Merge branch 'bpf: Support calling kernel function'

Martin KaFai says:

====================

This series adds support to allow bpf program calling kernel function.

The use case included in this set is to allow bpf-tcp-cc to directly
call some tcp-cc helper functions (e.g. "tcp_cong_avoid_ai()").  Those
functions have already been used by some kernel tcp-cc implementations.

This set will also allow the bpf-tcp-cc program to directly call the
kernel tcp-cc implementation,  For example, a bpf_dctcp may only want to
implement its own dctcp_cwnd_event() and reuse other dctcp_*() directly
from the kernel tcp_dctcp.c instead of reimplementing (or
copy-and-pasting) them.

The tcp-cc kernel functions mentioned above will be white listed
for the struct_ops bpf-tcp-cc programs to use in a later patch.
The white listed functions are not bounded to a fixed ABI contract.
Those functions have already been used by the existing kernel tcp-cc.
If any of them has changed, both in-tree and out-of-tree kernel tcp-cc
implementations have to be changed.  The same goes for the struct_ops
bpf-tcp-cc programs which have to be adjusted accordingly.

Please see individual patch for details.

v2:
- Patch 2 in v1 is removed.  No need to support extern func in kernel.
  Changed libbpf to adjust the .ksyms datasec for extern func
  in patch 11. (Andrii)
- Name change: btf_check_func_arg_match() and btf_check_subprog_arg_match()
  in patch 2. (Andrii)
- Always set unreliable on any error in patch 2 since it does not
  matter. (Andrii)
- s/kern_func/kfunc/ and s/descriptor/desc/ in this set. (Andrii)
- Remove some unnecessary changes in disasm.h and disasm.c
  in patch 3.  In particular, no need to change the function
  signature in bpf_insn_revmap_call_t.  Also, removed the changes
  in print_bpf_insn().
- Fixed an issue in check_kfunc_call() when the calling kernel function
  returns a pointer in patch 3.  Added a selftest.
- Adjusted the verifier selftests due to the changes in the verifier log
  in patch 3.
- Fixed a comparison issue in kfunc_desc_cmp_by_imm() in patch 3. (Andrii)
- Name change: is_ldimm64_insn(),
  new helper: is_call_insn() in patch 10 (Andrii)
- Move btf_func_linkage() from btf.h to libbpf.c in patch 11. (Andrii)
- Fixed the linker error when CONFIG_BPF_SYSCALL is not defined.
  Moved the check_kfunc_call from filter.c to test_run.c in patch 14.
  (kernel test robot)
====================

Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 18 insertions, 18 deletions

diff --git a/tools/testing/selftests/bpf/progs/bpf_cubic.c b/tools/testing/selftests/bpf/progs/bpf_cubic.c
index 6939bfd8690f..f62df4d023f9 100644
--- a/tools/testing/selftests/bpf/progs/bpf_cubic.c
+++ b/tools/testing/selftests/bpf/progs/bpf_cubic.c
@@ -174,8 +174,8 @@ static __always_inline void bictcp_hystart_reset(struct sock *sk)
  * as long as it is used in one of the func ptr
  * under SEC(".struct_ops").
  */
-SEC("struct_ops/bictcp_init")
-void BPF_PROG(bictcp_init, struct sock *sk)
+SEC("struct_ops/bpf_cubic_init")
+void BPF_PROG(bpf_cubic_init, struct sock *sk)
 {
 	struct bictcp *ca = inet_csk_ca(sk);
 
@@ -192,7 +192,7 @@ void BPF_PROG(bictcp_init, struct sock *sk)
  * The remaining tcp-cubic functions have an easier way.
  */
 SEC("no-sec-prefix-bictcp_cwnd_event")
-void BPF_PROG(bictcp_cwnd_event, struct sock *sk, enum tcp_ca_event event)
+void BPF_PROG(bpf_cubic_cwnd_event, struct sock *sk, enum tcp_ca_event event)
 {
 	if (event == CA_EVENT_TX_START) {
 		struct bictcp *ca = inet_csk_ca(sk);
@@ -384,7 +384,7 @@ tcp_friendliness:
 }
 
