[PATCH bpf-next v2 8/9] libbpf: add support for the multi-link of tracing

Menglong Dong
2024-03-11T09:35:31Z

Add support for the attach types of:

BPF_TRACE_FENTRY_MULTI
BPF_TRACE_FEXIT_MULTI
BPF_MODIFY_RETURN_MULTI

Signed-off-by: Menglong Dong <dongmenglong.8@bytedance.com>
---
tools/bpf/bpftool/common.c | 3 +
tools/lib/bpf/bpf.c | 10 +++
tools/lib/bpf/bpf.h | 6 ++
tools/lib/bpf/libbpf.c | 168 ++++++++++++++++++++++++++++++++++++-
tools/lib/bpf/libbpf.h | 14 ++++
tools/lib/bpf/libbpf.map | 1 +
6 files changed, 199 insertions(+), 3 deletions(-)

diff --git a/tools/bpf/bpftool/common.c b/tools/bpf/bpftool/common.c
index cc6e6aae2447..ffc85256671d 100644
--- a/tools/bpf/bpftool/common.c
+++ b/tools/bpf/bpftool/common.c
@@ -1089,6 +1089,9 @@ const char *bpf_attach_type_input_str(enum bpf_attach_type t)
case BPF_TRACE_FENTRY: return "fentry";
case BPF_TRACE_FEXIT: return "fexit";
case BPF_MODIFY_RETURN: return "mod_ret";
+ case BPF_TRACE_FENTRY_MULTI: return "fentry_multi";
+ case BPF_TRACE_FEXIT_MULTI: return "fexit_multi";
+ case BPF_MODIFY_RETURN_MULTI: return "mod_ret_multi";
case BPF_SK_REUSEPORT_SELECT: return "sk_skb_reuseport_select";
case BPF_SK_REUSEPORT_SELECT_OR_MIGRATE: return "sk_skb_reuseport_select_or_migrate";
default: return libbpf_bpf_attach_type_str(t);
diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c
index 97ec005c3c47..63d4734dbae4 100644
--- a/tools/lib/bpf/bpf.c
+++ b/tools/lib/bpf/bpf.c
@@ -793,6 +793,16 @@ int bpf_link_create(int prog_fd, int target_fd,
if (!OPTS_ZEROED(opts, tracing))
return libbpf_err(-EINVAL);
break;
+ case BPF_TRACE_FENTRY_MULTI:
+ case BPF_TRACE_FEXIT_MULTI:
+ case BPF_MODIFY_RETURN_MULTI:
+ attr.link_create.tracing_multi.btf_ids = ptr_to_u64(OPTS_GET(opts, tracing_multi.btf_ids, 0));
+ attr.link_create.tracing_multi.tgt_fds = ptr_to_u64(OPTS_GET(opts, tracing_multi.tgt_fds, 0));
+ attr.link_create.tracing_multi.cookies = ptr_to_u64(OPTS_GET(opts, tracing_multi.cookies, 0));
+ attr.link_create.tracing_multi.cnt = OPTS_GET(opts, tracing_multi.cnt, 0);
+ if (!OPTS_ZEROED(opts, tracing_multi))
+ return libbpf_err(-EINVAL);
+ break;
case BPF_NETFILTER:
attr.link_create.netfilter.pf = OPTS_GET(opts, netfilter.pf, 0);
attr.link_create.netfilter.hooknum = OPTS_GET(opts, netfilter.hooknum, 0);
diff --git a/tools/lib/bpf/bpf.h b/tools/lib/bpf/bpf.h
index df0db2f0cdb7..e28c88d6cfa4 100644
--- a/tools/lib/bpf/bpf.h
+++ b/tools/lib/bpf/bpf.h
@@ -419,6 +419,12 @@ struct bpf_link_create_opts {
struct {
__u64 cookie;
} tracing;
+ struct {
+ __u32 cnt;
+ const __u32 *btf_ids;
+ const __u32 *tgt_fds;
+ const __u64 *cookies;
+ } tracing_multi;
struct {
__u32 pf;
__u32 hooknum;
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index fd5428494a7e..821214774941 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -132,6 +132,9 @@ 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_FENTRY_MULTI] = "trace_fentry_multi",
+ [BPF_TRACE_FEXIT_MULTI] = "trace_fexit_multi",
+ [BPF_MODIFY_RETURN_MULTI] = "modify_return_multi",
};

