[PATCHv3 4/7] libbpf: Add support for uprobe multi session attach

Jiri Olsa
2024-09-09T07:46:47Z

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.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
---
tools/lib/bpf/bpf.c | 1 +
tools/lib/bpf/libbpf.c | 50 ++++++++++++++++++++++++++++++++++++++++--
tools/lib/bpf/libbpf.h | 4 +++-
3 files changed, 52 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 274441674f92..7b72a29b09a7 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -9345,6 +9345,7 @@ static int attach_trace(const struct bpf_program *prog, long cookie, struct bpf_
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_uprobe_session(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);

@@ -9363,8 +9364,10 @@ 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_session),
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_session),
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),
@@ -11699,6 +11702,39 @@ static int attach_uprobe_multi(const struct bpf_program *prog, long cookie, stru
return ret;
}

+static int attach_uprobe_session(const struct bpf_program *prog, long cookie, struct bpf_link **link)
+{
+ LIBBPF_OPTS(bpf_uprobe_multi_opts, opts, .session = true);
+ char *binary_path = NULL, *func_name = NULL;
+ int n, ret = -EINVAL;
+ const char *spec;
+
+ *link = NULL;
+
+ spec = prog->sec_name + sizeof("uprobe.session/") - 1;
+ if (cookie & SEC_SLEEPABLE)
+ spec += 2; /* extra '.s' */
+ n = sscanf(spec, "%m[^:]:%m[^\n]", &binary_path, &func_name);
+
+ switch (n) {
+ case 1:
+ /* but auto-attach is impossible. */
+ ret = 0;
+ break;
+ case 2:
+ *link = bpf_program__attach_uprobe_multi(prog, -1, binary_path, func_name, &opts);
+ ret = *link ? 0 : -errno;
+ break;
+ default:
+ pr_warn("prog '%s': invalid format of section definition '%s'\n", prog->name,
+ prog->sec_name);
+ break;
+ }
+ free(binary_path);
+ free(func_name);
+ return ret;
+}
+
static void gen_uprobe_legacy_event_name(char *buf, size_t buf_sz,
const char *binary_path, uint64_t offset)
{
@@ -11933,10 +11969,12 @@ 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;
@@ -12007,12 +12045,20 @@ 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();
@@ -12026,7 +12072,7 @@ 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 64a6a3d323e3..f6a7835dc519 100644
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h
@@ -569,10 +569,12 @@ 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
--
2.46.0