diff --git a/stand/loader.mk b/stand/loader.mk
index de717ce7b18b..0f2ff31a5343 100644
--- a/stand/loader.mk
+++ b/stand/loader.mk
@@ -1,179 +1,205 @@
-
 .PATH: ${LDRSRC} ${BOOTSRC}/libsa
 
 CFLAGS+=-I${LDRSRC}
 
 SRCS+=	boot.c commands.c console.c devopen.c interp.c 
 SRCS+=	interp_backslash.c interp_parse.c ls.c misc.c 
 SRCS+=	modinfo.c
 SRCS+=	module.c nvstore.c pnglite.c tslog.c
 
 CFLAGS.module.c += -I$(SRCTOP)/sys/teken -I${SRCTOP}/contrib/pnglite
 
 .PATH: ${SRCTOP}/contrib/pnglite
 CFLAGS.pnglite.c+= -I${SRCTOP}/contrib/pnglite
 CFLAGS.pnglite.c+= -DHAVE_MEMCPY -I${SRCTOP}/sys/contrib/zlib
 
 .if ${MACHINE} == "i386" || ${MACHINE_CPUARCH} == "amd64"
 SRCS+=	load_elf32.c load_elf32_obj.c reloc_elf32.c
 SRCS+=	load_elf64.c load_elf64_obj.c reloc_elf64.c
 .elif ${MACHINE_CPUARCH} == "aarch64"
 SRCS+=	load_elf64.c reloc_elf64.c
 .elif ${MACHINE_CPUARCH} == "arm"
 SRCS+=	load_elf32.c reloc_elf32.c
 .elif ${MACHINE_CPUARCH} == "powerpc"
 SRCS+=	load_elf32.c reloc_elf32.c
 SRCS+=	load_elf64.c reloc_elf64.c
 SRCS+=	metadata.c
 .elif ${MACHINE_CPUARCH} == "riscv"
 SRCS+=	load_elf64.c reloc_elf64.c
 SRCS+=	metadata.c
 .endif
 
+#
+# LOADER_*_SUPPORT variables are used to subset the boot loader in the various
+# configurations each platform supports. These are typically used to omit broken
+# options, or to size optimize for space constrained instances. These are set in
+# loader Makefiles (which include loader.mk) to control which subset of features
+# are enabled. These cannot generally be set in src.conf since that would affect
+# all loaders, but also not all loaders are setup for overrides like that and
+# not all combinations of the following have been tested or even work. Sometimes
+# non-default values won't work due to buggy support for that component being
+# optional.
+#
+# LOADER_BZIP2_SUPPORT	Add support for bzip2 compressed files
+# LOADER_CD9660_SUPPORT	Add support for iso9660 filesystems
+# LOADER_DISK_SUPPORT	Adds support for disks and mounting filesystems on it
+# LOADER_EXT2FS_SUPPORT	Add support for ext2 Linux filesystems
+# LOADER_GPT_SUPPORT	Add support for GPT partitions
+# LOADER_GZIP_SUPPORT	Add support for gzip compressed files
+# LOADER_INSTALL_SUPPORT Add support for booting off of installl ISOs
+# LOADER_MBR_SUPPORT	Add support for MBR partitions
+# LOADER_MSDOS_SUPPORT	Add support for FAT filesystems
+# LOADER_NET_SUPPORT	Adds networking support (useless w/o net drivers sometimes)
+# LOADER_NFS_SUPPORT	Add NFS support
+# LOADER_TFTP_SUPPORT	Add TFTP support
+# LOADER_UFS_SUPPORT	Add support for UFS filesystems
+# LOADER_ZFS_SUPPORT	Add support for ZFS filesystems
+#
+
 .if ${LOADER_DISK_SUPPORT:Uyes} == "yes"
 CFLAGS.part.c+= -DHAVE_MEMCPY -I${SRCTOP}/sys/contrib/zlib
 SRCS+=	disk.c part.c vdisk.c
 .endif
 
 .if ${LOADER_NET_SUPPORT:Uno} == "yes"
 SRCS+= dev_net.c
 .endif
 
 .if defined(HAVE_BCACHE)
 SRCS+=  bcache.c
 .endif
 
 .if defined(MD_IMAGE_SIZE)
 CFLAGS+= -DMD_IMAGE_SIZE=${MD_IMAGE_SIZE}
 SRCS+=	md.c
 .else
 CLEANFILES+=	md.o
 .endif
 
 # Machine-independent ISA PnP
 .if defined(HAVE_ISABUS)
 SRCS+=	isapnp.c
 .endif
 .if defined(HAVE_PNP)
 SRCS+=	pnp.c
 .endif
 
