loader/loader.mk: add docs for LOADER_*_SUPPORT variables

These are internal to the loader and generally can only be set in a
makefile that's compiling some variation of loader. Add caveats since
these aren't really user-serviceable parts, though some downstreams will
tweak individual makefiles for their own purposes.

Sponsored by:		Netflix
This commit is contained in:
Warner Losh 2024-10-24 20:22:51 -06:00
parent 23dee252da
commit 358752abdf

View File

@ -1,4 +1,3 @@
.PATH: ${LDRSRC} ${BOOTSRC}/libsa
CFLAGS+=-I${LDRSRC}
@ -30,6 +29,33 @@ 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