[PATCH bpf-next v3 0/3] Annotate kfuncs in .BTF_ids section

[PATCH bpf-next v3 0/3] Annotate kfuncs in .BTF_ids section

[Daniel Xu]

=== 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 changes (still needs some cleanup) can be viewed
here on this "frozen" branch [0].

[0]: https://github.com/danobi/pahole/tree/kfunc_btf-mailed

=== Changelog ===

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

Daniel Xu (3):
  bpf: btf: Support flags for BTF_SET8 sets
  bpf: btf: Add BTF_KFUNCS_START/END macro pair
  bpf: treewide: Annotate BPF kfuncs in BTF

 drivers/hid/bpf/hid_bpf_dispatch.c            |  8 +++----
 fs/verity/measure.c                           |  4 ++--
 include/linux/btf_ids.h                       | 21 +++++++++++++++----
 kernel/bpf/btf.c                              |  8 +++++++
 kernel/bpf/cpumask.c                          |  4 ++--
 kernel/bpf/helpers.c                          |  8 +++----
 kernel/bpf/map_iter.c                         |  4 ++--
 kernel/cgroup/rstat.c                         |  4 ++--
 kernel/trace/bpf_trace.c                      |  8 +++----
 net/bpf/test_run.c                            |  8 +++----
 net/core/filter.c                             | 16 +++++++-------
 net/core/xdp.c                                |  4 ++--
 net/ipv4/bpf_tcp_ca.c                         |  4 ++--
 net/ipv4/fou_bpf.c                            |  4 ++--
 net/ipv4/tcp_bbr.c                            |  4 ++--
 net/ipv4/tcp_cubic.c                          |  4 ++--
 net/ipv4/tcp_dctcp.c                          |  4 ++--
 net/netfilter/nf_conntrack_bpf.c              |  4 ++--
 net/netfilter/nf_nat_bpf.c                    |  4 ++--
 net/xfrm/xfrm_interface_bpf.c                 |  4 ++--
 net/xfrm/xfrm_state_bpf.c                     |  4 ++--
 .../selftests/bpf/bpf_testmod/bpf_testmod.c   |  8 +++----
 22 files changed, 81 insertions(+), 60 deletions(-)

-- 
2.42.1

[PATCH bpf-next v3 3/3] bpf: treewide: Annotate BPF kfuncs in BTF

[Daniel Xu]

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: Daniel Xu <dxu@dxuuu.xyz>
---
 drivers/hid/bpf/hid_bpf_dispatch.c               |  8 ++++----
 fs/verity/measure.c                              |  4 ++--
 kernel/bpf/btf.c                                 |  8 ++++++++
 kernel/bpf/cpumask.c                             |  4 ++--
 kernel/bpf/helpers.c                             |  8 ++++----
 kernel/bpf/map_iter.c                            |  4 ++--
 kernel/cgroup/rstat.c                            |  4 ++--
 kernel/trace/bpf_trace.c                         |  8 ++++----
 net/bpf/test_run.c                               |  8 ++++----
 net/core/filter.c                                | 16 ++++++++--------
 net/core/xdp.c                                   |  4 ++--
 net/ipv4/bpf_tcp_ca.c                            |  4 ++--
 net/ipv4/fou_bpf.c                               |  4 ++--
 net/ipv4/tcp_bbr.c                               |  4 ++--
 net/ipv4/tcp_cubic.c                             |  4 ++--
 net/ipv4/tcp_dctcp.c                             |  4 ++--
 net/netfilter/nf_conntrack_bpf.c                 |  4 ++--
 net/netfilter/nf_nat_bpf.c                       |  4 ++--
 net/xfrm/xfrm_interface_bpf.c                    |  4 ++--
 net/xfrm/xfrm_state_bpf.c                        |  4 ++--
 .../selftests/bpf/bpf_testmod/bpf_testmod.c      |  8 ++++----
 21 files changed, 64 insertions(+), 56 deletions(-)

diff --git a/drivers/hid/bpf/hid_bpf_dispatch.c b/drivers/hid/bpf/hid_bpf_dispatch.c
index d9ef45fcaeab..02c441aaa217 100644
--- a/drivers/hid/bpf/hid_bpf_dispatch.c
+++ b/drivers/hid/bpf/hid_bpf_dispatch.c
@@ -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,
diff --git a/fs/verity/measure.c b/fs/verity/measure.c
index bf7a5f4cccaf..3969d54158d1 100644
--- a/fs/verity/measure.c
+++ b/fs/verity/measure.c
@@ -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)
 {
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index 51e8b4bee0c8..618fdd557730 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -7802,6 +7802,14 @@ 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);
 }
diff --git a/kernel/bpf/cpumask.c b/kernel/bpf/cpumask.c
index 2e73533a3811..dad0fb1c8e87 100644
--- a/kernel/bpf/cpumask.c
+++ b/kernel/bpf/cpumask.c
@@ -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,
diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index be72824f32b2..277481eef361 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -2543,7 +2543,7 @@ __bpf_kfunc void bpf_throw(u64 cookie)
 
