Commands for kexts

KextUtil.sh

#!/bin/bash
# joevt Feb 10, 2024

#10.4 Tiger to 10.13 High Sierra
kextload=kextload

# Later macOS versions
command -v kextutil > /dev/null && kextload=kextutil

getkextidentifier () {
	local thekextpath="$1"
	if [[ ! -f "$thekextpath/Contents/Info.plist" ]]; then
		echo "# Missing Info.plist." 1>&2
		return 1
	fi
	# Mac OS X 10.4 doesn't have PlistBuddy so just use perl
	perl -0777 -n -e 'if (m|<key>CFBundleIdentifier</key>\s*<string>(.+)</string>|) { print $1 }' "$thekextpath/Contents/Info.plist"
}

checkkext () {
	local thekextpath="$1"
	if [[ -d "$thekextpath" ]]; then
		if [[ -f "$thekextpath/Contents/Info.plist" ]]; then
			local kextname
			kextname="$(basename "$thekextpath")"
			if grep -q -E "\.kext$" <<< "$kextname"; then
				local kextidentifier=""
				kextidentifier="$(getkextidentifier "$thekextpath")"
				local theerr=$?
				if (( theerr == 0 )); then
					return 0
				else
					echo "# Missing CFBundleIdentifier." 1>&2
					return 1
				fi
			else
				echo "# \"$kextname\" not a kext." 1>&2
				return 1
			fi
		else
			echo "# Missing Info.plist." 1>&2
			return 1
		fi
	else
		echo "# Expected a kext package directory." 1>&2
		return 1
	fi
}

unloadkext () {
	local thekextpath="$1"
	checkkext "$thekextpath" || return 1
	local kextname
	kextname="$(basename "$thekextpath")"
	local kextidentifier
	kextidentifier="$(getkextidentifier "$thekextpath")"
	echo "# kextname: $kextname"
	echo "# kextidentifier: $kextidentifier"
	if ( kextstat 2> /dev/null | grep -q "$kextidentifier" ); then
		while : ; do
			echo "# Unloading ${kextname}."
			sudo kextunload -b "$kextidentifier"
			( kextstat 2> /dev/null | grep -q "$kextidentifier" ) || break
			sleep 1
		done
		echo "# Unloaded ${kextname}."
	else
		echo "# ${kextname} is not loaded."
	fi
}

checkkextpermissions () {
	local thekextpath="$1"
	checkkext "$thekextpath" || return 1
	badpermissions="$(find "$thekextpath" -exec ls -ld {} \; | sed -E '/drwxr-xr-x.* root *wheel /d ; /-rw.r-.r-..* root *wheel /d')"
	if (( $(printf "%s" "$badpermissions" | wc -l) == 0 )); then
		return 0
	fi
	echo "# Permissions are not correct for the following:" 1>&2
	echo "$badpermissions" 1>&2
	return 1
}

fixkextpermissions () {
	local thekextpath="$1"
	checkkext "$thekextpath" || return 1
	if checkkextpermissions "$thekextpath" 2> /dev/null ; then
		echo "# Permissions are good. No changes were required."
		return 0
	fi
	sudo chown -R root:wheel "$thekextpath"
	sudo find "$thekextpath" -type d -exec /bin/chmod 0755 {} \;
	sudo find "$thekextpath" -type f -exec /bin/chmod 0644 {} \;
	if checkkextpermissions "$thekextpath" 2> /dev/null ; then
		echo "# Fixed permissions."
		return 0
	fi
	echo "# Could not fix permissions." 1>&2
	return 1
}

loadkext () {
	local thekextpath="$1"
	checkkext "$thekextpath" || return 1
	local kextname
	kextname="$(basename "$thekextpath")"

	local kextloadpath
	if fixkextpermissions "$thekextpath" > /dev/null 2>&1 ; then
		kextloadpath="$thekextpath"
	else
		echo "# Cannot fix permissions. Will load kext from temporary directory." 1>&2
		local kexttmpdir
		kexttmpdir="$(mktemp -d /tmp/KextUtil_XXXXXXX)"
		kextloadpath="$kexttmpdir/$kextname"
		sudo cp -R "$thekextpath" "$kextloadpath"
		if ! fixkextpermissions "$kextloadpath" ; then
			return 1
		fi
	fi

	unloadkext "$kextloadpath"
	if ( sudo "$kextload" "$kextloadpath" ); then
		echo "# Loaded ${kextname}."
		return 0
	else
		echo "# $kextname was not loaded." 1>&2
		return 1
	fi
}

mountsystemrw () {
	mount | grep ' on / ' | grep -q 'read-only' && sudo mount -uw /
}

installkext () {
	local doload=0
	local dosystem=0
	while (( $# )); do
		if [[ "$1" == "-l" ]]; then
			doload=1
		elif [[ "$1" == "-s" ]]; then
			dosystem=1
		else
			break
		fi
		shift 1
	done

	local thekextpath="$1"
	checkkext "$thekextpath" || return 1

	local kextname
	kextname="$(basename "$thekextpath")"
	local kextinstalldir="/Library/Extensions"
	if ((dosystem)) || [[ ! -d /Library/Extensions ]] ; then
		kextinstalldir="/System/Library/Extensions"
		dosystem=1
	fi
	local kextidentifier
	kextidentifier="$(getkextidentifier "$thekextpath")"

