this is called /boot/nextboot.conf. This file is required to have it's first
line be nextboot_enable="YES" for it to be read. Also, this file is
rewritten by the loader to nextboot_enable="NO"<space> after it is read.
This makes it so the file is read exactly once. Finally, the nextboot.conf
is removed shortly after the filesystems are mounted r/w.
Caution should be taken as you can shoot yourself in the foot. This is only
the loader piece. There will be a tool called nextboot(8) that will manage
the nextboot.conf file for you. It is coming shortly.
Reviewed by: dcs
Approved by: jake (mentor)
- Don't include ia64_cpu.h and cpu.h
- Guard definitions by _NO_NAMESPACE_POLLUTION
- Move definition of KERNBASE to vmparam.h
o Move definitions of IA64_RR_{BASE|MASK} to vmparam.h
o Move definitions of IA64_PHYS_TO_RR{6|7} to vmparam.h
o While here, remove some left-over Alpha references.
Get rid of the INTERNALSTATICLIB knob and just use plain INTERNALLIB.
INTERNALLIB now means to build static library only and don't install
anything. Added a NOINSTALLLIB knob for libpam/modules. To not
build any library at all, just do not set LIB.
default of -fguess-branch-probablility causes time optimizations (?)
like rewriting `if (foo) x++;' as
`if (!foo) goto forth; back: ; ...; forth: x++; goto back;". This is
pessimizes space especially well on i386's because one short branch
gets converted to 2 long ones.
Removed -fno-align-foo since it is implied by -Os. Previous commit
messages seem to have overstated the new alignment bugs in gcc. The
only case that affects boot2 is that -fno-align-functions (or
equivalently -falign-functions=1) actually gives -falign-functions=2.
This is caused by FUNCTION_BOUNDARY being 2 (bytes) instead of 1.
The default case where the optimization level is 1 and no alignment
options are given is more broken. All alignments are minimal, modulo
the bug in FUNCTION_BOUNDARY. This is caused by toplev.c setting
defaults too early.
Some hacks in previous commits ar not needed now, but may as well be
kept until gcc is fixed. The previous on in the Makefile saved 96
bytes of text due to the wrong FUNCTION_BOUNDARY and 32 bytes of data
due to unrelated bloat in the alignment of large objects. There aren't
even any options to control alignment of data.
to 4 bytes free. I removed a printf (the Keyboard yes/no) since it is of
marginal value and sed'ed the generated asm output to remove the unwanted
aligns. There's probably a better way to gain a few extra bytes than
losing the printf. Shortening strings is probably a better option but this
should get us over the hurdle.
than the first one on a controller, and work for secondary
controllers.
Due to the prom not having nodes for each disk, but a catch-all one,
we have to iterate over each device, trying to open it to determine
whether it is actually present.
Since probing this way takese some time (and spews some spurious
warnings), it should maybe be short-circuited if we use the
device we were booted from.
Implement lazy device probing, and correct slice/partiniton
handling in the ofwd_open() code. With this, I can now actually boot
a kernel from disk, and the loader does not create unnecessary
delays.
Submitted by: tmm
- Axe -fdata-sections as turning it on or off makes no difference. If
it did make a difference it would serve to bloat boot2 even further with
extra padding.
- Axe -fforce-addr. This gets us 32 bytes so we are down to only being
64-bytes over.
We still can't compile this with gcc 3.1. The problem seems to be that
the -fno-align-foo options don't actually work. Comparing the new and
old output it turns out that gcc is 4-byte padding all the functions and
labels and what not despite the passed in arguments thus adding the
unfortunate bloat to boot2.
loader variable, which let users specify the root mount point
the exact way one does after booting the kernel.
Let's take this opportunity to document it...
around. If the kernel boots successfully, the record of this kernel
is erased, it is intended to be a one-shot option for testing
kernels.
This could be improved by having the loader remove the record of
the next kernel to boot, it is currently removed in /etc/rc immediately
after disks are mounted r/w.
I'd like to MFC this before the 4.6 freeze unless there is violent
objection.
Reviewed by: Several on IRC
MFC after: 4 days
o We don't expect the PLT relocations to follow the .rela section
anymore. We still assume that PLT relocations are long formed,
o Document register usage,
o Improve ILP,
o Fix the FPTR relocation by creating unique OPDs per function.