 __bpf_kfunc_end_defs();
 
-BTF_SET8_START(generic_btf_ids)
+BTF_KFUNCS_START(generic_btf_ids)
 #ifdef CONFIG_KEXEC_CORE
 BTF_ID_FLAGS(func, crash_kexec, KF_DESTRUCTIVE)
 #endif
@@ -2572,7 +2572,7 @@ BTF_ID_FLAGS(func, bpf_task_get_cgroup1, KF_ACQUIRE | KF_RCU | KF_RET_NULL)
 #endif
 BTF_ID_FLAGS(func, bpf_task_from_pid, KF_ACQUIRE | KF_RET_NULL)
 BTF_ID_FLAGS(func, bpf_throw)
-BTF_SET8_END(generic_btf_ids)
+BTF_KFUNCS_END(generic_btf_ids)
 
 static const struct btf_kfunc_id_set generic_kfunc_set = {
 	.owner = THIS_MODULE,
@@ -2588,7 +2588,7 @@ BTF_ID(struct, cgroup)
 BTF_ID(func, bpf_cgroup_release_dtor)
 #endif
 
-BTF_SET8_START(common_btf_ids)
+BTF_KFUNCS_START(common_btf_ids)
 BTF_ID_FLAGS(func, bpf_cast_to_kern_ctx)
 BTF_ID_FLAGS(func, bpf_rdonly_cast)
 BTF_ID_FLAGS(func, bpf_rcu_read_lock)
@@ -2617,7 +2617,7 @@ BTF_ID_FLAGS(func, bpf_dynptr_is_null)
 BTF_ID_FLAGS(func, bpf_dynptr_is_rdonly)
 BTF_ID_FLAGS(func, bpf_dynptr_size)
 BTF_ID_FLAGS(func, bpf_dynptr_clone)
-BTF_SET8_END(common_btf_ids)
+BTF_KFUNCS_END(common_btf_ids)
 
 static const struct btf_kfunc_id_set common_kfunc_set = {
 	.owner = THIS_MODULE,
diff --git a/kernel/bpf/map_iter.c b/kernel/bpf/map_iter.c
index 6abd7c5df4b3..9575314f40a6 100644
--- a/kernel/bpf/map_iter.c
+++ b/kernel/bpf/map_iter.c
@@ -213,9 +213,9 @@ __bpf_kfunc s64 bpf_map_sum_elem_count(const struct bpf_map *map)
 
 __bpf_kfunc_end_defs();
 
-BTF_SET8_START(bpf_map_iter_kfunc_ids)
+BTF_KFUNCS_START(bpf_map_iter_kfunc_ids)
 BTF_ID_FLAGS(func, bpf_map_sum_elem_count, KF_TRUSTED_ARGS)
-BTF_SET8_END(bpf_map_iter_kfunc_ids)
+BTF_KFUNCS_END(bpf_map_iter_kfunc_ids)
 
 static const struct btf_kfunc_id_set bpf_map_iter_kfunc_set = {
 	.owner = THIS_MODULE,
diff --git a/kernel/cgroup/rstat.c b/kernel/cgroup/rstat.c
index c0adb7254b45..127858046712 100644
--- a/kernel/cgroup/rstat.c
+++ b/kernel/cgroup/rstat.c
@@ -520,10 +520,10 @@ void cgroup_base_stat_cputime_show(struct seq_file *seq)
 }
 
 /* Add bpf kfuncs for cgroup_rstat_updated() and cgroup_rstat_flush() */
-BTF_SET8_START(bpf_rstat_kfunc_ids)
+BTF_KFUNCS_START(bpf_rstat_kfunc_ids)
 BTF_ID_FLAGS(func, cgroup_rstat_updated)
 BTF_ID_FLAGS(func, cgroup_rstat_flush, KF_SLEEPABLE)
-BTF_SET8_END(bpf_rstat_kfunc_ids)
+BTF_KFUNCS_END(bpf_rstat_kfunc_ids)
 
 static const struct btf_kfunc_id_set bpf_rstat_kfunc_set = {
 	.owner          = THIS_MODULE,
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 7ac6c52b25eb..d786738ae5fa 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -1412,14 +1412,14 @@ __bpf_kfunc int bpf_verify_pkcs7_signature(struct bpf_dynptr_kern *data_ptr,
 
