Teach libbpf to search for BTF types in kernel modules for tracing BPF
programs. This allows attachment of raw_tp/fentry/fexit/fmod_ret/etc BPF
program types to tracepoints and functions in kernel modules.
Signed-off-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
---
tools/lib/bpf/bpf.c | 1 +
tools/lib/bpf/libbpf.c | 111 +++++++++++++++++++++++++-------
tools/lib/bpf/libbpf_internal.h | 1 +
3 files changed, 90 insertions(+), 23 deletions(-)
diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c
index e371ef91f5e8..dfdad932ef72 100644
--- a/tools/lib/bpf/bpf.c
+++ b/tools/lib/bpf/bpf.c
@@ -230,6 +230,7 @@ int libbpf__bpf_prog_load(const struct bpf_prog_load_params *load_attr)
attr.prog_type = load_attr->prog_type;
attr.expected_attach_type = load_attr->expected_attach_type;
+ attr.attach_btf_obj_id = load_attr->attach_btf_obj_id;
attr.attach_btf_id = load_attr->attach_btf_id;
attr.attach_prog_fd = load_attr->attach_prog_fd;
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 0280df77cf5f..95932d8701b1 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -278,6 +278,7 @@ struct bpf_program {
enum bpf_prog_type type;
enum bpf_attach_type expected_attach_type;
int prog_ifindex;
+ __u32 attach_btf_obj_id;
__u32 attach_btf_id;
__u32 attach_prog_fd;
void *func_info;
@@ -6831,6 +6832,7 @@ load_program(struct bpf_program *prog, struct bpf_insn *insns, int insns_cnt,
load_attr.license = license;
load_attr.attach_btf_id = prog->attach_btf_id;
load_attr.attach_prog_fd = prog->attach_prog_fd;
+ load_attr.attach_btf_obj_id = prog->attach_btf_obj_id;
load_attr.attach_btf_id = prog->attach_btf_id;
load_attr.kern_version = kern_version;
load_attr.prog_ifindex = prog->prog_ifindex;
@@ -6926,11 +6928,11 @@ load_program(struct bpf_program *prog, struct bpf_insn *insns, int insns_cnt,
return ret;
}
-static int libbpf_find_attach_btf_id(struct bpf_program *prog);
+static int libbpf_find_attach_btf_id(struct bpf_program *prog, int *btf_obj_id, int *btf_type_id);
int bpf_program__load(struct bpf_program *prog, char *license, __u32 kern_ver)
{
- int err = 0, fd, i, btf_id;
+ int err = 0, fd, i;
if (prog->obj->loaded) {
pr_warn("prog '%s': can't load after object was loaded\n", prog->name);
@@ -6940,10 +6942,14 @@ int bpf_program__load(struct bpf_program *prog, char *license, __u32 kern_ver)
if ((prog->type == BPF_PROG_TYPE_TRACING ||
prog->type == BPF_PROG_TYPE_LSM ||
prog->type == BPF_PROG_TYPE_EXT) && !prog->attach_btf_id) {
- btf_id = libbpf_find_attach_btf_id(prog);
- if (btf_id <= 0)
- return btf_id;
- prog->attach_btf_id = btf_id;
+ int btf_obj_id = 0, btf_type_id = 0;
+
+ err = libbpf_find_attach_btf_id(prog, &btf_obj_id, &btf_type_id);
+ if (err)
+ return err;
+
+ prog->attach_btf_id = btf_type_id;
+ prog->attach_btf_obj_id = btf_obj_id;
}
if (prog->instances.nr < 0 || !prog->instances.fds) {
@@ -8795,8 +8801,8 @@ static int find_btf_by_prefix_kind(const struct btf *btf, const char *prefix,
return btf__find_by_name_kind(btf, btf_type_name, kind);
}
-static inline int __find_vmlinux_btf_id(struct btf *btf, const char *name,
- enum bpf_attach_type attach_type)
+static inline int find_attach_btf_id(struct btf *btf, const char *name,
+ enum bpf_attach_type attach_type)
{
int err;
@@ -8812,9 +8818,6 @@ static inline int __find_vmlinux_btf_id(struct btf *btf, const char *name,
else
err = btf__find_by_name_kind(btf, name, BTF_KIND_FUNC);
- if (err <= 0)
- pr_warn("%s is not found in vmlinux BTF\n", name);
-
return err;
}
