spectre-meltdown-checker/spectre-meltdown-checker.sh

#! /bin/sh
# Spectre & Meltdown checker
#
# Check for the latest version at:
# https://github.com/speed47/spectre-meltdown-checker
# git clone https://github.com/speed47/spectre-meltdown-checker.git
# or wget https://raw.githubusercontent.com/speed47/spectre-meltdown-checker/master/spectre-meltdown-checker.sh
#
# Stephane Lesimple
#
VERSION='0.34+'

show_usage()
{
	# shellcheck disable=SC2086
	cat <<EOF
	Usage:
		Live mode:    $(basename $0) [options] [--live]
		Offline mode: $(basename $0) [options] [--kernel <vmlinux_file>] [--config <kernel_config>] [--map <kernel_map_file>]

	Modes:
		Two modes are available.

		First mode is the "live" mode (default), it does its best to find information about the currently running kernel.
		To run under this mode, just start the script without any option (you can also use --live explicitly)

		Second mode is the "offline" mode, where you can inspect a non-running kernel.
		You'll need to specify the location of the vmlinux file, config and System.map files:

		--kernel vmlinux_file		Specify a (possibly compressed) vmlinux file
		--config kernel_config		Specify a kernel config file
		--map	 kernel_map_file	Specify a kernel System.map file

	Options:
		--no-color			Don't use color codes
		--verbose, -v			Increase verbosity level
		--no-sysfs			Don't use the /sys interface even if present
		--sysfs-only			Only use the /sys interface, don't run our own checks
		--coreos			Special mode for CoreOS (use an ephemeral toolbox to inspect kernel)
		--batch text			Produce machine readable output, this is the default if --batch is specified alone
		--batch json			Produce JSON output formatted for Puppet, Ansible, Chef...
		--batch nrpe			Produce machine readable output formatted for NRPE
		--variant [1,2,3]		Specify which variant you'd like to check, by default all variants are checked
						Can be specified multiple times (e.g. --variant 2 --variant 3)

	Return codes:
		0 (not vulnerable), 2 (vulnerable), 3 (unknown), 255 (error)

	IMPORTANT:
	A false sense of security is worse than no security at all.
	Please use the --disclaimer option to understand exactly what this script does.

EOF
}

show_disclaimer()
{
	cat <<EOF
Disclaimer:

This tool does its best to determine whether your system is immune (or has proper mitigations in place) for the
collectively named "speculative execution" vulnerabilities. It doesn't attempt to run any kind of exploit, and can't guarantee
that your system is secure, but rather helps you verifying whether your system has the known correct mitigations in place.
However, some mitigations could also exist in your kernel that this script doesn't know (yet) how to detect, or it might
falsely detect mitigations that in the end don't work as expected (for example, on backported or modified kernels).

Your system exposure also depends on your CPU. As of now, AMD and ARM processors are marked as immune to some or all of these
vulnerabilities (except some specific ARM models). All Intel processors manufactured since circa 1995 are thought to be vulnerable,
except some specific/old models, such as some early Atoms. Whatever processor one uses, one might seek more information
from the manufacturer of that processor and/or of the device in which it runs.

The nature of the discovered vulnerabilities being quite new, the landscape of vulnerable processors can be expected
to change over time, which is why this script makes the assumption that all CPUs are vulnerable, except if the manufacturer
explicitly stated otherwise in a verifiable public announcement.

Please also note that for Spectre vulnerabilities, all software can possibly be exploited, this tool only verifies that the
kernel (which is the core of the system) you're using has the proper protections in place. Verifying all the other software
is out of the scope of this tool. As a general measure, ensure you always have the most up to date stable versions of all
the softwares you use, especially for those who are exposed to the world, such as network daemons and browsers.

This tool has been released in the hope that it'll be useful, but don't use it to jump to conclusions about your security.

