Re: kernel loading

[Nick Hudson <nick.hudson%gmx.co.uk@localhost>]

On 11/11/2018 11:57, Robert Swindells wrote:
> Nick Hudson <nick.hudson%gmx.co.uk@localhost> wrote:
> > On 11 Nov 2018, at 11:01, Robert Swindells <rjs%fdy2.co.uk@localhost> wrote:
> > > Nick Hudson <nick.hudson%gmx.co.uk@localhost> wrote:
> > > > > On 10/11/2018 19:45, Robert Swindells wrote:
> > > > >
> > > > > How is loading and running of a 32-bit kernel by u-boot expected to
> > > > > work ?
> > > > >
> > > > > I have copied std.generic and mk.generic to use with fdt zynq sources.
> > > > >
> > > > > The kernel_noload flag to mkubootimage(1) looks to make u-boot execute
> > > > > the kernel in place. What address should I load netbsd.ub at ?
> > > > your uboot "should" have a kernel_addr_r and a fdt_addr_r variable for
> > > > where it'll load the kernel and FDT.  The kernel should be aligned to a
> > > > least L1_S_SIZE (10x00100000).  I guess your old u-boot doesn't.
> > > >
> > > > http://src.illumos.org/source/xref/netbsd-src/sys/arch/arm/include/arm32/pte.h#100
> > > >
> > > > The netbsd.ub is loaded at the aligned address with the header and the
> > > > code is straight after the header, ie. at an offset of 64 bytes.
> > > Ok, thanks.
> > >
> > > I have got further by using -T kernel for the u-boot image with it
> > > linked at the second L1 boundary.
> > Your uboot doesn’t understand kernel_noload?
> I seems to treat kernel_noload as an instruction to not copy the kernel
> to the load address that is in the header.

That's exactly the point.

uboot loads the kernel_noload image at its choice of PA which needs to 
be L1_S_SIZE aligned for us.  The generic start code works out PA and 
creates the appropriate mappings.


> I tried explicitly loading netbsd.ub at 0x0 but that caused the panic
> from arm_bad_vtopdiff.

If RAM starts at 0x0 and isn't used by uboot that should be fine.

What's the full debug output here?

> > > Maybe we will need a PARALLELLA kernel as well as ZYNQ or GENERIC with
> > > them built from the same sources but linked at different addresses.
> > I’ll look to see if there’s a way to get a kernel_noload and a kernel
> > uboot image with a best fit load address.
> Which comes back to my question on what is supposed to happen at boot
> time.
>
> The kernel that I have now is booting fine.

See above? I'm a bit confused what you're asking.

Nick