Comparing functions is valid now,
o The IPLT relocation naturally handles the addend. Deal with it.
We ignore the addend for FPTR relocations for now. It's not at
all clear what it means anyway.
Fix ABI misinterpretation:
o For Elf_Rela relocations, the addend is explicit and should not
be loaded from the memory address we're relocating. Only do that
for Elf_Rel relocations (ie the short form).
o DIR64LSB is not the same as REL64LSB. DIR64LSB applies to a
symbol (S+A), whereas REL64LSB applies to the base address (BD+A),
up the module_path string, we would walk one past the end of the buffer.
This hurting ia64 originally, but it was probably also happening on i386
occasionally as well. The effects were usually harmless, it would add
bogus "binary" search directories to the places it actually looked for
files.
the S_IFREG bit for regular files. This caused the path search code to
skip it when it finally did find the kernel (after the common/module.c
buffer overrun bug was fixed)
detects and uses the gas section merge support. As a result, a whole bunch
of new sections arrive, including .rodata.str1.8, which was not included
in our custom ldscript.ia64. The result was a loader binary that EFI
rejected.
While here, collect the loader shell commands linker set and include it
in the data area rather than having its own section.
/boot/loader.efi was the last holdout for having a 100% self built ia64
system.
special-case make rule
2.) Cleanups, remove superfluous expicit rules, add -nostdlib to LDFLAGS,
remove -X and -g, remove -g from CFLAGS
3.) Add BINDIR
4.) Build install the loader help file, add an empty help.sparc64
5.) Change the default configuration to only support booting from disk
6.) Get libofw.a from a path relative ${.OBJDIR}, not ${.CURDIR}
Submitted by: jake (1 - 5), obrien (6)
register r8. We continue to write the bootinfo block at the same
hardwired address, because the kernel still expects it there.
It is expected that future kernels use register r8 to get to the
bootinfo block and don't depend on the hardwired address anymore.
Bump the loader version once again due to the interface change.
only care if it's network or not at this time. If we're loaded from
the network, we set currdev (=loaddev) so that the kernel is loaded
from the network as well. In all other cases we initialize to disk.
This makes netbooting more convenient and can easily be enhanced to
do more elaborate checking.
Most significantly (from an interfacing point of view) is the
support for the FPSWA pointer passing. Even though that was added
4 months ago, it's probably not a bad idea to bump the version
number to reflect this.
o Query the state field of the protocol mode to determine whether
we need to start and/or initialize the protocol. When we're
loaded across the network, the protocol has already been started
and is already initialized. When no networking has happened yet,
we have to start and initialize the protocol ourselves.
o After initialization, we have to set the receive filters. Not
doing this results in a deaf interface. We set the unicast and
broadcast filters. Multicast may not be supported. This specific
change fixes the problem we had that we could not netboot if
the loader was started from the EFI shell.
o To help future debugging, add a function that dumps the current
mode of the interface. It's conditional on EFINET_DEBUG.
o To help in runtime problems, emit a diagnostic message when we
could not initialize the protocol properly.
an efi_devdesc structure. When we're netbooting, f->f_devdata holds
the address of the network socket variable. Dereferencing this caused
some very unpredictable behaviour, including proper functioning.
So, as a sanity check, we first make sure f->f_dev points to our
own devsw. If not, the open will fail before we use f->f_devdata.
This solves the netboot hangs I invariably got whenever I used the
latest toolchain to compile the EFI loader.
layer to signal transmission of the packet. This resolves the
problem I'm seeing that an immediate call to net->Receive
after calling net->Transmit returns EFI_DEVICE_ERROR. This
condition seems to be sufficiently persistent that BOOTP and
RARP fail.
o While here, unify all functions to have 'nif' defined. Some
have it as arguments. The others now have them as locals. We
now always get the protocol interface by using the 'nif' var.
The current status of netbooting is that even though we now reliably
have BOOTP working (again), opening a file (ie loading a kernel)
across the network causes the loader to hang. I'm working on that now.
exists, otherwise we install it anyway. I interpret this as a very
high desire to install ${PROG}.help. Alas, ${PROG}.help doesn't exist
at the moment and neither does loader.help, so in practice this just
doesn't work, no matter how you interpret it. The compromise is to
install ${PROG}.help IFF it exists. I realize we lost creativity with
this commit, but style should have been preserved, AFAICT :-)
put a bunch of crap before the code in .text. Since the firmware
doesn't seem to honour the a.out entry point, we need to include
a little assmbler file which jumps to where we want to be in C.