 __bpf_kfunc_end_defs();
 
-BTF_SET8_START(key_sig_kfunc_set)
+BTF_KFUNCS_START(key_sig_kfunc_set)
 BTF_ID_FLAGS(func, bpf_lookup_user_key, KF_ACQUIRE | KF_RET_NULL | KF_SLEEPABLE)
 BTF_ID_FLAGS(func, bpf_lookup_system_key, KF_ACQUIRE | KF_RET_NULL)
 BTF_ID_FLAGS(func, bpf_key_put, KF_RELEASE)
 #ifdef CONFIG_SYSTEM_DATA_VERIFICATION
 BTF_ID_FLAGS(func, bpf_verify_pkcs7_signature, KF_SLEEPABLE)
 #endif
-BTF_SET8_END(key_sig_kfunc_set)
+BTF_KFUNCS_END(key_sig_kfunc_set)
 
 static const struct btf_kfunc_id_set bpf_key_sig_kfunc_set = {
 	.owner = THIS_MODULE,
@@ -1475,9 +1475,9 @@ __bpf_kfunc int bpf_get_file_xattr(struct file *file, const char *name__str,
 
 __bpf_kfunc_end_defs();
 
-BTF_SET8_START(fs_kfunc_set_ids)
+BTF_KFUNCS_START(fs_kfunc_set_ids)
 BTF_ID_FLAGS(func, bpf_get_file_xattr, KF_SLEEPABLE | KF_TRUSTED_ARGS)
-BTF_SET8_END(fs_kfunc_set_ids)
+BTF_KFUNCS_END(fs_kfunc_set_ids)
 
 static int bpf_get_file_xattr_filter(const struct bpf_prog *prog, u32 kfunc_id)
 {
diff --git a/net/bpf/test_run.c b/net/bpf/test_run.c
index dfd919374017..5535f9adc658 100644
--- a/net/bpf/test_run.c
+++ b/net/bpf/test_run.c
@@ -617,21 +617,21 @@ CFI_NOSEAL(bpf_kfunc_call_memb_release_dtor);
 
 __bpf_kfunc_end_defs();
 
-BTF_SET8_START(bpf_test_modify_return_ids)
+BTF_KFUNCS_START(bpf_test_modify_return_ids)
 BTF_ID_FLAGS(func, bpf_modify_return_test)
 BTF_ID_FLAGS(func, bpf_modify_return_test2)
 BTF_ID_FLAGS(func, bpf_fentry_test1, KF_SLEEPABLE)
-BTF_SET8_END(bpf_test_modify_return_ids)
+BTF_KFUNCS_END(bpf_test_modify_return_ids)
 
 static const struct btf_kfunc_id_set bpf_test_modify_return_set = {
 	.owner = THIS_MODULE,
 	.set   = &bpf_test_modify_return_ids,
 };
 
-BTF_SET8_START(test_sk_check_kfunc_ids)
+BTF_KFUNCS_START(test_sk_check_kfunc_ids)
 BTF_ID_FLAGS(func, bpf_kfunc_call_test_release, KF_RELEASE)
 BTF_ID_FLAGS(func, bpf_kfunc_call_memb_release, KF_RELEASE)
-BTF_SET8_END(test_sk_check_kfunc_ids)
+BTF_KFUNCS_END(test_sk_check_kfunc_ids)
 
 static void *bpf_test_init(const union bpf_attr *kattr, u32 user_size,
 			   u32 size, u32 headroom, u32 tailroom)
diff --git a/net/core/filter.c b/net/core/filter.c
index 24061f29c9dd..1f2303b9cce7 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -11853,17 +11853,17 @@ int bpf_dynptr_from_skb_rdonly(struct sk_buff *skb, u64 flags,
 	return 0;
 }
 
-BTF_SET8_START(bpf_kfunc_check_set_skb)
+BTF_KFUNCS_START(bpf_kfunc_check_set_skb)
 BTF_ID_FLAGS(func, bpf_dynptr_from_skb)
-BTF_SET8_END(bpf_kfunc_check_set_skb)
+BTF_KFUNCS_END(bpf_kfunc_check_set_skb)
 
-BTF_SET8_START(bpf_kfunc_check_set_xdp)
+BTF_KFUNCS_START(bpf_kfunc_check_set_xdp)
 BTF_ID_FLAGS(func, bpf_dynptr_from_xdp)
-BTF_SET8_END(bpf_kfunc_check_set_xdp)
+BTF_KFUNCS_END(bpf_kfunc_check_set_xdp)
 
-BTF_SET8_START(bpf_kfunc_check_set_sock_addr)
+BTF_KFUNCS_START(bpf_kfunc_check_set_sock_addr)
 BTF_ID_FLAGS(func, bpf_sock_addr_set_sun_path)
-BTF_SET8_END(bpf_kfunc_check_set_sock_addr)
+BTF_KFUNCS_END(bpf_kfunc_check_set_sock_addr)
 
 static const struct btf_kfunc_id_set bpf_kfunc_set_skb = {
 	.owner = THIS_MODULE,
@@ -11936,9 +11936,9 @@ __bpf_kfunc int bpf_sock_destroy(struct sock_common *sock)
 
