[RFC,hid,v1,03/10] HID: add a tool to convert a bpf source into a generic bpf loader

diff --git a/MAINTAINERS b/MAINTAINERS
index 752126fba795..8580895e280f 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -9102,6 +9102,7 @@  F:	drivers/hid/
 F:	include/linux/hid*
 F:	include/uapi/linux/hid*
 F:	samples/hid/
+F:	tools/hid
 F:	tools/testing/selftests/hid/
 
 HID LOGITECH DRIVERS
diff --git a/drivers/hid/bpf/progs/Makefile b/drivers/hid/bpf/progs/Makefile
new file mode 100644
index 000000000000..ee0203d3349a
--- /dev/null
+++ b/drivers/hid/bpf/progs/Makefile
@@ -0,0 +1,105 @@ 
+# SPDX-License-Identifier: GPL-2.0
+OUTPUT := .output
+abs_out := $(abspath $(OUTPUT))
+
+CLANG ?= clang
+LLC ?= llc
+LLVM_STRIP ?= llvm-strip
+
+TOOLS_PATH := $(abspath ../../../../tools)
+BPFTOOL_SRC := $(TOOLS_PATH)/bpf/bpftool
+BPFTOOL_OUTPUT := $(abs_out)/bpftool
+DEFAULT_BPFTOOL := $(BPFTOOL_OUTPUT)/bootstrap/bpftool
+BPFTOOL ?= $(DEFAULT_BPFTOOL)
+
+LIBBPF_SRC := $(TOOLS_PATH)/lib/bpf
+LIBBPF_OUTPUT := $(abs_out)/libbpf
+LIBBPF_DESTDIR := $(LIBBPF_OUTPUT)
+LIBBPF_INCLUDE := $(LIBBPF_DESTDIR)/include
+BPFOBJ := $(LIBBPF_OUTPUT)/libbpf.a
+
+HID_BPF_CONVERTER := $(TOOLS_PATH)/hid/build_progs_list.py
+
+INCLUDES := -I$(OUTPUT) -I$(LIBBPF_INCLUDE) -I$(TOOLS_PATH)/include/uapi
+CFLAGS := -g -Wall
+
+VMLINUX_BTF_PATHS ?= $(if $(O),$(O)/vmlinux)				\
+		     $(if $(KBUILD_OUTPUT),$(KBUILD_OUTPUT)/vmlinux)	\
+		     ../../../../vmlinux				\
+		     /sys/kernel/btf/vmlinux				\
+		     /boot/vmlinux-$(shell uname -r)
+VMLINUX_BTF ?= $(abspath $(firstword $(wildcard $(VMLINUX_BTF_PATHS))))
+ifeq ($(VMLINUX_BTF),)
+$(error Cannot find a vmlinux for VMLINUX_BTF at any of "$(VMLINUX_BTF_PATHS)")
+endif
+
+ifeq ($(V),1)
+Q =
+msg =
+else
+Q = @
+msg = @printf '  %-8s %s%s\n' "$(1)" "$(notdir $(2))" "$(if $(3), $(3))";
+MAKEFLAGS += --no-print-directory
+submake_extras := feature_display=0
+endif
+
+.DELETE_ON_ERROR:
+
+.PHONY: all
+
+TARGETS = $(patsubst %.bpf.c,%.hidbpf.h, $(wildcard *.bpf.c))
+TARGETS += hid_bpf_progs.h
+
+all: $(TARGETS)
+
+clean:
+	$(call msg,CLEAN)
+	$(Q)rm -rf $(OUTPUT) $(TARGETS)
+
+$(OUTPUT)/%.json: $(OUTPUT)/%.bpf.o | $(BPFTOOL)
+	$(call msg,GEN-SKEL,$@)
+	$(Q)$(BPFTOOL) gen skeleton -L -j $< > $@
+
+%.hidbpf.h: $(OUTPUT)/%.json | $(HID_BPF_CONVERTER)
+	$(call msg,GEN-HIDBPF,$@)
+	$(Q)$(HID_BPF_CONVERTER) build_prog $< -o $@
+
+hid_bpf_progs.h: $(addprefix $(OUTPUT)/,$(patsubst %.bpf.c,%.json, $(wildcard *.bpf.c))) | $(HID_BPF_CONVERTER)
+	$(call msg,GEN-HIDBPF-LIST,$@)
+	$(Q)$(HID_BPF_CONVERTER) build_list $< -o $@
+
+$(OUTPUT)/%.bpf.o: %.bpf.c $(OUTPUT)/vmlinux.h $(BPFOBJ) | $(OUTPUT)
+	$(call msg,BPF,$@)
+	$(Q)$(CLANG) -g -O2 -target bpf $(INCLUDES)				\
+		 -c $(filter %.c,$^) -o $@ &&					\
+	$(LLVM_STRIP) -g $@
+
+$(OUTPUT)/vmlinux.h: $(VMLINUX_BTF) $(BPFTOOL) | $(INCLUDE_DIR)
+ifeq ($(VMLINUX_H),)
+	$(call msg,GEN,,$@)
+	$(Q)$(BPFTOOL) btf dump file $(VMLINUX_BTF) format c > $@
+else
+	$(call msg,CP,,$@)
+	$(Q)cp "$(VMLINUX_H)" $@
+endif
+
+$(OUTPUT) $(LIBBPF_OUTPUT) $(BPFTOOL_OUTPUT):
+	$(call msg,MKDIR,$@)
+	$(Q)mkdir -p $@
+