EOF
}

# parse options
opt_kernel=''
opt_config=''
opt_map=''
opt_live_explicit=0
opt_live=1
opt_no_color=0
opt_batch=0
opt_batch_format="text"
opt_verbose=1
opt_variant1=0
opt_variant2=0
opt_variant3=0
opt_allvariants=1
opt_no_sysfs=0
opt_sysfs_only=0
opt_coreos=0

global_critical=0
global_unknown=0
nrpe_vuln=""

# find a sane `echo` command
# we'll try to avoid using shell builtins that might not take options
if which echo >/dev/null 2>&1; then
	echo_cmd=$(which echo)
else
	[ -x /bin/echo        ] && echo_cmd=/bin/echo
	[ -x /system/bin/echo ] && echo_cmd=/system/bin/echo
fi
# still empty ? fallback to builtin
[ -z "$echo_cmd" ] && echo_cmd=echo
__echo()
{
	opt="$1"
	shift
	_msg="$*"

	if [ "$opt_no_color" = 1 ] ; then
		# strip ANSI color codes
		# some sed versions (i.e. toybox) can't seem to handle
		# \033 aka \x1B correctly, so do it for them.
		_ctrlchar=$($echo_cmd -e "\033")
		_msg=$($echo_cmd -e "$_msg" | sed -r "s/$_ctrlchar\[([0-9][0-9]?(;[0-9][0-9]?)?)?m//g")
	fi
	# shellcheck disable=SC2086
	$echo_cmd $opt -e "$_msg"
}

_echo()
{
	if [ "$opt_verbose" -ge "$1" ]; then
		shift
		__echo '' "$*"
	fi
}

_echo_nol()
{
	if [ "$opt_verbose" -ge "$1" ]; then
		shift
		__echo -n "$*"
	fi
}

_warn()
{
	_echo 0 "\033[31m$*\033[0m" >&2
}

_info()
{
	_echo 1 "$*"
}

_info_nol()
{
	_echo_nol 1 "$*"
}

_verbose()
{
	_echo 2 "$*"
}

_verbose_nol()
{
	_echo_nol 2 "$*"
}

_debug()
{
	_echo 3 "\033[34m(debug) $*\033[0m"
}

is_cpu_vulnerable_cached=0
_is_cpu_vulnerable_cached()
{
	# shellcheck disable=SC2086
	[ "$1" = 1 ] && return $variant1
	# shellcheck disable=SC2086
	[ "$1" = 2 ] && return $variant2
	# shellcheck disable=SC2086
	[ "$1" = 3 ] && return $variant3
	echo "$0: error: invalid variant '$1' passed to is_cpu_vulnerable()" >&2
	exit 255
}

is_cpu_vulnerable()
{
	# param: 1, 2 or 3 (variant)
	# returns 0 if vulnerable, 1 if not vulnerable
	# (note that in shell, a return of 0 is success)
	# by default, everything is vulnerable, we work in a "whitelist" logic here.
	# usage: is_cpu_vulnerable 2 && do something if vulnerable
	if [ "$is_cpu_vulnerable_cached" = 1 ]; then
		_is_cpu_vulnerable_cached "$1"
		return $?
	fi

	variant1=''
	variant2=''
	variant3=''

