linux-kernel - Re: [x86, vdso] BUG: unable to handle kernel paging request at d34bd000

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Date:	Sun, 9 Mar 2014 21:46:21 -0700
From:	Andy Lutomirski <luto@...capital.net>
To:	"H. Peter Anvin" <hpa@...ux.intel.com>
Cc:	Stefani Seibold <stefani@...bold.net>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Martin Runge <Martin.Runge@...de-schwarz.com>,
	Andreas Brief <Andreas.Brief@...de-schwarz.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [x86, vdso] BUG: unable to handle kernel paging request at d34bd000

On Sun, Mar 9, 2014 at 8:18 PM, Andy Lutomirski <luto@...capital.net> wrote:
> (Of course, I haven't the faintest idea what l_addr in glibc means.
> If there was a way to arrange for l_addr to be zero, then maybe none
> of this would matter.  Hmm, I wonder if just not relocating the vdso
> at all would have the desired effect.  Anyone out there understand
> glibc?)

No, that won't work.  The bug is that glibc expects PT_DYNAMIC's vaddr
to be the virtual address of the dynamic table.  This can only be true
if the vdso is mapped at the address that the kernel relocated it to.

I also learned that glibc's code is really hideous.  Wow.

--Andy
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