Re: [PATCH bpf-next v2 1/2] libbpf: Introduce bpf_program__clone()

["Emil Tsalapatis" <emil@etsalapatis.com>]

On Mon Feb 23, 2026 at 12:59 PM EST, Mykyta Yatsenko wrote:
> "Emil Tsalapatis" <emil@etsalapatis.com> writes:
>
>> On Fri Feb 20, 2026 at 2:18 PM EST, Mykyta Yatsenko wrote:
>>> From: Mykyta Yatsenko <yatsenko@meta.com>
>>>
>>> Add bpf_program__clone() API that loads a single BPF program from a
>>> prepared BPF object into the kernel, returning a file descriptor owned
>>> by the caller.
>>>
>>> After bpf_object__prepare(), callers can use bpf_program__clone() to
>>> load individual programs with custom bpf_prog_load_opts, instead of
>>> loading all programs at once via bpf_object__load(). Non-zero fields in
>>> opts override the defaults derived from the program and object
>>> internals; passing NULL opts populates everything automatically.
>>>
>>> Internally, bpf_program__clone() resolves BTF-based attach targets
>>> (attach_btf_id, attach_btf_obj_fd) and the sleepable flag, fills
>>> func/line info, fd_array, license, and kern_version from the
>>> prepared object before calling bpf_prog_load().
>>>
>>> Signed-off-by: Mykyta Yatsenko <yatsenko@meta.com>
>>> ---
>>>  tools/lib/bpf/libbpf.c   | 64 ++++++++++++++++++++++++++++++++++++++++++++++++
>>>  tools/lib/bpf/libbpf.h   | 17 +++++++++++++
>>>  tools/lib/bpf/libbpf.map |  1 +
>>>  3 files changed, 82 insertions(+)
>>>
>>
>> The code looks in order, one issue below.
>>
>>> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
>>> index 0c8bf0b5cce4..4b084bda3f47 100644
>>> --- a/tools/lib/bpf/libbpf.c
>>> +++ b/tools/lib/bpf/libbpf.c
>>> @@ -9793,6 +9793,70 @@ __u32 bpf_program__line_info_cnt(const struct bpf_program *prog)
>>>  	return prog->line_info_cnt;
>>>  }
>>>  
>>> +int bpf_program__clone(struct bpf_program *prog, const struct bpf_prog_load_opts *opts)
>>> +{
>>> +	LIBBPF_OPTS(bpf_prog_load_opts, attr);
>>> +	struct bpf_prog_load_opts *pattr = &attr;
>>> +	struct bpf_object *obj;
>>> +	int err, fd;
>>> +
>>> +	if (!prog)
>>> +		return libbpf_err(-EINVAL);
>>> +
>>> +	if (!OPTS_VALID(opts, bpf_prog_load_opts))
>>> +		return libbpf_err(-EINVAL);
>>> +
>>> +	obj = prog->obj;
>>> +	if (obj->state < OBJ_PREPARED)
>>> +		return libbpf_err(-EINVAL);
>>> +
>>> +	/* Copy caller opts, fall back to prog/object defaults */
>>> +	OPTS_SET(pattr, expected_attach_type,
>>> +		 OPTS_GET(opts, expected_attach_type, 0) ?: prog->expected_attach_type);
>>> +	OPTS_SET(pattr, attach_btf_id, OPTS_GET(opts, attach_btf_id, 0) ?: prog->attach_btf_id);
>>> +	OPTS_SET(pattr, attach_btf_obj_fd,
>>> +		 OPTS_GET(opts, attach_btf_obj_fd, 0) ?: prog->attach_btf_obj_fd);
>>> +	OPTS_SET(pattr, attach_prog_fd, OPTS_GET(opts, attach_prog_fd, 0) ?: prog->attach_prog_fd);
>>> +	OPTS_SET(pattr, prog_flags, OPTS_GET(opts, prog_flags, 0) ?: prog->prog_flags);
>>> +	OPTS_SET(pattr, prog_ifindex, OPTS_GET(opts, prog_ifindex, 0) ?: prog->prog_ifindex);
>>> +	OPTS_SET(pattr, kern_version, OPTS_GET(opts, kern_version, 0) ?: obj->kern_version);
>>> +	OPTS_SET(pattr, fd_array, OPTS_GET(opts, fd_array, NULL) ?: obj->fd_array);
>>> +	OPTS_SET(pattr, token_fd, OPTS_GET(opts, token_fd, 0) ?: obj->token_fd);
>>> +	if (attr.token_fd)
>>> +		attr.prog_flags |= BPF_F_TOKEN_FD;
>>> +
>>> +	/* BTF func/line info */
>>> +	if (obj->btf && btf__fd(obj->btf) >= 0) {
>>> +		OPTS_SET(pattr, prog_btf_fd, OPTS_GET(opts, prog_btf_fd, 0) ?: btf__fd(obj->btf));
>>> +		OPTS_SET(pattr, func_info, OPTS_GET(opts, func_info, NULL) ?: prog->func_info);
>>> +		OPTS_SET(pattr, func_info_cnt,
>>> +			 OPTS_GET(opts, func_info_cnt, 0) ?: prog->func_info_cnt);
>>> +		OPTS_SET(pattr, func_info_rec_size,
>>> +			 OPTS_GET(opts, func_info_rec_size, 0) ?: prog->func_info_rec_size);
>>> +		OPTS_SET(pattr, line_info, OPTS_GET(opts, line_info, NULL) ?: prog->line_info);
>>> +		OPTS_SET(pattr, line_info_cnt,
>>> +			 OPTS_GET(opts, line_info_cnt, 0) ?: prog->line_info_cnt);
>>> +		OPTS_SET(pattr, line_info_rec_size,
>>> +			 OPTS_GET(opts, line_info_rec_size, 0) ?: prog->line_info_rec_size);
>>> +	}
>>> +
>>> +	OPTS_SET(pattr, log_buf, OPTS_GET(opts, log_buf, NULL));
>>> +	OPTS_SET(pattr, log_size, OPTS_GET(opts, log_size, 0));
>>> +	OPTS_SET(pattr, log_level, OPTS_GET(opts, log_level, 0));
>>> +
>>
>> Can we make it so that cloning  prepared but not loaded programs does
>> not load them? The name of the method itself implies the new instance is
>> identical to the old one, which is not the case - we're currently
>> loading the cloned program even if the original is not loaded. I don't 
>> see why for OBJ_PREPARED progrmas this shouldn't be explicitly done by the 
>> caller with bpf_prog_load() instead.
> Mekes sense, but there are few problems:
> we won't be cloning a program, but rather it's
> attributes (struct bpf_prog_load_opts); I don't think we can do true
> cloning with returning a new struct bpf_program.
>
> So the best we can do is to change to something like
> bpf_program__clone_attrs() (or bpf_program__load_attrs()) then in
> veristat do:
>
> attrs = bpf_program__clone_attrs(prog)
> bpf_prog_load(bpf_program__insn(prog), attrs)
>
> Let's see what option maintainers prefer.

I like clone_attrs(), though if we rename it so let's skip the bpf_prog_load()
regardless of whether the original program is already loaded.

>>
>> If we do make it so that the cloned program's obj->state is identical to the
>> original's let's also add a test that checks that.
>>
>>> +	/* Resolve BTF attach targets, set sleepable/XDP flags, etc. */
>>> +	if (prog->sec_def && prog->sec_def->prog_prepare_load_fn) {
>>> +		err = prog->sec_def->prog_prepare_load_fn(prog, pattr, prog->sec_def->cookie);
>>> +		if (err)
>>> +			return libbpf_err(err);
>>> +	}
>>> +
>>> +	fd = bpf_prog_load(prog->type, prog->name, obj->license, prog->insns, prog->insns_cnt,
>>> +			   pattr);
>>> +
>>> +	return libbpf_err(fd);
>>> +}
>>> +
>>>  #define SEC_DEF(sec_pfx, ptype, atype, flags, ...) {			    \
>>>  	.sec = (char *)sec_pfx,						    \
>>>  	.prog_type = BPF_PROG_TYPE_##ptype,				    \
>>> diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
>>> index dfc37a615578..0be34852350f 100644
>>> --- a/tools/lib/bpf/libbpf.h
>>> +++ b/tools/lib/bpf/libbpf.h
>>> @@ -2021,6 +2021,23 @@ LIBBPF_API int libbpf_register_prog_handler(const char *sec,
>>>   */
>>>  LIBBPF_API int libbpf_unregister_prog_handler(int handler_id);
>>>  
>>> +/**
>>> + * @brief **bpf_program__clone()** loads a single BPF program from a prepared
>>> + * BPF object into the kernel, returning its file descriptor.
>>> + *
>>> + * The BPF object must have been previously prepared with
>>> + * **bpf_object__prepare()**. If @opts is provided, any non-zero field
>>> + * overrides the defaults derived from the program/object internals.
>>> + * If @opts is NULL, all fields are populated automatically.
>>> + *
>>> + * The returned FD is owned by the caller and must be closed with close().
>>> + *
>>> + * @param prog BPF program from a prepared object
>>> + * @param opts Optional load options; non-zero fields override defaults
>>> + * @return program FD (>= 0) on success; negative error code on failure
>>> + */
>>> +LIBBPF_API int bpf_program__clone(struct bpf_program *prog, const struct bpf_prog_load_opts *opts);
>>> +
>>>  #ifdef __cplusplus
>>>  } /* extern "C" */
>>>  #endif
>>> diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
>>> index d18fbcea7578..e727a54e373a 100644
>>> --- a/tools/lib/bpf/libbpf.map
>>> +++ b/tools/lib/bpf/libbpf.map
>>> @@ -452,6 +452,7 @@ LIBBPF_1.7.0 {
>>>  		bpf_map__set_exclusive_program;
>>>  		bpf_map__exclusive_program;
>>>  		bpf_prog_assoc_struct_ops;
>>> +		bpf_program__clone;
>>>  		bpf_program__assoc_struct_ops;
>>>  		btf__permute;
>>>  } LIBBPF_1.6.0;