Date: Tue, 7 Oct 2014 17:51:33 +0100 From: Andrew Turner <andrew@fubar.geek.nz> To: Jaemin Yoo <zaemin.yoo@gmail.com> Cc: freebsd-arm@freebsd.org Subject: Re: Q: linking method for armv8 kernel build Message-ID: <20141007175133.6a26bcc5@bender.lan> In-Reply-To: <5433DD2E.1050807@gmail.com> References: <5432A1B5.30406@gmail.com> <20141006154314.1b909772@bender.lan> <5433DD2E.1050807@gmail.com>
next in thread | previous in thread | raw e-mail | index | archive | help
On Tue, 07 Oct 2014 21:31:42 +0900 Jaemin Yoo <zaemin.yoo@gmail.com> wrote: > 2014-10-06 PM 11:43, Andrew Turner wrote: > > On Mon, 06 Oct 2014 23:05:41 +0900 > > Jaemin Yoo <zaemin.yoo@gmail.com> wrote: > > > >> Hello, I just began to download and build kernel for armv8 > >> according to the following howto page. > >> (https://wiki.freebsd.org/arm64) > >> > >> I could create the kernel image without problem. But 'file' says > >> it's dynamically linked. I expected statically linked image to load > >> it on dram using uboot. > >> > >> Is it meant to be? or am I missing some configuration? > > > > All examples of the FreeBSD kernel I've looked at say they are > > dynamically linked. The requirement is the kernel needs to be > > loaded at a 2MiB aligned address for the VA->PA translation to > > work. It will create the page table so the kernel base points to > > the load address. > > > > You may have problems loading it with U-Boot. It expects to be > > loaded by the loader as it passes in the device tree. U-Boot has > > been found to be difficult to support on 32-bit arm. Is there a > > reason to prefer it over UEFI? > > > > Andrew > > > > Thanks. I'm doing most work at linux and vmlinux is mostly(?) > statically linked. So I thought same goes for freebsd too. There are > some 'UND' functions in kernel but I guess it's okay if they are not > used. The only undefined data I get in my arm64 kernel is for uart data. These are specifically set up like this to simplify the code. > I got a 64bit arm board which runs linux from APM. It came with binary > and source codes of u-boot. So I planned to enable bootelf and load > kernel on dram after adding uart driver for the board. I just want to > see freebsd kernel boot on arm64 with minimal changes. You will have issues as the kernel expects to read the dtb from the data provided by the loader. In the short term you could use a static DTB in the kernel however the code to do so has not been written as the kernel should work on all supported hardware. If you go down this route you don't need to use the bootelf command, instead you can either create a U-Boot image using mkimage, or have U-Boot jump to the entry point directly using the go command. Note that the go command may leave the d-cache on causing issues. In the long term the loader should be ported to work on U-Boot. Some of the existing work to have it run on 32-bit ARM can be reused. You will also need to change the early putc function in arm64/arm64/machdep.c. It appears from [1] and [2] the UART is mapped at 0x1c020000. This is within the range set up for the Foundation Model so you should only need up update the early_putc function. It's written for a pl011 with the assumption we will never overflow the fifo. You will need to change this as the APM SoC appears to have an ns16550. At this point you should start to get kernel messages on the serial port, this includes any panic messages if something got missed. Andrew [1] https://github.com/torvalds/linux/blob/master/arch/arm64/boot/dts/apm-mustang.dts [2] https://github.com/torvalds/linux/blob/master/arch/arm64/boot/dts/apm-storm.dtsi
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?20141007175133.6a26bcc5>