Mike Gerwitz

Activist for User Freedom

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+#!/bin/bash
+# Daemon for accepting TAME commands (compilers, linker, etc)
+#
+# Copyright (C) 2018 R-T Specialty, LLC.
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program. If not, see <http://www.gnu.org/licenses/>.
+##
+
+set -euo pipefail
+
+declare -r mypath=$( dirname "$( readlink -f "$0" )" )
+
+declare -ri EX_RUNNING=1
+declare -ri EX_USAGE=64 # incorrect usage; sysexits.h
+declare -ri EX_CANTCREAT=73 # cannot create file; sysexits.h
+
+# set by `main', global for `cleanup'
+declare root=
+
+
+# Create FIFOs for runner
+#
+# The FIFOs are intended to be attached to stderr and stdout
+# of the runner and will be created relative to the given
+# root path ROOT.
+#
+# If a FIFO cannot be created, exit with EX_CANTCREAT.
+mkfifos()
+{
+ local -r root="${1?Missing root path}"
+
+ mkdir -p "$root"
+
+ # note that there's no stderr; see `add-runner'
+ for n in 0 1; do
+ rm -f "$root-$n"
+
+ mkfifo -m 0600 "$root/$n" || {
+ echo "fatal: failed to create FIFO at $in"
+ exit $EX_CANTCREAT
+ }
+ done
+}
+
+
+# Spawn a runner
+#
+# A new runner is created by spawning dslc and attaching
+# new FIFOs under the given id ID relative to the given
+# run path ROOT. The PID of the runner will be stored
+# alongside the FIFOs in a pidfile `pid'.
+spawn-runner()
+{
+ local -ri id="${1?Missing id}"
+ local -r root="${2?Missing root run path}"
+
+ local -r base="$root/$id"
+
+ mkfifos "$base"
+
+ # TODO: should we separate back out std{out,err}?
+ # XXX: why does dslc quit (with a 0 exit code) occsionally? stdin?
+ while true; do
+ "$mypath/dslc" < <( persistent-cat "$base/0" ) \
+ >"$base/1" \
+ 2>&1
+ echo "warning: runner $id exited with code $?; restarting"
+ done &
+
+ echo "$!" > "$base/pid"
+
+ echo "runner $id ($!): $base"
+}
+
+
+# Persistently read commands from FIFO IN
+#
+# This will continue to read from the FIFO as long as it is
+# readable. This is necessary since SIGPIPE gets sent to
+# processes reading/writing from/to the FIFO whenever a
+# process detaches from it.
+persistent-cat()
+{
+ local -r in="${1?Missing input path}"
+
+ while test -r "$in"; do
+ read -r < "$in" || return
+ echo "$REPLY"
+ done
+}
+
+
+# Exit if tamed is already running at path ROOT
+#
+# If tamed is already running at ROOT, exit with status
+# EX_RUNNING; otherwise, do nothing except output a warning
+# if a stale pid file exists.
+abort-if-running()
+{
+ local -r root="${1?Missing root rundir}"
+
+ local -ri pid=$( cat "$root/pid" 2>/dev/null )
+
+ test "$pid" -gt 0 || return 0
+
+ ! ps "$pid" &>/dev/null || {
+ echo "fatal: tamed is already running at $root (pid $pid)!"
+ exit $EX_RUNNING
+ }
+
+ test -z "$pid" || {
+ echo "warning: clearing stale tamed (pid $pid)"
+ }
+}
+
+
+# Kill running tamed at path ROOT
+#
+# If no pidfile is found at ROOT, do nothing. This sends a
+# signal only to the parent tamed process, _not_ individual
+# runners; the target tamed is expected to clean up itself.
+# Consequently, if a tamed terminated abnormally without
+# cleaning up, this will not solve that problem.
+kill-running()
+{
+ local -r root="${1?Missing root}"
+
+ local -r pid=$( cat "$root"/pid 2>/dev/null )
+
+ test -n "$pid" || return 0
+
+ echo "killing tamed at $root ($pid)..."
+ kill "$pid"
+}
+
+
+# Clean up child processes before exit
+#
+# This should be called before exit (perhaps by a trap). Kills
+# the entire process group.
+#
+# Do not attach this to a SIGTERM trap or it will infinitely
+# recurse.
+cleanup()
+{
+ echo "killing remaining runners..."
+
+ rm -rf "$root"
+ kill 0
+}
+
+
+# Output usage information and exit
+usage()
+{
+ cat <<EOF
+Usage: $0 [--kill] [runpath]
+Start tamed and runners. Do not fork into background process.
+
+The default value of RUNPATH is \`/run/user/$UID/tamed'.
+
+Only one runner is currently supported.
+
+Options:
+ --kill kill a runing tamed at path RUNPATH
+ --help show this message
+EOF
+
+ exit $EX_USAGE
+}
+
+
+# Run tamed
+main()
+{
+ local kill=
+ case "${1:-}" in
+ --kill) kill=1; shift;;
+ --help) usage;;
+ esac
+
+ root="${1:-/run/user/$UID/tamed}"
+
+ # kill if requested
+ test -z "$kill" || {
+ kill-running "$root"
+ exit
+ }
+
+ abort-if-running "$root"
+
+ # clean up background processes before we exit
+ trap exit TERM
+ trap cleanup EXIT
+
+ # start fresh
+ rm -rf "$root"; mkdir -p "$root"
+ echo $$ > "$root/pid"
+
+ # only a single runner for now
+ spawn-runner 0 "$root"
+
+ wait -n
+}
+
+main "$@"