baremetal-helloworld: Enable x86 and x86-64 ports

- The qemux86 port for helloworld-baremetal builds in the standard way, however,
  it uses NASM syntax for the startup code, hence we include a dependency to
  nasm-native, QEMU forces us to use an ELF file rather than a bin file to boot
  from this architecture using the -kernel parameter.

- QEMU refuses to boot using the -kernel parameter for files containing an ELF64
  header [1], instead, it requires a multiboot2 compatible image.

  We could create an image that contains a multiboot2 header by piggybacking
  into grub2-native, specifically grub-mkrescue, but it requires some extra
  runtime dependencies (xorriso which is currently part of meta-oe), and assumes
  a grub installation exists on the host.

  Due to host contamination and dependency complications, we dont rely on grub2,
  but rather do this process manually instead, the x86-64 port contains a stage1
  bootloader, stage2 bootloader and a 64 bit baremetal app (multiboot2
  compatible), booting into real (16 bit), protected (32 bit) and long (64 bit)
  modes, eventually running the helloworld-baremetal app. This is the reason why
  we need the code changes to use a separate Makefile, and create an image
  specifically for qemux86-64.

$ runqemu nographic
Booting from ROM..
Hello OpenEmbedded on x86!

$ runqemu nographic
Starting Stage 1 Bootloader
Loading Stage 2 Bootloader
Stage 2 Loaded.
Jumping to Stage2 Bootloader
In Stage 2
Done

Hello OpenEmbedded on x86-64!

[1] https://gitlab.com/qemu-project/qemu/-/blob/v7.2.0/hw/i386/multiboot.c#L199

(From OE-Core rev: 1dffd81b2991f90ab95cb36d8ff7626efd21434f)

Signed-off-by: Alejandro Enedino Hernandez Samaniego <alejandro@enedino.org>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta-skeleton/recipes-baremetal/baremetal-examples/baremetal-helloworld_git.bb

@@ -4,7 +4,7 @@ DESCRIPTION = "These are introductory examples to showcase the use of QEMU to ru
 LICENSE = "MIT"
 LIC_FILES_CHKSUM = "file://LICENSE;md5=39346640a23c701e4f459e05f56f4449"
 
-SRCREV = "31b4e5a337018b4a00a7426b0e5ed83b81df30c7"
+SRCREV = "22016ecbb9fb6c5f3a7a06698aea7ff8a701c166"
 PV = "0.1+git${SRCPV}"
 
 SRC_URI = "git://github.com/aehs29/baremetal-helloqemu.git;protocol=https;branch=master"
@@ -23,12 +23,15 @@ IMAGE_NAME_SUFFIX ?= ""
 inherit baremetal-image
 
 
+# startup code for x86 uses NASM syntax
+DEPENDS:qemux86:append = " nasm-native"
+
 # These parameters are app specific for this example
 # This will be translated automatically to the architecture and
 # machine that QEMU uses on OE, e.g. -machine virt -cpu cortex-a57
 # but the examples can also be run on other architectures/machines
 # such as vexpress-a15 by overriding the setting on the machine.conf
-COMPATIBLE_MACHINE = "qemuarmv5|qemuarm|qemuarm64|qemuriscv64|qemuriscv32"
+COMPATIBLE_MACHINE = "qemuarmv5|qemuarm|qemuarm64|qemuriscv64|qemuriscv32|qemux86|qemux86-64"
 
 BAREMETAL_QEMUARCH ?= ""
 BAREMETAL_QEMUARCH:qemuarmv5 = "versatile"
@@ -36,9 +39,15 @@ BAREMETAL_QEMUARCH:qemuarm = "arm"
 BAREMETAL_QEMUARCH:qemuarm64 = "aarch64"
 BAREMETAL_QEMUARCH:qemuriscv64 = "riscv64"
 BAREMETAL_QEMUARCH:qemuriscv32 = "riscv32"
+BAREMETAL_QEMUARCH:qemux86 = "x86"
+BAREMETAL_QEMUARCH:qemux86-64 = "x86-64"
 
 EXTRA_OEMAKE:append = " QEMUARCH=${BAREMETAL_QEMUARCH} V=1"
 
+# qemux86-64 uses a different Makefile
+do_compile:prepend:qemux86-64(){
+    cd x86-64
+}
 
 # Install binaries on the proper location for baremetal-image to fetch and deploy
 do_install(){
@@ -51,3 +60,12 @@ FILES:${PN} += " \
     ${base_libdir}/firmware/${BAREMETAL_BINNAME}.bin \
     ${base_libdir}/firmware/${BAREMETAL_BINNAME}.elf \
 "
+
+# qemux86-64 boots from iso rather than -kernel, create image to boot from
+do_image:append:qemux86-64(){
+    dd if=/dev/zero of=${B}/build/img.iso bs=1M count=10 status=none
+    dd if=${B}/build/stage1.bin of=${B}/build/img.iso bs=512 count=1 conv=notrunc
+    dd if=${B}/build/stage2.bin of=${B}/build/img.iso bs=512 seek=1 count=64 conv=notrunc
+    dd if=${B}/build/hello_baremetal_x86-64.bin of=${B}/build/img.iso bs=512 seek=65 conv=notrunc
+    install ${B}/build/img.iso ${IMGDEPLOYDIR}/${IMAGE_LINK_NAME}.iso
+}

meta/classes-recipe/baremetal-image.bbclass

@@ -86,6 +86,11 @@ QB_DEFAULT_FSTYPE ?= "bin"
 QB_DTB ?= ""
 QB_OPT_APPEND:append = " -nographic"
 
+# QEMU x86 requires an .elf kernel to boot rather than a .bin
+QB_DEFAULT_KERNEL:qemux86 ?= "${IMAGE_LINK_NAME}.elf"
+# QEMU x86-64 refuses to boot from -kernel, needs a multiboot compatible image
+QB_DEFAULT_FSTYPE:qemux86-64 ?= "iso"
+
 # RISC-V tunes set the BIOS, unset, and instruct QEMU to
 # ignore the BIOS and boot from -kernel
 QB_DEFAULT_BIOS:qemuriscv64 = ""