#!/usr/bin/lua

local posix = require 'posix'
local invoker = require 'invoker'

local g_pid = arg[1]
local g_range = arg[2]
local g_start, g_end = nil, nil

local function check_args()
	if type(g_pid) ~= "string" or string.len(g_pid) == 0 then
		io.stderr:write("Error, invalid PID specified.\n")
		io.stderr:flush()
		return false
	end
	local maps = string.format("/proc/%s/maps", g_pid)
	if not posix.access(maps) then
		io.stderr:write(string.format("Error, invalid PID specified: %s\n", g_pid))
		io.stderr:flush()
		return false
	end

	if type(g_range) ~= "string" then
		io.stderr:write("Error, invalid range specified.\n")
		io.stderr:flush()
		return false
	end

	local saddr, eaddr = string.match(g_range, "^(%x+)-(%x+)$")
	if type(saddr) ~= "string" or type(eaddr) ~= "string" then
		io.stderr:write(string.format("Error, invalid range specified: '%s'\n", g_range))
		io.stderr:flush()
		return false
	end

	g_start = saddr
	g_end = eaddr
	return true
end

local function dump_binary()
	local rexe = string.format("/proc/%s/exe", g_pid)
	rexe = invoker.readlink(rexe)
	if type(rexe) == "string" then
		local exer = string.match(rexe, "/([^/]+)$")
		if exer then rexe = exer else rexe = "unknown" end
	else
		rexe = "unknown"
	end
	local binfile = string.format("%s-%s-%s-%s.bin", rexe, g_pid, g_start, g_end)
	local cmds = { "gdb", "--nx", "--batch", "-ex", "set pagination off",
		"-ex", "set height 0", "-ex", "set width 0" }
	cmds[#cmds + 1] = "-ex"
	cmds[#cmds + 1] = string.format("attach %s", g_pid)
	cmds[#cmds + 1] = "-ex"
	cmds[#cmds + 1] = string.format("dump binary memory %s 0x%s 0x%s",
		binfile, g_start, g_end)
	cmds[#cmds + 1] = "-ex"
	cmds[#cmds + 1] = "detach"
	cmds[#cmds + 1] = "-ex"
	cmds[#cmds + 1] = "quit"

	io.stdout:write(string.format("Calling to write '%s' =>\n'%s'\n",
		binfile, table.concat(cmds, "' '")))
	io.stdout:flush()
	invoker.invoke(invoker.NOSTDIO, cmds)
	return true
end

if not check_args() then os.exit(1) end
dump_binary()
os.exit(0)