Intel64

Architecture-Specific Directories

Architecture-specific directories hold common source files shared for by implementations of specific x86_64 architectures.

intel64

: This directory holds logic appropriate for any instantiation of the 64-bit intel64 architecture.

Chip-Specific directories

The same x86 architecture may be realized in different chip implementations. For SoC chips, in particular, on-chip devices and differing interrupt structures may require special, chip-specific definitions in these chip-specific directories.

qemu

: This is the implementation of NuttX on the QEMU x86_64. It's empty for now.

Features

Hardware acceleration

Configurable hardware acceleration: SSE, AVX2, AVX512 support.

FMA, AVX and AVX512 support requires XSAVE instructions support which is controlled with CONFIG_ARCH_X86_64_HAVE_XSAVE option.

IRQs

IRQs are managed by LAPIC(X2APIC) and IOAPIC.

Clock source

TSC DEADLINE timer, APIC timer or HPET can be used as system clock.

SMP

SMP is supported up to 4 cores now (BSP + 3 AP), but can be easily extended.

HPET

High Precision Event Timer (HPET) is supported as oneshot timer.

RDRAND

The /dev/random device support with RDRAND instruction is enabled with CONFIG_ARCH_INTEL64_HAVE_RDRAND=y

PCI bus

PCI bus is supported with legacy interrupts, MSI and MSI-X.

Multiboot Framebuffer

Multiboot2 framebuffer is supported with CONFIG_MULTBOOT2_FB_TERM=y.

It is very possible that the framebuffer is mapped in a memory region above 4GB, so you may also need to set CONFIG_MM_PGALLOC=y.

To enable framebuffer support in QEMU, omit the -nographic argument and use -cdrom boot.iso (multiboot2 framebuffer doesn't work with -kernel option).

Also, your GRUB configuration (grub.cfg) should insert the appropriate video module, in many cases insmod all_video should be enough.

Kernel build

Kernel build is supported.

Warning

IMPORTANT: the current implementation doesn't include any protection against speculative execution vulnerabilities (Spectre, Meltdown and others) !

Creating a bootable disk

This build supports multiboot2, which means that usual multiboot2 bootloaders, e.g. grub can be used. To create a bootable disk with grub2, create a directory named iso with grub configuration file and the compiled nuttx.elf.

Directory and file hierarchy:

- iso/
  - boot/
    - grub/
      - grub.cfg
    - nuttx.elf

The grub.cfg should contain the boot entry of NuttX:

set timeout=0
set default=0
menuentry "kernel" {
  multiboot2 /boot/nuttx.elf
}

Making the disk

Use the following command to create the disk. P.S. In some distros, grub-mkrescue is called grub2-mkrescue:

grub-mkrescue -o boot.iso iso

Grub with UEFI

This flow is very similar except you need to have the BOOTX64.EFI file. You can find this in most Linux distributions:

iso/
└── boot
    ├── efi
    │   └── EFI
    │       └── BOOT
    │           └── BOOTX64.EFI
    ├── grub
    │   └── grub.cfg
    └── nuttx.elf

Supported Boards

boards//