Copy stable/9 to releng/9.3 as part of the 9.3-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

MFC 228738:
Allow boot0cfg to force a PXE boot via boot0 on the next boot.
- Fix boot0 to check for PXE when using the pre-set setting for the
preferred slice.
- Update boot0cfg to use slice 6 to select PXE. Accept a 'pxe' argument
instead of a number for the 's' option as a way to select PXE as well.

Copy head to stable/9 as part of 9.0-RELEASE release cycle.

Approved by: re (implicit)

A number of small changes to make the 'save choice to disk' safer,
and re-enable it as default.

In particular:

+ re-enable the 'update' flag in the Makefile (of course!);

+ commit Warner's patch "orb $NOUPDATE,_FLAGS(%bp)"
to avoid writing to disk in case of a timeout/default choice;

+ fix an off-by-one count in the partition scan code that would
print the wrong name for unknown partitions;

+ unconditionally change the boot prompt to 'Boot:' instead of 'Default:'
to make room for the extra code/checks/messages. Some of the changes
listed below are also made to save space;

+ rearrange and fix comments for known partition types. Right now we
explicitly recognise *BSD, Linux, FAT16 (type 6, used on many USB keys),
NTFS (type 7), FAT32 (type 11).
Depending on other options we also recognise Extended (type 5),
FAT12 (type 1) and FAT16 < 32MB (type 4).

+ Add an entry "F6 PXE" when the code is built with -DPXE (which is
a default now). Technically, F6 boots through INT18, so the prompt 'PXE'
is a bit misleading. Unfortunately the name INT18
is too long and does not fit in - we could use ROM perhaps.
The reason I picked 'PXE' is that on many (I believe) new systems
INT18 calls PXE.

Apart from the choice of the name for PXE/ROM/INT18, this should close
pending issues on the 1-sector boot0 code and we should be able to
move the code to RELENG_7 when it reopens.

No boot0cfg changes are necessary.

MFC after: 3 weeks

Fix typo in the comment %is -> %si.

Another, hopefully final set of changes to boot0 and boot0cfg.

boot0.S changes:

+ import a patch from Christoph Mallon to rearrange the various
print functions and save another couple of bytes;

+ implement the suggestion in PR 70531 to enable booting from
any valid partition because even the extended partitions that
were previously in our kill list may contain a valid boot loader.
This simplifies the code and saves some bytes;

+ followwing up PR 127764, implement conditional code to preserve
the 'Volume ID' which might be used by other OS (NT, XP, Vista)
and is located at offset 0x1b8. This requires a relocation of the
parameter block within the boot sector -- there is no other
possible workaround.
To address this, boot0cfg has been updated to handle both
versions of the boot code;

+ slightly rearrange the strings printed in the menus to make
the code buildable with all options. Given the tight memory
budget, this means that with certain options we need to
shrink or remove certain labels.

and especially:

make -DVOLUME_LABEL -DPXE the default options.

This means that the newly built boot0 block will preserve the
Volume ID, and has the (hidden) option F6 to boot from INT18/PXE.
I think the extra functionality is well worth the change.

The most visible difference here is that the 'Default: ' string
now becomes 'Boot: ' (it can be reverted to the old value
but then we need to nuke 1/2 partition name or entries to
make up for the extra room).

boot0cfg changes:

+ modify the code to recognise the new boot0 structure (with the
relocated options block to make room for the Volume id).

+ add two options, '-i xxxx-xxxx' to set the volume ID, -e c
to modify the character printed in case of bad input

PR: 127764 70531
Submitted by: Christoph Mallon (portions)
MFC after: 4 weeks

This commits brings in a lot of documentation and some enhancement
of the boot0.S code, with a number of compile-time selectable options,
the most interesting one being the ability to select PXE booting.

The code is completely compatible with the previous one, and with
the boot0cfg program. Even the actual code is largely unmodified,
with only minor rearrangements or fixes to make room for the new
features.

The behaviour of the standard build differs from the previous
version in the following, minor things:

+ 'noupdate' is the default, which means the code does not
write back the selection to disk. You can enable the feature
at runtime with boot0cfg, or changing the flags in the Makefile.

