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From:   Sean Young <sean@mess.org>
To:     linux-media@vger.kernel.org, linux-kernel@vger.kernel.org,
        Alexei Starovoitov <ast@kernel.org>,
        Mauro Carvalho Chehab <mchehab@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>, netdev@vger.kernel.org,
        Matthias Reichl <hias@horus.com>,
        Devin Heitmueller <dheitmueller@kernellabs.com>
Subject: [PATCH v1 1/4] media: rc: introduce BPF_PROG_IR_DECODER
Date:   Mon, 14 May 2018 22:10:58 +0100
Message-Id: <32a944171d5c48abf126259595b0088ce3122c91.1526331777.git.sean@mess.org>
In-Reply-To: <cover.1526331777.git.sean@mess.org>
References: <cover.1526331777.git.sean@mess.org>
In-Reply-To: <cover.1526331777.git.sean@mess.org>
References: <cover.1526331777.git.sean@mess.org>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

Add support for BPF_PROG_IR_DECODER. This type of BPF program can call
rc_keydown() to reported decoded IR scancodes, or rc_repeat() to report
that the last key should be repeated.

Signed-off-by: Sean Young <sean@mess.org>
---
 drivers/media/rc/Kconfig          |  8 +++
 drivers/media/rc/Makefile         |  1 +
 drivers/media/rc/ir-bpf-decoder.c | 93 +++++++++++++++++++++++++++++++
 include/linux/bpf_types.h         |  3 +
 include/uapi/linux/bpf.h          | 16 +++++-
 5 files changed, 120 insertions(+), 1 deletion(-)
 create mode 100644 drivers/media/rc/ir-bpf-decoder.c

diff --git a/drivers/media/rc/Kconfig b/drivers/media/rc/Kconfig
index eb2c3b6eca7f..10ad6167d87c 100644
--- a/drivers/media/rc/Kconfig
+++ b/drivers/media/rc/Kconfig
@@ -120,6 +120,14 @@ config IR_IMON_DECODER
 	   remote control and you would like to use it with a raw IR
 	   receiver, or if you wish to use an encoder to transmit this IR.
 
+config IR_BPF_DECODER
+	bool "Enable IR raw decoder using BPF"
+	depends on BPF_SYSCALL
+	depends on RC_CORE=y
+	help
+	   Enable this option to make it possible to load custom IR
+	   decoders written in BPF.
+
 endif #RC_DECODERS
 
