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 | 5 +-
tools/lib/bpf/libbpf.c | 138 +++++++++++++++++++++++++-------
tools/lib/bpf/libbpf_internal.h | 1 +
3 files changed, 112 insertions(+), 32 deletions(-)
diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c
index 5d681ce32b37..bba48ff4c5c0 100644
--- a/tools/lib/bpf/bpf.c
+++ b/tools/lib/bpf/bpf.c
@@ -231,8 +231,11 @@ 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;
+ if (load_attr->attach_prog_fd)
+ attr.attach_prog_fd = load_attr->attach_prog_fd;
+ else
+ attr.attach_btf_obj_fd = load_attr->attach_btf_obj_fd;
attr.attach_btf_id = load_attr->attach_btf_id;
- attr.attach_prog_fd = load_attr->attach_prog_fd;
attr.prog_ifindex = load_attr->prog_ifindex;
attr.kern_version = load_attr->kern_version;
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 103d66e27406..912e01b946fe 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_fd;
__u32 attach_btf_id;
__u32 attach_prog_fd;
void *func_info;
@@ -408,6 +409,7 @@ struct module_btf {
struct btf *btf;
char *name;
__u32 id;
+ int fd;
};
struct bpf_object {
@@ -4766,8 +4768,7 @@ static int load_module_btfs(struct bpf_object *obj)
if (err) {
err = -errno;
pr_warn("failed to get BTF object #%d info: %d\n", id, err);
- close(fd);
- return err;
+ goto err_out;
}
/* ignore non-module BTFs */
@@ -4777,25 +4778,33 @@ static int load_module_btfs(struct bpf_object *obj)
}
btf = btf_get_from_fd(fd, obj->btf_vmlinux);
- close(fd);
if (IS_ERR(btf)) {
pr_warn("failed to load module [%s]'s BTF object #%d: %ld\n",
name, id, PTR_ERR(btf));
- return PTR_ERR(btf);
+ err = PTR_ERR(btf);
+ goto err_out;
}
err = btf_ensure_mem((void **)&obj->btf_modules, &obj->btf_module_cap,
sizeof(*obj->btf_modules), obj->btf_module_cnt + 1);
if (err)
- return err;
+ goto err_out;
mod_btf = &obj->btf_modules[obj->btf_module_cnt++];
mod_btf->btf = btf;
mod_btf->id = id;
+ mod_btf->fd = fd;
mod_btf->name = strdup(name);
- if (!mod_btf->name)
- return -ENOMEM;
+ if (!mod_btf->name) {
+ err = -ENOMEM;
+ goto err_out;
+ }
+ continue;
+
+err_out:
+ close(fd);
+ return err;
}
return 0;
@@ -6841,7 +6850,10 @@ load_program(struct bpf_program *prog, struct bpf_insn *insns, int insns_cnt,
load_attr.insn_cnt = insns_cnt;
load_attr.license = license;
load_attr.attach_btf_id = prog->attach_btf_id;
- load_attr.attach_prog_fd = prog->attach_prog_fd;
+ if (prog->attach_prog_fd)
+ load_attr.attach_prog_fd = prog->attach_prog_fd;
+ else
+ load_attr.attach_btf_obj_fd = prog->attach_btf_obj_fd;
load_attr.attach_btf_id = prog->attach_btf_id;
load_attr.kern_version = kern_version;
load_attr.prog_ifindex = prog->prog_ifindex;
@@ -6937,11 +6949,11 @@ 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_fd, 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);
@@ -6951,10 +6963,14 @@ 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_fd = 0, btf_type_id = 0;
+
+ err = libbpf_find_attach_btf_id(prog, &btf_obj_fd, &btf_type_id);
+ if (err)
+ return err;
+
+ prog->attach_btf_obj_fd = btf_obj_fd;
+ prog->attach_btf_id = btf_type_id;
}
if (prog->instances.nr < 0 || !prog->instances.fds) {
@@ -7467,6 +7483,7 @@ int bpf_object__load_xattr(struct bpf_object_load_attr *attr)
/* clean up module BTFs */
for (i = 0; i < obj->btf_module_cnt; i++) {
+ close(obj->btf_modules[i].fd);
btf__free(obj->btf_modules[i].btf);
free(obj->btf_modules[i].name);
}
@@ -8821,8 +8838,8 @@ 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;
@@ -8838,9 +8855,6 @@ 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;
}
@@ -8856,7 +8870,10 @@ 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;
}
@@ -8894,11 +8911,49 @@ 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_fd, int *btf_type_id)
+{
+ int ret, i;
+
+ ret = find_attach_btf_id(obj->btf_vmlinux, attach_name, attach_type);
+ if (ret > 0) {
+ *btf_obj_fd = 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_fd = mod->fd;
+ *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_fd, 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)
@@ -8909,17 +8964,37 @@ 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_fd = 0;
+ *btf_type_id = err;
+ return 0;
+ }
+
+ /* kernel/module BTF ID */
+ err = find_kernel_btf_id(prog->obj, attach_name, attach_type, btf_obj_fd, 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,
@@ -10808,6 +10883,7 @@ int bpf_program__set_attach_target(struct bpf_program *prog,
return btf_id;
prog->attach_btf_id = btf_id;
+ prog->attach_btf_obj_fd = 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..969d0ac592ba 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_fd;
__u32 attach_btf_id;
__u32 prog_ifindex;
__u32 prog_btf_fd;
--
2.24.1