static const char * const link_type_name[] = {
@@ -381,6 +384,8 @@ enum sec_def_flags {
SEC_XDP_FRAGS = 16,
/* Setup proper attach type for usdt probes. */
SEC_USDT = 32,
+ /* attachment target is multi-link */
+ SEC_ATTACH_BTF_MULTI = 64,
};

struct bpf_sec_def {
@@ -7160,9 +7165,9 @@ static int libbpf_prepare_prog_load(struct bpf_program *prog,
if ((def & SEC_USDT) && kernel_supports(prog->obj, FEAT_UPROBE_MULTI_LINK))
prog->expected_attach_type = BPF_TRACE_UPROBE_MULTI;

- if ((def & SEC_ATTACH_BTF) && !prog->attach_btf_id) {
+ if ((def & (SEC_ATTACH_BTF | SEC_ATTACH_BTF_MULTI)) && !prog->attach_btf_id) {
int btf_obj_fd = 0, btf_type_id = 0, err;
- const char *attach_name;
+ const char *attach_name, *name_end;

attach_name = strchr(prog->sec_name, '/');
if (!attach_name) {
@@ -7181,7 +7186,27 @@ static int libbpf_prepare_prog_load(struct bpf_program *prog,
}
attach_name++; /* skip over / */

- err = libbpf_find_attach_btf_id(prog, attach_name, &btf_obj_fd, &btf_type_id);
+ name_end = strchr(attach_name, ',');
+ /* for multi-link tracing, use the first target symbol during
+ * loading.
+ */
+ if ((def & SEC_ATTACH_BTF_MULTI) && name_end) {
+ int len = name_end - attach_name + 1;
+ char *first_tgt;
+
+ first_tgt = malloc(len);
+ if (!first_tgt)
+ return -ENOMEM;
+ strncpy(first_tgt, attach_name, len);
+ first_tgt[len - 1] = '\0';
+ err = libbpf_find_attach_btf_id(prog, first_tgt, &btf_obj_fd,
+ &btf_type_id);
+ free(first_tgt);
+ } else {
+ err = libbpf_find_attach_btf_id(prog, attach_name, &btf_obj_fd,
+ &btf_type_id);
+ }
+
if (err)
return err;

@@ -9149,6 +9174,7 @@ static int attach_kprobe_multi(const struct bpf_program *prog, long cookie, stru
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);
+static int attach_trace_multi(const struct bpf_program *prog, long cookie, struct bpf_link **link);