@@ -8830,7 +8833,10 @@ int libbpf_find_vmlinux_btf_id(const char *name,
return -EINVAL;
}
- err = __find_vmlinux_btf_id(btf, name, attach_type);
+ err = find_attach_btf_id(btf, name, attach_type);
+ if (err <= 0)
+ pr_warn("%s is not found in vmlinux BTF\n", name);
+
btf__free(btf);
return err;
}
@@ -8868,11 +8874,49 @@ static int libbpf_find_prog_btf_id(const char *name, __u32 attach_prog_fd)
return err;
}
-static int libbpf_find_attach_btf_id(struct bpf_program *prog)
+static int find_kernel_btf_id(struct bpf_object *obj, const char *attach_name,
+ enum bpf_attach_type attach_type,
+ int *btf_obj_id, int *btf_type_id)
+{
+ int ret, i;
+
+ ret = find_attach_btf_id(obj->btf_vmlinux, attach_name, attach_type);
+ if (ret > 0) {
+ *btf_obj_id = 0; /* vmlinux BTF */
+ *btf_type_id = ret;
+ return 0;
+ }
+ if (ret != -ENOENT)
+ return ret;
+
+ ret = load_module_btfs(obj);
+ if (ret)
+ return ret;
+
+ for (i = 0; i < obj->btf_module_cnt; i++) {
+ const struct module_btf *mod = &obj->btf_modules[i];
+
+ ret = find_attach_btf_id(mod->btf, attach_name, attach_type);
+ if (ret > 0) {
+ *btf_obj_id = mod->id;
+ *btf_type_id = ret;
+ return 0;
+ }
+ if (ret == -ENOENT)
+ continue;
+
+ return ret;
+ }
+
+ return -ESRCH;
+}
+
+static int libbpf_find_attach_btf_id(struct bpf_program *prog, int *btf_obj_id, int *btf_type_id)
{
enum bpf_attach_type attach_type = prog->expected_attach_type;
__u32 attach_prog_fd = prog->attach_prog_fd;
- const char *name = prog->sec_name;
+ const char *name = prog->sec_name, *attach_name;
+ const struct bpf_sec_def *sec = NULL;
int i, err;
if (!name)
@@ -8883,17 +8927,37 @@ static int libbpf_find_attach_btf_id(struct bpf_program *prog)
continue;
if (strncmp(name, section_defs[i].sec, section_defs[i].len))
continue;
- if (attach_prog_fd)
- err = libbpf_find_prog_btf_id(name + section_defs[i].len,
- attach_prog_fd);
- else
- err = __find_vmlinux_btf_id(prog->obj->btf_vmlinux,
- name + section_defs[i].len,
- attach_type);
+
+ sec = §ion_defs[i];
+ break;
+ }
+
+ if (!sec) {
+ pr_warn("failed to identify BTF ID based on ELF section name '%s'\n", name);
+ return -ESRCH;
+ }
+ attach_name = name + sec->len;
+
+ /* BPF program's BTF ID */
+ if (attach_prog_fd) {
+ err = libbpf_find_prog_btf_id(attach_name, attach_prog_fd);
+ if (err < 0) {
+ pr_warn("failed to find BPF program (FD %d) BTF ID for '%s': %d\n",
+ attach_prog_fd, attach_name, err);
+ return err;
+ }
+ *btf_obj_id = 0;
+ *btf_type_id = err;
+ return 0;
+ }
+
+ /* kernel/module BTF ID */
+ err = find_kernel_btf_id(prog->obj, attach_name, attach_type, btf_obj_id, btf_type_id);
+ if (err) {
+ pr_warn("failed to find kernel BTF type ID of '%s': %d\n", attach_name, err);
return err;
}
- pr_warn("failed to identify btf_id based on ELF section name '%s'\n", name);
- return -ESRCH;
+ return 0;
}
int libbpf_attach_type_by_name(const char *name,
@@ -10782,6 +10846,7 @@ int bpf_program__set_attach_target(struct bpf_program *prog,
return btf_id;
prog->attach_btf_id = btf_id;
+ prog->attach_btf_obj_id = 0;
prog->attach_prog_fd = attach_prog_fd;
return 0;
}
diff --git a/tools/lib/bpf/libbpf_internal.h b/tools/lib/bpf/libbpf_internal.h
index 681073a67ae3..36236b4430ff 100644
--- a/tools/lib/bpf/libbpf_internal.h
+++ b/tools/lib/bpf/libbpf_internal.h
@@ -160,6 +160,7 @@ struct bpf_prog_load_params {
const char *license;
__u32 kern_version;
__u32 attach_prog_fd;
+ __u32 attach_btf_obj_id;
__u32 attach_btf_id;
__u32 prog_ifindex;
__u32 prog_btf_fd;
--
2.24.1
