arm64 broken in -next by commit 08d53aa58cb1 (of/fdt: export fdt blob as /sys/firmware/fdt)

[Catalin Marinas]

On Wed, Dec 10, 2014 at 12:31:57PM +0000, Ard Biesheuvel wrote:
> On 10 December 2014 at 13:22, Catalin Marinas <catalin.marinas at arm.com> wrote:
> > On Wed, Dec 10, 2014 at 12:13:26PM +0000, Catalin Marinas wrote:
> >> On Wed, Dec 10, 2014 at 12:04:23PM +0000, Catalin Marinas wrote:
> >> > Ard,
> >> >
> >> > I noticed that linux-next no longer boots on Juno. Bisecting, I ended up
> >> > on your commit above and reverting it gets things going again. I
> >> > initially thought it has something to do with the hardware crypto since
> >> > you added some crc32_be() calls but disabling arm64 hw crypto didn't
> >> > make any difference.
> >>
> >> Commenting out crc32_be() in early_init_dt_verify() allows it to boot.
> >> Some printk, it shows:
> >>
> >> initial_boot_params = 0xffffffc01fe00000
> >> fdt_totalsize(initial_boot_params) = 2108105
> >>
> >> Isn't it quite big?
> >
> > We assume that the DT blob is maximum 2MB in the initial kernel mapping.
> > I'm not sure why it is that big here but early_init_dt_verify() most
> > likely doesn't have the areas around initial_boot_params mapped, only
> > 2MB section. The crc probably triggers a very early data abort.
> >
> 
> Looking at the patch history, I just noticed that the crc() call got
> moved to before fdt_check_header(), which means initial_boot_params
> may point to something else than an FDT.
> How exactly that may happen, and how the system ends up booting after
> all is not clear to me, but the crc32() call should be moved down
> regardless

In linux-next, it looks ok to me, crc32 is called after
fdt_check_header():

bool __init early_init_dt_verify(void *params)
{
	if (!params)
		return false;

	/* check device tree validity */
	if (fdt_check_header(params))
		return false;

	/* Setup flat device-tree pointer */
	initial_boot_params = params;
	of_fdt_crc32 = crc32_be(~0, initial_boot_params,
				fdt_totalsize(initial_boot_params));
	return true;
}

-- 
Catalin