Adding support to attach program in uprobe session mode
with bpf_program__attach_uprobe_multi function.

Adding session bool to bpf_uprobe_multi_opts struct that allows
to load and attach the bpf program via uprobe session.
the attachment to create uprobe multi session.

Also adding new program loader section that allows:
  SEC("uprobe.session/bpf_fentry_test*")

and loads/attaches uprobe program as uprobe session.

Adding sleepable hook (uprobe.session.s) as well.

Acked-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
---
 tools/lib/bpf/bpf.c    |  1 +
 tools/lib/bpf/libbpf.c | 18 ++++++++++++++++--
 tools/lib/bpf/libbpf.h |  4 +++-
 3 files changed, 20 insertions(+), 3 deletions(-)

diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c
index 2a4c71501a17..becdfa701c75 100644
--- a/tools/lib/bpf/bpf.c
+++ b/tools/lib/bpf/bpf.c
@@ -776,6 +776,7 @@ int bpf_link_create(int prog_fd, int target_fd,
 			return libbpf_err(-EINVAL);
 		break;
 	case BPF_TRACE_UPROBE_MULTI:
+	case BPF_TRACE_UPROBE_SESSION:
 		attr.link_create.uprobe_multi.flags = OPTS_GET(opts, uprobe_multi.flags, 0);
 		attr.link_create.uprobe_multi.cnt = OPTS_GET(opts, uprobe_multi.cnt, 0);
 		attr.link_create.uprobe_multi.path = ptr_to_u64(OPTS_GET(opts, uprobe_multi.path, 0));
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index e650809e7170..c45cd48840ae 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -9410,8 +9410,10 @@ static const struct bpf_sec_def section_defs[] = {
 	SEC_DEF("kprobe.session+",	KPROBE,	BPF_TRACE_KPROBE_SESSION, SEC_NONE, attach_kprobe_session),
 	SEC_DEF("uprobe.multi+",	KPROBE,	BPF_TRACE_UPROBE_MULTI, SEC_NONE, attach_uprobe_multi),
 	SEC_DEF("uretprobe.multi+",	KPROBE,	BPF_TRACE_UPROBE_MULTI, SEC_NONE, attach_uprobe_multi),
+	SEC_DEF("uprobe.session+",	KPROBE,	BPF_TRACE_UPROBE_SESSION, SEC_NONE, attach_uprobe_multi),
 	SEC_DEF("uprobe.multi.s+",	KPROBE,	BPF_TRACE_UPROBE_MULTI, SEC_SLEEPABLE, attach_uprobe_multi),
 	SEC_DEF("uretprobe.multi.s+",	KPROBE,	BPF_TRACE_UPROBE_MULTI, SEC_SLEEPABLE, attach_uprobe_multi),
+	SEC_DEF("uprobe.session.s+",	KPROBE,	BPF_TRACE_UPROBE_SESSION, SEC_SLEEPABLE, attach_uprobe_multi),
 	SEC_DEF("ksyscall+",		KPROBE,	0, SEC_NONE, attach_ksyscall),
 	SEC_DEF("kretsyscall+",		KPROBE, 0, SEC_NONE, attach_ksyscall),
 	SEC_DEF("usdt+",		KPROBE,	0, SEC_USDT, attach_usdt),
@@ -11733,7 +11735,9 @@ static int attach_uprobe_multi(const struct bpf_program *prog, long cookie, stru
 		ret = 0;
 		break;
 	case 3:
+		opts.session = str_has_pfx(probe_type, "uprobe.session");
 		opts.retprobe = str_has_pfx(probe_type, "uretprobe.multi");
+
 		*link = bpf_program__attach_uprobe_multi(prog, -1, binary_path, func_name, &opts);
 		ret = libbpf_get_error(*link);
 		break;
@@ -11982,10 +11986,12 @@ bpf_program__attach_uprobe_multi(const struct bpf_program *prog,
 	const unsigned long *ref_ctr_offsets = NULL, *offsets = NULL;
 	LIBBPF_OPTS(bpf_link_create_opts, lopts);
 	unsigned long *resolved_offsets = NULL;
+	enum bpf_attach_type attach_type;
 	int err = 0, link_fd, prog_fd;
 	struct bpf_link *link = NULL;
 	char errmsg[STRERR_BUFSIZE];
 	char full_path[PATH_MAX];
+	bool retprobe, session;
 	const __u64 *cookies;
 	const char **syms;
 	size_t cnt;
@@ -12056,12 +12062,20 @@ bpf_program__attach_uprobe_multi(const struct bpf_program *prog,
 		offsets = resolved_offsets;
 	}
 
+	retprobe = OPTS_GET(opts, retprobe, false);
+	session  = OPTS_GET(opts, session, false);
+
+	if (retprobe && session)
+		return libbpf_err_ptr(-EINVAL);
+
+	attach_type = session ? BPF_TRACE_UPROBE_SESSION : BPF_TRACE_UPROBE_MULTI;
+
 	lopts.uprobe_multi.path = path;
 	lopts.uprobe_multi.offsets = offsets;
 	lopts.uprobe_multi.ref_ctr_offsets = ref_ctr_offsets;
 	lopts.uprobe_multi.cookies = cookies;
 	lopts.uprobe_multi.cnt = cnt;
-	lopts.uprobe_multi.flags = OPTS_GET(opts, retprobe, false) ? BPF_F_UPROBE_MULTI_RETURN : 0;
+	lopts.uprobe_multi.flags = retprobe ? BPF_F_UPROBE_MULTI_RETURN : 0;
 
 	if (pid == 0)
 		pid = getpid();
@@ -12075,7 +12089,7 @@ bpf_program__attach_uprobe_multi(const struct bpf_program *prog,
 	}
 	link->detach = &bpf_link__detach_fd;
 
-	link_fd = bpf_link_create(prog_fd, 0, BPF_TRACE_UPROBE_MULTI, &lopts);
+	link_fd = bpf_link_create(prog_fd, 0, attach_type, &lopts);
 	if (link_fd < 0) {
 		err = -errno;
 		pr_warn("prog '%s': failed to attach multi-uprobe: %s\n",
diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
index 91484303849c..b2ce3a72b11d 100644
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h
@@ -577,10 +577,12 @@ struct bpf_uprobe_multi_opts {
 	size_t cnt;
 	/* create return uprobes */
 	bool retprobe;
+	/* create session kprobes */
+	bool session;
 	size_t :0;
 };
 
-#define bpf_uprobe_multi_opts__last_field retprobe
+#define bpf_uprobe_multi_opts__last_field session
 
 /**
  * @brief **bpf_program__attach_uprobe_multi()** attaches a BPF program
-- 
2.46.2