+$(BPFOBJ): $(wildcard $(LIBBPF_SRC)/*.[ch] $(LIBBPF_SRC)/Makefile) | $(LIBBPF_OUTPUT)
+	$(Q)$(MAKE) $(submake_extras) -C $(LIBBPF_SRC)				\
+		    OUTPUT=$(abspath $(dir $@))/ prefix=			\
+		    DESTDIR=$(LIBBPF_DESTDIR) $(abspath $@) install_headers
+
+ifeq ($(CROSS_COMPILE),)
+$(DEFAULT_BPFTOOL): $(BPFOBJ) | $(BPFTOOL_OUTPUT)
+	$(Q)$(MAKE) $(submake_extras) -C $(BPFTOOL_SRC)				\
+		    OUTPUT=$(BPFTOOL_OUTPUT)/					\
+		    LIBBPF_BOOTSTRAP_OUTPUT=$(LIBBPF_OUTPUT)/			\
+		    LIBBPF_BOOTSTRAP_DESTDIR=$(LIBBPF_DESTDIR)/ bootstrap
+else
+$(DEFAULT_BPFTOOL): $(BPFTOOL_OUTPUT)
+	$(Q)$(MAKE) $(submake_extras) -C $(BPFTOOL_SRC)				\
+		    OUTPUT=$(BPFTOOL_OUTPUT)/ bootstrap
+endif
diff --git a/drivers/hid/bpf/progs/hid_bpf.h b/drivers/hid/bpf/progs/hid_bpf.h
new file mode 100644
index 000000000000..7ee371cac2e1
--- /dev/null
+++ b/drivers/hid/bpf/progs/hid_bpf.h
@@ -0,0 +1,15 @@ 
+/* SPDX-License-Identifier: GPL-2.0-only */
+/* Copyright (c) 2022 Benjamin Tissoires
+ */
+
+#ifndef ____HID_BPF__H
+#define ____HID_BPF__H
+
+struct hid_bpf_probe_args {
+	unsigned int hid;
+	unsigned int rdesc_size;
+	unsigned char rdesc[4096];
+	int retval;
+};
+
+#endif /* ____HID_BPF__H */
diff --git a/drivers/hid/bpf/progs/hid_bpf_helpers.h b/drivers/hid/bpf/progs/hid_bpf_helpers.h
new file mode 100644
index 000000000000..4c4e63a516b3
--- /dev/null
+++ b/drivers/hid/bpf/progs/hid_bpf_helpers.h
@@ -0,0 +1,22 @@ 
+/* SPDX-License-Identifier: GPL-2.0-only */
+/* Copyright (c) 2022 Benjamin Tissoires
+ */
+
+#ifndef __HID_BPF_HELPERS_H
+#define __HID_BPF_HELPERS_H
+
+#include "vmlinux.h"
+#include <bpf/bpf_helpers.h>
+
+extern __u8 *hid_bpf_get_data(struct hid_bpf_ctx *ctx,
+			      unsigned int offset,
+			      const size_t __sz) __ksym;
+extern struct hid_bpf_ctx *hid_bpf_allocate_context(unsigned int hid_id) __ksym;
+extern void hid_bpf_release_context(struct hid_bpf_ctx *ctx) __ksym;
+extern int hid_bpf_hw_request(struct hid_bpf_ctx *ctx,
+			      __u8 *data,
+			      size_t buf__sz,
+			      enum hid_report_type type,
+			      enum hid_class_request reqtype) __ksym;
+
+#endif /* __HID_BPF_HELPERS_H */
diff --git a/drivers/hid/bpf/progs/hid_bpf_progs.h b/drivers/hid/bpf/progs/hid_bpf_progs.h
new file mode 100644
index 000000000000..430e0fb47484
--- /dev/null
+++ b/drivers/hid/bpf/progs/hid_bpf_progs.h
@@ -0,0 +1,49 @@ 
+/* SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause) */
+/* THIS FILE IS AUTOGENERATED BY build_progs_list.py ! */
+
+#ifndef __HID_BPF_PROGS_H__
+#define __HID_BPF_PROGS_H__
+
+/**
+ * struct hid_bpf_map: custom HID representation of a map
+ */
+struct hid_bpf_map {
+	unsigned int size;
+	unsigned int mmap_sz;
+	char *data;
+};
+
+/**
+ * struct hid_bpf_prog: custom HID representation of a program
+ */
+struct hid_bpf_prog {
+};
+
+/**
+ * struct hid_bpf_object: custom HID representation of a BPF object
+ * @map_cnt: number of maps available in the BPF object
+ * @prog_cnt: number of programs available
+ * @probe: index of the probe program if any (greater than prog_cnt if none)
+ */
+struct hid_bpf_object {
+	struct hid_device_id id;
+	unsigned int map_cnt;
+	struct hid_bpf_map maps[0];
