Messages in this thread | | | Subject | Re: [PATCH 11/14] MIPS: memblock: Print out kernel virtual mem layout | From | Matt Redfearn <> | Date | Fri, 19 Jan 2018 07:59:43 +0000 |
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Hi Serge,
On 18/01/18 20:18, Serge Semin wrote: > On Thu, Jan 18, 2018 at 12:03:03PM -0800, Florian Fainelli <f.fainelli@gmail.com> wrote: >> On 01/17/2018 02:23 PM, Serge Semin wrote: >>> It is useful to have the kernel virtual memory layout printed >>> at boot time so to have the full information about the booted >>> kernel. In some cases it might be unsafe to have virtual >>> addresses freely visible in logs, so the %pK format is used if >>> one want to hide them. >>> >>> Signed-off-by: Serge Semin <fancer.lancer@gmail.com> >> >> I personally like having that information because that helps debug and >> have a quick reference, but there appears to be a trend to remove this >> in the name of security: >> >> https://patchwork.kernel.org/patch/10124007/ >> >> maybe hide this behind a configuration option? > > Yeah, arm code was the place I picked the function up.) But in my case > I've used %pK so the pointers would disappear from logging when > kptr_restrict sysctl is 1 or 2. > I agree, that we might need to make the printouts optional. If there is > any kernel config, which for instance increases the kernel security we > could also use it or anything else to discard the printouts at compile > time.
Certainly, when KASLR is active it would be preferable to hide this information, so you could use CONFIG_RELOCATABLE. The existing KASLR stuff additionally hides this kind of information behind CONFIG_DEBUG_KERNEL, so that only people actively debugging the kernel see it:
http://elixir.free-electrons.com/linux/v4.15-rc8/source/arch/mips/kernel/setup.c#L604
Thanks, Matt
> >> -- >> Florian
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