	if is_cpu_specex_free; then
		variant1=immune
		variant2=immune
		variant3=immune
	elif [ "$cpu_vendor" = GenuineIntel ]; then
		# Intel
		# https://github.com/crozone/SpectrePoC/issues/1 ^F E5200 => spectre 2 not vulnerable
		# https://github.com/paboldin/meltdown-exploit/issues/19 ^F E5200 => meltdown vulnerable
		# model name : Pentium(R) Dual-Core  CPU      E5200  @ 2.50GHz
		if grep -qE '^model name.+ Pentium\(R\) Dual-Core[[:space:]]+CPU[[:space:]]+E[0-9]{4}K? ' /proc/cpuinfo; then
			variant1=vuln
			[ -z "$variant2" ] && variant2=immune
			variant3=vuln
		fi
		if [ "$capabilities_rdcl_no" = 1 ]; then
			# capability bit for future Intel processor that will explicitly state
			# that they're not vulnerable to Meltdown
			# this var is set in check_cpu()
			variant3=immune
			_debug "is_cpu_vulnerable: RDCL_NO is set so not vuln to meltdown"
		fi
	elif [ "$cpu_vendor" = AuthenticAMD ]; then
		# AMD revised their statement about variant2 => vulnerable
		# https://www.amd.com/en/corporate/speculative-execution
		variant1=vuln
		variant2=vuln
		[ -z "$variant3" ] && variant3=immune
	elif [ "$cpu_vendor" = ARM ]; then
		# ARM
		# reference: https://developer.arm.com/support/security-update
		# some devices (phones or other) have several ARMs and as such different part numbers,
		# an example is "bigLITTLE". we shouldn't rely on the first CPU only, so we check the whole list
		i=0
		for cpupart in $cpu_part_list
		do
			i=$(( i + 1 ))
			# do NOT quote $cpu_arch_list below
			# shellcheck disable=SC2086
			cpuarch=$(echo $cpu_arch_list | awk '{ print $'$i' }')
			_debug "checking cpu$i: <$cpupart> <$cpuarch>"
			# some kernels report AArch64 instead of 8
			[ "$cpuarch" = "AArch64" ] && cpuarch=8
			if [ -n "$cpupart" ] && [ -n "$cpuarch" ]; then
				# Cortex-R7 and Cortex-R8 are real-time and only used in medical devices or such
				# I can't find their CPU part number, but it's probably not that useful anyway
				# model R7 R8 A9    A15   A17   A57   A72    A73    A75
				# part   ?  ? 0xc09 0xc0f 0xc0e 0xd07 0xd08  0xd09  0xd0a
				# arch  7? 7? 7     7     7     8     8      8      8
				#
				# variant 1 & variant 2
				if [ "$cpuarch" = 7 ] && echo "$cpupart" | grep -Eq '^0x(c09|c0f|c0e)$'; then
					# armv7 vulnerable chips
					_debug "checking cpu$i: this armv7 vulnerable to spectre 1 & 2"
					variant1=vuln
					variant2=vuln
				elif [ "$cpuarch" = 8 ] && echo "$cpupart" | grep -Eq '^0x(d07|d08|d09|d0a)$'; then
					# armv8 vulnerable chips
					_debug "checking cpu$i: this armv8 vulnerable to spectre 1 & 2"
					variant1=vuln
					variant2=vuln
				else
					_debug "checking cpu$i: this arm non vulnerable to 1 & 2"
					# others are not vulnerable
					[ -z "$variant1" ] && variant1=immune
					[ -z "$variant2" ] && variant2=immune
				fi

				# for variant3, only A75 is vulnerable
				if [ "$cpuarch" = 8 ] && [ "$cpupart" = 0xd0a ]; then
					_debug "checking cpu$i: arm A75 vulnerable to meltdown"
					variant3=vuln
				else
					_debug "checking cpu$i: this arm non vulnerable to meltdown"
					[ -z "$variant3" ] && variant3=immune
				fi
			fi
			_debug "is_cpu_vulnerable: for cpu$i and so far, we have <$variant1> <$variant2> <$variant3>"
		done
	fi
	_debug "is_cpu_vulnerable: temp results are <$variant1> <$variant2> <$variant3>"
	# if at least one of the cpu is vulnerable, then the system is vulnerable
	[ "$variant1" = "immune" ] && variant1=1 || variant1=0
	[ "$variant2" = "immune" ] && variant2=1 || variant2=0
	[ "$variant3" = "immune" ] && variant3=1 || variant3=0
	_debug "is_cpu_vulnerable: final results are <$variant1> <$variant2> <$variant3>"
	is_cpu_vulnerable_cached=1
	_is_cpu_vulnerable_cached "$1"
	return $?
}

