Re: [RFC 1/1] add support of `--initrd` for ELF-ARM kernels

[Lankes, Stefan]

Hello Peter,

I totally agree. We are developing a unikernel (https://github.com/hermitcore/rusty-hermit). On x86, we are using the multiboot specification. I thought that this specification is only available on x86.

In principle, a unikernel is a single application, which runs directly on the hardware/VM. Our ELF loader parse the ELF application to determine the thread local storage. On x86, Qemu loads the unikernel as initrd into the memory. The loader just initialize the system. I miss a similar feature on ARM. Maybe I oversee something.

Cheers 

Stefan 

Am 14.04.2023 um 11:03 schrieb Peter Maydell <peter.maydell@linaro.org>:

On Fri, 14 Apr 2023 at 08:35, Stefan Lankes

<slankes@eonerc.rwth-aachen.de> wrote:

Currently, the flag `--initrd` is only support for Linux ARM kernels.

However, also other ELF kernels could depend on an initial ramdisk.

This PR loads also the initrd for ELF kernels and announce the

location by the nodes "/chosen/initrd-start" and

"/chosen/initrd-end" within the device tree.

What are these "other ELF kernels" ? Is there some defined

specification of bootloader you're trying to implement here?

Currently QEMU for Arm supports two things:

(1) I am a Linux kernel, load me like the Linux kernel defines

(2) I'm just a bare-metal image (ELF file or raw)

Adding support for some third type of loading would need a

pretty solid justification, eg that this is a very common kind

of image to load, that there is a well defined specification,

that it's supported by lots of other bootloaders, etc.

The bootloading code is too complicated already and I am

very reluctant to add more to it.

thanks

-- PMM

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