io_uring/bpf-ops: restrict ctx access to BPF

BPF programs should have no need in looking into struct io_ring_ctx, if
anything, most of such cases would be anti patterns like looking up ring
indices directly via the context.

Replace it with a new empty structure, which is just an alias to struct
io_ring_ctx. It'll create a new BTF type and fail verification if a BPF
program tries to access it (beyond the first byte). It'll also give more
flexibility for the future, and otherwise it can be made aligned with
io_ring_ctx as before with struct groups if ever needed or extended in a
different way.

Fixes: d0e437b76bd3c ("io_uring/bpf-ops: implement loop_step with BPF struct_ops")
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://patch.msgid.link/5f6ca3649e9e0bae8667db4357e28dd00cd07901.1780394491.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 10 insertions, 0 deletions

diff --git a/io_uring/loop.h b/io_uring/loop.h
index d7718b9ce61e..4dd4fb3aefef 100644
--- a/io_uring/loop.h
+++ b/io_uring/loop.h
@@ -24,4 +24,14 @@ static inline bool io_has_loop_ops(struct io_ring_ctx *ctx)
 
 int io_run_loop(struct io_ring_ctx *ctx);
 
+static inline struct iou_ctx *io_loop_mangle_ctx(struct io_ring_ctx *ctx)
+{
+	return (struct iou_ctx *)ctx;
+}
+
+static inline struct io_ring_ctx *io_loop_demangle_ctx(struct iou_ctx *ctx)
+{
+	return (struct io_ring_ctx *)ctx;
+}
+
 #endif