 __bpf_kfunc_end_defs();
 
-BTF_SET8_START(bpf_sk_iter_kfunc_ids)
+BTF_KFUNCS_START(bpf_sk_iter_kfunc_ids)
 BTF_ID_FLAGS(func, bpf_sock_destroy, KF_TRUSTED_ARGS)
-BTF_SET8_END(bpf_sk_iter_kfunc_ids)
+BTF_KFUNCS_END(bpf_sk_iter_kfunc_ids)
 
 static int tracing_iter_filter(const struct bpf_prog *prog, u32 kfunc_id)
 {
diff --git a/net/core/xdp.c b/net/core/xdp.c
index 4869c1c2d8f3..034fb80f3fbe 100644
--- a/net/core/xdp.c
+++ b/net/core/xdp.c
@@ -771,11 +771,11 @@ __bpf_kfunc int bpf_xdp_metadata_rx_vlan_tag(const struct xdp_md *ctx,
 
 __bpf_kfunc_end_defs();
 
-BTF_SET8_START(xdp_metadata_kfunc_ids)
+BTF_KFUNCS_START(xdp_metadata_kfunc_ids)
 #define XDP_METADATA_KFUNC(_, __, name, ___) BTF_ID_FLAGS(func, name, KF_TRUSTED_ARGS)
 XDP_METADATA_KFUNC_xxx
 #undef XDP_METADATA_KFUNC
-BTF_SET8_END(xdp_metadata_kfunc_ids)
+BTF_KFUNCS_END(xdp_metadata_kfunc_ids)
 
 static const struct btf_kfunc_id_set xdp_metadata_kfunc_set = {
 	.owner = THIS_MODULE,
diff --git a/net/ipv4/bpf_tcp_ca.c b/net/ipv4/bpf_tcp_ca.c
index ae8b15e6896f..edecdf8229df 100644
--- a/net/ipv4/bpf_tcp_ca.c
+++ b/net/ipv4/bpf_tcp_ca.c
@@ -195,13 +195,13 @@ bpf_tcp_ca_get_func_proto(enum bpf_func_id func_id,
 	}
 }
 
-BTF_SET8_START(bpf_tcp_ca_check_kfunc_ids)
+BTF_KFUNCS_START(bpf_tcp_ca_check_kfunc_ids)
 BTF_ID_FLAGS(func, tcp_reno_ssthresh)
 BTF_ID_FLAGS(func, tcp_reno_cong_avoid)
 BTF_ID_FLAGS(func, tcp_reno_undo_cwnd)
 BTF_ID_FLAGS(func, tcp_slow_start)
 BTF_ID_FLAGS(func, tcp_cong_avoid_ai)
-BTF_SET8_END(bpf_tcp_ca_check_kfunc_ids)
+BTF_KFUNCS_END(bpf_tcp_ca_check_kfunc_ids)
 
 static const struct btf_kfunc_id_set bpf_tcp_ca_kfunc_set = {
 	.owner = THIS_MODULE,
diff --git a/net/ipv4/fou_bpf.c b/net/ipv4/fou_bpf.c
index 4da03bf45c9b..06e5572f296f 100644
--- a/net/ipv4/fou_bpf.c
+++ b/net/ipv4/fou_bpf.c
@@ -100,10 +100,10 @@ __bpf_kfunc int bpf_skb_get_fou_encap(struct __sk_buff *skb_ctx,
 
 __bpf_kfunc_end_defs();
 
-BTF_SET8_START(fou_kfunc_set)
+BTF_KFUNCS_START(fou_kfunc_set)
 BTF_ID_FLAGS(func, bpf_skb_set_fou_encap)
 BTF_ID_FLAGS(func, bpf_skb_get_fou_encap)
-BTF_SET8_END(fou_kfunc_set)
+BTF_KFUNCS_END(fou_kfunc_set)
 
 static const struct btf_kfunc_id_set fou_bpf_kfunc_set = {
 	.owner = THIS_MODULE,
diff --git a/net/ipv4/tcp_bbr.c b/net/ipv4/tcp_bbr.c
index 22358032dd48..05dc2d05bc7c 100644
--- a/net/ipv4/tcp_bbr.c
+++ b/net/ipv4/tcp_bbr.c
@@ -1155,7 +1155,7 @@ static struct tcp_congestion_ops tcp_bbr_cong_ops __read_mostly = {
 	.set_state	= bbr_set_state,
 };
 
