Re: commit 7ffb791423c7 breaks steam game

[Bert Karwatzki]

Am Mittwoch, dem 12.03.2025 um 12:24 +1100 schrieb Balbir Singh:
> > >
> > > >
> > > > As a sidenote, I've tested several kernel with nokaslr as command line parameter
> > > > (6.1.128, 6.8.12, 6.12.17 (the debian sid distributional kernel)) and nokaslr is
> > > > not recognized as a command line parameter in any of them
> > > >
> > >
> > > Please see my comment above about booting. How did you check if nokaslr is being
> > > recognized, is it via looking up dmesg?
> > >
> > When I boot with nokaslr I get the following messages in dmesg
> > [    T0] Unknown kernel command line parameters "nokaslr
> > BOOT_IMAGE=/boot/vmlinuz-6.14.0-rc5-next-20250307-master", will be passed to
> > user space.
> >
> > This also happens when I use the debian kernel with standard .config
>
> That is quite strange, I can see nokaslr handling in choose_random_location() in
> arch/x86/boot/compressed/kaslr.c (which depends on CONFIG_RANDOMIZE_BASE)
>
> Thanks,
> Balbir

The command line parameter nokaslr does actually work, I tested that by booting
the kernel with and without nokaslr and checked /proc/iomem for the physical
address of the kernel. With nokalsr it's always at 0x1200000.

The warning message in the code
	if (cmdline_find_option_bool("nokaslr")) {
		warn("KASLR disabled: 'nokaslr' on cmdline.");
		return;
	}
on the other hand is not shown, because warn is basically __putstr() which
outputs to the serial console and the screen, not the log buffer (Which we do
not have this early in boot anyway, I assume).

So with this solved I tested stellaris with a kernel without CONFIG_PCI_P2PDMA
and nokaslr and found the same buggy behaviour (i.e. laggy input while stellaris
is running).

Bert Karwatzki