to 0x600 via a 'rep movsw'. Once that was done, %cx was zero, so we could
simply use 'movb' to update the lower byte of %cx in preparation for
zeroing out the fake partition entry used to boot to other drives via F5.
Well, in the new boot0, we don't actually relocate ourselves, instead it
is easier to create the fake partition entry first and then just use it to
get the BIOS to load all of boot0 into memory at 0x600. However, since we
aren't doing the relocate code anymore, we don't know that %cx == 0 when
we hit the 'movb' to setup %cx for clearning the fake partition entry.
Thus, if %ch != 0 when the BIOS started boot0, then it would end up zeroing
a lot more memory than just 8 words. The solution is to do a word move of
$8 into %cx.
Debugging help from: David Wolfskill <dhw@whistle.com>
Linux kernel image, and is designed to be dropped into a Linux system
and booted via LILO. Once booted, the user is greeted by the FreeBSD
loader. This still isn't quite complete, as the the root= specification
from LILO isn't currently passed to the loader yet.
- Autodetection and support of the BIOS EDD extensions to work around the
1024 cylinder limit on all but really ancient BIOS's.
- To work around some BIOS's which break when EDD is used with older drives,
we only attempt to use EDD if the cylinder is > 1023.
- Since this new code required more space than we had left, expand boot0 to
2 sectors (1024 bytes) in length.
- Add support for boot0 being multiple sectors using predefined constants.
If boot0 needs to be extended in the future, all that is required is
bumping the NUM_SECTORS constant.
- Now that we have more room to work with, add a few more fs type
descriptions while making others more verbose.
use the BIOS Equipment List to determine how many hard drives are
installed and if the drive number we received in %dl is valid.
- Don't bother to disable interrupts when setting up the stack. The 8086
and beyond implicitly disable interrupts after an instruction that sets
%ss (for example, a pop or a mov) so that you can safely set %ss and %sp
in two consecutive instructions. An exception to this is the lss
instruction, which can set both registers simultaneously and thus doesn't
need this hack.
- Add support for EDD BIOS extensions to support booting off of hard drives
of nearly arbitrary length.
- Add in support for the EDD (Enhanced Disk Drive) BIOS extensions to
use LBA mode for accessing drives past cylinder 1024. This should allow
us to load a kernel from anywhere on a newer drive up to 2 TB. Part
of this came from the PR below.
PR: i386/13847
Submitted by: Tor Egge <Tor.Egge@fast.no>
theory, this should allow the K7V Athlon motherboard to boot ok with boot
virus protection enabled. However, I have no hardware to test this. It
shouldn't break anything though. :)
Prodded by: Kelly Yancey <kbyanc@posi.net>
with the new binutils. Now that we have a decent assembler, all the old
m4 macros are no longer needed. Instead, straight assembly can be used
since as(1) now understands 16-bit addressing, branches, etc. Also,
several bugs have been fixed in as(1), allowing boot0.s to be further
cleaned up.
code instead of using 32-bit code and having to just "know" that it's
really 16-bit instructions when things run. This also allows the code
to use fewer macros and more actual assembly statements, which eases
maintenance. Unfortunately, due to as(1) brokenness, we still use m4
macros for all 16-bit addresses, and all short jumps (i.e., 8-bit
relative addresses in the jump instruction) must be wrapped in .code32
directives to avoid useless bloat by as(1). This also fixes a few
problems that were preventing boot0 from compiling with the latest
and greatest version of as(1).
below). This did not work previously because interrupts were
disabled when PXE calls were being made, and they must be enabled.
This should also allow us to be compliant with all newer PXE rom's
from Intel.
For PXE 0.99, this has been tested using the Intel N440BX motherboard
and I am confident it will work on the Intel L440GX motherboard.
Lots of help/information from: jhb, peter
I would like to thank Michael Johnston <michael.johnston@intel.com>,
Mike Henry <mike.henry@intel.com>, and all the other PXE developers
at Intel for their help, and information in helping solve this
problem.
from user mode. Don't disable interrupts when returning from vm86 mode
to user mode either. Now, we only disable interrupts before calling a
hardware interrupt handler, which is the only time we _should_ be
disabling interrupts.
Because of this, err, feature, any routine that one called in vm86 mode
had to re-enable interrupts by setting the interrupt flag or interrupts
would remain disabled even after the routine returned. For example, I
have a simple debugging routine that uses a vm86 mode function to dump
any arbitrary memory word that I use to read the BIOS timer or any other
memory location. This function does 1 load instruction from memory and
then returns. Since it didn't re-enable interrupts, the first time I
called it to read the BIOS timer, it disabled interrupts. This also
affected the PXE bootstrap as it needs interrupts enabled while it is
processing. This patch fixes both of those situations so that those
functions do not worry about having to enable interrupts. Hardware
interrupt handlers worked fine with the old code because they always
enable interrupts as part of their routine.
If you have any problems with the loader after this commit, please
let me know. I'd like to MFC it in a week or two since PXE support
needs it.
Noticed by: ps, Michael Johnston <michael.johnston@intel.com>
You may specify TFTP or NFS via compile time options in the loader,
but not both at this time.
Also, remove a warning about not knowing how to boot from network
devices. We can obviously do that now.
- Don't hard code 0x10000 as the entry point for the loader. Instead add
src/sys/boot/i386/Makefile.inc which defines a make variable with the
entry point for the loader. Move the loader's entry point up to
0x20000, which makes PXE happy.
- Don't try to use cpp to parse btxldr for the optional BTXLDR_VERBOSE,
instead use m4 to achieve this. Also, add a BTXLDR_VERBOSE knob in the
btxldr Makefile to turn this option on.