is_cpu_specex_free()
{
	# return true (0) if the CPU doesn't do speculative execution, false (1) if it does.
	# if it's not in the list we know, return false (1).
	# source: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/x86/kernel/cpu/common.c#n882
	# { X86_VENDOR_INTEL,     6, INTEL_FAM6_ATOM_CEDARVIEW,   X86_FEATURE_ANY },
	# { X86_VENDOR_INTEL,     6, INTEL_FAM6_ATOM_CLOVERVIEW,  X86_FEATURE_ANY },
	# { X86_VENDOR_INTEL,     6, INTEL_FAM6_ATOM_LINCROFT,    X86_FEATURE_ANY },
	# { X86_VENDOR_INTEL,     6, INTEL_FAM6_ATOM_PENWELL,     X86_FEATURE_ANY },
	# { X86_VENDOR_INTEL,     6, INTEL_FAM6_ATOM_PINEVIEW,    X86_FEATURE_ANY },
	# { X86_VENDOR_CENTAUR,   5 },
	# { X86_VENDOR_INTEL,     5 },
	# { X86_VENDOR_NSC,       5 },
	# { X86_VENDOR_ANY,       4 },
	set -u
	if [ "$cpu_vendor" = GenuineIntel ]; then
		if [ "$cpu_family" = 6 ]; then
			if [ "$cpu_model" = "$INTEL_FAM6_ATOM_CEDARVIEW"  ]      || \
				[ "$cpu_model" = "$INTEL_FAM6_ATOM_CLOVERVIEW" ] || \
				[ "$cpu_model" = "$INTEL_FAM6_ATOM_LINCROFT"   ] || \
				[ "$cpu_model" = "$INTEL_FAM6_ATOM_PENWELL"    ] || \
				[ "$cpu_model" = "$INTEL_FAM6_ATOM_PINEVIEW"   ]; then
				set +u
				return 0
			fi
		elif [ "$cpu_family" = 5 ]; then
			set +u
			return 0
		fi
	fi
	set +u
	[ "$cpu_family" -eq 4 ] && return 0
	return 1
}

show_header()
{
	_info "\033[1;34mSpectre and Meltdown mitigation detection tool v$VERSION\033[0m"
	_info
}

parse_opt_file()
{
	# parse_opt_file option_name option_value
	option_name="$1"
	option_value="$2"
	if [ -z "$option_value" ]; then
		show_header
		show_usage
		echo "$0: error: --$option_name expects one parameter (a file)" >&2
		exit 1
	elif [ ! -e "$option_value" ]; then
		show_header
		echo "$0: error: couldn't find file $option_value" >&2
		exit 1
	elif [ ! -f "$option_value" ]; then
		show_header
		echo "$0: error: $option_value is not a file" >&2
		exit 1
	elif [ ! -r "$option_value" ]; then
		show_header
		echo "$0: error: couldn't read $option_value (are you root?)" >&2
		exit 1
	fi
	echo "$option_value"
	exit 0
}