+	unsigned int prog_cnt;
+	struct hid_bpf_prog progs[0];
+	unsigned int probe;
+	unsigned int rodata;
+	unsigned int data_sz;
+	char *data;
+	unsigned int insns_sz;
+	char *insns;
+};
+
+static struct hid_bpf_object hid_objects[] = {
+
+
+	{ },
+};
+
+#endif /* __HID_BPF_PROGS_H__ */
+
diff --git a/tools/hid/build_progs_list.py b/tools/hid/build_progs_list.py
new file mode 100755
index 000000000000..8103bc2f433f
--- /dev/null
+++ b/tools/hid/build_progs_list.py
@@ -0,0 +1,231 @@ 
+#!/bin/env python3
+# SPDX-License-Identifier: GPL-2.0-only
+# Copyright (c) 2022 Benjamin Tissoires
+
+import argparse
+import json
+import re
+import sys
+
+from pathlib import Path
+
+
+def create_header(fp, max_maps_cnt, max_progs_cnt):
+    print(
+        f"""/* SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause) */
+/* THIS FILE IS AUTOGENERATED BY build_progs_list.py ! */
+
+#ifndef __HID_BPF_PROGS_H__
+#define __HID_BPF_PROGS_H__
+
+/**
+ * struct hid_bpf_map: custom HID representation of a map
+ */
+struct hid_bpf_map {{
+	unsigned int size;
+	unsigned int mmap_sz;
+	char *data;
+}};
+
+/**
+ * struct hid_bpf_prog: custom HID representation of a program
+ */
+struct hid_bpf_prog {{
+}};
+
+/**
+ * struct hid_bpf_object: custom HID representation of a BPF object
+ * @map_cnt: number of maps available in the BPF object
+ * @prog_cnt: number of programs available
+ * @probe: index of the probe program if any (greater than prog_cnt if none)
+ */
+struct hid_bpf_object {{
+	struct hid_device_id id;
+	unsigned int map_cnt;
+	struct hid_bpf_map maps[{max_maps_cnt}];
+	unsigned int prog_cnt;
+	struct hid_bpf_prog progs[{max_progs_cnt}];
+	unsigned int probe;
+	unsigned int rodata;
+	unsigned int data_sz;
+	char *data;
+	unsigned int insns_sz;
+	char *insns;
+}};
+
+static struct hid_bpf_object hid_objects[] = {{
+""",
+        file=fp,
+    )
+
+
+def create_footer(fp):
+    print(
+        """
+	{ },
+};
+
+#endif /* __HID_BPF_PROGS_H__ */
+""",
+        file=fp,
+    )
+
+
+def get_bus_group_vid_pid(json_data):
+    path_regex = re.compile(
+        r"b([0-9a-fA-F]{4})g([0-9a-fA-F]{4})v([0-9a-fA-F]{4})p([0-9a-fA-F]{4}).*"
+    )
+    return path_regex.match(json_data["name"])
+
+
+def is_valid_bpf_json(json_data):
+    return get_bus_group_vid_pid(json_data) is not None and json_data["use_loader"]
+
+
+def build_prog_list(args):
+    input_files = [Path(p) for p in args.path]
+    output = args.output
+    max_maps_cnt = 0
+    max_progs_cnt = 0
+    valid_files = []
+
+    for prog in input_files:
+        with open(prog) as f:
+            data = json.load(f)
+        if not is_valid_bpf_json(data):
+            print(f"ignoring {prog.relative_to('.')}", file=sys.stderr)
+            continue
+        generated_name = prog.name.replace(".json", ".hidbpf.h")
+        max_maps_cnt = max(max_maps_cnt, len(data["maps"]))
+        max_progs_cnt = max(max_progs_cnt, len(data["progs"]))
+
+        valid_files.append(generated_name)
+
+    create_header(output, max_maps_cnt, max_progs_cnt)
+
+    valid_files.sort()
+
+    for file in valid_files:
+        print(f'#include "{file}"', file=output)
