Re: [PATCH v2] ARM: initialize jump labels before setup_machine_fdt()

[Phil Elwell]

Jason,

On 07/06/2022 16:14, Jason A. Donenfeld wrote:
> Hey again,
>
> On Tue, Jun 07, 2022 at 10:15:27AM +0100, Phil Elwell wrote:
> > On 07/06/2022 09:43, Jason A. Donenfeld wrote:
> > > Hi Phil,
> > >
> > > On Tue, Jun 7, 2022 at 10:29 AM Phil Elwell <phil@xxxxxxxxxxxxxxx> wrote:
> > > > This patch is fatal for me in the downstream Raspberry Pi kernel - it locks up
> > > > on boot even before the earlycon output is available. Hacking jump_label_init to
> > > > skip the jump_entry for "crng_is_ready" allows it to boot, but is likely to have
> > > > consequences further down the line.
> > >
> > > Also, reading this a few times, I'm not 100% sure I understand what
> > > you did to hack around this and why that works. Think you could paste
> > > your hackpatch just out of interest to the discussion (but obviously
> > > not to be applied)?
> >
> > This is the minimal version of my workaround patch that at least allows the
> > board to boot. Bear in mind that it was written with no previous knowledge of
> > jump labels and was arrived at by iteratively bisecting the list of jump_labels
> > until the first dangerous one was found, then later working out that there was
> > only one.
>
> Looks like this patch fails due to CONFIG_STRICT_KERNEL_RWX.
> Investigating deeper now, but that for starters seems to be the
> differentiating factor between my prior test rig and one that reproduces
> the error. I assume your raspi also sets CONFIG_STRICT_KERNEL_RWX.

Yes, it does, as does multi_v7_defconfig.

Phil