On 07/06/2022 16:44, Jason A. Donenfeld wrote:
Hi Phil,
On Tue, Jun 07, 2022 at 04:35:32PM +0100, Phil Elwell wrote:
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@raspberrypi.com 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.
Oh good. Adjusting my CI now to have that.
Having tickled arch/arm/ a little bit now, this is looking sort of complicated. So I think I might be leaning toward giving up and just rolling with https://git.zx2c4.com/linux-rng/commit/?id=78f79dda.
Unless of course somebody has some ARM chops and can think of a quick easy fix.
I've not looked at the performance implications (if any), but in terms of when the RNG initilialization completes and the lack of a WARN I'm happy with that patch, a.k.a. [1].
Phil
[1] https://lore.kernel.org/lkml/20220607100210.683136-1-Jason@zx2c4.com/