Some BIOSes (observed with an AMI BIOS on a SunFire X2200) seem to
reset the BIOS drive counter at 40:75 after a failed boot attempt.
This causes problems when attempting a Windows direct-to-iSCSI
installation: bootmgr.exe calls INT 13,0800 and gets told that there
are no hard disks, so never bothers to read the MBR in order to obtain
the boot disk signature.  The Windows iSCSI initiator will detect the
iBFT and connect to the target, and everything will appear to work
except for the error message "This computer's hardware may not support
booting to this disk.  Ensure that the disk's controller is enabled in
the computer's BIOS menu."

Fix by checking the BIOS drive counter on every INT 13 call, and
updating it whenever necessary.

INT 13,15 should return the number of sectors, not the number of
cylinders.

The case of an unsupported SAN protocol will currently not result in
any error message.  Fix by printing the error message at the top level
using strerror(), rather than using hard-coded error messages in the
error paths.

This disgustingly ugly hack just keeps getting worse.

The SRP Boot Firmware Table serves a similar role to the iSCSI and AoE
Boot Firmware Tables; it provides information required by the loaded
OS in order to establish a connection back to the SRP boot device.

SRP is the SCSI RDMA Protocol.  It allows for a method of SAN booting
whereby the target is responsible for reading and writing data using
Remote DMA directly to the initiator's memory.  The software initiator
merely sends and receives SCSI commands; it never has to touch the
actual data.

Add FILE_LICENCE declarations to almost all files that make up the
various standard builds of gPXE.

Avoid passing credentials in the iBFT that were available but not
required for login.  This works around a problem in the Microsoft
iSCSI initiator, which will refuse to initiate sessions if the CHAP
password is fewer than 12 characters, even if the target ends up not
asking for CHAP authentication.

If it happens that _textdata_memsz ends up being an exact multiple of
4kB, then this will cause the .textdata section (after relocation) to
start on a page boundary.  This means that the hidden memory region
(which is rounded down to the nearest page boundary) will start
exactly at virtual address 0, i.e. UNULL.  This means that
init_eheap() will erroneously assume that it has failed to allocate a
an external heap, since it typically ends up choosing the area that
lies immediately below .textdata, which in this case will be the
region with top==UNULL.

A subsequent error is that memtop_urealloc() passes through the error
return status -ENOMEM to the caller, which (rightly) assumes that the
result represents a valid userptr_t address.

Fixed by using alternative tests for heap non-existence, and by
returning UNULL in case of an error from init_eheap().

EFI provides a copy of the SMBIOS table accessible via the EFI system
table, which we should use instead of manually scanning through the
F000:0000 segment.

Remove the assortment of miscellaneous hacks to guess the "network
boot device", and replace them each with a call to last_opened_netdev().

It still isn't guaranteed correct, but it won't be any worse than
before, and it will at least be consistent.

Signed-off-by: Laurent Vivier <Laurent.Vivier@bull.net>

__cdecl is a misleading name, since it currently encapsulates both
cdecl and regparm(0) attributes.  Rename to __asmcall.

Code paths that automatically allocate memory from the FBMS at 40:13
should also free it, if possible.

Freeing this memory will not be possible if either

  1. The FBMS has been modified since our allocation, or

  2. We have not been able to unhook one or more BIOS interrupt vectors.

We now have two implementations for the timer API: one using the
time-of-day counter at 40:70 and one using RDTSC.  Both make use of
timer2_udelay().

Shifting all INT13 drive numbers causes problems on systems that use a
sparse drive number space (e.g. qemu BIOS, which uses 0xe0 for the CD-ROM
drive).

The strategy now is:

  Each drive is assigned a "natural" drive number, being the next
  available drive number in the system (based on the BIOS drive count).

  Each drive is accessed using its specified drive number.  If the
  specified drive number is -1, the natural drive number will be used.

  Accesses to the specified drive number will be delivered to the
  emulated drive, masking out any preexisting drive using this number.

  Accesses to the natural drive number, if different, will be remapped to
  the masked-out drive.

The overall upshot is that, for examples:

  System has no drives.  Emulated INT13 drive gets natural number 0x80
  and specified number 0x80.  Accesses to drive 0x80 go to the emulated
  drive, and there is no remapping.

  System has one drive.  Emulated INT13 drive gets natural number 0x81
  and specified number 0x80.  Accesses to drive 0x80 go to the emulated
  drive.  Accesses to drive 0x81 get remapped to the original drive 0x80.

Added redundant call to get_memmap() in int13_boot() immediately
before jumping to boot sector, to assist in debugging.

Added redundant call to get_memmap() in int13_boot() immediately
before jumping to boot sector, to assist in debugging.

require that we use drive 0x80, so it should probably be the default.

already handled the INT13 call.

emulation support) for an unknown purpose, and breaks grub.

int13.h.

INT 13,08 : read number of drives from 40:75
INT 13,15 : do nothing
all others : restore original value of %dl

on failure).

Added basic El Torito ISO image boot capability

manage to return control.

defined in vsprintf.h.  (This may change, since vsprintf.h is a
non-standard name, but for now it's the one to use.)

There should be no need to include vsprintf.h just for DBG() statements,
since include/compiler.h forces it in for a debug build anyway.

actually do anything with the result, since it carried on using us
even when we returned failure).

our manual ".code32" will break a KEEP_IT_REAL build.

Allow our functions to return a non-zero, non-error status (since the
INT 13 Extensions Check has to return the API version in the register
that is otherwise always used for the error code).

Report a non-zero API version from the INT 13 Extensions Check; GRUB
now uses extended reads.

install() now calls relocate(), moves the protected-mode code to the new
location, and calls hide_etherboot().

int13_boot() now does its own segment register save and restore, ready
for the removal of segment register restoration from the libkir
generic code.

Tidied up debug messages; the log now contains one line per INT 13
operation, looking like

 INT 13,08 (80): Get drive parameters
 INT 13,02 (80): Read: C/H/S 0/47/14 = LBA 0xb9e <-> 1084:0000 (count 106)

the kernel), which encapsulates the information needed to refer to an
external buffer.  Under normal operation, this can just be a void *
equivalent, but under -DKEEP_IT_REAL it would be a segoff_t equivalent.

Use this concept to avoid the need for bounce buffers in int13.c,
which reduces memory usage and opens up the possibility of using
multi-sector reads.

Extend the block-device API and the SCSI block device implementation
to support multi-sector reads.

Update iscsi.c to use user buffers.

Move the obsolete portions of realmode.h to old_realmode.h.

MS-DOS now boots an order of magnitude faster over iSCSI (~10 seconds
from power-up to C:> prompt in bochs).

linear calls to load the MS-DOS boot sector in my test setup.