syscall: Create a script to export the data as json

Create a script to export the parsed data as json. Include the
annotations for the system call arguments, since they are helpful to
downstream uses.

Sponsored by:		Netflix
Reviewed by:		brooks
Differential Revision:	https://reviews.freebsd.org/D56408

1 files changed, 126 insertions, 0 deletions

diff --git a/sys/tools/syscalls/scripts/syscall_json.lua b/sys/tools/syscalls/scripts/syscall_json.lua
new file mode 100644
index 000000000000..a29510a9c4c9
--- /dev/null
+++ b/sys/tools/syscalls/scripts/syscall_json.lua
@@ -0,0 +1,126 @@
+#!/usr/libexec/flua
+--
+-- SPDX-License-Identifier: BSD-2-Clause
+--
+-- Copyright (c) 2026 Warner Losh <imp@bsdimp.com>
+--
+
+-- Setup to be a module, or ran as its own script.
+local syscall_json = {}
+local script = not pcall(debug.getlocal, 4, 1)	-- TRUE if script.
+if script then
+	-- Add library root to the package path.
+	local path = arg[0]:gsub("/[^/]+.lua$", "")
+	package.path = package.path .. ";" .. path .. "/../?.lua"
+end
+
+local FreeBSDSyscall = require("core.freebsd-syscall")
+local ucl = require("ucl")
+
+-- Convert the type flags set (table with flag=true entries) to a sorted list.
+local function flagsToList(typetbl)
+	local flags = {}
+	for k, _ in pairs(typetbl) do
+		table.insert(flags, k)
+	end
+	table.sort(flags)
+	return flags
+end
+
+-- Convert a single syscall object to a plain table suitable for JSON export.
+-- Much of the data is available only as a method call.
+local function syscallToTable(v)
+	local entry = {
+		num = v.num,
+		name = v.name or "",
+		alias = v.alias or "",
+		audit = v.audit or "",
+		flags = flagsToList(v.type),
+		compat_level = v:compatLevel(),
+		compat_prefix = v:compatPrefix(),
+		symbol = v:symbol(),
+		rettype = v.rettype or "int",
+		cap = v.cap or "0",
+		thr = v.thr or "SY_THR_STATIC",
+		changes_abi = v.changes_abi or false,
+		noproto = v.noproto or false,
+		args_size = v.args_size or "0",
+		arg_alias = v.arg_alias or "",
+	}
+
+	-- Export arguments with annotations.
+	local args = {}
+	if v.args ~= nil then
+		for _, a in ipairs(v.args) do
+			arg = {
+				type = a.type,
+				name = a.name,
+			}
+			if a.annotation ~= nil and a.annotation ~= "" then
+				arg.annotation = a.annotation
+			end
+			table.insert(args, arg)
+		end
+	end
+	entry.args = args
+
+	-- Export altname/alttag/rettype if present (loadable syscalls).
+	if v.altname ~= nil then
+		entry.altname = v.altname
+	end
+	if v.alttag ~= nil then
+		entry.alttag = v.alttag
+	end
+
+	return entry
+end
+
+function syscall_json.generate(tbl, config)
+	-- Build the syscalls array.
+	local syscalls = {}
+	for _, v in pairs(tbl.syscalls) do
+		table.insert(syscalls, syscallToTable(v))
+	end
+
+	-- Build the structs data into a nicer structure
+	local structs = {}
+	if tbl.structs ~= nil then
+		for k, _ in pairs(tbl.structs) do
+			table.insert(structs, k)
+		end
+		table.sort(structs)
+	end
+
+	local root = {
+		syscalls = syscalls,
+		structs = structs,
+	}
+
+	local json = ucl.to_json(root)
+
+	-- Write to stdout.
+	io.write(json)
+	io.write("\n")
+end
+
+-- Entry of script:
+if script then
+	local config = require("config")
+
+	if #arg < 1 or #arg > 2 then
+		error("usage: " .. arg[0] .. " syscall.master [config]")
+	end
+
+	local sysfile, configfile = arg[1], arg[2]
+
+	config.merge(configfile)
+	config.mergeCompat()
+
+	-- The parsed system call table.
+	local tbl = FreeBSDSyscall:new{sysfile = sysfile, config = config}
+
+	syscall_json.generate(tbl, config)
+end
+
+-- Return the module.
+return syscall_json