A handle_events program should be able to parse the CQ and submit new
requests, add kfuncs to cover that. The only essential kfunc here is
bpf_io_uring_submit_sqes, and the rest are likely be removed in a
non-RFC version in favour of a more general approach.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---
 io_uring/bpf.c | 53 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 53 insertions(+)

diff --git a/io_uring/bpf.c b/io_uring/bpf.c
index 683e87f1a58b..006cea78cc10 100644
--- a/io_uring/bpf.c
+++ b/io_uring/bpf.c
@@ -3,10 +3,55 @@
 
 #include "bpf.h"
 #include "register.h"
+#include "memmap.h"
 
 static DEFINE_MUTEX(io_bpf_ctrl_mutex);
 static const struct btf_type *loop_state_type;
 
+__bpf_kfunc_start_defs();
+
+__bpf_kfunc int bpf_io_uring_submit_sqes(struct io_ring_ctx *ctx, u32 nr)
+{
+	return io_submit_sqes(ctx, nr);
+}
+
+__bpf_kfunc
+__u8 *bpf_io_uring_get_region(struct io_ring_ctx *ctx, __u32 region_id,
+			      const size_t rdwr_buf_size)
+{
+	struct io_mapped_region *r;
+
+	switch (region_id) {
+	case 0:
+		r = &ctx->ring_region;
+		break;
+	case 1:
+		r = &ctx->sq_region;
+		break;
+	case 2:
+		r = &ctx->param_region;
+		break;
+	default:
+		return NULL;
+	}
+
+	if (unlikely(rdwr_buf_size > io_region_size(r)))
+		return NULL;
+	return io_region_get_ptr(r);
+}
+
+__bpf_kfunc_end_defs();
+
+BTF_KFUNCS_START(io_uring_kfunc_set)
+BTF_ID_FLAGS(func, bpf_io_uring_submit_sqes, KF_SLEEPABLE | KF_TRUSTED_ARGS);
+BTF_ID_FLAGS(func, bpf_io_uring_get_region, KF_RET_NULL | KF_TRUSTED_ARGS);
+BTF_KFUNCS_END(io_uring_kfunc_set)
+
+static const struct btf_kfunc_id_set bpf_io_uring_kfunc_set = {
+	.owner = THIS_MODULE,
+	.set = &io_uring_kfunc_set,
+};
+
 static int io_bpf_ops__loop(struct io_ring_ctx *ctx, struct iou_loop_state *ls)
 {
 	return IOU_RES_STOP;
@@ -68,12 +113,20 @@ io_lookup_struct_type(struct btf *btf, const char *name)
 
 static int bpf_io_init(struct btf *btf)
 {
+	int ret;
+
 	loop_state_type = io_lookup_struct_type(btf, "iou_loop_state");
 	if (!loop_state_type) {
 		pr_err("io_uring: Failed to locate iou_loop_state\n");
 		return -EINVAL;
 	}
 
+	ret = register_btf_kfunc_id_set(BPF_PROG_TYPE_STRUCT_OPS,
+					&bpf_io_uring_kfunc_set);
+	if (ret) {
+		pr_err("io_uring: Failed to register kfuncs (%d)\n", ret);
+		return ret;
+	}
 	return 0;
 }
 
-- 
2.49.0