Using "lret $2" to return from an interrupt causes interrupts to be
disabled in the calling program, since the INT instruction will have
disabled interrupts.  Instead, patch CF on the stack and use iret to
return.

Interestingly, the original PC BIOS had this bug in at least one
place.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Michael Brown <mcb30@etherboot.org>

When handling a redirection event, we need to close the existing
connection before opening the new connection.

This is not strictly an entry requirement, but it does mean that a PXE
NBP returning without setting %ax will appear to have returned
success.

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.

The PXE 1.x spec specifies that on NBP entry or on return from INT
1Ah AX=5650h, EDX shall point to the physical address of the PXENV+
structure.  The PXE 2.x spec drops this requirement, simply stating
that EDX is clobbered.  Given the principle "be conservative in what
you send, liberal in what you accept", however, we should implement
this anyway.

COMBOOT images use INTs to issue API calls; these end up making calls
into gPXE from real mode, and so temporarily change the real-mode
stack pointer.  When our COMBOOT code uses a longjmp() to implement
the various "exit COMBOOT image" API calls, this leaves the real-mode
stack pointer stuck with its temporary value, which causes problems if
we eventually try to exit out of gPXE back to the BIOS.

Fix by adding rmsetjmp() and rmlongjmp() calls (analogous to
sigsetjmp()/siglongjmp()); these save and restore the additional state
needed for real-mode calls to function correctly.

When chaining COMBOOT images, the old images now get freed correctly.

Multi-level menus via COMBOOT rely on the COMBOOT program being able
to exit and invoke a new COMBOOT program (the next menu).  This works,
but rapidly (within about five iterations) runs out of space in gPXE's
internal stack, since each new image is executed in a new function
context.

Fix by allowing tail recursion between images; an image can now
specify a replacement image for itself, and image_exec() will perform
the necessary tail recursion.

Try to avoid future problems caused by implicit section flags and/or
type information by instituting a policy that all .section
declarations must explicitly state the flags and type.

Most of this change was achieved using

    perl -pi \
      -e 's/".text"$/".text", "ax", \@progbits/ ; ' \
      -e 's/".text16"$/".text16", "ax", \@progbits/ ; ' \
      -e 's/".text16.null"$/".text16.null", "ax", \@progbits/ ; ' \
      -e 's/".text16.data"$/".text16.data", "aw", \@progbits/ ; ' \
      -e 's/".data"$/".data", "aw", \@progbits/ ; ' \
      -e 's/".data16"$/".data16", "aw", \@progbits/ ; ' \
      -e 's/".bss"$/".bss", "aw", \@nobits/ ; ' \
      -e 's/".bss16"$/".bss16", "aw", \@nobits/ ; ' \
      -e 's/".prefix"$/".prefix", "ax", \@progbits/ ; ' \
      -e 's/".prefix.lib"$/".prefix.lib", "awx", \@progbits/ ; ' \
      -e 's/".prefix.data"$/".prefix.data", "aw", \@progbits/ ; ' \
      -e 's/".weak"$/".weak", "a", \@nobits/ ; ' \
      `git grep -l '\.section'`

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().

The DHCP client code now implements only the mechanism of the DHCP and
PXE Boot Server protocols.  Boot Server Discovery can be initiated
manually using the "pxebs" command.  The menuing code is separated out
into a user-level function on a par with boot_root_path(), and is
entered in preference to a normal filename boot if the DHCP vendor
class is "PXEClient" and the PXE boot menu option exists.

pxe_tftp.c assumes that the first seek on its data-transfer interface
represents the block size.  Apart from being an ugly hack, this will
also screw up file size calculation for files smaller than one block.

The proper solution would be to extend the data-transfer interface to
support the reporting of stat()-like data.  This is not going to
happen until the cost of adding interface methods is reduced (a fix I
have planned since June 2008).

In the meantime, abuse the xfer_window() method to return the block
size, since it is not being used for anything else and is vaguely
justifiable.

Astonishingly, having returned the incorrect TFTP blocksize via
PXENV_TFTP_OPEN for almost a year seems not to have affected any of
the test cases run during that time; this bug was found only when
someone tried running the heavily-patched version of pxegrub found in
OpenSolaris.

Currently the only supported platform for x86_64 is EFI.

Building an EFI64 gPXE requires a version of gcc that supports
__attribute__((ms_abi)).  This currently means a development build of
gcc; the feature should be present when gcc 4.4 is released.

In the meantime; you can grab a suitable gcc tree from

  git://git.etherboot.org/scm/people/mcb30/gcc/.git

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>

This brings us in to line with Linux definitions, and also simplifies
adding x86_64 support since both platforms have 2-byte shorts, 4-byte
ints and 8-byte long longs.

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

The initial PXE implementation in Etherboot had the goal of being
architecture-agnostic, but this goal has not been realised.

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 have EFI APIs for CPU I/O, PCI I/O, timers, console I/O, user
access and user memory allocation.

EFI executables are created using the vanilla GNU toolchain, with the
EXE header handcrafted in assembly and relocations generated by a
custom efilink utility.

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().

Reduce the number of sections within the linker script to match the
number of practical sections within the output file.

Define _section, _msection, _esection, _section_filesz, _section_memsz,
and _section_lma for each section, replacing the mixture of symbols that
previously existed.

In particular, replace _text and _end with _textdata and _etextdata, to
make it explicit within code that uses these symbols that the .text and
.data sections are always treated as a single contiguous block.

Based on a patch provided by XenSource for Etherboot 5.4.

Wyse Streaming Manager server (WLDRM13.BIN) assumes that the PXENV+
entry point is at UNDI_CS:0000; apparently, somebody at Wyse has
difficulty distinguishing between the words "may" and "must"...

Add a dummy entry point at UNDI_CS:0000, which just jumps to the
correct entry point.

IBM's iSCSI Firmware Initiator checks the UNDIROMID pointer in the
!PXE structure that gets created by the UNDI loader.  We didn't
previously fill this value in.

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.

__from_data16 and __from_text16 now take a pointer to a
.data16/.text16 variable, and return the real-mode offset within the
appropriate segment.  This matches the use case for every occurrence
of these macros, and prevents potential future bugs such as that fixed
in commit d51d80f.  (The bug arose essentially because "&pointer" is
still syntactically valid.)

Add FILE_API_CHECK to the PXEXT API so the NBP can query the
availability and status of the API.

This allows pxelinux to execute arbitrary gPXE commands.  This is
remarkably unsafe (not least because some of the commands will assume
full ownership of memory and do nasty things like edit the e820 map
underneath the calling pxelinux), but it does allow access to the
"sanboot" command.

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