static const struct bpf_sec_def section_defs[] = {
SEC_DEF("socket", SOCKET_FILTER, 0, SEC_NONE),
@@ -9192,6 +9218,13 @@ static const struct bpf_sec_def section_defs[] = {
SEC_DEF("fentry.s+", TRACING, BPF_TRACE_FENTRY, SEC_ATTACH_BTF | SEC_SLEEPABLE, attach_trace),
SEC_DEF("fmod_ret.s+", TRACING, BPF_MODIFY_RETURN, SEC_ATTACH_BTF | SEC_SLEEPABLE, attach_trace),
SEC_DEF("fexit.s+", TRACING, BPF_TRACE_FEXIT, SEC_ATTACH_BTF | SEC_SLEEPABLE, attach_trace),
+ SEC_DEF("tp_btf+", TRACING, BPF_TRACE_RAW_TP, SEC_ATTACH_BTF, attach_trace),
+ SEC_DEF("fentry.multi+", TRACING, BPF_TRACE_FENTRY_MULTI, SEC_ATTACH_BTF_MULTI, attach_trace_multi),
+ SEC_DEF("fmod_ret.multi+", TRACING, BPF_MODIFY_RETURN_MULTI, SEC_ATTACH_BTF_MULTI, attach_trace_multi),
+ SEC_DEF("fexit.multi+", TRACING, BPF_TRACE_FEXIT_MULTI, SEC_ATTACH_BTF_MULTI, attach_trace_multi),
+ SEC_DEF("fentry.multi.s+", TRACING, BPF_TRACE_FENTRY_MULTI, SEC_ATTACH_BTF_MULTI | SEC_SLEEPABLE, attach_trace_multi),
+ SEC_DEF("fmod_ret.multi.s+", TRACING, BPF_MODIFY_RETURN_MULTI, SEC_ATTACH_BTF_MULTI | SEC_SLEEPABLE, attach_trace_multi),
+ SEC_DEF("fexit.multi.s+", TRACING, BPF_TRACE_FEXIT_MULTI, SEC_ATTACH_BTF_MULTI | SEC_SLEEPABLE, attach_trace_multi),
SEC_DEF("freplace+", EXT, 0, SEC_ATTACH_BTF, attach_trace),
SEC_DEF("lsm+", LSM, BPF_LSM_MAC, SEC_ATTACH_BTF, attach_lsm),
SEC_DEF("lsm.s+", LSM, BPF_LSM_MAC, SEC_ATTACH_BTF | SEC_SLEEPABLE, attach_lsm),
@@ -12300,6 +12333,135 @@ static int attach_trace(const struct bpf_program *prog, long cookie, struct bpf_
return libbpf_get_error(*link);
}