while [ -n "$1" ]; do
	if [ "$1" = "--kernel" ]; then
		opt_kernel=$(parse_opt_file kernel "$2"); ret=$?
		[ $ret -ne 0 ] && exit 255
		shift 2
		opt_live=0
	elif [ "$1" = "--config" ]; then
		opt_config=$(parse_opt_file config "$2"); ret=$?
		[ $ret -ne 0 ] && exit 255
		shift 2
		opt_live=0
	elif [ "$1" = "--map" ]; then
		opt_map=$(parse_opt_file map "$2"); ret=$?
		[ $ret -ne 0 ] && exit 255
		shift 2
		opt_live=0
	elif [ "$1" = "--live" ]; then
		opt_live_explicit=1
		shift
	elif [ "$1" = "--no-color" ]; then
		opt_no_color=1
		shift
	elif [ "$1" = "--no-sysfs" ]; then
		opt_no_sysfs=1
		shift
	elif [ "$1" = "--sysfs-only" ]; then
		opt_sysfs_only=1
		shift
	elif [ "$1" = "--coreos" ]; then
		opt_coreos=1
		shift
	elif [ "$1" = "--coreos-within-toolbox" ]; then
		# don't use directly: used internally by --coreos
		opt_coreos=0
		shift
	elif [ "$1" = "--batch" ]; then
		opt_batch=1
		opt_verbose=0
		shift
		case "$1" in
			text|nrpe|json) opt_batch_format="$1"; shift;;
			--*) ;;    # allow subsequent flags
			'') ;;     # allow nothing at all
			*)
				echo "$0: error: unknown batch format '$1'" >&2
				echo "$0: error: --batch expects a format from: text, nrpe, json" >&2
				exit 255
				;;
		esac
	elif [ "$1" = "-v" ] || [ "$1" = "--verbose" ]; then
		opt_verbose=$(( opt_verbose + 1 ))
		shift
	elif [ "$1" = "--variant" ]; then
		if [ -z "$2" ]; then
			echo "$0: error: option --variant expects a parameter (1, 2 or 3)" >&2
			exit 255
		fi
		case "$2" in
			1) opt_variant1=1; opt_allvariants=0;;
			2) opt_variant2=1; opt_allvariants=0;;
			3) opt_variant3=1; opt_allvariants=0;;
			*)
				echo "$0: error: invalid parameter '$2' for --variant, expected either 1, 2 or 3" >&2;
				exit 255
				;;
		esac
		shift 2
	elif [ "$1" = "-h" ] || [ "$1" = "--help" ]; then
		show_header
		show_usage
		exit 0
	elif [ "$1" = "--version" ]; then
		opt_no_color=1
		show_header
		exit 0
	elif [ "$1" = "--disclaimer" ]; then
		show_header
		show_disclaimer
		exit 0
	else
		show_header
		show_usage
		echo "$0: error: unknown option '$1'"
		exit 255
	fi
done

show_header

if [ "$opt_no_sysfs" = 1 ] && [ "$opt_sysfs_only" = 1 ]; then
	_warn "Incompatible options specified (--no-sysfs and --sysfs-only), aborting"
	exit 255
fi

# print status function
pstatus()
{
	if [ "$opt_no_color" = 1 ]; then
		_info_nol "$2"
	else
		case "$1" in
			red)    col="\033[41m\033[30m";;
			green)  col="\033[42m\033[30m";;
			yellow) col="\033[43m\033[30m";;
			blue)   col="\033[44m\033[30m";;
			*)      col="";;
		esac
		_info_nol "$col $2 \033[0m"
	fi
	[ -n "$3" ] && _info_nol " ($3)"
	_info
}

# Print the final status of a vulnerability (incl. batch mode)
# Arguments are: CVE UNK/OK/VULN description
pvulnstatus()
{
	if [ "$opt_batch" = 1 ]; then
		case "$opt_batch_format" in
			text) _echo 0 "$1: $2 ($3)";;
			json)
				case "$1" in
					CVE-2017-5753) aka="SPECTRE VARIANT 1";;
					CVE-2017-5715) aka="SPECTRE VARIANT 2";;
					CVE-2017-5754) aka="MELTDOWN";;
				esac
				case "$2" in
					UNK)  is_vuln="null";;
					VULN) is_vuln="true";;
					OK)   is_vuln="false";;
				esac
				json_output="${json_output:-[}{\"NAME\":\"$aka\",\"CVE\":\"$1\",\"VULNERABLE\":$is_vuln,\"INFOS\":\"$3\"},"
				;;

			nrpe)	[ "$2" = VULN ] && nrpe_vuln="$nrpe_vuln $1";;
		esac
	fi

	# always fill global_* vars because we use that do decide the program exit code
	case "$2" in
		UNK)  global_unknown="1";;
		VULN) global_critical="1";;
	esac

	# display info if we're not in quiet/batch mode
	vulnstatus="$2"
	shift 2
	_info_nol "> \033[46m\033[30mSTATUS:\033[0m "
	case "$vulnstatus" in
		UNK)  pstatus yellow 'UNKNOWN'        "$@";;
		VULN) pstatus red    'VULNERABLE'     "$@";;
		OK)   pstatus green  'NOT VULNERABLE' "$@";;
	esac
}


# The 3 below functions are taken from the extract-linux script, available here:
# https://github.com/torvalds/linux/blob/master/scripts/extract-vmlinux
# The functions have been modified for better integration to this script
# The original header of the file has been retained below