 /* Or simply use the BPF_STRUCT_OPS to avoid the SEC boiler plate. */
-void BPF_STRUCT_OPS(bictcp_cong_avoid, struct sock *sk, __u32 ack, __u32 acked)
+void BPF_STRUCT_OPS(bpf_cubic_cong_avoid, struct sock *sk, __u32 ack, __u32 acked)
 {
 	struct tcp_sock *tp = tcp_sk(sk);
 	struct bictcp *ca = inet_csk_ca(sk);
@@ -403,7 +403,7 @@ void BPF_STRUCT_OPS(bictcp_cong_avoid, struct sock *sk, __u32 ack, __u32 acked)
 	tcp_cong_avoid_ai(tp, ca->cnt, acked);
 }
 
-__u32 BPF_STRUCT_OPS(bictcp_recalc_ssthresh, struct sock *sk)
+__u32 BPF_STRUCT_OPS(bpf_cubic_recalc_ssthresh, struct sock *sk)
 {
 	const struct tcp_sock *tp = tcp_sk(sk);
 	struct bictcp *ca = inet_csk_ca(sk);
@@ -420,7 +420,7 @@ __u32 BPF_STRUCT_OPS(bictcp_recalc_ssthresh, struct sock *sk)
 	return max((tp->snd_cwnd * beta) / BICTCP_BETA_SCALE, 2U);
 }
 
-void BPF_STRUCT_OPS(bictcp_state, struct sock *sk, __u8 new_state)
+void BPF_STRUCT_OPS(bpf_cubic_state, struct sock *sk, __u8 new_state)
 {
 	if (new_state == TCP_CA_Loss) {
 		bictcp_reset(inet_csk_ca(sk));
@@ -496,7 +496,7 @@ static __always_inline void hystart_update(struct sock *sk, __u32 delay)
 	}
 }
 
-void BPF_STRUCT_OPS(bictcp_acked, struct sock *sk,
+void BPF_STRUCT_OPS(bpf_cubic_acked, struct sock *sk,
 		    const struct ack_sample *sample)
 {
 	const struct tcp_sock *tp = tcp_sk(sk);
@@ -525,21 +525,21 @@ void BPF_STRUCT_OPS(bictcp_acked, struct sock *sk,
 		hystart_update(sk, delay);
 }
 
-__u32 BPF_STRUCT_OPS(tcp_reno_undo_cwnd, struct sock *sk)
-{
-	const struct tcp_sock *tp = tcp_sk(sk);
+extern __u32 tcp_reno_undo_cwnd(struct sock *sk) __ksym;
 
-	return max(tp->snd_cwnd, tp->prior_cwnd);
+__u32 BPF_STRUCT_OPS(bpf_cubic_undo_cwnd, struct sock *sk)
+{
+	return tcp_reno_undo_cwnd(sk);
 }
 
 SEC(".struct_ops")
 struct tcp_congestion_ops cubic = {
-	.init		= (void *)bictcp_init,
-	.ssthresh	= (void *)bictcp_recalc_ssthresh,
-	.cong_avoid	= (void *)bictcp_cong_avoid,
-	.set_state	= (void *)bictcp_state,
-	.undo_cwnd	= (void *)tcp_reno_undo_cwnd,
-	.cwnd_event	= (void *)bictcp_cwnd_event,
-	.pkts_acked     = (void *)bictcp_acked,
+	.init		= (void *)bpf_cubic_init,
+	.ssthresh	= (void *)bpf_cubic_recalc_ssthresh,
+	.cong_avoid	= (void *)bpf_cubic_cong_avoid,
+	.set_state	= (void *)bpf_cubic_state,
+	.undo_cwnd	= (void *)bpf_cubic_undo_cwnd,
+	.cwnd_event	= (void *)bpf_cubic_cwnd_event,
+	.pkts_acked     = (void *)bpf_cubic_acked,
 	.name		= "bpf_cubic",
 };