netdev - [RFC PATCH bpf-next 3/4] xdp: introduce xdp

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Date:   Wed, 13 Nov 2019 21:47:36 +0100
From:   Björn Töpel <bjorn.topel@...il.com>
To:     netdev@...r.kernel.org, ast@...nel.org, daniel@...earbox.net
Cc:     Björn Töpel <bjorn.topel@...el.com>,
        bpf@...r.kernel.org, magnus.karlsson@...il.com,
        magnus.karlsson@...el.com, jonathan.lemon@...il.com
Subject: [RFC PATCH bpf-next 3/4] xdp: introduce xdp_call

From: Björn Töpel <bjorn.topel@...el.com>

The xdp_call.h header wraps a more user-friendly API around the BPF
dispatcher. A user adds a trampoline/XDP caller using the
DEFINE_XDP_CALL macro, and updates the BPF dispatcher via
xdp_call_update(). The actual dispatch is done via xdp_call().

The next commit will show-case how the i40e uses xdp_call.

When static_call, especially the inlined version, is upstreamed it
will be used by xdp_call.h.

Signed-off-by: Björn Töpel <bjorn.topel@...el.com>
---
 include/linux/xdp_call.h | 49 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 49 insertions(+)
 create mode 100644 include/linux/xdp_call.h

diff --git a/include/linux/xdp_call.h b/include/linux/xdp_call.h
new file mode 100644
index 000000000000..e736a4d3c961
--- /dev/null
+++ b/include/linux/xdp_call.h
@@ -0,0 +1,49 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/* Copyright(c) 2019 Intel Corporation. */
+#ifndef _LINUX_XDP_CALL_H
+#define _LINUX_XDP_CALL_H
+
+#include <linux/filter.h>
+
+#if defined(CONFIG_BPF_JIT) && defined(CONFIG_RETPOLINE)
+
+void bpf_dispatcher_change_prog(void *func, struct bpf_prog *from,
+				struct bpf_prog *to);
+
+#define XDP_CALL_TRAMP(name)	____xdp_call_##name##_tramp
+
+#define DEFINE_XDP_CALL(name)						\
+	unsigned int XDP_CALL_TRAMP(name)(				\
+		const void *xdp_ctx,					\
+		const struct bpf_insn *insnsi,				\
+		unsigned int (*bpf_func)(const void *,			\
+					 const struct bpf_insn *))	\
+	{								\
+		return bpf_func(xdp_ctx, insnsi);			\
+	}
+
+#define DECLARE_XDP_CALL(name)						\
+	unsigned int XDP_CALL_TRAMP(name)(				\
+		const void *xdp_ctx,					\
+		const struct bpf_insn *insnsi,				\
+		unsigned int (*bpf_func)(const void *,			\
+					 const struct bpf_insn *))
+
+#define xdp_call_run(name, xdp_prog, xdp)				\
+	XDP_CALL_TRAMP(name)(xdp, xdp_prog->insnsi,			\
+			     xdp_prog->bpf_func)
+
+#define xdp_call_update(name, from_xdp_prog, to_xdp_prog)	\
+	bpf_dispatcher_change_prog(&XDP_CALL_TRAMP(name),	\
+				   from_xdp_prog,		\
+				   to_xdp_prog)
+
+#else /* !defined(CONFIG_BPF_JIT) || !defined(CONFIG_RETPOLINE) */
+
+#define DEFINE_XDP_CALL(name)
+#define DECLARE_XDP_CALL(name)
+#define xdp_call_run(name, xdp_prog, xdp) bpf_prog_run_xdp(xdp_prog, xdp)
+#define xdp_call_update(name, from_xdp_prog, to_xdp_prog)
+
+#endif /* defined(CONFIG_BPF_JIT) && defined(CONFIG_RETPOLINE) */
+#endif /* _LINUX_XDP_CALL_H */
-- 
2.20.1