Submitted by: jake
modules split across several physical medias. Following is how it works:
The splitfs code, when asked to open "foo" looks for a file "foo.split"
which is a text file containing a list of filenames and media names, e.g.
foo.aa "Kernel floppy 1"
foo.ab "Kernel floppy 2"
foo.ac "Kernel and modules floppy"
For each file segment, the process is:
- try to open the file
- prompt "Insert the disk labelled <whatever> and press any key..."
- try to open the file
- return error if file could not be located
RE team is free to use this feature in the upcoming 5.0-DP1.
Reviewed by: msmith, dcs
deep in <stand.h> to eventually include <time.h> to declare the user
version.
This is not quite the right place to declare it, but <stand.h> would
be worse because time() is very MD so it isn't in libstand.
Many places in the boot sources still get the user version using only
1 layer of pollution (#include <sys/time.h>. Some pollute themselves
directly (#include <time.h>). But the boot Makefiles are too broken
to enable warnings for redeclarations.
watchpoint support for debugging (under LOADER_DEBUG). Claim the
physical and virtual addresses used to map the kernel from the prom;
we map it ourselves behind the scenes though. Add a reboot command.
Submitted by: tmm
- Remove change for my local configuration that slipped in with
the last commit; I am having problems booting when multiple SCSI
disks are attached, so I will change this part as soon as I find
a solution, anyway.
- Remove two constants that were needed in conjuction with the
NetBSD disklabel header. Use the FreeBSD equivalents.
To boot from NetBSD/sparc64 partitions, define LABELOFFSET to
be 128.
- Do not use the complete open firmware path to filter out cdrom drives.
No path containing "cdrom" is detected as a disk now.
- Simplify some code.
This allows obtaining crash dumps from the panics occured during late stages
of kernel initialisation before system enters into single-user mode.
MFC after: 2 weeks
a simple version of bcopy() so we avoid picking up the overly-complex
implementation in libc (via libstand). This is not necessary on
-current, but RELENG_4 has apparently just exceeded the 15-sector
limit for boot1.
Reviewed by: wilko
because the buffers we use could end up spanning a 64k boundary.
Unfortunately it causes too much bloat (228 -> 72 bytes free) to
just reinstate the old malloc() function.
Instead, define a structure that contains all 4 buffers which must
not cross 64k boundaries. We allocate a 64k-aligned instance in
main() using the magic that was in the old boot2 malloc() function.
This brings the free space down to 168 bytes, but that is still
better than it was before revision 1.35 (136 bytes).
Reported by: Mike Brancato <funnyguy@digitalsmackdown.net>
Pointy-hat to: iedowse
done with boot1 on the alpha. We use 4k buffers regardless of the
actual filesystem block size.
Remove the simple malloc() implementation, as it is no longer used.
larger than 8k. We now use 4k buffers regardless of the filesystem
block size, so there is no longer a static limit.
Simply increasing the buffer size from 8k to 16k as done on the
i386 doesn't work on the alpha, probably because it causes us
to overshoot boot1's 48k runtime memory limit.
Tested by: naddy
All the alpha loaders should use the same version file. Also, we might
should merge the various loaders (cdboot, loader, netboot) into one loader
that can boot off of disks, CD's, and network devices. The version bump
is needed so the FICL scripts won't bomb out thinking that the netboot
binary is too old.
backing out the 1024 sector boot0, but revision 1.12 had nothing to do with
that. Instead, it documented various compile time options for boot0 and
allowed them to be overridden via make.conf or options on the make
command line.
- Change the 'fopen' keyword to accept a mode parameter. Note that this
will break existing 4th scripts that use fopen. Thus, the loader
version has been bumped and loader.4th has been changed to check for a
sufficient version on i386 and alpha. Be sure that you either do a full
world build or install or full build and install of sys/boot after this
since loader.old won't work with the new 4th files and vice versa.
PR: kern/32389
Submitted by: Jonathan Mini <mini@haikugeek.com>
Sponsored by: ClickArray, Inc.
This flag adds a pausing utility. When ran with -p, during the kernel
probing phase, the kernel will pause after each line of output.
This pausing can be ended with the '.' key, and is automatically
suspended when entering ddb.
