In tg3_chip_reset(), the PCI_EXPRESS change is taken from the Linux
tg3 driver. I am not sure what exactly it does (it is not documented
in the Linux driver), but it is necessary for the NIC to work
correctly.

Add yet another ugly hack to iscsiboot.c, this time to allow the user to
inhibit the shutdown/removal of the iSCSI INT13 device (and the network
devices, since they are required for the iSCSI device to function).

On the plus side, the fact that shutdown() now takes flags to
differentiate between shutdown-for-exit and shutdown-for-boot means that
another ugly hack (to allow returning via the PXE stack on BIOSes that
have broken INT 18 calls) will be easier.

I feel dirty.

We can just treat all non-kernel images as initrds, which matches our
behaviour for multiboot kernels.  This allows us to eliminate initrd as
an image type, and treat the "initrd" command as just another synonym for
"imgfetch".

This commit implements GDB over UDP.  Using UDP is more complex than
serial and has required some restructuring.

The GDB stub is now built using one or both of GDBSERIAL and GDBUDP
config.h options.

To enter the debugger, execute the gPXE shell command:
gdbstub <transport> [<options>...]

Where <transport> is "serial" or "udp".  For "udp", the name of a
configured network device is required:
gdbstub udp net0

The GDB stub listens on UDP port 43770 by default.

Some drivers that still use the legacy-driver wrapper (tg3 in particular)
apparently do not specify their alignment constraints properly.  This
hack forces any __shared data to be maximally aligned.

Note that this provides only 16-byte alignment; it is not possible to
request alignment to any greater than 16 bytes using
__attribute__((aligned)), since the relocation code will preserve only 16
byte alignment (and operation under -DKEEP_IT_REAL cannot preserve more
that 16 byte alignment).

Idea proposed by Tim Hockin <thockin@google.com>

Allow for timers to be started with fixed timeouts.

Tested against the mini-slamd server located in contrib/mini-slamd
with a single client, on a lossy network.

UDP sockets can be used for multicast, at which point it becomes
plausible that we could receive packets that aren't destined for us
but that still match on a port number.

Delete ELF as a generic image type.  The method for invoking an
ELF-based image (as well as any tables that must be set up to allow it
to boot) will always depend on the specific architecture.  core/elf.c
now only provides the elf_load() function, to avoid duplicating
functionality between ELF-based image types.

Add arch/i386/image/elfboot.c, to handle the generic case of 32-bit
x86 ELF images.  We don't currently set up any multiboot tables, ELF
notes, etc.  This seems to be sufficient for loading kernels generated
using both wraplinux and coreboot's mkelfImage.

Note that while Etherboot 5.4 allowed ELF images to return, we don't.
There is no callback mechanism for the loaded image to shut down gPXE,
which means that we have to shut down before invoking the image.  This
means that we lose device state, protection against being trampled on,
etc.  It is not safe to continue afterwards.

Return the most appropriate of EACCES, EPERM, ENODEV, ENOTSUP, EIO or
EINVAL depending on the exact error returned by the target, rather than
just always returning EPERM.

Also, ensure that error strings exist for these errors.

Various specification documents disagree about the byte ordering of
UUIDs.  However, SMBIOS seems to use the standard in which everything is
in network-endian order.

This doesn't affect anything sent on the wire; only what gets printed on
the screen when the "uuid" variable is displayed.

From: Stefan Hajnoczi <stefanha@gmail.com>

Drivers are not allowed to call printf().  Converted eprintf() to DBG(),
and removed spurious startup banner.

Fixed hardcoded inclusion of little_bswap.h

Use EIO rather than 1 as an error number.

Add ability for network devices to flag link up/down state to the
networking core.

Autobooting code will now wait for link-up before attempting DHCP.

IPoIB reflects the Infiniband link state as the network device link state
(which is not strictly correct; we also need a succesful IPoIB IPv4
broadcast group join), but is probably more informative.