+struct bpf_link *bpf_program__attach_trace_multi_opts(const struct bpf_program *prog,
+ const struct bpf_trace_multi_opts *opts)
+{
+ LIBBPF_OPTS(bpf_link_create_opts, link_opts);
+ __u32 *btf_ids = NULL, *tgt_fds = NULL;
+ struct bpf_link *link = NULL;
+ char errmsg[STRERR_BUFSIZE];
+ int prog_fd, pfd, cnt, err;
+
+ if (!OPTS_VALID(opts, bpf_trace_multi_opts))
+ return libbpf_err_ptr(-EINVAL);
+
+ prog_fd = bpf_program__fd(prog);
+ if (prog_fd < 0) {
+ pr_warn("prog '%s': can't attach before loaded\n", prog->name);
+ return libbpf_err_ptr(-EINVAL);
+ }
+
+ cnt = OPTS_GET(opts, cnt, 0);
+ if (opts->syms) {
+ int btf_obj_fd, btf_type_id, i;
+
+ if (opts->btf_ids || opts->tgt_fds) {
+ pr_warn("can set both opts->syms and opts->btf_ids\n");
+ return libbpf_err_ptr(-EINVAL);
+ }
+
+ btf_ids = malloc(sizeof(*btf_ids) * cnt);
+ tgt_fds = malloc(sizeof(*tgt_fds) * cnt);
+ if (!btf_ids || !tgt_fds) {
+ err = -ENOMEM;
+ goto err_free;
+ }
+ for (i = 0; i < cnt; i++) {
+ btf_obj_fd = btf_type_id = 0;
+
+ err = find_kernel_btf_id(prog->obj, opts->syms[i],
+ prog->expected_attach_type, &btf_obj_fd,
+ &btf_type_id);
+ if (err)
+ goto err_free;
+ btf_ids[i] = btf_type_id;
+ tgt_fds[i] = btf_obj_fd;
+ }
+ link_opts.tracing_multi.btf_ids = btf_ids;
+ link_opts.tracing_multi.tgt_fds = tgt_fds;
+ } else {
+ link_opts.tracing_multi.btf_ids = OPTS_GET(opts, btf_ids, 0);
+ link_opts.tracing_multi.tgt_fds = OPTS_GET(opts, tgt_fds, 0);
+ }
+
+ link = calloc(1, sizeof(*link));
+ if (!link) {
+ err = -ENOMEM;
+ goto err_free;
+ }
+ link->detach = &bpf_link__detach_fd;
+
+ link_opts.tracing_multi.cookies = OPTS_GET(opts, cookies, 0);
+ link_opts.tracing_multi.cnt = cnt;
+
+ pfd = bpf_link_create(prog_fd, 0, bpf_program__expected_attach_type(prog), &link_opts);
+ if (pfd < 0) {
+ err = -errno;
+ pr_warn("prog '%s': failed to attach: %s\n",
+ prog->name, libbpf_strerror_r(pfd, errmsg, sizeof(errmsg)));
+ goto err_free;
+ }
+ link->fd = pfd;
+
+ free(btf_ids);
+ free(tgt_fds);
+ return link;
+err_free:
+ free(btf_ids);
+ free(tgt_fds);
+ free(link);
+ return libbpf_err_ptr(err);
+}
+
+static int attach_trace_multi(const struct bpf_program *prog, long cookie, struct bpf_link **link)
+{
+ LIBBPF_OPTS(bpf_trace_multi_opts, opts);
+ int i, err, len, cnt = 1;
+ char **syms, *buf, *name;
+ const char *spec;
+
+ spec = strchr(prog->sec_name, '/');
+ if (!spec || !*(++spec))
+ return -EINVAL;
+
+ len = strlen(spec);
+ buf = malloc(len + 1);
+ if (!buf)
+ return -ENOMEM;
+
+ strcpy(buf, spec);
+ for (i = 0; i < len; i++) {
+ if (buf[i] == ',')
+ cnt++;
+ }
+
+ syms = malloc(sizeof(*syms) * cnt);
+ if (!syms) {
+ err = -ENOMEM;
+ goto out_free;
+ }
+
+ opts.syms = (const char **)syms;
+ opts.cnt = cnt;
+ name = buf;
+ err = -EINVAL;
+ while (name) {
+ if (*name == '\0')
+ goto out_free;
+ *(syms++) = name;
+ name = strchr(name, ',');
+ if (name)
+ *(name++) = '\0';
+ }
+
+ *link = bpf_program__attach_trace_multi_opts(prog, &opts);
+ err = libbpf_get_error(*link);
+out_free:
+ free(buf);
+ free(opts.syms);
+ return err;
+}
+
static int attach_lsm(const struct bpf_program *prog, long cookie, struct bpf_link **link)
{
*link = bpf_program__attach_lsm(prog);
diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
index c41a909ea4c1..9bca44d5adfa 100644
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h
@@ -790,6 +790,20 @@ bpf_program__attach_xdp(const struct bpf_program *prog, int ifindex);
LIBBPF_API struct bpf_link *
bpf_program__attach_freplace(const struct bpf_program *prog,
int target_fd, const char *attach_func_name);
+struct bpf_trace_multi_opts {
+ /* size of this struct, for forward/backward compatibility */
+ size_t sz;
+ const char **syms;
+ __u32 *btf_ids;
+ __u32 *tgt_fds;
+ __u64 *cookies;
+ size_t cnt;
+};
+#define bpf_trace_multi_opts__last_field cnt
+
+LIBBPF_API struct bpf_link *
+bpf_program__attach_trace_multi_opts(const struct bpf_program *prog,
+ const struct bpf_trace_multi_opts *opts);

struct bpf_netfilter_opts {
/* size of this struct, for forward/backward compatibility */
diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
index 57642b78917f..94933898df44 100644
--- a/tools/lib/bpf/libbpf.map
+++ b/tools/lib/bpf/libbpf.map
@@ -414,4 +414,5 @@ LIBBPF_1.4.0 {
btf__new_split;
btf_ext__raw_data;
bpf_object__free_btfs;
+ bpf_program__attach_trace_multi_opts;
} LIBBPF_1.3.0;
--
2.39.2