This flag comes in handy at systems without a serial port that either hang
during booting or reser.
Reviewed by: (partly by jlemon)
MFC after: 1 week
On OFW based machines, it is just too confusing having the firmware and
OS loader giving the same prompt. This is a nice compromise that 99% of the
users on non-OFW platforms will probably not even notice.
instead of looping until the disk is full. This kind of failure can
especially happen when a version of awk that doesn't support POSIX
character classes is used.
Submitted by: David Wolfskill <david@catwhisker.org>
- Add S4BIOS sleep implementation. This will works well if MIB
hw.acpi.s4bios is set (and of course BIOS supports it and hibernation
is enabled correctly).
- Add DSDT overriding support which is submitted by takawata originally.
If loader tunable acpi_dsdt_load="YES" and DSDT file is set to
acpi_dsdt_name (default DSDT file name is /boot/acpi_dsdt.aml),
ACPI CA core loads DSDT from given file rather than BIOS memory block.
DSDT file can be generated by iasl in ports/devel/acpicatools/.
- Add new files so that we can add our proposed additional code to Intel
ACPI CA into these files temporary. They will be removed when
similar code is added into ACPI CA officially.
no emulation mode. Unlike other BIOS devices, this device uses 2048 byte
sectors. Also, the bioscd driver does not have to worry about slices
or partitions.
etc. The only bit of debugging left is performing dual output to both
the screen and COM1. Also, the twiddle is still disabled since it seems
to do weird things to the serial dump. cdboot now has 880 bytes to spare.
to the El Torito standard for CD booting, a CD may boot in "No emulation"
mode without using a floppy image. In this mode, the BIOS loads a program
off of the CD into memory and creates a BIOS device using 2048 byte sectors
for the CD. According to the standard, this program can be up to 0xFFFF
virtual (512-byte) sectors long. The old cdldr depended on this by having
the BIOS load the entire loader and the small cdldr stub as one binary
similar to pxeboot so that cdldr didn't have to read the CD to find the
loader. However, the NT no emulation loader just uses 1 disk sector
(4 virtual sectors), so it seems that at least some BIOS writers just did
enough to get NT to boot by only loading 1 sector and ignoring the sector
count. Thus, while cdldr should have worked in theory, it doesn't in
practice. This replacment fits entirely in 1 sector and includes simple
ISO 9660 support. It looks for /boot/loader on the CD and loads it up
using the BIOS. This allows us to not have to depend on the limited size
of floppy images but use a full GENERIC kernel for CD-ROM installs in the
future, among other things.
This version of cdboot is a bit bloated as it includes some useful
debugging routines that people can pull to use in other x86 assembly
modules. Even with all the debugging cruft, we still have 272 bytes to
spare.
devices in 'lsdev' output rather than printing out a pointer to the
print function since the user really could care less about the pointer
value. Perhaps this was intended to be a debugging printf?
when debugging boot problems. It is not on by default but is enabled via
the BTX_SERIAL variable. The port and speed can be set via the same
variables used by boot2 and the loader.
o Make <stdint.h> a symbolic link to <sys/stdint.h>.
o Move most of <sys/inttypes.h> into <sys/stdint.h>, as per C99.
o Remove <sys/inttypes.h>.
o Adjust includes in sys/types.h and boot/efi/include/ia64/efibind.h
to reflect new location of integer types in <sys/stdint.h>.
o Remove previously symbolicly linked <inttypes.h>, instead create a
new file.
o Add MD headers <machine/_inttypes.h> from NetBSD.
o Include <sys/stdint.h> in <inttypes.h>, as required by C99; and
include <machine/_inttypes.h> in <inttypes.h>, to fill in the
remaining requirements for <inttypes.h>.
o Add additional integer types in <machine/ansi.h> and
<machine/limits.h> which are included via <sys/stdint.h>.
Partially obtain from: NetBSD
Tested on: alpha, i386
Discussed on: freebsd-standards@bostonradio.org
Reviewed by: bde, fenner, obrien, wollman
dedicated" mode. This was specifying that there are 256 (illegal!)
heads on the disk. If bioses store that in a byte, and it gets truncated
to 0, then that almost certainly causes the infamous divide-by-zero
nightmare.