-BTF_SET8_START(tcp_bbr_check_kfunc_ids)
+BTF_KFUNCS_START(tcp_bbr_check_kfunc_ids)
 #ifdef CONFIG_X86
 #ifdef CONFIG_DYNAMIC_FTRACE
 BTF_ID_FLAGS(func, bbr_init)
@@ -1168,7 +1168,7 @@ BTF_ID_FLAGS(func, bbr_min_tso_segs)
 BTF_ID_FLAGS(func, bbr_set_state)
 #endif
 #endif
-BTF_SET8_END(tcp_bbr_check_kfunc_ids)
+BTF_KFUNCS_END(tcp_bbr_check_kfunc_ids)
 
 static const struct btf_kfunc_id_set tcp_bbr_kfunc_set = {
 	.owner = THIS_MODULE,
diff --git a/net/ipv4/tcp_cubic.c b/net/ipv4/tcp_cubic.c
index 0fd78ecb67e7..44869ea089e3 100644
--- a/net/ipv4/tcp_cubic.c
+++ b/net/ipv4/tcp_cubic.c
@@ -485,7 +485,7 @@ static struct tcp_congestion_ops cubictcp __read_mostly = {
 	.name		= "cubic",
 };
 
-BTF_SET8_START(tcp_cubic_check_kfunc_ids)
+BTF_KFUNCS_START(tcp_cubic_check_kfunc_ids)
 #ifdef CONFIG_X86
 #ifdef CONFIG_DYNAMIC_FTRACE
 BTF_ID_FLAGS(func, cubictcp_init)
@@ -496,7 +496,7 @@ BTF_ID_FLAGS(func, cubictcp_cwnd_event)
 BTF_ID_FLAGS(func, cubictcp_acked)
 #endif
 #endif
-BTF_SET8_END(tcp_cubic_check_kfunc_ids)
+BTF_KFUNCS_END(tcp_cubic_check_kfunc_ids)
 
 static const struct btf_kfunc_id_set tcp_cubic_kfunc_set = {
 	.owner = THIS_MODULE,
diff --git a/net/ipv4/tcp_dctcp.c b/net/ipv4/tcp_dctcp.c
index bb23bb5b387a..e33fbe4933e4 100644
--- a/net/ipv4/tcp_dctcp.c
+++ b/net/ipv4/tcp_dctcp.c
@@ -260,7 +260,7 @@ static struct tcp_congestion_ops dctcp_reno __read_mostly = {
 	.name		= "dctcp-reno",
 };
 
-BTF_SET8_START(tcp_dctcp_check_kfunc_ids)
+BTF_KFUNCS_START(tcp_dctcp_check_kfunc_ids)
 #ifdef CONFIG_X86
 #ifdef CONFIG_DYNAMIC_FTRACE
 BTF_ID_FLAGS(func, dctcp_init)
@@ -271,7 +271,7 @@ BTF_ID_FLAGS(func, dctcp_cwnd_undo)
 BTF_ID_FLAGS(func, dctcp_state)
 #endif
 #endif
-BTF_SET8_END(tcp_dctcp_check_kfunc_ids)
+BTF_KFUNCS_END(tcp_dctcp_check_kfunc_ids)
 
 static const struct btf_kfunc_id_set tcp_dctcp_kfunc_set = {
 	.owner = THIS_MODULE,
diff --git a/net/netfilter/nf_conntrack_bpf.c b/net/netfilter/nf_conntrack_bpf.c
index 475358ec8212..d2492d050fe6 100644
--- a/net/netfilter/nf_conntrack_bpf.c
+++ b/net/netfilter/nf_conntrack_bpf.c
@@ -467,7 +467,7 @@ __bpf_kfunc int bpf_ct_change_status(struct nf_conn *nfct, u32 status)
 
 __bpf_kfunc_end_defs();
 
-BTF_SET8_START(nf_ct_kfunc_set)
+BTF_KFUNCS_START(nf_ct_kfunc_set)
 BTF_ID_FLAGS(func, bpf_xdp_ct_alloc, KF_ACQUIRE | KF_RET_NULL)
 BTF_ID_FLAGS(func, bpf_xdp_ct_lookup, KF_ACQUIRE | KF_RET_NULL)
 BTF_ID_FLAGS(func, bpf_skb_ct_alloc, KF_ACQUIRE | KF_RET_NULL)
@@ -478,7 +478,7 @@ BTF_ID_FLAGS(func, bpf_ct_set_timeout, KF_TRUSTED_ARGS)
 BTF_ID_FLAGS(func, bpf_ct_change_timeout, KF_TRUSTED_ARGS)
 BTF_ID_FLAGS(func, bpf_ct_set_status, KF_TRUSTED_ARGS)
 BTF_ID_FLAGS(func, bpf_ct_change_status, KF_TRUSTED_ARGS)
-BTF_SET8_END(nf_ct_kfunc_set)
+BTF_KFUNCS_END(nf_ct_kfunc_set)
 
 static const struct btf_kfunc_id_set nf_conntrack_kfunc_set = {
 	.owner = THIS_MODULE,
diff --git a/net/netfilter/nf_nat_bpf.c b/net/netfilter/nf_nat_bpf.c
index 6e3b2f58855f..481be15609b1 100644
--- a/net/netfilter/nf_nat_bpf.c
+++ b/net/netfilter/nf_nat_bpf.c
@@ -54,9 +54,9 @@ __bpf_kfunc int bpf_ct_set_nat_info(struct nf_conn___init *nfct,
 
