scripts: Add script to generate hypervisor configure options.

To avoid a proliferation of scripts and config files from specifying
different sets of hypervisor configuration options, this script must
be run to generate the correct set of options.

Each option group has been documented explaining why it has been
specified.

The script currently only supports qemu-based hypervisors.

Fixes #44.

Signed-off-by: James O. D. Hunt <james.o.hunt@intel.com>

scripts/README.md

@@ -0,0 +1,17 @@
+# Packaging scripts
+
+This directory contains useful packaging scripts.
+
+## `configure-hypervisor.sh`
+
+This script generates the official set of QEMU-based hypervisor build
+configuration options. All repositories that need to build a hypervisor
+from source **MUST** use this script to ensure the hypervisor is built
+in a known way since using a different set of options can impact many
+areas including performance, memory footprint and security.
+
+Example usage:
+
+```
+  $ configure-hypervisor.sh qemu-lite
+```

scripts/configure-hypervisor.sh

@@ -0,0 +1,301 @@
+#!/bin/bash
+
+# Copyright (c) 2017 Intel Corporation
+#
+# 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.
+
+#---------------------------------------------------------------------
+# Description: This script is the *ONLY* place where "qemu*" build options
+# should be defined.
+#
+# Note to maintainers:
+#
+# XXX: Every option group *MUST* be documented explaining why it has
+# been specified.
+#---------------------------------------------------------------------
+
+script_name=${0##*/}
+
+# Display message to stderr and exit indicating script failed.
+die()
+{
+    local msg="$*"
+    echo >&2 "$script_name: ERROR: $msg"
+    exit 1
+}
+
+# Display usage to stdout.
+usage()
+{
+cat <<EOT
+Overview:
+
+    Display configure options required to build the specified
+    hypervisor.
+
+Usage:
+
+    $script_name [options] <hypervisor-name>
+
+Options:
+
+    -m : Display options one per line (includes continuation characters).
+
+Example:
+
+    $ $script_name qemu-lite
+
+EOT
+}
+
+# Display an array to stdout.
+#
+# If 2 arguments are specified, split array across multiple lines,
+# one per element with a backslash at the end of all lines except
+# the last.
+#
+# Arguments:
+#
+# $1: *Name* of array variable (no leading '$'!!)
+# $2: any value (optional)
+show_array()
+{
+    local -n _array="$1"
+
+    local show_multi_line=no
+
+    [ -n "$2" ] && show_multi_line=yes
+
+    if [ "$show_multi_line" = no ]; then
+        echo "${_array[@]}"
+        return
+    fi
+
+    local -i size="${#_array[*]}"
+    local -i i=1
+    local suffix
+    local elem
+
+    for elem in "${_array[@]}"
+    do
+        if [ $i -eq $size ]
+        then
+            suffix=""
+        else
+            suffix=" \\"
+        fi
+
+        printf '%s%s\n' "$elem" "$suffix"
+        i+=1
+    done
+}
+
+# Entry point
+main()
+{
+    typeset -a qemu_options
+    multi_line=no
+
+    while getopts "hm" opt
+    do
+        case "$opt" in
+            h)
+                usage
+                exit 0
+                ;;
+
+            m)
+                multi_line="yes"
+                ;;
+        esac
+    done
+
+    shift $[$OPTIND-1]
+
+    [ -z "$1" ] && die "need hypervisor name"
+    hypervisor="$1"
+
+    #---------------------------------------------------------------------
+    # Disabled options
+
+    # bluetooth support not required
+    qemu_options+=(--disable-bluez)
+
+    # braille support not required
+    qemu_options+=(--disable-brlapi)
+
+    # Don't build documentation
+    qemu_options+=(--disable-docs)
+
+    # Disable GUI (graphics)
+    qemu_options+=(--disable-curses)
+    qemu_options+=(--disable-gtk)
+    qemu_options+=(--disable-opengl)
+    qemu_options+=(--disable-sdl)
+    qemu_options+=(--disable-spice)
+    qemu_options+=(--disable-vte)
+
+    # Disable graphical network access
+    qemu_options+=(--disable-vnc)
+    qemu_options+=(--disable-vnc-jpeg)
+    qemu_options+=(--disable-vnc-png)
+    qemu_options+=(--disable-vnc-sasl)
+
+    # Disable unused filesystem support
+    qemu_options+=(--disable-fdt)
+    qemu_options+=(--disable-glusterfs)
+    qemu_options+=(--disable-libiscsi)
+    qemu_options+=(--disable-libnfs)
+    qemu_options+=(--disable-libssh2)
+    qemu_options+=(--disable-rbd)
+
+    # Disable unused compression support
