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Date:   Mon, 3 Aug 2020 13:11:27 -0700
From:   Kees Cook <keescook@chromium.org>
To:     "Frank Ch. Eigler" <fche@redhat.com>
Cc:     Joe Lawrence <joe.lawrence@redhat.com>,
        Evgenii Shatokhin <eshatokhin@virtuozzo.com>,
        Kristen Carlson Accardi <kristen@linux.intel.com>,
        Miroslav Benes <mbenes@suse.cz>, tglx@linutronix.de,
        mingo@redhat.com, bp@alien8.de, arjan@linux.intel.com,
        x86@kernel.org, linux-kernel@vger.kernel.org,
        kernel-hardening@lists.openwall.com, rick.p.edgecombe@intel.com,
        live-patching@vger.kernel.org,
        Josh Poimboeuf <jpoimboe@redhat.com>,
        Jessica Yu <jeyu@kernel.org>
Subject: Re: [PATCH v4 00/10] Function Granular KASLR
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On Mon, Aug 03, 2020 at 03:38:37PM -0400, Frank Ch. Eigler wrote:
> Hi -
> 
> > > While this does seem to be the right solution for the extant problem, I
> > > do want to take a moment and ask if the function sections need to be
> > > exposed at all? What tools use this information, and do they just want
> > > to see the bounds of the code region? (i.e. the start/end of all the
> > > .text* sections) Perhaps .text.* could be excluded from the sysfs
> > > section list?
> 
> > [[cc += FChE, see [0] for Evgenii's full mail ]]
> 
> Thanks!
> 
> > It looks like debugging tools like systemtap [1], gdb [2] and its
> > add-symbol-file cmd, etc. peek at the /sys/module/<MOD>/section/ info.
> > But yeah, it would be preferable if we didn't export a long sysfs
> > representation if nobody actually needs it.
> 
> Systemtap needs to know base addresses of loaded text & data sections,
> in order to perform relocation of probe point PCs and context data
> addresses.  It uses /sys/module/...., kind of under protest, because
> there seems to exist no MODULE_EXPORT'd API to get at that information
> some other way.

Wouldn't /proc/kallsysms entries cover this? I must be missing
something...

-- 
Kees Cook