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From: Heiko Carstens <heiko.carstens@de.ibm.com>
To: Andy Lutomirski <luto@amacapital.net>
Cc: Nadav Amit <nadav.amit@gmail.com>,
	Kees Cook <keescook@chromium.org>,
	Josh Poimboeuf <jpoimboe@redhat.com>,
	Borislav Petkov <bp@alien8.de>, X86 ML <x86@kernel.org>,
	"kernel-hardening@lists.openwall.com" 
	<kernel-hardening@lists.openwall.com>,
	Brian Gerst <brgerst@gmail.com>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: [PATCH 00/13] Virtually mapped stacks with guard pages (x86, core)
Date: Mon, 20 Jun 2016 09:07:24 +0200	[thread overview]
Message-ID: <20160620070724.GB3266@osiris> (raw)
In-Reply-To: <CALCETrUgpbTXnvkmLNZz9sSq8fgz1g8eoGv=1Lif2dhyB6GrSg@mail.gmail.com>

On Sun, Jun 19, 2016 at 11:01:48PM -0700, Andy Lutomirski wrote:
> > The tmll instruction tests if any of the higher bits within the 16k
> > stackframe address are set. In this specific case that would be bits 7-15
> > (mask 0x3f80). If no bit would be set we know that only up to 128 bytes
> > would be left on the stack, and thus trigger an exception.
> >
> > This check does of course only work if a 16k stack is also 16k aligned,
> > which is always the case.
> >
> 
> Oh, interesting.  How do you handle the case of a single function that
> uses more than 128 bytes of stack?

The compiler uses the next larger value of the stackframe size that is a
power of 2 for checking. So another example with a stackframe size of 472
bytes would be the below one with a mask of 0x3e00:

0000000000392db8 <htree_inlinedir_to_tree>:
  392db8:       eb 6f f0 48 00 24       stmg    %r6,%r15,72(%r15)
  392dbe:       a7 f1 3e 00             tmll    %r15,15872
  392dc2:       b9 04 00 ef             lgr     %r14,%r15
  392dc6:       a7 84 00 01             je      392dc8 <htree_inlinedir_to_tree+0x10>
  392dca:       e3 f0 fe 28 ff 71       lay     %r15,-472(%r15)

  reply	other threads:[~2016-06-20  7:35 UTC|newest]

Thread overview: 60+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-06-16  0:28 [PATCH 00/13] Virtually mapped stacks with guard pages (x86, core) Andy Lutomirski
2016-06-16  0:28 ` [PATCH 01/13] x86/mm/hotplug: Don't remove PGD entries in remove_pagetable() Andy Lutomirski
2016-06-16  0:28 ` [PATCH 02/13] x86/cpa: In populate_pgd, don't set the pgd entry until it's populated Andy Lutomirski
2016-06-16  0:28 ` [PATCH 03/13] x86/cpa: Warn if kernel_unmap_pages_in_pgd is used inappropriately Andy Lutomirski
2016-06-16  0:28 ` [PATCH 04/13] mm: Track NR_KERNEL_STACK in pages instead of number of stacks Andy Lutomirski
2016-06-16 11:10   ` Vladimir Davydov
2016-06-16 17:21     ` Andy Lutomirski
2016-06-16 19:20       ` Andy Lutomirski
2016-06-16 15:33   ` Josh Poimboeuf
2016-06-16 17:39     ` Andy Lutomirski
2016-06-16 19:39       ` Josh Poimboeuf
2016-06-16  0:28 ` [PATCH 05/13] mm: Move memcg stack accounting to account_kernel_stack Andy Lutomirski
2016-06-16  0:28 ` [PATCH 06/13] fork: Add generic vmalloced stack support Andy Lutomirski
2016-06-16 17:25   ` Kees Cook
2016-06-16 17:37     ` Andy Lutomirski
2016-06-16  0:28 ` [PATCH 07/13] x86/die: Don't try to recover from an OOPS on a non-default stack Andy Lutomirski
2016-06-16  0:28 ` [PATCH 08/13] x86/dumpstack: When OOPSing, rewind the stack before do_exit Andy Lutomirski
2016-06-16 17:50   ` Josh Poimboeuf
2016-06-16 17:57     ` Andy Lutomirski
2016-06-16  0:28 ` [PATCH 09/13] x86/dumpstack: When dumping stack bytes due to OOPS, start with regs->sp Andy Lutomirski
2016-06-16 11:56   ` Borislav Petkov
2016-07-08 12:07   ` [tip:x86/debug] x86/dumpstack: Honor supplied @regs arg tip-bot for Andy Lutomirski
2016-06-16  0:28 ` [PATCH 10/13] x86/dumpstack: Try harder to get a call trace on stack overflow Andy Lutomirski
2016-06-16 18:16   ` Josh Poimboeuf
2016-06-16 18:22     ` Andy Lutomirski
2016-06-16 18:33       ` Josh Poimboeuf
2016-06-16 18:37         ` Andy Lutomirski
2016-06-16 18:54           ` Josh Poimboeuf
2016-06-16  0:28 ` [PATCH 11/13] x86/dumpstack/64: Handle faults when printing the "Stack:" part of an OOPS Andy Lutomirski
2016-06-16  0:28 ` [PATCH 12/13] x86/mm/64: Enable vmapped stacks Andy Lutomirski
2016-06-16  4:17   ` Mika Penttilä
2016-06-16  5:33     ` Andy Lutomirski
2016-06-16 13:11       ` [kernel-hardening] " Rik van Riel
2016-06-16  0:28 ` [PATCH 13/13] x86/mm: Improve stack-overflow #PF handling Andy Lutomirski
2016-06-16  6:05 ` [PATCH 00/13] Virtually mapped stacks with guard pages (x86, core) Heiko Carstens
2016-06-16 17:50   ` Andy Lutomirski
2016-06-16 18:14     ` Andy Lutomirski
2016-06-16 21:27       ` Andy Lutomirski
2016-06-17  3:58   ` Andy Lutomirski
2016-06-17  7:27     ` Heiko Carstens
2016-06-17 17:38       ` Andy Lutomirski
2016-06-20  5:58         ` Heiko Carstens
2016-06-20  6:01           ` Andy Lutomirski
2016-06-20  7:07             ` Heiko Carstens [this message]
2016-06-16 17:24 ` Kees Cook
2016-07-04 22:31 [PATCH -v2 0/3] x86/MSR: Improve unhandled MSR access error message Borislav Petkov
2016-07-04 22:31 ` [PATCH -v2 1/3] x86/dumpstack: Honor supplied @regs arg Borislav Petkov
2016-07-04 22:31 ` [PATCH -v2 2/3] printk: Make the printk*once() variants return a value Borislav Petkov
2016-07-08 12:08   ` [tip:x86/debug] " tip-bot for Borislav Petkov
2016-07-09  2:40     ` Joe Perches
2016-07-09  7:50       ` Borislav Petkov
2016-07-09 17:56         ` Joe Perches
2016-07-10  6:49           ` Borislav Petkov
2016-07-10  8:23             ` Joe Perches
2016-07-10 12:06               ` Borislav Petkov
2016-07-10 12:33                 ` Joe Perches
2016-07-04 22:31 ` [PATCH -v2 3/3] x86/dumpstack: Add show_stack_regs() and use it Borislav Petkov
2016-07-08 12:08   ` [tip:x86/debug] " tip-bot for Borislav Petkov
2016-07-06 12:58 ` [PATCH -v2 0/3] x86/MSR: Improve unhandled MSR access error message Andy Lutomirski
2016-07-06 13:11   ` Borislav Petkov

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