Merge branch 'bpf-introduce-kprobe_multi-session-attach'

Jiri Olsa says:

====================
bpf: Introduce kprobe_multi session attach

hi,
adding support to attach kprobe program through kprobe_multi link
in a session mode, which means:
  - program is attached to both function entry and return
  - entry program can decided if the return program gets executed
  - entry program can share u64 cookie value with return program

The initial RFC for this was posted in [0] and later discussed more
and which ended up with the session idea [1]

Having entry together with return probe for given function is common
use case for tetragon, bpftrace and most likely for others.

At the moment if we want both entry and return probe to execute bpf
program we need to create two (entry and return probe) links. The link
for return probe creates extra entry probe to setup the return probe.
The extra entry probe execution could be omitted if we had a way to
use just single link for both entry and exit probe.

In addition the possibility to control the return program execution
and sharing data within entry and return probe allows for other use
cases.

v2 changes:
  - renamed BPF_TRACE_KPROBE_MULTI_SESSION to BPF_TRACE_KPROBE_SESSION
    [Andrii]
  - use arrays for results in selftest [Andrii]
  - various small selftests and libbpf changes [Andrii]
  - moved the verifier cookie setup earlier in check_kfunc_call [Andrii]
  - added acks

Also available at:
  https://git.kernel.org/pub/scm/linux/kernel/git/jolsa/perf.git
  bpf/session_data

thanks,
jirka

[0] https://lore.kernel.org/bpf/20240207153550.856536-1-jolsa@kernel.org/
[1] https://lore.kernel.org/bpf/20240228090242.4040210-1-jolsa@kernel.org/
---
====================

Link: https://lore.kernel.org/r/20240430112830.1184228-1-jolsa@kernel.org
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>

1 files changed, 38 insertions, 2 deletions

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 898d5d34ecea..7667671187e9 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -132,6 +132,7 @@ static const char * const attach_type_name[] = {
 	[BPF_TRACE_UPROBE_MULTI]	= "trace_uprobe_multi",
 	[BPF_NETKIT_PRIMARY]		= "netkit_primary",
 	[BPF_NETKIT_PEER]		= "netkit_peer",
+	[BPF_TRACE_KPROBE_SESSION]	= "trace_kprobe_session",
 };
 
 static const char * const link_type_name[] = {
@@ -9273,6 +9274,7 @@ static int attach_tp(const struct bpf_program *prog, long cookie, struct bpf_lin
 static int attach_raw_tp(const struct bpf_program *prog, long cookie, struct bpf_link **link);
 static int attach_trace(const struct bpf_program *prog, long cookie, struct bpf_link **link);
 static int attach_kprobe_multi(const struct bpf_program *prog, long cookie, struct bpf_link **link);
+static int attach_kprobe_session(const struct bpf_program *prog, long cookie, struct bpf_link **link);
 static int attach_uprobe_multi(const struct bpf_program *prog, long cookie, struct bpf_link **link);
 static int attach_lsm(const struct bpf_program *prog, long cookie, struct bpf_link **link);
 static int attach_iter(const struct bpf_program *prog, long cookie, struct bpf_link **link);
@@ -9289,6 +9291,7 @@ static const struct bpf_sec_def section_defs[] = {
 	SEC_DEF("uretprobe.s+",		KPROBE, 0, SEC_SLEEPABLE, attach_uprobe),
 	SEC_DEF("kprobe.multi+",	KPROBE,	BPF_TRACE_KPROBE_MULTI, SEC_NONE, attach_kprobe_multi),
 	SEC_DEF("kretprobe.multi+",	KPROBE,	BPF_TRACE_KPROBE_MULTI, SEC_NONE, attach_kprobe_multi),
+	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.multi.s+",	KPROBE,	BPF_TRACE_UPROBE_MULTI, SEC_SLEEPABLE, attach_uprobe_multi),
@@ -11381,13 +11384,14 @@ bpf_program__attach_kprobe_multi_opts(const struct bpf_program *prog,
 	struct kprobe_multi_resolve res = {
 		.pattern = pattern,
 	};
+	enum bpf_attach_type attach_type;
 	struct bpf_link *link = NULL;
 	char errmsg[STRERR_BUFSIZE];
 	const unsigned long *addrs;
 	int err, link_fd, prog_fd;
+	bool retprobe, session;
 	const __u64 *cookies;
 	const char **syms;
-	bool retprobe;
 	size_t cnt;
 
 	if (!OPTS_VALID(opts, bpf_kprobe_multi_opts))
@@ -11426,6 +11430,12 @@ bpf_program__attach_kprobe_multi_opts(const struct bpf_program *prog,
 	}
 
 	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_KPROBE_SESSION : BPF_TRACE_KPROBE_MULTI;
 
 	lopts.kprobe_multi.syms = syms;
 	lopts.kprobe_multi.addrs = addrs;
@@ -11440,7 +11450,7 @@ bpf_program__attach_kprobe_multi_opts(const struct bpf_program *prog,
 	}
 	link->detach = &bpf_link__detach_fd;
 
-	link_fd = bpf_link_create(prog_fd, 0, BPF_TRACE_KPROBE_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: %s\n",
@@ -11546,6 +11556,32 @@ static int attach_kprobe_multi(const struct bpf_program *prog, long cookie, stru
 	return libbpf_get_error(*link);
 }
 
+static int attach_kprobe_session(const struct bpf_program *prog, long cookie,
+				 struct bpf_link **link)
+{
+	LIBBPF_OPTS(bpf_kprobe_multi_opts, opts, .session = true);
+	const char *spec;
+	char *pattern;
+	int n;
+
+	*link = NULL;
+
+	/* no auto-attach for SEC("kprobe.session") */
+	if (strcmp(prog->sec_name, "kprobe.session") == 0)
+		return 0;
+
+	spec = prog->sec_name + sizeof("kprobe.session/") - 1;
+	n = sscanf(spec, "%m[a-zA-Z0-9_.*?]", &pattern);
+	if (n < 1) {
+		pr_warn("kprobe session pattern is invalid: %s\n", pattern);
+		return -EINVAL;
+	}
+
+	*link = bpf_program__attach_kprobe_multi_opts(prog, pattern, &opts);
+	free(pattern);
+	return *link ? 0 : -errno;
+}
+
 static int attach_uprobe_multi(const struct bpf_program *prog, long cookie, struct bpf_link **link)
 {
 	char *probe_type = NULL, *binary_path = NULL, *func_name = NULL;