[PATCHv3 bpf-next 09/24] bpf: Add support for tracing multi link
From: Jiri Olsa <jolsa@kernel.org>
Date: 2026-03-16 07:53:24
Also in:
linux-trace-kernel
Subsystem:
bpf [core], bpf [general] (safe dynamic programs and tools), bpf [library] (libbpf), bpf [security & lsm] (security audit and enforcement using bpf), bpf [tracing], the rest, tracing · Maintainers:
Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko, Eduard Zingerman, Kumar Kartikeya Dwivedi, KP Singh, Matt Bobrowski, Song Liu, Linus Torvalds, Steven Rostedt, Masami Hiramatsu
Adding new link to allow to attach program to multiple function
BTF IDs. The link is represented by struct bpf_tracing_multi_link.
To configure the link, new fields are added to bpf_attr::link_create
to pass array of BTF IDs;
struct {
__aligned_u64 ids;
__u32 cnt;
} tracing_multi;
Each BTF ID represents function (BTF_KIND_FUNC) that the link will
attach bpf program to.
We use previously added bpf_trampoline_multi_attach/detach functions
to attach/detach the link.
The linkinfo/fdinfo callbacks will be implemented in following changes.
Note this is supported only for archs (x86_64) with ftrace direct and
have single ops support.
CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS &&
CONFIG_HAVE_SINGLE_FTRACE_DIRECT_OPS
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
---
include/linux/bpf_types.h | 1 +
include/linux/trace_events.h | 6 +++
include/uapi/linux/bpf.h | 5 ++
kernel/bpf/syscall.c | 2 +
kernel/trace/bpf_trace.c | 90 ++++++++++++++++++++++++++++++++++
tools/include/uapi/linux/bpf.h | 6 +++
tools/lib/bpf/libbpf.c | 1 +
7 files changed, 111 insertions(+)
diff --git a/include/linux/bpf_types.h b/include/linux/bpf_types.h
index b13de31e163f..96575b5b563e 100644
--- a/include/linux/bpf_types.h
+++ b/include/linux/bpf_types.h@@ -155,3 +155,4 @@ BPF_LINK_TYPE(BPF_LINK_TYPE_PERF_EVENT, perf) BPF_LINK_TYPE(BPF_LINK_TYPE_KPROBE_MULTI, kprobe_multi) BPF_LINK_TYPE(BPF_LINK_TYPE_STRUCT_OPS, struct_ops) BPF_LINK_TYPE(BPF_LINK_TYPE_UPROBE_MULTI, uprobe_multi) +BPF_LINK_TYPE(BPF_LINK_TYPE_TRACING_MULTI, tracing_multi)
diff --git a/include/linux/trace_events.h b/include/linux/trace_events.h
index 37eb2f0f3dd8..b6d4c745bdac 100644
--- a/include/linux/trace_events.h
+++ b/include/linux/trace_events.h@@ -783,6 +783,7 @@ int bpf_get_perf_event_info(const struct perf_event *event, u32 *prog_id, unsigned long *missed); int bpf_kprobe_multi_link_attach(const union bpf_attr *attr, struct bpf_prog *prog); int bpf_uprobe_multi_link_attach(const union bpf_attr *attr, struct bpf_prog *prog); +int bpf_tracing_multi_attach(struct bpf_prog *prog, const union bpf_attr *attr); #else static inline unsigned int trace_call_bpf(struct trace_event_call *call, void *ctx) {
@@ -835,6 +836,11 @@ bpf_uprobe_multi_link_attach(const union bpf_attr *attr, struct bpf_prog *prog) { return -EOPNOTSUPP; } +static inline int +bpf_tracing_multi_attach(struct bpf_prog *prog, const union bpf_attr *attr) +{ + return -EOPNOTSUPP; +} #endif enum {
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 68600972a778..7f5c51f27a36 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h@@ -1180,6 +1180,7 @@ enum bpf_link_type { BPF_LINK_TYPE_UPROBE_MULTI = 12, BPF_LINK_TYPE_NETKIT = 13, BPF_LINK_TYPE_SOCKMAP = 14, + BPF_LINK_TYPE_TRACING_MULTI = 15, __MAX_BPF_LINK_TYPE, };
@@ -1863,6 +1864,10 @@ union bpf_attr { }; __u64 expected_revision; } cgroup; + struct { + __aligned_u64 ids; + __u32 cnt; + } tracing_multi; }; } link_create;
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 2680740e9c09..94c6a9c81ef0 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c@@ -5749,6 +5749,8 @@ static int link_create(union bpf_attr *attr, bpfptr_t uattr) ret = bpf_iter_link_attach(attr, uattr, prog); else if (prog->expected_attach_type == BPF_LSM_CGROUP) ret = cgroup_bpf_link_attach(attr, prog); + else if (is_tracing_multi(prog->expected_attach_type)) + ret = bpf_tracing_multi_attach(prog, attr); else ret = bpf_tracing_prog_attach(prog, attr->link_create.target_fd,