 menuconfig RC_DEVICES
diff --git a/drivers/media/rc/Makefile b/drivers/media/rc/Makefile
index 2e1c87066f6c..12e1118430d0 100644
--- a/drivers/media/rc/Makefile
+++ b/drivers/media/rc/Makefile
@@ -5,6 +5,7 @@ obj-y += keymaps/
 obj-$(CONFIG_RC_CORE) += rc-core.o
 rc-core-y := rc-main.o rc-ir-raw.o
 rc-core-$(CONFIG_LIRC) += lirc_dev.o
+rc-core-$(CONFIG_IR_BPF_DECODER) += ir-bpf-decoder.o
 obj-$(CONFIG_IR_NEC_DECODER) += ir-nec-decoder.o
 obj-$(CONFIG_IR_RC5_DECODER) += ir-rc5-decoder.o
 obj-$(CONFIG_IR_RC6_DECODER) += ir-rc6-decoder.o
diff --git a/drivers/media/rc/ir-bpf-decoder.c b/drivers/media/rc/ir-bpf-decoder.c
new file mode 100644
index 000000000000..aaa5e208b1a5
--- /dev/null
+++ b/drivers/media/rc/ir-bpf-decoder.c
@@ -0,0 +1,93 @@
+// SPDX-License-Identifier: GPL-2.0
+// ir-bpf-decoder.c - handles bpf decoders
+//
+// Copyright (C) 2018 Sean Young <sean@mess.org>
+
+#include <linux/bpf.h>
+#include <linux/filter.h>
+#include "rc-core-priv.h"
+
+/*
+ * BPF interface for raw IR decoder
+ */
+const struct bpf_prog_ops ir_decoder_prog_ops = {
+};
+
+BPF_CALL_1(bpf_rc_repeat, struct ir_raw_event*, event)
+{
+	struct ir_raw_event_ctrl *ctrl;
+
+	ctrl = container_of(event, struct ir_raw_event_ctrl, prev_ev);
+
+	rc_repeat(ctrl->dev);
+	return 0;
+}
+
+static const struct bpf_func_proto rc_repeat_proto = {
+	.func	   = bpf_rc_repeat,
+	.gpl_only  = true, // rc_repeat is EXPORT_SYMBOL_GPL
+	.ret_type  = RET_VOID,
+	.arg1_type = ARG_PTR_TO_CTX,
+};
+
+BPF_CALL_4(bpf_rc_keydown, struct ir_raw_event*, event, u32, protocol,
+	   u32, scancode, u32, toggle)
+{
+	struct ir_raw_event_ctrl *ctrl;
+
+	ctrl = container_of(event, struct ir_raw_event_ctrl, prev_ev);
+	rc_keydown(ctrl->dev, protocol, scancode, toggle != 0);
+	return 0;
+}
+
+static const struct bpf_func_proto rc_keydown_proto = {
+	.func	   = bpf_rc_keydown,
+	.gpl_only  = true, // rc_keydown is EXPORT_SYMBOL_GPL
+	.ret_type  = RET_VOID,
+	.arg1_type = ARG_PTR_TO_CTX,
+	.arg2_type = ARG_ANYTHING,
+	.arg3_type = ARG_ANYTHING,
+	.arg4_type = ARG_ANYTHING,
+};
+
+static const struct bpf_func_proto *ir_decoder_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
+{
+	switch (func_id) {
+	case BPF_FUNC_rc_repeat:
+		return &rc_repeat_proto;
+	case BPF_FUNC_rc_keydown:
+		return &rc_keydown_proto;
+	case BPF_FUNC_map_lookup_elem:
+		return &bpf_map_lookup_elem_proto;
+	case BPF_FUNC_map_update_elem:
+		return &bpf_map_update_elem_proto;
+	case BPF_FUNC_map_delete_elem:
+		return &bpf_map_delete_elem_proto;
+	case BPF_FUNC_ktime_get_ns:
+		return &bpf_ktime_get_ns_proto;
+	case BPF_FUNC_tail_call:
+		return &bpf_tail_call_proto;
+	case BPF_FUNC_get_prandom_u32:
+		return &bpf_get_prandom_u32_proto;
+	default:
+		return NULL;
+	}
+}
+
+static bool ir_decoder_is_valid_access(int off, int size,
+				       enum bpf_access_type type,
+				       const struct bpf_prog *prog,
+				       struct bpf_insn_access_aux *info)
+{
+	if (type == BPF_WRITE)
+		return false;
+	if (off < 0 || off + size > sizeof(struct ir_raw_event))
+		return false;
+
+	return true;
+}
+
+const struct bpf_verifier_ops ir_decoder_verifier_ops = {
+	.get_func_proto  = ir_decoder_func_proto,
+	.is_valid_access = ir_decoder_is_valid_access
+};
diff --git a/include/linux/bpf_types.h b/include/linux/bpf_types.h
index 2b28fcf6f6ae..ee5355715ee0 100644
--- a/include/linux/bpf_types.h
+++ b/include/linux/bpf_types.h
@@ -25,6 +25,9 @@ BPF_PROG_TYPE(BPF_PROG_TYPE_RAW_TRACEPOINT, raw_tracepoint)
 #ifdef CONFIG_CGROUP_BPF
 BPF_PROG_TYPE(BPF_PROG_TYPE_CGROUP_DEVICE, cg_dev)
 #endif
+#ifdef CONFIG_IR_BPF_DECODER
+BPF_PROG_TYPE(BPF_PROG_TYPE_RAWIR_DECODER, ir_decoder)
+#endif
 
 BPF_MAP_TYPE(BPF_MAP_TYPE_ARRAY, array_map_ops)
 BPF_MAP_TYPE(BPF_MAP_TYPE_PERCPU_ARRAY, percpu_array_map_ops)
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index c5ec89732a8d..6ad053e831c0 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -137,6 +137,7 @@ enum bpf_prog_type {
 	BPF_PROG_TYPE_SK_MSG,
 	BPF_PROG_TYPE_RAW_TRACEPOINT,
 	BPF_PROG_TYPE_CGROUP_SOCK_ADDR,
+	BPF_PROG_TYPE_RAWIR_DECODER,
 };
 
 enum bpf_attach_type {
@@ -755,6 +756,17 @@ union bpf_attr {
  *     @addr: pointer to struct sockaddr to bind socket to
  *     @addr_len: length of sockaddr structure
  *     Return: 0 on success or negative error code
+ *
+ * int bpf_rc_keydown(ctx, protocol, scancode, toggle)
+ *	Report decoded scancode with toggle value
+ *	@ctx: pointer to ctx
+ *	@protocol: decoded protocol
+ *	@scancode: decoded scancode
+ *	@toggle: set to 1 if button was toggled, else 0
+ *
+ * int bpf_rc_repeat(ctx)
+ *	Repeat the last decoded scancode
+ *	@ctx: pointer to ctx
  */
 #define __BPF_FUNC_MAPPER(FN)		\
 	FN(unspec),			\
@@ -821,7 +833,9 @@ union bpf_attr {
 	FN(msg_apply_bytes),		\
 	FN(msg_cork_bytes),		\
 	FN(msg_pull_data),		\
-	FN(bind),
+	FN(bind),			\
+	FN(rc_repeat),			\
+	FN(rc_keydown),
 
 /* integer value in 'imm' field of BPF_CALL instruction selects which helper
  * function eBPF program intends to call
-- 
2.17.0