+    qemu_options+=(--disable-bzip2)
+    qemu_options+=(--disable-lzo)
+    qemu_options+=(--disable-snappy)
+
+    # SECURITY: Disable unused security options
+    qemu_options+=(--disable-seccomp)
+    qemu_options+=(--disable-tpm)
+
+    # Disable userspace network access ("-net user")
+    qemu_options+=(--disable-slirp)
+
+    # Disable USB
+    qemu_options+=(--disable-libusb)
+    qemu_options+=(--disable-usb-redir)
+
+    # SECURITY: Don't build a static binary (lowers security)
+    qemu_options+=(--disable-static)
+
+    # Not required as "-uuid ..." is always passed to the qemu binary
+    qemu_options+=(--disable-uuid)
+
+    # Disable debug
+    qemu_options+=(--disable-debug-tcg)
+    qemu_options+=(--disable-qom-cast-debug)
+    qemu_options+=(--disable-tcg-interpreter)
+    qemu_options+=(--disable-tcmalloc)
+
+    # SECURITY: Disallow network downloads
+    qemu_options+=(--disable-curl)
+
+    # Disable Remote Direct Memory Access (Live Migration)
+    # https://wiki.qemu.org/index.php/Features/RDMALiveMigration
+    qemu_options+=(--disable-rdma)
+
+    # Don't build the qemu-io, qemu-nbd and qemu-image tools
+    qemu_options+=(--disable-tools)
+
+    # Disable XEN driver
+    qemu_options+=(--disable-xen)
+
+    # FIXME: why is this disabled?
+    # (for reference, it's explicitly enabled in Ubuntu 17.10 and
+    # implicitly enabled in Fedora 27).
+    qemu_options+=(--disable-linux-aio)
+
+    # In "passthrough" security mode
+    # (-fsdev "...,security_model=passthrough,..."), qemu uses a helper
+    # application called virtfs-proxy-helper(1) to make certain 9p
+    # operations safer. We don't need that, so disable it (and it's
+    # dependencies).
+    qemu_options+=(--disable-virtfs)
+    qemu_options+=(--disable-attr)
+    qemu_options+=(--disable-cap-ng)
+
+    #---------------------------------------------------------------------
+    # Enabled options
+
+    # Enable kernel Virtual Machine support.
+    # This is the default, but be explicit to avoid any future surprises
+    qemu_options+=(--enable-kvm)
+
+    # Required for fast network access
+    qemu_options+=(--enable-vhost-net)
+
+    # Always strip binaries
+    qemu_options+=(--enable-strip)
+
+    #---------------------------------------------------------------------
+    # Other options
+
+    # 64-bit only
+    qemu_options+=(--target-list=x86_64-softmmu)
+
+    _qemu_cflags=""
+
+    # compile with high level of optimisation
+    _qemu_cflags+=" -O3"
+
+    # Improve code quality by assuming identical semantics for interposed
+    # synmbols.
+    _qemu_cflags+=" -fno-semantic-interposition"
+
+    # Performance optimisation
+    _qemu_cflags+=" -falign-functions=32"
+
+    # SECURITY: make the compiler check for common security issues
+    # (such as argument and buffer overflows checks).
+    _qemu_cflags+=" -D_FORTIFY_SOURCE=2"
+
+    # SECURITY: Create binary as a Position Independant Executable,
+    # and take advantage of ASLR, making ROP attacks much harder to perform.
+    # (https://wiki.debian.org/Hardening)
+    _qemu_cflags+=" -fPIE"
+
+    # Set compile options
+    qemu_options+=("--extra-cflags=\"${_qemu_cflags}\"")
+
+    unset _qemu_cflags
+
+    _qemu_ldflags=""
+
+    # SECURITY: Link binary as a Position Independant Executable,
+    # and take advantage of ASLR, making ROP attacks much harder to perform.
+    # (https://wiki.debian.org/Hardening)
+    _qemu_ldflags+=" -pie"
+
+    # SECURITY: Disallow executing code on the stack.
+    _qemu_ldflags+=" -z noexecstack"
+
+    # SECURITY: Make the linker set some program sections to read-only
+    # before the program is run to stop certain attacks.
+    _qemu_ldflags+=" -z relro"
+
+    # SECURITY: Make the linker resolve all symbols immediately on program
+    # load.
+    _qemu_ldflags+=" -z now"
+
+    qemu_options+=("--extra-ldflags=\"${_qemu_ldflags}\"")
+
+    unset _qemu_ldflags
+
+    # Where to install qemu libraries
+    qemu_options+=(--libdir=/usr/lib64/${hypervisor})
+
+    # Where to install qemu helper binaries
+    qemu_options+=(--libexecdir=/usr/libexec/${hypervisor})
+
+    # Where to install data files
+    qemu_options+=(--datadir=/usr/share/${hypervisor})
+
+    if [ "$multi_line" = yes ]
+    then
+        show_array qemu_options true
+    else
+        show_array qemu_options
+    fi
+}
+
+main $@