This is also most likely the reason why the Thinkpad T20/A20 series
were locking up when FreeBSD was installed. This is also the most likely
reason why a boot1 being present causes an IA64 box to lock up at boot.
(removing the "part4" stuff from boot1.s fixes the IA64 boxes and would
most likely have fixed the T20/A20 and some TP600E series thinkpads)
Remove asm functions to call the openfirmware and kernel entry points;
we can just call them directly.
Don't use the stack pointer for an intermediate result in setx.
Put the stack in the bss.
Firmware.
- Add a temporary disklabel header to boot off a NetBSD/sparc64
partition. This file can be deleted when we have got a FCode
bootblock.
The disklabel header was obtained from NetBSD.
- Use unsigned types for the (32-bit) Open Firmware device handles
to avoid sign extension on 64-bit architectures.
- Add a standard type definition for Open Firmware arguments.
- Flesh out ofw_readin routine.
- Add OpenFirmware load and exec routines.
- Make sure memory allocation for the kernel is done correctly.
- Change the way the heap is allocated so as to make it easier to deallocate
when we hand over.
- Add a command to print memory maps similar to the one for ia64.
With this patch, I can now load and hand over to a kernel on my iMac. There
are some problems with OpenFirmware routines failing after the hand over that
still need to be addressed.
- When the video BIOS is called to clear the region (x, y)-(79, 24)
(by scrolling), the slashed region in Fig.1 is cleared. CD() is
supposed to clear the region shown in Fig.2.
x x
+-------+ +-------+
| | | |
y| ////| y| ////|
| ////| |///////|
| ////| |///////|
+-------+ +-------+
Fig.1 Fig.2
- Don't move the cursor during this operation.
- Be consistent about placing spaces around keywords and
operators; don't mix statements like "if(A==B)" and "if (X == Y)",
"return(0)" and "return (-1)", "P=10" and "Q = 0", etc.
- Consitently indent lines. It's not good to indent by 8 columns
in one part of the file, and by 4 columns in the other part.
is turned off by default and could be enabled by defining LOADER_BZIP2_SUPPORT
make variable. Also make gzip support optional (turned on by default) -
it could be turned off via LOADER_NO_GZIP_SUPPORT make variable.
Please note, that due to limit on the amount of memory available to the
loader(8), it is possible to load modules/kernels compressed with the smallest
block size supported by the bzip2 - 100k (`-1' bzip2(1) option), however
even in this mode bzip2(1) usually provides better compression ratio than
gzip(1) in its best compression mode.
MFC after: 1 month
the ACPI module if the system apperars to be ACPI compliant.
This is an initial cut; the load should really be done by Forth support
code, and we should check both the BIOS build date and a blacklist.
information. The default limits only effect machines with > 1GB of ram
and can be overriden with two new kernel conf variables VM_SWZONE_SIZE_MAX
and VM_BCACHE_SIZE_MAX, or with loader variables kern.maxswzone and
kern.maxbcache. This has the effect of leaving more KVM available for
sizing NMBCLUSTERS and 'maxusers' and should avoid tripups where a sysad
adds memory to a machine and then sees the kernel panic on boot due to
running out of KVM.
Also change the default swap-meta auto-sizing calculation to allocate half
of what it was previously allocating. The prior defaults were way too high.
Note that we cannot afford to run out of swap-meta structures so we still
stay somewhat conservative here.
actual end of the section. The new gas (binutils) puts in additional padding
which was misaligning the concatenated btx loader.
Reported by: Oliver Hartmann <ohartman@klima.physik.uni-mainz.de>,
Harti Brandt <brandt@fokus.gmd.de>
Tested by: Oliver Hartmann <ohartman@klima.physik.uni-mainz.de>,
David Wolfskill <dhw@whistle.com>, ps
Reviewed by: jhb
MFC after: 1 day
the first sector of the emulated floppy to contain a valid MS-DOS BPB that
it can modify. Since boot1 is the first sector of boot.flp, this resulted
in the BIOS overwriting part of boot1: specifically the function used to
read in sectors from the disk.
Submitted by: Mark Peek <mark@whistle.com>
Submitted by: Doug Ambrisko <ambrisko@ambrisko.com>
PR: i386/26382
Obtained from: NetBSD, OpenBSD (the example BPB)
MFC after: 1 month
make(1) wants to build loader.sym *before* the .o files. Eliminating
one seeminly intermediate step avoids the problem. Somehow, it seems
that variables are not getting expanded at the right time.
