Commit b3d3e293 authored by Alexei Starovoitov's avatar Alexei Starovoitov
Browse files

Merge branch 'annotate-kfuncs-in-btf_ids-section' 

Daniel Xu says:

====================
Annotate kfuncs in .BTF_ids section

=== Description ===

This is a bpf-treewide change that annotates all kfuncs as such inside
.BTF_ids. This annotation eventually allows us to automatically generate
kfunc prototypes from bpftool.

We store this metadata inside a yet-unused flags field inside struct
btf_id_set8 (thanks Kumar!). pahole will be taught where to look.

More details about the full chain of events are available in commit 3's
description.

The accompanying pahole and bpftool changes can be viewed
here on these "frozen" branches [0][1].

[0]: https://github.com/danobi/pahole/tree/kfunc_btf-v3-mailed
[1]: https://github.com/danobi/linux/tree/kfunc_bpftool-mailed



=== Changelog ===

Changes from v3:
* Rebase to bpf-next and add missing annotation on new kfunc

Changes from v2:
* Only WARN() for vmlinux kfuncs

Changes from v1:
* Move WARN_ON() up a call level
* Also return error when kfunc set is not properly tagged
* Use BTF_KFUNCS_START/END instead of flags
* Rename BTF_SET8_KFUNC to BTF_SET8_KFUNCS
====================

Acked-by: default avatarJiri Olsa <jolsa@kernel.org>
Link: https://lore.kernel.org/r/cover.1706491398.git.dxu@dxuuu.xyz


Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parents 2ef61296 6f3189f3

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)

{

include/linux/btf_ids.h

+17 −4
Original line number Diff line number Diff line
@@ -8,6 +8,9 @@ struct btf_id_set { 
	u32 ids[];

};



/* This flag implies BTF_SET8 holds kfunc(s) */

#define BTF_SET8_KFUNCS		(1 << 0)



struct btf_id_set8 {

	u32 cnt;

	u32 flags;
@@ -21,6 +24,7 @@ struct btf_id_set8 { 


#include <linux/compiler.h> /* for __PASTE */

#include <linux/compiler_attributes.h> /* for __maybe_unused */

#include <linux/stringify.h>



/*

 * Following macros help to define lists of BTF IDs placed
@@ -183,17 +187,18 @@ extern struct btf_id_set name; 
 * .word (1 << 3) | (1 << 1) | (1 << 2)

 *

 */

#define __BTF_SET8_START(name, scope)			\

#define __BTF_SET8_START(name, scope, flags)		\

__BTF_ID_LIST(name, local)				\

asm(							\

".pushsection " BTF_IDS_SECTION ",\"a\";       \n"	\

"." #scope " __BTF_ID__set8__" #name ";        \n"	\

"__BTF_ID__set8__" #name ":;                   \n"	\

".zero 8                                       \n"	\

".zero 4                                       \n"	\

".long " __stringify(flags)                   "\n"	\

".popsection;                                  \n");



#define BTF_SET8_START(name)				\

__BTF_ID_LIST(name, local)				\

__BTF_SET8_START(name, local)

__BTF_SET8_START(name, local, 0)



#define BTF_SET8_END(name)				\

asm(							\
@@ -202,6 +207,12 @@ asm( \ 
".popsection;                                 \n");	\

extern struct btf_id_set8 name;



#define BTF_KFUNCS_START(name)				\

__BTF_SET8_START(name, local, BTF_SET8_KFUNCS)



#define BTF_KFUNCS_END(name)				\

BTF_SET8_END(name)



#else



#define BTF_ID_LIST(name) static u32 __maybe_unused name[64];
@@ -216,6 +227,8 @@ extern struct btf_id_set8 name; 
#define BTF_SET_END(name)

#define BTF_SET8_START(name) static struct btf_id_set8 __maybe_unused name = { 0 };

#define BTF_SET8_END(name)

#define BTF_KFUNCS_START(name) static struct btf_id_set8 __maybe_unused name = { .flags = BTF_SET8_KFUNCS };

#define BTF_KFUNCS_END(name)



#endif /* CONFIG_DEBUG_INFO_BTF */

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);

}