[pcbios] Add extra debugging messages when unhiding iPXE from memory

Signed-off-by: Michael Brown <mcb30@ipxe.org>
[nbiprefix] Set up real-mode stack before jumping to .text16

Signed-off-by: Michael Brown <mcb30@ipxe.org>
[prefix] Use %cs as implicit parameter to uninstall()

romprefix.S currently calls uninstall() with an invalid value in %ax.
Consequently, base memory is not freed after a ROM boot attempt (or
after entering iPXE during POST).

The uninstall() function is physically present in .text16, and so can
use %cs to determine the .text16 segment address.  The .data16 segment
address is not required, since uninstall() is called only by code
paths which set up .data16 to immediately follow .text16.

Signed-off-by: Michael Brown <mcb30@ipxe.org>
[pcbios] Inhibit all calls to INT 15,e820 and INT 15,e801 during POST

Many BIOSes do not construct the full system memory map until after
calling the option ROM initialisation entry points.  For several
years, we have added sanity checks and workarounds to accommodate
charming quirks such as BIOSes which report the entire 32-bit address
space (including all memory-mapped PCI BARs) as being usable RAM.

The IBM x3650 takes quirky behaviour to a new extreme.  Calling either
INT 15,e820 or INT 15,e801 during POST doesn't just get you invalid
data.  We could cope with invalid data.  Instead, these nominally
read-only API calls manage to trash some internal BIOS state, with the
result that the system memory map is _never_ constructed.  This tends
to confuse subsequent bootloaders and operating systems.

[ GRUB 0.97 fails in a particularly amusing way.  Someone thought it
would be a good idea for memcpy() to check that the destination memory
region is a valid part of the system memory map; if not, then memcpy()
will sulk, fail, and return NULL.  This breaks pretty much every use
of memcpy() including, for example, those inserted implicitly by gcc
to copy non-const initialisers.  Debugging is _fun_ when a simple call
to printf() manages to create an infinite recursion, exhaust the
available stack space, and shut down the CPU. ]

Fix by completely inhibiting calls to INT 15,e820 and INT 15,e801
during POST.

We do now allow relocation during POST up to the maximum address
returned by INT 15,88 (which seems so far to always be safe).  This
allows us to continue to have a reasonable size of external heap, even
if the PMM allocation is close to the 1MB mark.

The downside of allowing relocation during POST is that we may
overwrite PMM-allocated memory in use by other option ROMs.  However,
the downside of inhibiting relocation, when combined with also
inhibiting calls to INT 15,e820 and INT 15,e801, would be that we
might have no external heap available: this would make booting an OS
impossible and could prevent some devices from even completing
initialisation.

On balance, the lesser evil is probably to allow relocation during
POST (up to the limit provided by INT 15,88).  Entering iPXE during
POST is a rare operation; on the even rarer systems where doing so
happens to overwrite a PMM-allocated region, then there exists a
fairly simple workaround: if the user enters iPXE during POST and
wishes to exit iPXE, then the user must reboot.  This is an acceptable
cost, given the rarity of the situation and the simplicity of the
workaround.

Signed-off-by: Michael Brown <mcb30@ipxe.org>
[romprefix] Display only one "Ctrl-B" prompt per PCI device during POST

If a multifunction PCI device exposes an iPXE ROM via each function,
then each function will display a "Press Ctrl-B to configure iPXE"
prompt, and delay for two seconds.  Since a single instance of iPXE
can drive all functions on the multifunction device, this simply adds
unnecessary delay to the boot process.

Fix by inhibiting the "Press Ctrl-B" prompt for all except the first
function on a PCI device.

Signed-off-by: Michael Brown <mcb30@ipxe.org>
[efi] Update to latest EDK2 headers

Signed-off-by: Michael Brown <mcb30@ipxe.org>
[autoboot] Split main control flow out of main() into a new function ipxe()

Signed-off-by: Michael Brown <mcb30@ipxe.org>
[efi] Add last_opened_snpdev()

Signed-off-by: Michael Brown <mcb30@ipxe.org>
[efi] Expose downloaded images via EFI_SIMPLE_FILE_SYSTEM_PROTOCOL

Expose iPXE's images as a UEFI file system, allowing the booted image
to access all images downloaded by iPXE.

This functionality is complementary to the custom iPXE download
protocol.  The iPXE download protocol allows a booted image to utilise
iPXE to download arbitrary URIs, but requires the booted image to
specifically support the custom iPXE download protocol.  The new
functionality limits the booted image to accessing only files that
were already downloaded by iPXE (e.g. as part of a script), but can
work with any generic UEFI image (e.g. the UEFI shell).  Both
protocols are provided simultaneously, and are attached to the SNP
device handle.

Signed-off-by: Michael Brown <mcb30@ipxe.org>
[efi] Add our own EFI_LOAD_FILE_PROTOCOL implementation

When iPXE is used as a UEFI driver, the UEFI PXE base code currently
provides the TCP/IP stack, network protocols, and user interface.
This represents a substantial downgrade from the standard BIOS iPXE
user experience.

Fix by installing our own EFI_LOAD_FILE_PROTOCOL implementation which
initiates the standard iPXE boot procedure.  This upgrades the UEFI
iPXE user experience to match the standard BIOS iPXE user experience.

Signed-off-by: Michael Brown <mcb30@ipxe.org>
[efi] Fix building with newer binutils

Newer versions of bfd.h require definitions for the PACKAGE and
PACKAGE_VERSION macros used by autotools.  Work around this by
manually defining these macros before including bfd.h.

Originally-fixed-by: Brandon Penglase <bpenglase-ipxe@spaceservices.net>
Tested-by: Brandon Penglase <bpenglase-ipxe@spaceservices.net>
Signed-off-by: Michael Brown <mcb30@ipxe.org>
[lkrnprefix] Allow relocation when no initrd is present

Commit 2629b7e ("[pcbios] Inhibit all calls to INT 15,e820 and INT
15,e801 during POST") introduced a regression into .lkrn images when
used with no corresponding initrd.

Specifically, the semantics of the "maximum address for relocation"
value passed to install_prealloc() in %ebp changed so that zero became
a special value meaning "inhibit use of INT 15,e820 and INT 15,e801".
The %ebp value meaing "no upper limit on relocation" was changed from
zero to 0xffffffff, and all prefixes providing fixed values for %ebp
were updated to match the new semantics.

The .lkrn prefix provides the initrd base address as the maximum
address for relocation.  When no initrd is present, this address will
be zero, and so will unintentionally trigger the "inhibit INT 15,e820
and INT 15,e801" behaviour.

Fix by explicitly setting %ebp to 0xffffffff if no initrd is present
before calling install_prealloc().

Reported-by: Ján ONDREJ (SAL) <ondrejj@salstar.sk>
Tested-by: Ján ONDREJ (SAL) <ondrejj@salstar.sk>
Signed-off-by: Michael Brown <mcb30@ipxe.org>