- Redo parts of cdldr's Makefile so that it now builds and installs cdboot
instead of having i386/loader/Makefile do that. Also, add in some more
variables to make the pxeldr Makefile almost identical and thus to ease
maintainability.
- Teach cdldr about the a.out format. Cdldr now parsers the a.out header
of the loader binary and relocates it based on that. The entry point of
the loader no longer has to be hardcoded into cdldr. Also, the boot
info table from mkisofs is no longer required to get a useful cdboot.
- Update the lsdev function for BIOS disks to parse other file systems
(such as DOS FAT) that we currently support. This is still buggy as
it assumes that a floppy with a DOS boot sector actually has a MBR and
parses it as such. I'll be fixing this in the future.
- The biggie: Add in support for booting off of PXE-enabled network
adapters. Currently, we use the TFTP API provided by the PXE BIOS.
Eventually we will switch to using the low-level NIC driver thus
allowing both TFTP and NFS to be used, but for now it's just TFTP.
Submitted by: ps, alfred
Testing by: Benno Rice <benno@netizen.com.au>
necessary. Pass an absolute block number too, instead of receiving a
relative one in realstrategy(), as bcache_strategy() requires this.
The fix is sligthly different from the one in the PR.
PR: 17098
Submitted by: John Hood <jhood@sitaranetworks.com>
1) Fix a bug in the int15 function 87 emulation where we only copied half
of what the BIOS asked for. This caused the Mylex RAID adapter to go
haywire and start trashing memory when you tried to boot from it.
2) Don't use interrupt 19 to reboot. Instead, set the reboot flag to a warm
boot and jump to the BIOS's reboot handler. int 19 doesn't clear memory
or restore the interrupt vector table, and thus really isn't safe. For
example, when booting off of PXE, the PXE BIOS eats up a chunk of memory
for its internal data and structures. Since we rebooted via int 19,
using the 'reboot' command in the loader resulted in that memory not
being reclaimed by the BIOS. Thus, after a few PXE boots, the system
was out of lower memory.
3) Catch any int 19 calls made by a BTX client or a user pressing
Ctrl-Alt-Delete and shutdown BTX and reboot the machine cleanly. This
fixes Ctrl-Alt-Delete in the loader and in boot2 instead of presenting
the user with a BTX fault.
Approved by: jkh
Found by: 1) by msmith
- Fix btxldr to preserve a NULL bootinfo pointer when it copies the kernel
arguments.
- Add the cdldr bootstrap program. This program is tacked onto the
beginning of the standard 3rd stage boot loader (/boot/loader) to form
the CD boot loader (/boot/cdboot). When a CD is booted, the cdboot file
is copied into memory instead and executed. The cdldr stub emulates the
environment normally provided by boot2 and then starts the loader. This
booting method does not emulate a floppy drive, but boots directly off of
the CD. This should fix the problems some BIOS's have with emulating a
2.88 MB floppy image.
- Add support to the loader to recognize that it has been booted by cdldr
instead of boot2 and use a simpler method of extracting the BIOS boot
device.
of %cr0 wasn't reloaded into %eax before being modified to turn protected
mode off if PAGING was not defined. The result was that the processor did
not exit protected mode, so when it tried to jump to segment 0x0 in the
next instruction to clear the prefetch cache like one should when leaving
protected mode, it actually tried to jump to a null selector, causing a
GPF.
for our use. Use the same search order for BIOS memory size functions
as the kernel will later use.
Allow the loader to use all of the detected physical memory (this will
greatly help people trying to load enormous memory disk images).
More correctly handle running out of memory when loading an object.
Use the end of base memory for the top of the heap, rather than
blindly hoping that there is 384k left.
Add copyrights to a couple of files I forgot.
-fschedule-insns as it wasn't such a big win with 2.95 after all.
Add the *BIG* win "-mpreferred-stack-boundary=2" optimiztion submitted by
Dima. GCC 2.95 ensures the stack frame is always properly [opitimally]
aligned by surrounding every function call by code simular to
"addl $-12, %esp" / "addl $12, %esp". Here we need the reduction in space,
with speed not an issue.
Remove some printf() calls, reduce size of buffers, and abbreviate
some strings.
Hopefully the boot people will fix this spamage after the cut over to
Gcc 2.95.2 as the system compiler.
either one gives us an additional 32 bytes of additional space available
when using EGCS 1.1.2. With GCC 2.95.2 -fforce-addr gives us 12 more bytes,
and adding -fschedule-insns gives us an additional 4 bytes.
Memory" called as function 0x87 of interrupt 0x15. Since the Mylex RAID
adapter's BIOS used this function to access memory (actually PCI bus
space) beyond 16 MB, this patch also allows BTX to address all 4 Gig of
possible address space on i386+. Since the loader does not have room for
4 MB of page tables, this was done by turning off paging.
Paging was turned off via a compile time setting which defaults to off.
To enable paging, simply define the make variable PAGING.
rnordier might want to clean this up later.
Submitted by: W. Gerald Hicks <wghicks@bellsouth.net>,
Bosko Milekic <bmilekic@ares.dsuper.net>
Reviewed by: msmith
Required by: Mylex RAID adapter's BIOS
numbers that we have been doing in the past, and read /etc/fstab off the
proposed root filesystem to determine the actual device name and vfs
type for the root filesystem. These are then exported to the kernel
via the environment variable vfs.root.mountfrom.
This should resolve the problem raised in PR 12315, and incidentally
makes it easier to determine what geometry the BIOS is actually using
(by way of boot -v and dmesg).
flag to the kernel to mount a CDROM as the root filesystem. Alternatively,
the boot_cdrom env var can be set.
As Mike Smith noted, "-C is the "wrong" way to do this", but this is
an acceptable stopgap in lieu of a better way.
PR: bin/11884
Reviewed by: msmith@freebsd.org