	if ((doload)); then
		# unloadkext will do these echo lines for us:
		# echo "# kextname: $kextname"
		# echo "# kextidentifier: $kextidentifier"
		unloadkext "$thekextpath"
	else
		echo "# kextname: $kextname"
		echo "# kextidentifier: $kextidentifier"
	fi

	local kexttmpdir
	kexttmpdir="$(mktemp -d /tmp/KextUtil_XXXXXXX)"
	kextloadpath="$kexttmpdir/$kextname"
	sudo cp -R "$thekextpath" "$kextloadpath"
	if ! fixkextpermissions "$kextloadpath" ; then
		return 1
	fi

	if [[ -d "/System/Library/Extensions/$kextname" ]]; then
		mountsystemrw
		sudo rm -R "/System/Library/Extensions/$kextname"
	fi
	if [[ -d "/Library/Extensions/$kextname" ]]; then
		sudo rm -R "/Library/Extensions/$kextname"
	fi
	if ((dosystem)); then
		mountsystemrw
	fi
	sudo mv "$kextloadpath" "$kextinstalldir"
	echo "# Installed ${kextname}."
	if ((doload)); then
		sudo "$kextload" "$kextinstalldir/$kextname"
		kextstat 2> /dev/null | grep "$kextidentifier"
		echo "# Loaded ${kextname}."
	fi
}

removekext () {
	local thekextpath="$1"
	checkkext "$thekextpath" || return 1
	local kextname
	kextname="$(basename "$thekextpath")"
	if [[ "$thekextpath" == /System/Library/* ]] ; then
		mountsystemrw
	fi
	sudo rm -R "$thekextpath" && echo "# Removed ${kextname}." || echo "# Error removing ${kextname}."
}

rebuildkextcache () {
	sudo kextcache -i /
}

Usage

Load the commands into the terminal like this:
source KextUtil.sh

Utility Functions

These utility functions are used by the main functions listed below.

getkextidentifier kextpath

• Outputs the CFBundleIdentifier for the kext. This can be used to find the kext in kextstat or to unload the kext.

checkkext kextpath

• Returns status 0 if the kext is ok (it's a kext directory and contains an Info.plist that has a CFBundleIdentifier).
• Returns status 1 otherwise. The problem is output to stderr.
• All commands below will use checkkext before attempting to do anything.

checkkextpermissions kextpath

• Returns status 0 if the kext's permissions are ok.
• Returns status 1 otherwise. The problem files are listed to stderr.
• This is used by fixkextpermissions to see if the permissions need to be fixed.

fixkextpermissions kextpath

• Fixes the permissions of the files and directories of the kext.
• Returns status 0 if successful. It will report if the permissions were good already or if they were fixed.
• Returns status 1 otherwise.
• This is used by loadkext, unloadkext, and installkext.

Main Functions

loadkext kextpath

• Loads a kext.
• Returns status 0 if successful.
• Returns status 1 otherwise.
• Before loading, it will:

1. Fix permissions if necessary. If the permissions cannot be fixed (for example, when it is on a volume that ignores permissions), then the kext is copied to a temporary directory where the permissions can be fixed.
2. Unload previously loaded kext if necessary.

unloadkext kextpath

• Unloads the kext. It will report if the kext was not loaded in the first place. It will try to unload the kext once per second until it is unloaded. The kextpath is not necessarily the same version of the kext that was loaded. The CFBundleIdentifier is used to unload the kext.

installkext [-s] [-l] kextpath

• Installs a kext to /Library/Extensions. if -s is specified then the install location is /System/Library/Extensions. Do not use -s for Big Sur and later.
• Loads the kext if -l is specified. It will first unload previously loaded kext if necessary.
• Before installing the kext it will:

1. Copy the kext to a staging location (a temporary directory) so no changes are done to the original.
2. Fix permissions if necessary.
3. Remove kext of the same name from /System/Library/Extensions if it exists there. It will mount the root volume as read/write if necessary (works in the case of Catalina; for later macOS it is expected that the kext will not be in /System).
4. Remove kext of the same name from /Library/Extensions if it exists there.
5. Move the kext from the staging location to the install location.

removekext kextpath

• Removes the kext if it exists and is a kext.
• Will mount the root volume as read/write if necessary (works in the case of Catalina; for later macOS it is expected that the kext will not be in /System).

Updates

Feb 10, 2024

• Don't install to /Library/Extensions if it doesn't exist (as in Mac OS X 10.4 Tiger).

May 9, 2023

• Corrections to changes made yesterday for loadkext and installkext.
• Improved logging in checkkext, installkext, and removekext.

May 8, 2023

• Minor updates to log and error messages.
• Minor cleanup.
• Remove 1 second delay for first attempt of unloadkext.
• Added checkkextpermissions so that chown and chmod are not used unnecessarily.
• fixkextpermissions now returns a status if the permissions needed to be fixed but could not be fixed.
• loadkext will now load a kext from its current location if possible. It may modify permissions if necessary. It will revert to using a temporary directory if necessary.
• Added mountsystemrw for mounting the / root volume as read write. This is useful for Catalina.
• removekext now mounts the root volume as read write if necessary.

Jan 31, 2023

• Add -s option for installkext to install to /System/Library/Extensions. This is required to load unsigned kexts in OS X 10.9 Mavericks.

Jan 6, 2023

• Fixed kext staging location so that it's temporary and allows changing permissions.

Dec 8, 2022

• Added compatibility with Mac OS X 10.4.