# ----------------------------------------------------------------------
# extract-vmlinux - Extract uncompressed vmlinux from a kernel image
#
# Inspired from extract-ikconfig
# (c) 2009,2010 Dick Streefland <dick@streefland.net>
#
# (c) 2011      Corentin Chary <corentin.chary@gmail.com>
#
# Licensed under the GNU General Public License, version 2 (GPLv2).
# ----------------------------------------------------------------------

vmlinux=''
vmlinux_err=''
check_vmlinux()
{
	readelf -h "$1" >/dev/null 2>&1 && return 0
	return 1
}

try_decompress()
{
	# The obscure use of the "tr" filter is to work around older versions of
	# "grep" that report the byte offset of the line instead of the pattern.

	# Try to find the header ($1) and decompress from here
	for     pos in $(tr "$1\n$2" "\n$2=" < "$6" | grep -abo "^$2")
	do
		_debug "try_decompress: magic for $3 found at offset $pos"
		if ! which "$3" >/dev/null 2>&1; then
			vmlinux_err="missing '$3' tool, please install it, usually it's in the '$5' package"
			return 0
		fi
		pos=${pos%%:*}
		# shellcheck disable=SC2086
		tail -c+$pos "$6" 2>/dev/null | $3 $4 > "$vmlinuxtmp" 2>/dev/null
		if check_vmlinux "$vmlinuxtmp"; then
			vmlinux="$vmlinuxtmp"
			_debug "try_decompress: decompressed with $3 successfully!"
			return 0
		else
			_debug "try_decompress: decompression with $3 did not work"
		fi
	done
	return 1
}

extract_vmlinux()
{
	[ -n "$1" ] || return 1
	# Prepare temp files:
	vmlinuxtmp="$(mktemp /tmp/vmlinux-XXXXXX)"
	# single quotes in trap cmd: will be expanded when signalled
	trap 'rm -f $vmlinuxtmp' EXIT INT

	# Initial attempt for uncompressed images or objects:
	if check_vmlinux "$1"; then
		cat "$1" > "$vmlinuxtmp"
		vmlinux=$vmlinuxtmp
		return 0
	fi

	# That didn't work, so retry after decompression.
	try_decompress '\037\213\010'     xy    gunzip  ''      gunzip      "$1" && return 0
	try_decompress '\3757zXZ\000'     abcde unxz    ''      xz-utils    "$1" && return 0
	try_decompress 'BZh'              xy    bunzip2 ''      bzip2       "$1" && return 0
	try_decompress '\135\0\0\0'       xxx   unlzma  ''      xz-utils    "$1" && return 0
	try_decompress '\211\114\132'     xy    'lzop'  '-d'    lzop        "$1" && return 0
	try_decompress '\002\041\114\030' xyy   'lz4'   '-d -l' liblz4-tool "$1" && return 0
	return 1
}

# end of extract-vmlinux functions

mount_debugfs()
{
	if [ ! -e /sys/kernel/debug/sched_features ]; then
		# try to mount the debugfs hierarchy ourselves and remember it to umount afterwards
		mount -t debugfs debugfs /sys/kernel/debug 2>/dev/null && mounted_debugfs=1
	fi
}

umount_debugfs()
{
	if [ "$mounted_debugfs" = 1 ]; then
		# umount debugfs if we did mount it ourselves
		umount /sys/kernel/debug
	fi
}

load_msr()
{
	modprobe msr 2>/dev/null && insmod_msr=1
	_debug "attempted to load module msr, insmod_msr=$insmod_msr"
}

unload_msr()
{
	if [ "$insmod_msr" = 1 ]; then
		# if we used modprobe ourselves, rmmod the module
		rmmod msr 2>/dev/null
		_debug "attempted to unload module msr, ret=$?"
	fi
}

load_cpuid()
{
	modprobe cpuid 2>/dev/null && insmod_cpuid=1
	_debug "attempted to load module cpuid, insmod_cpuid=$insmod_cpuid"
}