Any explanations would be appreciated...
Changing:
${BASE}.sym: ${OBJS} ${LIBSTAND} ${LIBFICL} ${LIBALPHA} ${CRT} vers.o
${LD} ...
To:
BASEOBJS= ${OBJS} ${LIBSTAND} ${LIBFICL} ${LIBALPHA} ${CRT} vers.o
${BASE}.sym: ${BASEOBJS}
echo ${BASEOBJS}
${LD} ...
.. the echo only shows LIBFICL, CRT and vers.o. ${OBJS} is not included.
(I'll be we know which compiler and platform they developed this on...)
Minimally change them to C89 comments to make GCC happy. (this is kinda funny
as the file has piece derived from FreeBDS 3.2)
Also fix FreeBSD id style.
page of the image to load section headers and if we let the text section
start at zero, it corrupts the section table when its loaded. With this
change, the loader gets as far as the 'ok' prompt.
they can be used with cell operators like !.
As I did this, I noticed the whole CELL thing might have problems with
big endian architectures with sizeof(int)!=sizeof(void*).
file is processed by passing its name in argv[1]:
return(mod_loadobj(typestr, argv[1]));
however, it is not tested to see if argv[1] actually is defined.
At best, mod_loadobj() near line 244 returns an error like
"can't find 'garbage'" but if the "filename" entered is sufficiently
long, some buffer gets overrun. Of course, "load -t filename" is
actually a typo because we meant to type "load -t mfs_root filename";
nevertheless, a hung machine seems like too harsh a punishment for
such a small typo...
PR: i386/27693
Submitted by: Adrian Steinmann <ast@marabu.ch>
MFC after: 1 week
longer includes machine/elf.h.
* consumers of elf.h now use the minimalist elf header possible.
This change is motivated by Binutils 2.11.0 and too much clashing over
our base elf headers and the Binutils elf headers.
This version has a step debugger, which now completely replaces the
old trace feature. Also, we moved all of the FreeBSD-specific MI
code to loader.c, reducing the diff between this and the official
FICL distribution.
fatal trap. Also, reload the GDT register to point to BTX's GDT before
playing around with the segment registers to return to real mode. This is
helpful if the kernel causes a fatal exception before it has setup its own
IDT and fault handlers. For example, if one happens to break mtx_init().
Without these changes BTX would recursively page fault (if paging was not
disabled) or triple fault and reset the CPU (without the GDT reload)
instead of providing a potentially useful register dump.
Reviewed by: rnordier
The release engineer keeps using the wrong /boot/cdboot when creating the
ISO images. So we'll add the 4.0-RELEASE cdboot to the tree until someone
bothers to fix the source so a working `cdboot' is built.
As of this patchset, the loader builds (under NetBSD/macppc), boots, interacts
and talks to BOOTP/NFS servers.
(main.c was moved from boot/ofw/libofw to boot/ofw/common but has no revision
history)
Reviewed by: obrien
This brings the loader up to the point where I can compile it under
NetBSD/macppc and have it boot, interact and talk to NFS servers.
sys/boot/ofw/libofw/main.c has been deleted (it has no revision history) and
replaced with sys/boot/ofw/common/main.c
Reviewed by: obrien
to reinstall boot1 after a 'make world'.
Unfortunately this means that people who have already installed a new
boot1 from a 'make world' after 2000/09/18 *must* reinstall it after
their next build using something like:
# disklabel -B /dev/da0c
expands beyond the limit we will extend the address space before trying
to zero the BSS. This should give us plenty of headroom for modest
expansion of the loader.
Previous revision of this file changed the "boot" commands to take
no arguments from the stack. This is only valid in the case where
a kernel has not been loaded. In that case, load_kernel_and_modules
will be called, which takes a list of arguments from the stack.
When a kernel is presently loaded, though, the list of arguments must
be passed to the boot command, which was the behaviour before the last
revision.
Fix things for both cases.
Noticed by: S-Max and others on that chat room
Taking over the sector following the MBR causes problems on some
machines, and the actual gains are fairly small in terms of how
the space is presently used.
Since we need a number of further features (eg. handling extended
partitions) that can't be readily accommodated in the basic boot0
design anyway, rather choose to implement the additional stuff
separately and concentrate on compatibility rather than features
here.
