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Message-ID: <705e95cec3dc5181ca2aa73722e6b84f63f3e91d.camel@web.de>
Date: Thu, 13 Mar 2025 10:22:53 +0100
From: Bert Karwatzki <spasswolf@....de>
To: Balbir Singh <balbirs@...dia.com>
Cc: Ingo Molnar <mingo@...nel.org>, Kees Cook <kees@...nel.org>, Bjorn
Helgaas <bhelgaas@...gle.com>, Linus Torvalds
<torvalds@...ux-foundation.org>, Peter Zijlstra <peterz@...radead.org>,
Andy Lutomirski <luto@...nel.org>, linux-kernel@...r.kernel.org
Subject: Re: commit 7ffb791423c7 breaks steam game
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
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