unload_cpuid()
{
	if [ "$insmod_cpuid" = 1 ]; then
		# if we used modprobe ourselves, rmmod the module
		rmmod cpuid 2>/dev/null
		_debug "attempted to unload module cpuid, ret=$?"
	fi
}

read_cpuid()
{
	_leaf="$1"
	_bytenum="$2"
	_and_operand="$3"

	if [ ! -e /dev/cpu/0/cpuid ]; then
		# try to load the module ourselves (and remember it so we can rmmod it afterwards)
		load_cpuid
	fi
	if [ ! -e /dev/cpu/0/cpuid ]; then
		return 2
	fi

	if [ "$opt_verbose" -ge 3 ]; then
		dd if=/dev/cpu/0/cpuid bs=16 skip="$_leaf" iflag=skip_bytes count=1 >/dev/null 2>/dev/null
		_debug "cpuid: reading leaf$_leaf of cpuid on cpu0, ret=$?"
		_debug "cpuid: leaf$_leaf eax-ebx-ecx-edx: $(   dd if=/dev/cpu/0/cpuid bs=16 skip="$_leaf" iflag=skip_bytes count=1 2>/dev/null | od -x -A n)"
		_debug "cpuid: leaf$_leaf edx higher byte is: $(dd if=/dev/cpu/0/cpuid bs=16 skip="$_leaf" iflag=skip_bytes count=1 2>/dev/null | dd bs=1 skip="$_bytenum" count=1 2>/dev/null | od -x -A n)"
	fi
	# getting proper byte of edx on leaf$_leaf of cpuinfo in decimal
	_reg_byte=$(dd if=/dev/cpu/0/cpuid bs=16 skip="$_leaf" iflag=skip_bytes count=1 2>/dev/null | dd bs=1 skip="$_bytenum" count=1 2>/dev/null | od -t u1 -A n | awk '{print $1}')
	_debug "cpuid: leaf$_leaf byte $_bytenum: $_reg_byte (decimal)"
	_reg_bit=$(( _reg_byte & _and_operand ))
	_debug "cpuid: leaf$_leaf byte $_bytenum & $_and_operand = $_reg_bit"
	[ "$_reg_bit" -eq 0 ] && return 1
	# $_reg_bit is > 0, so the bit was found: return true (aka 0)
	return 0
}

dmesg_grep()
{
	# grep for something in dmesg, ensuring that the dmesg buffer
	# has not been truncated
	dmesg_grepped=''
	if ! dmesg | grep -qE '(^|\] )Linux version [0-9]'; then
		# dmesg truncated
		return 2
	fi
	dmesg_grepped=$(dmesg | grep -E "$1" | head -1)
	# not found:
	[ -z "$dmesg_grepped" ] && return 1
	# found, output is in $dmesg_grepped
	return 0
}

is_coreos()
{
	which coreos-install >/dev/null 2>&1 && which toolbox >/dev/null 2>&1 && return 0
	return 1
}

parse_cpu_details()
{
	cpu_vendor=$(  grep '^vendor_id'  /proc/cpuinfo | awk '{print $3}' | head -1)
	cpu_friendly_name=$(grep '^model name' /proc/cpuinfo | cut -d: -f2- | head -1 | sed -e 's/^ *//')
	# special case for ARM follows
	if grep -qi 'CPU implementer[[:space:]]*:[[:space:]]*0x41' /proc/cpuinfo; then
		cpu_vendor='ARM'
		# some devices (phones or other) have several ARMs and as such different part numbers,
		# an example is "bigLITTLE", so we need to store the whole list, this is needed for is_cpu_vulnerable
		cpu_part_list=$(awk '/CPU part/         {print $4}' /proc/cpuinfo)
		cpu_arch_list=$(awk '/CPU architecture/ {print $3}' /proc/cpuinfo)
		# take the first one to fill the friendly name, do NOT quote the vars below
		# shellcheck disable=SC2086
		cpu_arch=$(echo $cpu_arch_list | awk '{ print $1 }')
		# shellcheck disable=SC2086
		cpu_part=$(echo $cpu_part_list | awk '{ print $1 }')
		[ "$cpu_arch" = "AArch64" ] && cpu_arch=8
		cpu_friendly_name="ARM"
		[ -n "$cpu_arch" ] && cpu_friendly_name="$cpu_friendly_name v$cpu_arch"
		[ -n "$cpu_part" ] && cpu_friendly_name="$cpu_friendly_name model $cpu_part"
	fi

