elf2efi converts a suitable ELF executable (containing relocation
information, and with appropriate virtual addresses) into an EFI
executable.  It is less tightly coupled with the gPXE build process
and, in particular, does not require the use of a hand-crafted PE
image header in efiprefix.S.

elf2efi correctly handles .bss sections, which significantly reduces
the size of the gPXE EFI executable.

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.

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.

Allow for the build CPU architecture and platform to be specified as part
of the make command goals.  For example:

  make bin/rtl8139.rom      # Standard i386 PC-BIOS build

  make bin-efi/rtl8139.efi  # i386 EFI build

The generic syntax is "bin[-[arch-]platform]", with the default
architecture being "i386" (regardless of the host architecture) and the
default platform being "pcbios".

Non-path targets such as "srcs" can be specified using e.g.

  make bin-efi srcs

Note that this changeset is merely Makefile restructuring to allow the
build architecture and platform to be determined by the make command
goals, and to export these to compiled code via the ARCH and PLATFORM
defines.  It doesn't actually introduce any new build platforms.

The arch/i386/Config file has long been marked as deprecated.  Move all
the pertinent bits to arch/i386/Makefile instead and remove
arch/i386/Config.

[] are shell metacharacters, and they can get confused by files in the
local directory.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>

?= in a Makefile means that that variable can be overridden by the
environment.  This is confusing to users, especially with a generic
name like "ARCH".

Signed-off-by: H. Peter Anvin <hpa@zytor.com>

Remove src/Config as it has no more users, and conflicts with
src/config on case-deficient filesystems.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>

stappers and xl0 pointed out that gnu make sets some variables, so ?=
is ineffective in some cases where we use it.. Cross-compilation
requires that some variables can be overridden in the
src/$(ARCH)/Config file, so include that file _after_ utility program
variables are set.

for "echo -e" on the host system.

suitable "echo -e" substitute.

implement the -e option.

(Thanks to Jim McQuillan for this suggestion.)

inside gPXE.

Experimentation reveals that gcc ignores -mrtd for the implicit
arithmetic functions (e.g. __udivdi3), but not for the implicit
memcpy() and memset() functions.  Mark the implicit arithmetic
functions with __attribute__((cdecl)) to compensate for this.

(Note: we cannot mark with with __cdecl, because we define __cdecl to
incorporate regparm(0) as well.)

Even though it is only currently used for rom-o-matic.net code,
it is good to make sure it gets built, and that the parsing code
is working.

bin/%.bin target.

This reverts commit 9dc2515d7e.

I want "make" to actually build something.

"boot" command to attempt booting from within the command shell, fall back
to shell if boot fails for any reason.