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 0b040a417442..4a92d47d1eaf 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c@@ -42,6 +42,7 @@ #define MAX_UPROBE_MULTI_CNT (1U << 20) #define MAX_KPROBE_MULTI_CNT (1U << 20) +#define MAX_TRACING_MULTI_CNT (1U << 20) #ifdef CONFIG_MODULES struct bpf_trace_module {
@@ -3594,3 +3595,92 @@ __bpf_kfunc int bpf_copy_from_user_task_str_dynptr(struct bpf_dynptr *dptr, u64 } __bpf_kfunc_end_defs(); + +#if defined(CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS) && \ + defined(CONFIG_HAVE_SINGLE_FTRACE_DIRECT_OPS) + +static void bpf_tracing_multi_link_release(struct bpf_link *link) +{ + struct bpf_tracing_multi_link *tr_link = + container_of(link, struct bpf_tracing_multi_link, link); + + WARN_ON_ONCE(bpf_trampoline_multi_detach(link->prog, tr_link)); +} + +static void bpf_tracing_multi_link_dealloc(struct bpf_link *link) +{ + struct bpf_tracing_multi_link *tr_link = + container_of(link, struct bpf_tracing_multi_link, link); + + kvfree(tr_link); +} + +static const struct bpf_link_ops bpf_tracing_multi_link_lops = { + .release = bpf_tracing_multi_link_release, + .dealloc_deferred = bpf_tracing_multi_link_dealloc, +}; + +int bpf_tracing_multi_attach(struct bpf_prog *prog, const union bpf_attr *attr) +{ + struct bpf_tracing_multi_link *link = NULL; + struct bpf_link_primer link_primer; + u32 cnt, *ids = NULL; + u32 __user *uids; + int err; + + uids = u64_to_user_ptr(attr->link_create.tracing_multi.ids); + cnt = attr->link_create.tracing_multi.cnt; + + if (!cnt || !uids) + return -EINVAL; + if (cnt > MAX_TRACING_MULTI_CNT) + return -E2BIG; + if (attr->link_create.flags) + return -EINVAL; + + ids = kvmalloc_objs(*ids, cnt); + if (!ids) + return -ENOMEM; + + if (copy_from_user(ids, uids, cnt * sizeof(*ids))) { + err = -EFAULT; + goto error; + } + + link = kvzalloc_flex(*link, nodes, cnt); + if (!link) { + err = -ENOMEM; + goto error; + } + + bpf_link_init(&link->link, BPF_LINK_TYPE_TRACING_MULTI, + &bpf_tracing_multi_link_lops, prog, prog->expected_attach_type); + + err = bpf_link_prime(&link->link, &link_primer); + if (err) + goto error; + + link->nodes_cnt = cnt; + + err = bpf_trampoline_multi_attach(prog, ids, link); + kvfree(ids); + if (err) { + bpf_link_cleanup(&link_primer); + return err; + } + return bpf_link_settle(&link_primer); + +error: + kvfree(ids); + kvfree(link); + return err; +} + +#else + +int bpf_tracing_multi_attach(struct bpf_prog *prog, const union bpf_attr *attr) +{ + return -EOPNOTSUPP; +} + +#endif /* CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS && CONFIG_HAVE_SINGLE_FTRACE_DIRECT_OPS */
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 61f0fe5bc0aa..7f5c51f27a36 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h@@ -1180,6 +1180,7 @@ enum bpf_link_type { BPF_LINK_TYPE_UPROBE_MULTI = 12, BPF_LINK_TYPE_NETKIT = 13, BPF_LINK_TYPE_SOCKMAP = 14, + BPF_LINK_TYPE_TRACING_MULTI = 15, __MAX_BPF_LINK_TYPE, };
@@ -1863,6 +1864,10 @@ union bpf_attr { }; __u64 expected_revision; } cgroup; + struct { + __aligned_u64 ids; + __u32 cnt; + } tracing_multi; }; } link_create;
@@ -7236,6 +7241,7 @@ enum { TCP_BPF_SOCK_OPS_CB_FLAGS = 1008, /* Get or Set TCP sock ops flags */ SK_BPF_CB_FLAGS = 1009, /* Get or set sock ops flags in socket */ SK_BPF_BYPASS_PROT_MEM = 1010, /* Get or Set sk->sk_bypass_prot_mem */ + }; enum {
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 6fa996e4969c..9f26ad0d7bce 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c@@ -156,6 +156,7 @@ static const char * const link_type_name[] = { [BPF_LINK_TYPE_UPROBE_MULTI] = "uprobe_multi", [BPF_LINK_TYPE_NETKIT] = "netkit", [BPF_LINK_TYPE_SOCKMAP] = "sockmap", + [BPF_LINK_TYPE_TRACING_MULTI] = "tracing_multi", }; static const char * const map_type_name[] = {
--
2.53.0