Merge branch 'libbpf: allow users to set kprobe/uprobe attach mode'

Menglong Dong says:

====================

From: Menglong Dong <imagedong@tencent.com>

By default, libbpf will attach the kprobe/uprobe BPF program in the
latest mode that supported by kernel. In this series, we add the support
to let users manually attach kprobe/uprobe in legacy/perf/link mode in
the 1th patch.

And in the 2th patch, we split the testing 'attach_probe' into multi
subtests, as Andrii suggested.

In the 3th patch, we add the testings for loading kprobe/uprobe in
different mode.

Changes since v3:
- rename eBPF to BPF in the doc
- use OPTS_GET() to get the value of 'force_ioctl_attach'
- error out on attach mode is not supported
- use test_attach_probe_manual__open_and_load() directly

Changes since v2:
- fix the typo in the 2th patch

Changes since v1:
- some small changes in the 1th patch, as Andrii suggested
- split 'attach_probe' into multi subtests
====================

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>

1 files changed, 47 insertions, 1 deletions

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index dacaae31b76a..a557718401e4 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -9724,6 +9724,7 @@ struct bpf_link *bpf_program__attach_perf_event_opts(const struct bpf_program *p
 	char errmsg[STRERR_BUFSIZE];
 	struct bpf_link_perf *link;
 	int prog_fd, link_fd = -1, err;
+	bool force_ioctl_attach;
 
 	if (!OPTS_VALID(opts, bpf_perf_event_opts))
 		return libbpf_err_ptr(-EINVAL);
@@ -9747,7 +9748,8 @@ struct bpf_link *bpf_program__attach_perf_event_opts(const struct bpf_program *p
 	link->link.dealloc = &bpf_link_perf_dealloc;
 	link->perf_event_fd = pfd;
 
-	if (kernel_supports(prog->obj, FEAT_PERF_LINK)) {
+	force_ioctl_attach = OPTS_GET(opts, force_ioctl_attach, false);
+	if (kernel_supports(prog->obj, FEAT_PERF_LINK) && !force_ioctl_attach) {
 		DECLARE_LIBBPF_OPTS(bpf_link_create_opts, link_opts,
 			.perf_event.bpf_cookie = OPTS_GET(opts, bpf_cookie, 0));
 
@@ -10106,6 +10108,7 @@ bpf_program__attach_kprobe_opts(const struct bpf_program *prog,
 				const struct bpf_kprobe_opts *opts)
 {
 	DECLARE_LIBBPF_OPTS(bpf_perf_event_opts, pe_opts);
+	enum probe_attach_mode attach_mode;
 	char errmsg[STRERR_BUFSIZE];
 	char *legacy_probe = NULL;
 	struct bpf_link *link;
@@ -10116,11 +10119,32 @@ bpf_program__attach_kprobe_opts(const struct bpf_program *prog,
 	if (!OPTS_VALID(opts, bpf_kprobe_opts))
 		return libbpf_err_ptr(-EINVAL);
 
+	attach_mode = OPTS_GET(opts, attach_mode, PROBE_ATTACH_MODE_DEFAULT);
 	retprobe = OPTS_GET(opts, retprobe, false);
 	offset = OPTS_GET(opts, offset, 0);
 	pe_opts.bpf_cookie = OPTS_GET(opts, bpf_cookie, 0);
 
 	legacy = determine_kprobe_perf_type() < 0;
+	switch (attach_mode) {
+	case PROBE_ATTACH_MODE_LEGACY:
+		legacy = true;
+		pe_opts.force_ioctl_attach = true;
+		break;
+	case PROBE_ATTACH_MODE_PERF:
+		if (legacy)
+			return libbpf_err_ptr(-ENOTSUP);
+		pe_opts.force_ioctl_attach = true;
+		break;
+	case PROBE_ATTACH_MODE_LINK:
+		if (legacy || !kernel_supports(prog->obj, FEAT_PERF_LINK))
+			return libbpf_err_ptr(-ENOTSUP);
+		break;
+	case PROBE_ATTACH_MODE_DEFAULT:
+		break;
+	default:
+		return libbpf_err_ptr(-EINVAL);
+	}
+
 	if (!legacy) {
 		pfd = perf_event_open_probe(false /* uprobe */, retprobe,
 					    func_name, offset,
@@ -10852,6 +10876,7 @@ bpf_program__attach_uprobe_opts(const struct bpf_program *prog, pid_t pid,
 	const char *archive_path = NULL, *archive_sep = NULL;
 	char errmsg[STRERR_BUFSIZE], *legacy_probe = NULL;
 	DECLARE_LIBBPF_OPTS(bpf_perf_event_opts, pe_opts);
+	enum probe_attach_mode attach_mode;
 	char full_path[PATH_MAX];
 	struct bpf_link *link;
 	size_t ref_ctr_off;
@@ -10862,6 +10887,7 @@ bpf_program__attach_uprobe_opts(const struct bpf_program *prog, pid_t pid,
 	if (!OPTS_VALID(opts, bpf_uprobe_opts))
 		return libbpf_err_ptr(-EINVAL);
 
+	attach_mode = OPTS_GET(opts, attach_mode, PROBE_ATTACH_MODE_DEFAULT);
 	retprobe = OPTS_GET(opts, retprobe, false);
 	ref_ctr_off = OPTS_GET(opts, ref_ctr_offset, 0);
 	pe_opts.bpf_cookie = OPTS_GET(opts, bpf_cookie, 0);
@@ -10903,6 +10929,26 @@ bpf_program__attach_uprobe_opts(const struct bpf_program *prog, pid_t pid,
 	}
 
 	legacy = determine_uprobe_perf_type() < 0;
+	switch (attach_mode) {
+	case PROBE_ATTACH_MODE_LEGACY:
+		legacy = true;
+		pe_opts.force_ioctl_attach = true;
+		break;
+	case PROBE_ATTACH_MODE_PERF:
+		if (legacy)
+			return libbpf_err_ptr(-ENOTSUP);
+		pe_opts.force_ioctl_attach = true;
+		break;
+	case PROBE_ATTACH_MODE_LINK:
+		if (legacy || !kernel_supports(prog->obj, FEAT_PERF_LINK))
+			return libbpf_err_ptr(-ENOTSUP);
+		break;
+	case PROBE_ATTACH_MODE_DEFAULT:
+		break;
+	default:
+		return libbpf_err_ptr(-EINVAL);
+	}
+
 	if (!legacy) {
 		pfd = perf_event_open_probe(true /* uprobe */, retprobe, binary_path,
 					    func_offset, pid, ref_ctr_off);