 .if ${LOADER_INTERP} == "lua"
 SRCS+=	interp_lua.c
 .include "${BOOTSRC}/lua.mk"
 LDR_INTERP=	${LIBLUA}
 LDR_INTERP32=	${LIBLUA32}
 CFLAGS.interp_lua.c= -DLUA_PATH=\"${LUAPATH}\" -I${FLUASRC}/modules
 .elif ${LOADER_INTERP} == "4th"
 SRCS+=	interp_forth.c
 .include "${BOOTSRC}/ficl.mk"
 LDR_INTERP=	${LIBFICL}
 LDR_INTERP32=	${LIBFICL32}
 .elif ${LOADER_INTERP} == "simp"
 SRCS+=	interp_simple.c
 .else
 .error Unknown interpreter ${LOADER_INTERP}
 .endif
 
 .include "${BOOTSRC}/veriexec.mk"
 
 .if defined(BOOT_PROMPT_123)
 CFLAGS+=	-DBOOT_PROMPT_123
 .endif
 
 .if defined(LOADER_INSTALL_SUPPORT)
 SRCS+=	install.c
 .endif
 
 # Filesystem support
 .if ${LOADER_CD9660_SUPPORT:Uno} == "yes"
 CFLAGS+=	-DLOADER_CD9660_SUPPORT
 .endif
 .if ${LOADER_EXT2FS_SUPPORT:Uno} == "yes"
 CFLAGS+=	-DLOADER_EXT2FS_SUPPORT
 .endif
 .if ${LOADER_MSDOS_SUPPORT:Uno} == "yes"
 CFLAGS+=	-DLOADER_MSDOS_SUPPORT
 .endif
 .if ${LOADER_UFS_SUPPORT:Uyes} == "yes"
 CFLAGS+=	-DLOADER_UFS_SUPPORT
 .endif
 
 # Compression
 .if ${LOADER_GZIP_SUPPORT:Uno} == "yes"
 CFLAGS+=	-DLOADER_GZIP_SUPPORT
 .endif
 .if ${LOADER_BZIP2_SUPPORT:Uno} == "yes"
 CFLAGS+=	-DLOADER_BZIP2_SUPPORT
 .endif
 
 # Network related things
 .if ${LOADER_NET_SUPPORT:Uno} == "yes"
 CFLAGS+=	-DLOADER_NET_SUPPORT
 .endif
 .if ${LOADER_NFS_SUPPORT:Uno} == "yes"
 CFLAGS+=	-DLOADER_NFS_SUPPORT
 .endif
 .if ${LOADER_TFTP_SUPPORT:Uno} == "yes"
 CFLAGS+=	-DLOADER_TFTP_SUPPORT
 .endif
 
 # Partition support
 .if ${LOADER_GPT_SUPPORT:Uyes} == "yes"
 CFLAGS+= -DLOADER_GPT_SUPPORT
 .endif
 .if ${LOADER_MBR_SUPPORT:Uyes} == "yes"
 CFLAGS+= -DLOADER_MBR_SUPPORT
 .endif
 
 .if ${HAVE_ZFS:Uno} == "yes"
 CFLAGS+=	-DLOADER_ZFS_SUPPORT
 CFLAGS+=	-I${ZFSSRC}
 CFLAGS+=	-I${SYSDIR}/cddl/boot/zfs
 CFLAGS+=	-I${SYSDIR}/cddl/contrib/opensolaris/uts/common
 SRCS+=		zfs_cmd.c
 .endif
 
 LIBFICL=	${BOOTOBJ}/ficl/libficl.a
 .if ${MACHINE} == "i386"
 LIBFICL32=	${LIBFICL}
 .else
 LIBFICL32=	${BOOTOBJ}/ficl32/libficl.a
 .endif
 
 LIBLUA=		${BOOTOBJ}/liblua/liblua.a
 .if ${MACHINE} == "i386"
 LIBLUA32=	${LIBLUA}
 .else
 LIBLUA32=	${BOOTOBJ}/liblua32/liblua.a
 .endif
 
 CLEANFILES+=	vers.c
 VERSION_FILE?=	${.CURDIR}/version
 .if ${MK_REPRODUCIBLE_BUILD} != no
 REPRO_FLAG=	-r
 .endif
 vers.c: ${LDRSRC}/newvers.sh ${VERSION_FILE}
 	sh ${LDRSRC}/newvers.sh ${REPRO_FLAG} ${VERSION_FILE} \
 	    ${NEWVERSWHAT}
 
 .if ${MK_LOADER_VERBOSE} != "no"
 CFLAGS+=	-DELF_VERBOSE
 .endif
 
 # Each loader variant defines their own help filename. Optional or
 # build-specific commands are included by augmenting HELP_FILES.
 .if !defined(HELP_FILENAME)
 .error Define HELP_FILENAME before including loader.mk
 .endif
 
 HELP_FILES+=	${LDRSRC}/help.common
 
 CFLAGS+=	-DHELP_FILENAME=\"${HELP_FILENAME}\"
 .if ${INSTALL_LOADER_HELP_FILE:Uyes} == "yes"
 CLEANFILES+=	${HELP_FILENAME}
 FILES+=		${HELP_FILENAME}
 .endif
 
 ${HELP_FILENAME}: ${HELP_FILES}
 	cat ${HELP_FILES} | awk -f ${LDRSRC}/merge_help.awk > ${.TARGET}