+
+    create_footer(output)
+
+
+def write_c_data(bytes):
+	outputs = ['"', '']
+	for b in bytes:
+		w = 2 if b == '0x00' else 4
+		if len(outputs[-1]) + w > 78:
+			outputs.append('')
+		if b != "0x00":
+			outputs[-1] += f"\\x{b[2:]}"
+		else:
+			outputs[-1] += "\\0"
+	outputs[-1] += '"'
+	return '\\\n'.join(outputs)
+
+
+def build_c_object(args):
+    input_file = Path(args.path[0])
+    output = args.output
+
+    with open(input_file) as f:
+        data = json.load(f)
+
+    if not is_valid_bpf_json(data):
+        print(f"ignoring {input_file.relative_to('.')}", file=sys.stderr)
+        return
+
+    try:
+        probe_idx = [p["name"] for p in data["progs"]].index("probe")
+    except ValueError:
+        probe_idx = len(data["progs"]) + 1
+
+    try:
+        rodata_idx = [m["ident"] for m in data["maps"]].index("rodata")
+    except ValueError:
+        rodata_idx = len(data["maps"]) + 1
+
+    header_marker = (
+        f"__{input_file.name}__".replace(".", "_")
+        .replace("-", "_")
+        .replace("json", "hidbpf_h")
+        .upper()
+    )
+    m = get_bus_group_vid_pid(data)
+    output.write(
+        f"""/* SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause) */
+/* THIS FILE IS AUTOGENERATED BY build_progs_list.py ! */
+
+#ifndef {header_marker}
+#define {header_marker}
+
+{{
+	.id = {{
+		.bus = 0x{m.group(1)},
+		.group = 0x{m.group(2)},
+		.vendor = 0x{m.group(3)},
+		.product = 0x{m.group(4)},
+	}},
+	.map_cnt = {len(data['maps'])},
+	.prog_cnt = {len(data['progs'])},
+	.probe = {probe_idx},
+	.rodata = {rodata_idx},
+	.maps = {{""")
+
+    for map in data['maps']:
+         output.write(f"""
+		{{
+			.size = {map['size']},
+			.mmap_sz = {map['mmap_sz']},
+			.data = {write_c_data(map['data'])},
+		}},""")
+
+    output.write(f"""
+	}},
+	.data_sz = {data['data_sz']},
+	.data = {write_c_data(data['data'])},
+	.insns_sz = {data['insns_sz']},
+	.insns = {write_c_data(data['insns'])},
+}},
+
+#endif /* {header_marker} */
+"""
+    )
+
+
+def main():
+    ap = argparse.ArgumentParser(description="custom HID BPF json converter")
+
+    def add_output(parser):
+        parser.add_argument(
+            "-o",
+            "--output",
+            nargs="?",
+            type=argparse.FileType("w"),
+            default=sys.stdout,
+            help="Output file, if not given, use stdout",
+        )
+
+    sp = ap.add_subparsers(help="sub-command help")
+
+    obj_parser = sp.add_parser(
+        "build_prog", help="Convert a JSON into a generic HID BPF header"
+    )
+    obj_parser.add_argument("path", nargs=1, help="Input file.", metavar="PATH")
+    add_output(obj_parser)
+    obj_parser.set_defaults(func=build_c_object)
+
+    list_parser = sp.add_parser(
+        "build_list", help="Convert a list of JSON into a generic HID BPF header list"
+    )
+    list_parser.add_argument("path", nargs="*", help="Input file(s).", metavar="PATH")
+    add_output(list_parser)
+    list_parser.set_defaults(func=build_prog_list)
+
+    args = ap.parse_args()
+    args.func(args)
+
+
+if __name__ == "__main__":
+    main()