 __bpf_kfunc_end_defs();
 
-BTF_SET8_START(nf_nat_kfunc_set)
+BTF_KFUNCS_START(nf_nat_kfunc_set)
 BTF_ID_FLAGS(func, bpf_ct_set_nat_info, KF_TRUSTED_ARGS)
-BTF_SET8_END(nf_nat_kfunc_set)
+BTF_KFUNCS_END(nf_nat_kfunc_set)
 
 static const struct btf_kfunc_id_set nf_bpf_nat_kfunc_set = {
 	.owner = THIS_MODULE,
diff --git a/net/xfrm/xfrm_interface_bpf.c b/net/xfrm/xfrm_interface_bpf.c
index 7d5e920141e9..5ea15037ebd1 100644
--- a/net/xfrm/xfrm_interface_bpf.c
+++ b/net/xfrm/xfrm_interface_bpf.c
@@ -93,10 +93,10 @@ __bpf_kfunc int bpf_skb_set_xfrm_info(struct __sk_buff *skb_ctx, const struct bp
 
 __bpf_kfunc_end_defs();
 
-BTF_SET8_START(xfrm_ifc_kfunc_set)
+BTF_KFUNCS_START(xfrm_ifc_kfunc_set)
 BTF_ID_FLAGS(func, bpf_skb_get_xfrm_info)
 BTF_ID_FLAGS(func, bpf_skb_set_xfrm_info)
-BTF_SET8_END(xfrm_ifc_kfunc_set)
+BTF_KFUNCS_END(xfrm_ifc_kfunc_set)
 
 static const struct btf_kfunc_id_set xfrm_interface_kfunc_set = {
 	.owner = THIS_MODULE,
diff --git a/net/xfrm/xfrm_state_bpf.c b/net/xfrm/xfrm_state_bpf.c
index 9e20d4a377f7..2248eda741f8 100644
--- a/net/xfrm/xfrm_state_bpf.c
+++ b/net/xfrm/xfrm_state_bpf.c
@@ -117,10 +117,10 @@ __bpf_kfunc void bpf_xdp_xfrm_state_release(struct xfrm_state *x)
 
 __bpf_kfunc_end_defs();
 
-BTF_SET8_START(xfrm_state_kfunc_set)
+BTF_KFUNCS_START(xfrm_state_kfunc_set)
 BTF_ID_FLAGS(func, bpf_xdp_get_xfrm_state, KF_RET_NULL | KF_ACQUIRE)
 BTF_ID_FLAGS(func, bpf_xdp_xfrm_state_release, KF_RELEASE)
-BTF_SET8_END(xfrm_state_kfunc_set)
+BTF_KFUNCS_END(xfrm_state_kfunc_set)
 
 static const struct btf_kfunc_id_set xfrm_state_xdp_kfunc_set = {
 	.owner = THIS_MODULE,
diff --git a/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c b/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c
index 91907b321f91..9faaefbe4a07 100644
--- a/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c
+++ b/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c
@@ -341,12 +341,12 @@ static struct bin_attribute bin_attr_bpf_testmod_file __ro_after_init = {
 	.write = bpf_testmod_test_write,
 };
 
-BTF_SET8_START(bpf_testmod_common_kfunc_ids)
+BTF_KFUNCS_START(bpf_testmod_common_kfunc_ids)
 BTF_ID_FLAGS(func, bpf_iter_testmod_seq_new, KF_ITER_NEW)
 BTF_ID_FLAGS(func, bpf_iter_testmod_seq_next, KF_ITER_NEXT | KF_RET_NULL)
 BTF_ID_FLAGS(func, bpf_iter_testmod_seq_destroy, KF_ITER_DESTROY)
 BTF_ID_FLAGS(func, bpf_kfunc_common_test)
-BTF_SET8_END(bpf_testmod_common_kfunc_ids)
+BTF_KFUNCS_END(bpf_testmod_common_kfunc_ids)
 
 static const struct btf_kfunc_id_set bpf_testmod_common_kfunc_set = {
 	.owner = THIS_MODULE,
@@ -492,7 +492,7 @@ __bpf_kfunc static u32 bpf_kfunc_call_test_static_unused_arg(u32 arg, u32 unused
 	return arg;
 }
 
