Re: [PATCH 3/3] [v4] lib/vsprintf: no_hash_pointers prints all addresses as unhashed

Geert Uytterhoeven
2021-03-02T19:56:57Z

Hi Steven,

On Tue, Mar 2, 2021 at 3:08 PM Steven Rostedt <rostedt@goodmis.org> wrote:
> On Tue, 2 Mar 2021 14:49:42 +0100
> Geert Uytterhoeven <geert@linux-m68k.org> wrote:
> > > So this is basically a kernel tinyfication issue, right? Is that still pursued
> > > today? Are there better config options suitable for this than CONFIG_DEBUG_KERNEL?
> >
> > As long as I hear about products running Linux on SoCs with 10 MiB of
> > SRAM, I think the answer is yes.
> > I'm not immediately aware of a better config option. There are no more
> > TINY options left, and EXPERT selects DEBUG_KERNEL.
>
> Since the trace_printk() uses the same type of notice, I wonder if we could
> make this into a helper function and just pass in the top part.
>
> + pr_warn("**********************************************************\n");
> + pr_warn("** NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE **\n");
> + pr_warn("** **\n");
>
>
> + pr_warn("** This system shows unhashed kernel memory addresses **\n");
> + pr_warn("** via the console, logs, and other interfaces. This **\n");
> + pr_warn("** might reduce the security of your system. **\n");
>
> Only the above section is really unique. The rest can be a boiler plate.

Good idea. drivers/iommu/iommu-debugfs.c has a third copy.

> + pr_warn("** **\n");
> + pr_warn("** If you see this message and you are not debugging **\n");
> + pr_warn("** the kernel, report this immediately to your system **\n");
> + pr_warn("** administrator! **\n");
> + pr_warn("** **\n");
> + pr_warn("** NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE **\n");
> + pr_warn("**********************************************************\n");

Fortunately gcc is already smart enough to deduplicate identical strings,
but only in the same source file.

Gr{oetje,eeting}s,

Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds