Commit 6f3189f3 authored by Daniel Xu's avatar Daniel Xu Committed by Alexei Starovoitov
Browse files

bpf: treewide: Annotate BPF kfuncs in BTF 



This commit marks kfuncs as such inside the .BTF_ids section. The upshot
of these annotations is that we'll be able to automatically generate
kfunc prototypes for downstream users. The process is as follows:

1. In source, use BTF_KFUNCS_START/END macro pair to mark kfuncs
2. During build, pahole injects into BTF a "bpf_kfunc" BTF_DECL_TAG for
   each function inside BTF_KFUNCS sets
3. At runtime, vmlinux or module BTF is made available in sysfs
4. At runtime, bpftool (or similar) can look at provided BTF and
   generate appropriate prototypes for functions with "bpf_kfunc" tag

To ensure future kfunc are similarly tagged, we now also return error
inside kfunc registration for untagged kfuncs. For vmlinux kfuncs,
we also WARN(), as initcall machinery does not handle errors.

Signed-off-by: default avatarDaniel Xu <dxu@dxuuu.xyz>
Acked-by: default avatarBenjamin Tissoires <bentiss@kernel.org>
Link: https://lore.kernel.org/r/e55150ceecbf0a5d961e608941165c0bee7bc943.1706491398.git.dxu@dxuuu.xyz


Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent a05e9042

Documentation/bpf/kfuncs.rst

+4 −4
Original line number Diff line number Diff line
@@ -177,10 +177,10 @@ In addition to kfuncs' arguments, verifier may need more information about the 
type of kfunc(s) being registered with the BPF subsystem. To do so, we define

flags on a set of kfuncs as follows::



        BTF_SET8_START(bpf_task_set)

        BTF_KFUNCS_START(bpf_task_set)

        BTF_ID_FLAGS(func, bpf_get_task_pid, KF_ACQUIRE | KF_RET_NULL)

        BTF_ID_FLAGS(func, bpf_put_pid, KF_RELEASE)

        BTF_SET8_END(bpf_task_set)

        BTF_KFUNCS_END(bpf_task_set)



This set encodes the BTF ID of each kfunc listed above, and encodes the flags

along with it. Ofcourse, it is also allowed to specify no flags.
@@ -347,10 +347,10 @@ Once the kfunc is prepared for use, the final step to making it visible is 
registering it with the BPF subsystem. Registration is done per BPF program

type. An example is shown below::



        BTF_SET8_START(bpf_task_set)

        BTF_KFUNCS_START(bpf_task_set)

        BTF_ID_FLAGS(func, bpf_get_task_pid, KF_ACQUIRE | KF_RET_NULL)

        BTF_ID_FLAGS(func, bpf_put_pid, KF_RELEASE)

        BTF_SET8_END(bpf_task_set)

        BTF_KFUNCS_END(bpf_task_set)



        static const struct btf_kfunc_id_set bpf_task_kfunc_set = {

                .owner = THIS_MODULE,

drivers/hid/bpf/hid_bpf_dispatch.c

+4 −4
Original line number Diff line number Diff line
@@ -172,9 +172,9 @@ hid_bpf_get_data(struct hid_bpf_ctx *ctx, unsigned int offset, const size_t rdwr 
 * The following set contains all functions we agree BPF programs

 * can use.

 */

BTF_SET8_START(hid_bpf_kfunc_ids)

BTF_KFUNCS_START(hid_bpf_kfunc_ids)

BTF_ID_FLAGS(func, hid_bpf_get_data, KF_RET_NULL)

BTF_SET8_END(hid_bpf_kfunc_ids)

BTF_KFUNCS_END(hid_bpf_kfunc_ids)



static const struct btf_kfunc_id_set hid_bpf_kfunc_set = {

	.owner = THIS_MODULE,
@@ -440,12 +440,12 @@ static const struct btf_kfunc_id_set hid_bpf_fmodret_set = { 
};



/* for syscall HID-BPF */

BTF_SET8_START(hid_bpf_syscall_kfunc_ids)

BTF_KFUNCS_START(hid_bpf_syscall_kfunc_ids)

BTF_ID_FLAGS(func, hid_bpf_attach_prog)

BTF_ID_FLAGS(func, hid_bpf_allocate_context, KF_ACQUIRE | KF_RET_NULL)

BTF_ID_FLAGS(func, hid_bpf_release_context, KF_RELEASE)

BTF_ID_FLAGS(func, hid_bpf_hw_request)

BTF_SET8_END(hid_bpf_syscall_kfunc_ids)

BTF_KFUNCS_END(hid_bpf_syscall_kfunc_ids)



static const struct btf_kfunc_id_set hid_bpf_syscall_kfunc_set = {

	.owner = THIS_MODULE,

fs/verity/measure.c

+2 −2
Original line number Diff line number Diff line
@@ -159,9 +159,9 @@ __bpf_kfunc int bpf_get_fsverity_digest(struct file *file, struct bpf_dynptr_ker 


__bpf_kfunc_end_defs();



BTF_SET8_START(fsverity_set_ids)

BTF_KFUNCS_START(fsverity_set_ids)

BTF_ID_FLAGS(func, bpf_get_fsverity_digest, KF_TRUSTED_ARGS)

BTF_SET8_END(fsverity_set_ids)

BTF_KFUNCS_END(fsverity_set_ids)



static int bpf_get_fsverity_digest_filter(const struct bpf_prog *prog, u32 kfunc_id)

{

kernel/bpf/btf.c

+8 −0
Original line number Diff line number Diff line
@@ -8124,6 +8124,14 @@ int register_btf_kfunc_id_set(enum bpf_prog_type prog_type, 
{

	enum btf_kfunc_hook hook;



	/* All kfuncs need to be tagged as such in BTF.

	 * WARN() for initcall registrations that do not check errors.

	 */

	if (!(kset->set->flags & BTF_SET8_KFUNCS)) {

		WARN_ON(!kset->owner);

		return -EINVAL;

	}



	hook = bpf_prog_type_to_kfunc_hook(prog_type);

	return __register_btf_kfunc_id_set(hook, kset);

}

kernel/bpf/cpumask.c

+2 −2
Original line number Diff line number Diff line
@@ -424,7 +424,7 @@ __bpf_kfunc u32 bpf_cpumask_weight(const struct cpumask *cpumask) 


__bpf_kfunc_end_defs();



BTF_SET8_START(cpumask_kfunc_btf_ids)

BTF_KFUNCS_START(cpumask_kfunc_btf_ids)

BTF_ID_FLAGS(func, bpf_cpumask_create, KF_ACQUIRE | KF_RET_NULL)

BTF_ID_FLAGS(func, bpf_cpumask_release, KF_RELEASE)

BTF_ID_FLAGS(func, bpf_cpumask_acquire, KF_ACQUIRE | KF_TRUSTED_ARGS)
@@ -450,7 +450,7 @@ BTF_ID_FLAGS(func, bpf_cpumask_copy, KF_RCU) 
BTF_ID_FLAGS(func, bpf_cpumask_any_distribute, KF_RCU)

BTF_ID_FLAGS(func, bpf_cpumask_any_and_distribute, KF_RCU)

BTF_ID_FLAGS(func, bpf_cpumask_weight, KF_RCU)

BTF_SET8_END(cpumask_kfunc_btf_ids)

BTF_KFUNCS_END(cpumask_kfunc_btf_ids)



static const struct btf_kfunc_id_set cpumask_kfunc_set = {

	.owner = THIS_MODULE,