Infiniband devices no longer block waiting for link-up in
register_ibdev().

Hermon driver needs to create an event queue and poll for link-up events.

Infiniband core needs to reread MAD parameters when link state changes.

IPoIB needs to cope with Infiniband link parameters being only partially
available at probe and open time.

03-19-2008, Hilko Bengen, Cleanups and fixes for newer cards
(successfully tested with 8110SC-d onboard NIC)

In particular, expose the system UUID as a setting ("smbios/uuid").

The PXE spec is (as usual) unclear on precisely when ProxyDHCPREQUESTs
should be issued.  We adapt the following, slightly paranoid approach:

  If an offer contains an IP address, then it is a normal DHCPOFFER.

  If an offer contains an option #60 "PXEClient", then it is a
  ProxyDHCPOFFER.  Note that the same packet can be both a normal
  DHCPOFFER and a ProxyDHCPOFFER.

  After receiving the normal DHCPACK, if we have received a
  ProxyDHCPOFFER, we unicast a ProxyDHCPREQUEST back to the ProxyDHCP
  server on port 4011.  If we time out waiting for a ProxyDHCPACK, we
  treat this as a non-fatal error.

Change the PXE return code for EWOULDBLOCK from PXENV_STATUS_FAILURE
to PXENV_STATUS_TFTP_OPEN.  This code is only used by the FILE_READ
PXEXT call, and is necessary to distinguish "error" from "no data" in
that call.

(The only other nonblocking call is UDP_READ, where the caller doesn't
care about the distinction, however, gPXE doesn't use EWOULDBLOCK
internally to represent this condition in that code.)

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

Allow for settings to be described by something other than a DHCP option
tag if desirable.  Currently used only for the MAC address setting.

Separate out fake DHCP packet creation code from dhcp.c to fakedhcp.c.

Remove notion of settings from dhcppkt.c.

Rationalise dhcp.c to use settings API only for final registration of the
DHCP options, rather than using {store,fetch}_setting throughout.

The home-grown versions don't work properly for static variadic
functions, when gcc can choose to use a non-standard calling convention.

Add dedicated functions create_dhcpdiscover(), create_dhcpack() and
create_proxydhcpack() for use by external code such as the PXE preboot
code.

Register ProxyDHCP options under the global scope "proxydhcp".

Unregister previously-acquired DHCP and ProxyDHCP settings when DHCP
succeeds.

Convert DHCP option applicators in dns.c and iscsi.c to settings
applicators.

Kill off DHCP option applicators.

Add a configuration settings block for each net device.  This will
provide the parent scope for settings applicable only to that network
device (e.g. non-volatile options stored on the NIC, options obtained via
DHCP, etc.).

Expose the MAC address as a setting.

Add the notion of the settings hierarchy, complete with
register/unregister routines.

Rename set->store and get->fetch to avoid naming conflicts with get/put
as used in reference counting.

Add the concept of an abstract configuration setting, comprising a (DHCP)
tag value and an associated byte sequence.

Add the concept of a settings namespace.

Add functions for extracting string, IPv4 address, and signed and
unsigned integer values from configuration settings (analogous to
dhcp_snprintf(), dhcp_ipv4_option(), etc.).

Update functions for parsing and formatting named/typed options to work
with new settings API.

Update NVO commands and config UI to use new settings API.

Timers are sometimes required before the call to initialise(), so we
cannot rely on initialise() to set up the timers before use.

Also fix a potential integer overflow issue in generic_currticks_udelay()

Add missing comments to timer code.

Lock system if no suitable timer source is found.

Fix initialisation order so that timers are initialised before code that
needs to use them.

show_setting() and related functions now return an "actual length" in the
style of snprintf().  This is to allow consumers to allocate buffers large
enough to hold the formatted setting.

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.

Signed-off-by: Alexey Zaytsev <alexey.zaytsev@gmail.com>