-BTF_SET8_START(bpf_testmod_check_kfunc_ids)
+BTF_KFUNCS_START(bpf_testmod_check_kfunc_ids)
 BTF_ID_FLAGS(func, bpf_testmod_test_mod_kfunc)
 BTF_ID_FLAGS(func, bpf_kfunc_call_test1)
 BTF_ID_FLAGS(func, bpf_kfunc_call_test2)
@@ -518,7 +518,7 @@ BTF_ID_FLAGS(func, bpf_kfunc_call_test_ref, KF_TRUSTED_ARGS | KF_RCU)
 BTF_ID_FLAGS(func, bpf_kfunc_call_test_destructive, KF_DESTRUCTIVE)
 BTF_ID_FLAGS(func, bpf_kfunc_call_test_static_unused_arg)
 BTF_ID_FLAGS(func, bpf_kfunc_call_test_offset)
-BTF_SET8_END(bpf_testmod_check_kfunc_ids)
+BTF_KFUNCS_END(bpf_testmod_check_kfunc_ids)
 
 static const struct btf_kfunc_id_set bpf_testmod_kfunc_set = {
 	.owner = THIS_MODULE,
-- 
2.42.1

Re: [PATCH bpf-next v3 0/3] Annotate kfuncs in .BTF_ids section

[Lorenz Bauer]

On Sat, Jan 6, 2024 at 7:25 PM Daniel Xu <dxu@dxuuu.xyz> wrote:
>
> === 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.

This is great, thanks for tackling this. With yout patches we can
figure out the full set of kfuncs. Is there a way to extend it so that
we can tell which program context a kfunc can be called from?

Re: [PATCH bpf-next v3 0/3] Annotate kfuncs in .BTF_ids section

[Daniel Xu]

Hi Lorenz,

On Mon, Jan 08, 2024 at 10:15:45AM +0100, Lorenz Bauer wrote:
> On Sat, Jan 6, 2024 at 7:25 PM Daniel Xu <dxu@dxuuu.xyz> wrote:
> >
> > === 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.
> 
> This is great, thanks for tackling this. With yout patches we can
> figure out the full set of kfuncs. Is there a way to extend it so that
> we can tell which program context a kfunc can be called from?

I think a potential approach would be to extend BTF_ID_FLAGS() with some
more flags if we want to continue with .BTF_ids parsing technique. But
it has some issues with program-type-less helpers that are associated with
attachpoints as well as struct_ops helpers.

Since it looks like we're in rather early stages of program-type-less
world, maybe it'd be good to defer solving this problem until more use
cases are established and we can find a good cut point to design around.
Even with uapi helpers there was no way before.

Thanks,
Daniel

Re: [PATCH bpf-next v3 0/3] Annotate kfuncs in .BTF_ids section

[Jiri Olsa]

On Sat, Jan 06, 2024 at 11:24:07AM -0700, Daniel Xu wrote:
> === 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 changes (still needs some cleanup) can be viewed
> here on this "frozen" branch [0].

so the plan is to have bpftool support to generate header file
with detected kfuncs?

jirka

> 
> [0]: https://github.com/danobi/pahole/tree/kfunc_btf-mailed
> 
> === Changelog ===
> 
> 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
> 
> Daniel Xu (3):
>   bpf: btf: Support flags for BTF_SET8 sets
>   bpf: btf: Add BTF_KFUNCS_START/END macro pair
>   bpf: treewide: Annotate BPF kfuncs in BTF
> 
>  drivers/hid/bpf/hid_bpf_dispatch.c            |  8 +++----
>  fs/verity/measure.c                           |  4 ++--
>  include/linux/btf_ids.h                       | 21 +++++++++++++++----
>  kernel/bpf/btf.c                              |  8 +++++++
>  kernel/bpf/cpumask.c                          |  4 ++--
>  kernel/bpf/helpers.c                          |  8 +++----
>  kernel/bpf/map_iter.c                         |  4 ++--
>  kernel/cgroup/rstat.c                         |  4 ++--
>  kernel/trace/bpf_trace.c                      |  8 +++----
>  net/bpf/test_run.c                            |  8 +++----
>  net/core/filter.c                             | 16 +++++++-------
>  net/core/xdp.c                                |  4 ++--
>  net/ipv4/bpf_tcp_ca.c                         |  4 ++--
>  net/ipv4/fou_bpf.c                            |  4 ++--
>  net/ipv4/tcp_bbr.c                            |  4 ++--
>  net/ipv4/tcp_cubic.c                          |  4 ++--
>  net/ipv4/tcp_dctcp.c                          |  4 ++--
>  net/netfilter/nf_conntrack_bpf.c              |  4 ++--
>  net/netfilter/nf_nat_bpf.c                    |  4 ++--
>  net/xfrm/xfrm_interface_bpf.c                 |  4 ++--
>  net/xfrm/xfrm_state_bpf.c                     |  4 ++--
>  .../selftests/bpf/bpf_testmod/bpf_testmod.c   |  8 +++----
>  22 files changed, 81 insertions(+), 60 deletions(-)
> 
> -- 
> 2.42.1
> 

Re: [PATCH bpf-next v3 0/3] Annotate kfuncs in .BTF_ids section

[Daniel Xu]

On Fri, Jan 12, 2024 at 05:20:39PM +0100, Jiri Olsa wrote:
> On Sat, Jan 06, 2024 at 11:24:07AM -0700, Daniel Xu wrote:
> > === 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 changes (still needs some cleanup) can be viewed
> > here on this "frozen" branch [0].
> 
> so the plan is to have bpftool support to generate header file
> with detected kfuncs?

