For legacy tracefs/debugfs kprobes,
reject this form explicitly.

Signed-off-by: Hoyeon Lee <hoyeon.lee@suse.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Link: https://lore.kernel.org/bpf/20260401143116.185049-3-hoyeon.lee@suse.com
This commit is contained in:
Hoyeon Lee
2026-04-01 23:29:30 +09:00
committed by Andrii Nakryiko
parent f547cf7947
commit e1621c7528
2 changed files with 34 additions and 7 deletions
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14
tools/lib/bpf/libbpf.c
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@@ -11843,6 +11843,8 @@ bpf_program__attach_kprobe_opts(const struct bpf_program *prog,
default:
return libbpf_err_ptr(-EINVAL);
}
if (!func_name && legacy)
return libbpf_err_ptr(-EOPNOTSUPP);
if (!legacy) {
pfd = perf_event_open_probe(false /* uprobe */, retprobe,
@@ -11863,20 +11865,20 @@ bpf_program__attach_kprobe_opts(const struct bpf_program *prog,
}
if (pfd < 0) {
err = pfd;
pr_warn("prog '%s': failed to create %s '%s+0x%zx' perf event: %s\n",
pr_warn("prog '%s': failed to create %s '%s%s0x%zx' perf event: %s\n",
prog->name, retprobe ? "kretprobe" : "kprobe",
func_name, offset,
errstr(err));
func_name ?: "", func_name ? "+" : "",
offset, errstr(err));
goto err_out;
}
link = bpf_program__attach_perf_event_opts(prog, pfd, &pe_opts);
err = libbpf_get_error(link);
if (err) {
close(pfd);
pr_warn("prog '%s': failed to attach to %s '%s+0x%zx': %s\n",
pr_warn("prog '%s': failed to attach to %s '%s%s0x%zx': %s\n",
prog->name, retprobe ? "kretprobe" : "kprobe",
func_name, offset,
errstr(err));
func_name ?: "", func_name ? "+" : "",
offset, errstr(err));
goto err_clean_legacy;
}
if (legacy) {