	cpu_family=$(  grep '^cpu family' /proc/cpuinfo | awk '{print $4}' | grep -E '^[0-9]+$' | head -1)
	cpu_model=$(   grep '^model'      /proc/cpuinfo | awk '{print $3}' | grep -E '^[0-9]+$' | head -1)
	cpu_stepping=$(grep '^stepping'   /proc/cpuinfo | awk '{print $3}' | grep -E '^[0-9]+$' | head -1)
	cpu_ucode=$(  grep '^microcode'   /proc/cpuinfo | awk '{print $3}' | head -1)

	# also define those that we will need in other funcs
	# taken from ttps://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/x86/include/asm/intel-family.h
	# shellcheck disable=SC2034
	{
	INTEL_FAM6_CORE_YONAH=$(( 0x0E ))

	INTEL_FAM6_CORE2_MEROM=$(( 0x0F ))
	INTEL_FAM6_CORE2_MEROM_L=$(( 0x16 ))
	INTEL_FAM6_CORE2_PENRYN=$(( 0x17 ))
	INTEL_FAM6_CORE2_DUNNINGTON=$(( 0x1D ))

	INTEL_FAM6_NEHALEM=$(( 0x1E ))
	INTEL_FAM6_NEHALEM_G=$(( 0x1F ))
	INTEL_FAM6_NEHALEM_EP=$(( 0x1A ))
	INTEL_FAM6_NEHALEM_EX=$(( 0x2E ))

	INTEL_FAM6_WESTMERE=$(( 0x25 ))
	INTEL_FAM6_WESTMERE_EP=$(( 0x2C ))
	INTEL_FAM6_WESTMERE_EX=$(( 0x2F ))

	INTEL_FAM6_SANDYBRIDGE=$(( 0x2A ))
	INTEL_FAM6_SANDYBRIDGE_X=$(( 0x2D ))
	INTEL_FAM6_IVYBRIDGE=$(( 0x3A ))
	INTEL_FAM6_IVYBRIDGE_X=$(( 0x3E ))

	INTEL_FAM6_HASWELL_CORE=$(( 0x3C ))
	INTEL_FAM6_HASWELL_X=$(( 0x3F ))
	INTEL_FAM6_HASWELL_ULT=$(( 0x45 ))
	INTEL_FAM6_HASWELL_GT3E=$(( 0x46 ))

	INTEL_FAM6_BROADWELL_CORE=$(( 0x3D ))
	INTEL_FAM6_BROADWELL_GT3E=$(( 0x47 ))
	INTEL_FAM6_BROADWELL_X=$(( 0x4F ))
	INTEL_FAM6_BROADWELL_XEON_D=$(( 0x56 ))

	INTEL_FAM6_SKYLAKE_MOBILE=$(( 0x4E ))
	INTEL_FAM6_SKYLAKE_DESKTOP=$(( 0x5E ))
	INTEL_FAM6_SKYLAKE_X=$(( 0x55 ))
	INTEL_FAM6_KABYLAKE_MOBILE=$(( 0x8E ))
	INTEL_FAM6_KABYLAKE_DESKTOP=$(( 0x9E ))

	# /* "Small Core" Processors (Atom) */

	INTEL_FAM6_ATOM_PINEVIEW=$(( 0x1C ))
	INTEL_FAM6_ATOM_LINCROFT=$(( 0x26 ))
	INTEL_FAM6_ATOM_PENWELL=$(( 0x27 ))
	INTEL_FAM6_ATOM_CLOVERVIEW=$(( 0x35 ))
	INTEL_FAM6_ATOM_CEDARVIEW=$(( 0x36 ))