Yep, that's the major use case. But I see other use cases as well like
precision probing of kfuncs. Rather than guess and check which progs can
load (in the event of backwards incompatible kfunc changes), programs
can look at kfunc type signature thru BTF.

Re: [PATCH bpf-next v3 0/3] Annotate kfuncs in .BTF_ids section

[Jiri Olsa]

On Fri, Jan 12, 2024 at 01:03:59PM -0700, Daniel Xu wrote:
> On Fri, Jan 12, 2024 at 05:20:39PM +0100, Jiri Olsa wrote:
> > On Sat, Jan 06, 2024 at 11:24:07AM -0700, Daniel Xu wrote:
> > > === 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 changes (still needs some cleanup) can be viewed
> > > here on this "frozen" branch [0].
> > 
> > so the plan is to have bpftool support to generate header file
> > with detected kfuncs?
> 
> Yep, that's the major use case. But I see other use cases as well like

ok, any chance you could already include it in the patchset?
would be a great way to test this.. maybe we could change
selftests to use that

thanks,
jirka


> precision probing of kfuncs. Rather than guess and check which progs can
> load (in the event of backwards incompatible kfunc changes), programs
> can look at kfunc type signature thru BTF.

Re: [PATCH bpf-next v3 0/3] Annotate kfuncs in .BTF_ids section

[Daniel Xu]

Hi Jiri,

On Sat, Jan 13, 2024 at 02:57:40PM +0100, Jiri Olsa wrote:
> On Fri, Jan 12, 2024 at 01:03:59PM -0700, Daniel Xu wrote:
> > On Fri, Jan 12, 2024 at 05:20:39PM +0100, Jiri Olsa wrote:
> > > On Sat, Jan 06, 2024 at 11:24:07AM -0700, Daniel Xu wrote:
> > > > === 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 changes (still needs some cleanup) can be viewed
> > > > here on this "frozen" branch [0].
> > > 
> > > so the plan is to have bpftool support to generate header file
> > > with detected kfuncs?
> > 
> > Yep, that's the major use case. But I see other use cases as well like
> 
> ok, any chance you could already include it in the patchset?
> would be a great way to test this.. maybe we could change
> selftests to use that

I haven't start working on that code yet, but I can.

Here is my plan FWIW:

1. Bump minimum required pahole version up. Or feature probe for
   kfunc decl tag support. Whatever is the standard practice here.

2. Teach bpftool to dump kfunc prototypes, guarded behind a flag.

3. Flip bpftool flag on in selftest build and remove all manual kfunc
   prototypes atomically in 1 commit.

I thought it'd be nicer to do it incrementally given all the moving
pieces. But if we want to land it all at once that is ok by me too.

Thanks,
Daniel

Re: [PATCH bpf-next v3 0/3] Annotate kfuncs in .BTF_ids section

[Jiri Olsa]

On Sat, Jan 13, 2024 at 09:17:44AM -0700, Daniel Xu wrote:
> Hi Jiri,
> 
> On Sat, Jan 13, 2024 at 02:57:40PM +0100, Jiri Olsa wrote:
> > On Fri, Jan 12, 2024 at 01:03:59PM -0700, Daniel Xu wrote:
> > > On Fri, Jan 12, 2024 at 05:20:39PM +0100, Jiri Olsa wrote:
> > > > On Sat, Jan 06, 2024 at 11:24:07AM -0700, Daniel Xu wrote:
> > > > > === 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 changes (still needs some cleanup) can be viewed
> > > > > here on this "frozen" branch [0].
> > > > 
> > > > so the plan is to have bpftool support to generate header file
> > > > with detected kfuncs?
> > > 
> > > Yep, that's the major use case. But I see other use cases as well like
> > 
> > ok, any chance you could already include it in the patchset?
> > would be a great way to test this.. maybe we could change
> > selftests to use that
> 
> I haven't start working on that code yet, but I can.
> 
> Here is my plan FWIW:
> 
> 1. Bump minimum required pahole version up. Or feature probe for
>    kfunc decl tag support. Whatever is the standard practice here.
> 
> 2. Teach bpftool to dump kfunc prototypes, guarded behind a flag.
> 
> 3. Flip bpftool flag on in selftest build and remove all manual kfunc
>    prototypes atomically in 1 commit.
> 
> I thought it'd be nicer to do it incrementally given all the moving
> pieces. But if we want to land it all at once that is ok by me too.

I think it'd be best to try the whole thing before we merge the change
to pahole.. I guess the tests changes can come later, but would be great
to try the kfunc dump and make sure it works as expected

jirka