On 5/3/26 06:21, Jiri Olsa wrote:
> Adding bpf_program__attach_tracing_multi function for attaching
> tracing program to multiple functions.
>
> struct bpf_link *
> bpf_program__attach_tracing_multi(const struct bpf_program *prog,
> const char *pattern,
> const struct bpf_tracing_multi_opts
> *opts);
>
> User can specify functions to attach with 'pattern' argument that
> allows wildcards (*?' supported) or provide BTF ids of functions
> in array directly via opts argument. These options are mutually
> exclusive.
>
> When using BTF ids, user can also provide cookie value for each
> provided id/function, that can be retrieved later in bpf program
> with bpf_get_attach_cookie helper. Each cookie value is paired with
> provided BTF id with the same array index.
>
> Adding support to auto attach programs with following sections:
>
> fsession.multi/<pattern>
> fsession.multi.s/<pattern>
> fentry.multi/<pattern>
> fexit.multi/<pattern>
> fentry.multi.s/<pattern>
> fexit.multi.s/<pattern>
>
> The provided <pattern> is used as 'pattern' argument in
> bpf_program__attach_kprobe_multi_opts function.
>
> The <pattern> allows to specify optional kernel module name with
> following syntax:
>
> <module>:<function_pattern>
>
> In order to attach tracing_multi link to a module functions:
> - program must be loaded with 'module' btf fd
> (in attr::attach_btf_obj_fd)
> - bpf_program__attach_kprobe_multi_opts must either have
> pattern with module spec or BTF ids from the module
>
> Signed-off-by: Jiri Olsa <[email protected]>
> ---
> tools/lib/bpf/libbpf.c | 309 +++++++++++++++++++++++++++++++++++++++
> tools/lib/bpf/libbpf.h | 15 ++
> tools/lib/bpf/libbpf.map | 1 +
> 3 files changed, 325 insertions(+)
>
> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> index 34987ce7cdc8..8842adcf8c8a 100644
> --- a/tools/lib/bpf/libbpf.c
> +++ b/tools/lib/bpf/libbpf.c
> @@ -7716,6 +7716,52 @@ static int bpf_object__sanitize_prog(struct bpf_object
> *obj, struct bpf_program
> static int libbpf_find_attach_btf_id(struct bpf_program *prog, const char
> *attach_name,
> int *btf_obj_fd, int *btf_type_id);
>
> +static inline bool is_tracing_multi(enum bpf_attach_type type)
> +{
> + return type == BPF_TRACE_FENTRY_MULTI || type == BPF_TRACE_FEXIT_MULTI
> ||
> + type == BPF_TRACE_FSESSION_MULTI;
> +}
> +
> +static int tracing_multi_mod_fd(struct bpf_program *prog, int *btf_obj_fd)
> +{
> + const char *attach_name, *sep, *mod_name = NULL;
> + int i, err, mod_len = 0;
> +
> + *btf_obj_fd = 0;
> + attach_name = strchr(prog->sec_name, '/');
> +
> + /* Program with no details in spec, using kernel btf. */
> + if (!attach_name)
> + return 0;
> +
> + attach_name++;
> + sep = strchr(attach_name, ':');
> + if (sep) {
> + mod_name = attach_name;
> + mod_len = sep - mod_name;
> + }
> +
> + /* Program with no module section, using kernel btf. */
> + if (!mod_name)
> + return 0;
> +
> + err = load_module_btfs(prog->obj);
> + if (err)
> + return err;
> +
> + for (i = 0; i < prog->obj->btf_module_cnt; i++) {
> + const struct module_btf *mod = &prog->obj->btf_modules[i];
> +
> + if (mod_name && strncmp(mod->name, mod_name, mod_len) == 0) {
strncmp() is not enough to exactly compare two module names, as
strncmp() only compares the first 'mod_len' bytes.
So, mod_name "foo" could match mod "foobar", since 'obj->btf_modules'
are not sorted by name after loading from kernel.
To find the exact module via module name, "strncmp() == 0 &&
mod->name[mod_len] == '\0'" would be better.
