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Date: Thu, 2 Nov 2017 22:41:35 +0100 (CET)
From: Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [PATCH 02/23] x86, kaiser: do not set _PAGE_USER for init_mm
 page tables
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To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andy Lutomirski <luto@amacapital.net>, Dave Hansen <dave.hansen@linux.intel.com>, Andy Lutomirski <luto@kernel.org>, "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>, "linux-mm@kvack.org" <linux-mm@kvack.org>, moritz.lipp@iaik.tugraz.at, Daniel Gruss <daniel.gruss@iaik.tugraz.at>, michael.schwarz@iaik.tugraz.at, Kees Cook <keescook@google.com>, Hugh Dickins <hughd@google.com>, X86 ML <x86@kernel.org>


On Thu, 2 Nov 2017, Linus Torvalds wrote:

> On Thu, Nov 2, 2017 at 11:40 AM, Thomas Gleixner <tglx@linutronix.de> wrote:
> >
> > Hmm. Not sure. IIRC you need to be able to read it to figure out where the
> > entry points are. They are at fixed offsets, but there is some voodoo out
> > there which reads the 'elf' to get to them.
> 
> That would actually be really painful.
> 
> But I *think* you're confusing it with the vdso case, which really
> does do that whole "generate ELF information for debuggers and dynamic
> linkers" thing. The vsyscall page never did that afaik, and purely
> relied on fixed addresses.

Yes, managed to confuse myself. The vsycall page has only the fixed offset
entry points at least when its in emulation mode.

Thanks,

	tglx


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