+ a drive number of 0x00 (floppy, or USB in floppy emulation) is
now accepted as valid. Previously, it was overridden with 0x80,
meaning that the partition table coming from the media was
used to access sectors on a possibly different media.
You can revert to the previous mode building with -DCHECK_DRIVE,
and you can always use the 'setdrv' option in boot0cfg

+ certain FAT or NTFS partitions are listed as WIN instead of DOS.

+ the 'bel' character on a bad selection is replaced by a '#' to
make it clear that the system is not hang even if the machine
does not have a speaker. This can be reverted back at compile
time, or at runtime with an upcoming boot0cfg option.

Additional features are available as compile time options,
and may be become the default if deemed useful. In particular:

+ INT18/PXE boot (make -DPXE)
This option enables booting through INT 18h (which on certain
BIOSes can be hooked to PXE) by pressing F6. There is unfortunately
no room to print the additional menu option.
Also, to make room for the code, the 'Default: ' string is
changed to 'Boot: '

+ print current drive number (make -DTEST)
Prints a line indicating the current drive number.
This is useful to figure out what is going on for machines/bioses
which remap drives in sometimes surprising ways.

+ disable numeric keys in console mode (make -DONLY_F_KEYS)
Not really a significant option, but it is needed to make
room for the -DTEST mode.

+ disable floppy support (make -DCHECK_DRIVE)
Revert to the old behaviour of only accepting 0x80 and above
as valid drive numbers.

MFC after: 6 weeks

Fix a typo in previous commit: must call "putn" to print a crlf,
instead of "puts" which prints whatever is at %si, followed by a CRLF.

It was not noticed during tests because at that point %si points
to a partition entry whose first byte is 0x80, which is both a
terminator for the string and a non printable character.

Submitted by: Christoph Mallon

Pass the pointer to the selected partition in %si to the next stage
boot code. The bug was introduced in rev.1.13, and went unnoticed
because FreeBSD's boot1 does not use it, but other systems might.

(I have been struggling for almost a full day trying to figure out
why a syslinux'ed partition would not boot when started with the
FreeBSD /boot/boot0, only to realize that the bug was ours!)

The space for the two extra bytes (push %si and pop %si) is reclaimed
by removing an extra CRLF that is printed before booting.

The bug is not a major one but if there is time it might be a good
thing to merge it into the upcoming releases.

Fix setting of serial port speed. A junk value was passed in AX when
bioscom is called to set up serial port parameters because COMSPEED
was treated as an address instead of an immediate value, causing
serial port parameters to never be set.

PR: i386/110828
Reviewed by: jhb
MFC after: 2 weeks

Restore the pre-5.x behavior of only beeping if the user makes a bad
selection and not always beeping on startup. The two bytes for the extra
'jmp' instruction were obtained by removing recognition of BSD/OS
partitions.

Requested by: many
Tested by: subset of many
Head nod: imp, keramida
MFC after: 2 weeks

Remove type 0x4 (FAT12 <32MB) to make room for type 0x7 (NTFS).

Only update the boot sector when there is a valid drive number provided.
(After squeezing a few more bytes out of boot0)

Discussed With: jhb, julian
PR: 66248
Submitted By: Hans Petter Selasky
MFC After: 1 week

- If the COMSPEED is set to 0, then don't try to initialize the serial port
and assume that the BIOS has set it up for us. This allows folks with a
serial-aware BIOS to set the BIOS to speeds above 9600 and allow boot0 to
just use the existing settings.
- Purge some gratuitous cpp comments as per style(9).

Submitted by: Danny Braniss danny at cs dot huji dot ac dot il (1)
MFC after: 1 month

Clean up the comments, rewording, adding missing punctuation
and other minor nits.

Approved by: jhb

Save a couple of bytes for the SIO case.

Merge boot0 and boot0sio so they behave the same.

Partly back out last revision that unnecessarily changed valid
assembler line comments and damaged the CVS history.

Prompted by: bde, jhb

Switch to using C99 comments in assembler preprocessed with cpp(1).

- Properly merge boot0sio.s and boot0.s into boot0.S.
boot0sio.s was repo-copied to boot0.S.

- Rename boot0ext.s to boot0ext.S, to stay consistent
with other preprocessed asm files around here, and
for better portability.

Repocopied by: joe