> + *btf_obj_fd = mod->fd;
> + return 0;
> + }
> + }
> +
> + /* Specified module was not found, let's bail out. */
> + return -EINVAL;
> +}
> +
> /* this is called as prog->sec_def->prog_prepare_load_fn for
> libbpf-supported sec_defs */
> static int libbpf_prepare_prog_load(struct bpf_program *prog,
> struct bpf_prog_load_opts *opts, long
> cookie)
> @@ -7779,6 +7825,18 @@ static int libbpf_prepare_prog_load(struct bpf_program
> *prog,
> opts->attach_btf_obj_fd = btf_obj_fd;
> opts->attach_btf_id = btf_type_id;
> }
> +
> + if (is_tracing_multi(prog->expected_attach_type)) {
> + int err, btf_obj_fd = 0;
> +
> + err = tracing_multi_mod_fd(prog, &btf_obj_fd);
> + if (err < 0)
> + return err;
> +
> + prog->attach_btf_obj_fd = btf_obj_fd;
> + opts->attach_btf_obj_fd = btf_obj_fd;
> + }
> +
> return 0;
> }
>
> @@ -9835,6 +9893,7 @@ static int attach_kprobe_session(const struct
> bpf_program *prog, long cookie, st
> 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_tracing_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),
> @@ -9883,6 +9942,12 @@ static const struct bpf_sec_def section_defs[] = {
> SEC_DEF("fexit.s+", TRACING, BPF_TRACE_FEXIT,
> SEC_ATTACH_BTF | SEC_SLEEPABLE, attach_trace),
> SEC_DEF("fsession+", TRACING, BPF_TRACE_FSESSION,
> SEC_ATTACH_BTF, attach_trace),
> SEC_DEF("fsession.s+", TRACING, BPF_TRACE_FSESSION,
> SEC_ATTACH_BTF | SEC_SLEEPABLE, attach_trace),
> + SEC_DEF("fsession.multi+", TRACING, BPF_TRACE_FSESSION_MULTI, 0,
> attach_tracing_multi),
> + SEC_DEF("fsession.multi.s+", TRACING, BPF_TRACE_FSESSION_MULTI,
> SEC_SLEEPABLE, attach_tracing_multi),
> + SEC_DEF("fentry.multi+", TRACING, BPF_TRACE_FENTRY_MULTI, 0,
> attach_tracing_multi),
> + SEC_DEF("fexit.multi+", TRACING, BPF_TRACE_FEXIT_MULTI, 0,
> attach_tracing_multi),
> + SEC_DEF("fentry.multi.s+", TRACING, BPF_TRACE_FENTRY_MULTI,
> SEC_SLEEPABLE, attach_tracing_multi),
> + SEC_DEF("fexit.multi.s+", TRACING, BPF_TRACE_FEXIT_MULTI,
> SEC_SLEEPABLE, attach_tracing_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),
> @@ -12258,6 +12323,250 @@ static int attach_uprobe_multi(const struct
> bpf_program *prog, long cookie, stru
> return ret;
> }
>
> +#define MAX_BPF_FUNC_ARGS 12
> +
> +static bool btf_type_is_modifier(const struct btf_type *t)
> +{
> + switch (BTF_INFO_KIND(t->info)) {
> + case BTF_KIND_TYPEDEF:
> + case BTF_KIND_VOLATILE:
> + case BTF_KIND_CONST:
> + case BTF_KIND_RESTRICT:
> + case BTF_KIND_TYPE_TAG:
> + return true;
> + default:
> + return false;
> + }
> +}
> +
> +static bool is_allowed_func(const struct btf *btf, const struct btf_type *t)
> +{
> + const struct btf_type *proto;
> + const struct btf_param *args;
> + __u32 i, nargs;
> + __s64 ret;
> +
> + proto = btf_type_by_id(btf, t->type);
> + if (BTF_INFO_KIND(proto->info) != BTF_KIND_FUNC_PROTO)
> + return false;
> +
> + args = (const struct btf_param *)(proto + 1);
> + nargs = btf_vlen(proto);
> + if (nargs > MAX_BPF_FUNC_ARGS)
> + return false;
> +
> + /* No support for struct/union return argument type. */
> + t = btf__type_by_id(btf, proto->type);
> + while (t && btf_type_is_modifier(t))
> + t = btf__type_by_id(btf, t->type);
> +
> + if (btf_is_struct(t) || btf_is_union(t))
> + return false;
> +
> + for (i = 0; i < nargs; i++) {
> + /* No support for variable args. */
> + if (i == nargs - 1 && args[i].type == 0)
> + return false;
> +
> + /* No support of struct argument size greater than 16 bytes. */
> + ret = btf__resolve_size(btf, args[i].type);
> + if (ret < 0 || ret > 16)
> + return false;
> + }
> +
> + return true;
> +}
> +
> +static int
> +collect_btf_func_ids_by_glob(const struct btf *btf, const char *pattern,
> __u32 **ids)
> +{
> + __u32 type_id, nr_types = btf__type_cnt(btf);
> + size_t cap = 0, cnt = 0;
> +
> + if (!pattern)
> + return -EINVAL;
> +
> + for (type_id = 1; type_id < nr_types; type_id++) {
> + const struct btf_type *t = btf__type_by_id(btf, type_id);
> + const char *name;
> + int err;
> +
> + if (btf_kind(t) != BTF_KIND_FUNC)
> + continue;
> + name = btf__name_by_offset(btf, t->name_off);
> + if (!name)
> + continue;
> +
> + if (!glob_match(name, pattern))
> + continue;
> + if (!is_allowed_func(btf, t))
> + continue;
> +
> + err = libbpf_ensure_mem((void **) ids, &cap, sizeof(**ids), cnt
> + 1);
> + if (err) {
> + free(*ids);
> + return -ENOMEM;
> + }
> + (*ids)[cnt++] = type_id;
> + }
> +
> + return cnt;
> +}
> +
> +static int collect_func_ids_by_glob(struct bpf_object *obj, const char
> *pattern, __u32 **ids)
> +{
> + const char *mod_name = NULL, *sep;
> + int i, err, mod_len = 0;
> + struct btf *btf = NULL;
> +
> + err = bpf_object__load_vmlinux_btf(obj, true);
> + if (err)
> + return err;
> +
> + /* In case we have module specified, we will find its btf and use that.
> */
> + sep = strchr(pattern, ':');
> + if (sep) {
> + mod_name = pattern;
> + mod_len = sep - pattern;
> + pattern = sep + 1;
> +
> + err = load_module_btfs(obj);
> + if (err)
> + goto cleanup;
> +
> + for (i = 0; i < obj->btf_module_cnt; i++) {
> + const struct module_btf *mod = &obj->btf_modules[i];
> +
> + if (!strncmp(mod->name, mod_name, mod_len)) {
Same concern here.
Would it be better to factor out a helper to find module via name?
Thanks,
Leon
[...]
