9.19. x86_64¶

9.19.1. amd64¶

This BSP offers only one variant, amd64. The BSP can run on UEFI-capable systems by using FreeBSD’s bootloader, which then loads the RTEMS executable (an ELF image).

Currently only the console driver and context initialization and switching are functional (to a bare minimum), but this is enough to run the hello.exe sample in the RTEMS testsuite.

9.19.1.1. Build Configuration Options¶

There are no options available to configure at build time, at the moment.

9.19.1.2. Testing with QEMU¶

To test with QEMU, we need to:

  • Build / install QEMU (most distributions should have it available on the package manager).
  • Build UEFI firmware that QEMU can use to simulate an x86-64 system capable of booting a UEFI-aware kernel, through the --bios flag.

9.19.1.2.1. Building TianoCore’s UEFI firmware, OVMF¶

Complete detailed instructions are available at TianoCore’s Github’s wiki.

Quick instructions (which may fall out of date) are:

$ git clone git://github.com/tianocore/edk2.git
$ cd edk2
$ make -C BaseTools
$ . edksetup.sh

Then edit Conf/target.txt to set:

ACTIVE_PLATFORM       = OvmfPkg/OvmfPkgX64.dsc
TARGET                = DEBUG
TARGET_ARCH           = X64
# You can use GCC46 as well, if you'd prefer
TOOL_CHAIN_TAG        = GCC5

Then run build in the edk2 directory - the output should list the location of the OVMF.fd file, which can be used with QEMU to boot into a UEFI shell.

You can find the OVMF.fd file like this as well in the edk2 directory:

$ find . -name "*.fd"
./Build/OvmfX64/DEBUG_GCC5/FV/MEMFD.fd
./Build/OvmfX64/DEBUG_GCC5/FV/OVMF.fd <-- the file we're looking for
./Build/OvmfX64/DEBUG_GCC5/FV/OVMF_CODE.fd
./Build/OvmfX64/DEBUG_GCC5/FV/OVMF_VARS.fd

9.19.1.3. Boot RTEMS via FreeBSD’s bootloader¶

The RTEMS executable produced (an ELF file) needs to be placed in the FreeBSD’s /boot/kernel/kernel’s place.

To do that, we first need a hard-disk image with FreeBSD installed on it. Download FreeBSD’s installer “memstick” image for amd64 and then run the following commands, replacing paths as appropriate.

$ qemu-img create freebsd.img 8G
$ OVMF_LOCATION=/path/to/ovmf/OVMF.fd
$ FREEBSD_MEMSTICK=/path/to/FreeBSD-11.2-amd64-memstick.img
$ qemu-system-x86_64 -m 1024 -serial stdio --bios $OVMF_LOCATION \
    -drive format=raw,file=freebsd.img \
    -drive format=raw,file=$FREEBSD_MEMSTICK

The first time you do this, continue through and install FreeBSD. FreeBSD’s installation guide may prove useful if required.

Once installed, build your RTEMS executable (an ELF file), for eg. hello.exe. We need to transfer this executable into freebsd.img’s filesystem, at either /boot/kernel/kernel or /boot/kernel.old/kernel.

If your host system supports mounting UFS filesystems as read-write (eg. FreeBSD), go ahead and:

  1. Mount freebsd.img as read-write
  2. Within the filesystem, back the existing FreeBSD kernel up (i.e. effectively cp -r /boot/kernel /boot/kernel.old).
  3. Place your RTEMS executable at /boot/kernel/kernel

If your host doesn’t support mounting UFS filesystems (eg. most Linux kernels), do something to the effect of the following.

On the host

# Upload hello.exe anywhere accessible within the host
$ curl --upload-file hello.exe https://transfer.sh/rtems

Then on the guest (FreeBSD), login with root and

# Back the FreeBSD kernel up
$ cp -r /boot/kernel/ /boot/kernel.old
# Bring networking online if it isn't already
$ dhclient em0
# You may need to add the --no-verify-peer depending on your server
$ fetch https://host.com/path/to/rtems/hello.exe
# Replace default kernel
$ cp hello.exe /boot/kernel/kernel
$ reboot

After rebooting, the RTEMS kernel should run after the UEFI firmware and FreeBSD’s bootloader. The -serial stdio QEMU flag will let the RTEMS console send its output to the host’s stdio stream.

9.19.1.4. Clock Driver¶

The clock driver currently uses the idle thread clock driver.

9.19.1.5. Console Driver¶

The console driver defaults to using the COM1 UART port (at I/O port 0x3F8), using the NS16550 polled driver.