nimd/src/main.nim

# Copyright 2021 Mattia Giambirtone & All Contributors
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#    http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
import parseopt
import strformat
import posix
import os


import util/[logging, constants, mount]


proc sleepSeconds(amount: SomeInteger) = sleep(amount * 1000)


proc handleControlC {.noconv.} =
    getDefaultLogger().warning("Main process received SIGINT: exiting")  # TODO: Call exit point
    quit(0)


proc mainLoop(logger: Logger) =
    ## NimD's main execution loop
    try:
        logger.info("Reading disk entries from /etc/fstab")
        for entry in parseFileSystemTable(readFile("/etc/fstab")):
            logger.debug(&"Mounting filesystem {entry.source} of type {entry.filesystemtype} at {entry.target} with mountflags {entry.mountflags} and mount options {entry.data}")
            logger.trace("Calling mount()")
            var retcode = mount(entry.source, entry.target, entry.filesystemtype, entry.mountflags, entry.data)
            logger.trace(&"mount() returned {retcode}")
            if retcode == -1:
                logger.warning(&"Mounting disk {entry.source} has failed with error {posix.errno}: {posix.strerror(posix.errno)}")
            else:
                logger.debug(&"Mounted {entry.source} at {entry.target}")
            posix.errno = cint(0)
    except IndexDefect:
        logger.fatal("Improperly formatted /etc/fstab, exiting")
        quit(131)
    logger.info("Disks mounted")
    while true:
        logger.info("NimD is running")
        sleepSeconds(5)


proc main(logger: Logger) = 
    ## NimD entry point
    logger.debug("Starting NimD: A minimal, self-contained dependency-based Linux init system written in Nim")
    logger.info(&"NimD version {NimdVersion.major}.{NimdVersion.minor}.{NimdVersion.patch} is starting up...")
    logger.trace("Calling getCurrentProcessId()")
    let pid = getCurrentProcessId()
    logger.trace(&"getCurrentProcessId() returned {pid}")
    if pid != 1:
        logger.warning(&"Expecting to run as PID 1, but current process ID is {pid}")
    logger.trace("Calling getuid()")
    let uid = posix.getuid()
    logger.trace(&"getuid() returned {uid}")
    if uid != 0:
        logger.fatal(&"NimD must run as root, but current user id is {uid}")
        quit(EPERM)   # EPERM - Operation not permitted
    logger.debug("Starting uninterruptible mainloop")
    mainLoop(logger)


when isMainModule:
    setControlCHook(handleControlC)
    var logger = getDefaultLogger()
    var optParser = initOptParser(commandLineParams())
    for kind, key, value in optParser.getopt():
        case kind:
            of cmdArgument:
                discard
            of cmdLongOption:
                case key:
                    of "help":
                        echo helpMessage
                        quit(0)
                    of "version":
                        echo &"NimD version {NimdVersion.major}.{NimdVersion.minor}.{NimdVersion.patch} ({CompileDate}, {CompileTime}, {hostOS}, {hostCPU}) compiled with Nim {NimVersion}"
                        quit(0)
                    of "verbose":
                        logger.setLevel(LogLevel.Debug)
                    of "extra":
                        logger.setLevel(LogLevel.Trace)
                    else:
                        logger.error(&"Unkown command-line long option '{key}'")
                        quit(EINVAL)  # EINVAL - Invalid argument
            of cmdShortOption:
                case key:
                    of "h":
                        echo helpMessage
                        quit(0)
                    of "v":
                        echo &"NimD version {NimdVersion.major}.{NimdVersion.minor}.{NimdVersion.patch} ({CompileDate}, {CompileTime}, {hostOS}, {hostCPU}) compiled with Nim {NimVersion}"
                        quit(0)
                    of "V":
                        logger.setLevel(LogLevel.Debug)
                    of "X":
                        logger.setLevel(LogLevel.Trace)
                    else:
                        logger.error(&"Unkown command-line short option '{key}'")
                        quit(EINVAL) # EINVAL - Invalid argument
            else:
                echo "Usage: nimd [options]"
                quit(EINVAL) # EINVAL - Invalid argument
    logger.debug("Calling NimD entry point")
    try:
        main(logger)
    except:
        logger.fatal(&"A fatal unrecoverable error has occurred during startup and NimD cannot continue: {getCurrentExceptionMsg()}")
        quit(131)  # ENOTRECOVERABLE - State not recoverable
        # This will almost certainly cause the kernel to crash with an error the likes of "Kernel not syncing, attempted to kill init!",
        # but, after all, there isn't much we can do if we can't even initialize *ourselves* is there?