From: Dave Hansen <dave.hansen@intel.com>
To: Thomas Gleixner <tglx@kernel.org>, Zach O'Keefe <zokeefe@google.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>,
David Stevens <stevensd@google.com>,
Pasha Tatashin <pasha.tatashin@soleen.com>,
Linus Walleij <linus.walleij@linaro.org>,
Will Deacon <willdeacon@google.com>,
Quentin Perret <qperret@google.com>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
x86@kernel.org, Andy Lutomirski <luto@kernel.org>,
Xin Li <xin@zytor.com>, Peter Zijlstra <peterz@infradead.org>,
Andrew Morton <akpm@linux-foundation.org>,
David Hildenbrand <david@kernel.org>,
Lorenzo Stoakes <ljs@kernel.org>,
"Liam R. Howlett" <Liam.Howlett@oracle.com>,
Vlastimil Babka <vbabka@kernel.org>,
Mike Rapoport <rppt@kernel.org>,
Suren Baghdasaryan <surenb@google.com>,
Michal Hocko <mhocko@suse.com>,
Uladzislau Rezki <urezki@gmail.com>, Kees Cook <kees@kernel.org>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [PATCH v2 00/13] Dynamic Kernel Stacks
Date: Mon, 29 Jun 2026 09:02:08 -0700 [thread overview]
Message-ID: <5604a47b-9457-4162-bd23-720e29cf1983@intel.com> (raw)
In-Reply-To: <87cxxgly12.ffs@fw13>
On 6/23/26 14:58, Thomas Gleixner wrote:
> So as you already confirmed that the number of offenders is really low,
> it'd be definitely a worthwhile effort to fix that for everyone and also
> make the compiler people to get their act together 🙂
One other thing comes to mind...
We have debugging options for looking at max stack depth, like
CONFIG_DEBUG_STACK_USAGE. But no distros seem to turn that on. There's
also some ftrace stuff, but I assume none of that is used at runtime either.
Do we need some max stack depth instrumentation that folks will actually
turn on? It would be nice if we spat out warnings when folks went
through 12k (or 8k) of stack so there was a chance of closing the loop
and getting feedback from them.
It could be done with really little overhead if the vmalloc()'d stacks
set Accessed=0 on their PTEs and then checked them near vfree(). The
PTEs are already getting touched there, so the cachelines should be hot
anyway.
The granularity would only be 4k, but it would be so cheap that we could
turn it on universally. It would also be 100% deterministic.
There are, of course, more games that could be played with stack depth
checks on normal interrupts or NMIs. But those would be less deterministic.
Thoughts?
next prev parent reply other threads:[~2026-06-29 16:02 UTC|newest]
Thread overview: 66+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-04-24 19:14 [PATCH v2 00/13] Dynamic Kernel Stacks David Stevens
2026-04-24 19:14 ` [PATCH v2 01/13] fork: Remove assumption that vm_area->nr_pages equals to THREAD_SIZE David Stevens
2026-04-24 19:14 ` [PATCH v2 02/13] fork: Don't assume fully populated stack during reuse David Stevens
2026-04-24 19:14 ` [PATCH v2 03/13] fork: Move vm_stack to the beginning of the stack David Stevens
2026-04-24 19:14 ` [PATCH v2 04/13] fork: separate vmap stack allocation and free calls David Stevens
2026-04-24 19:14 ` [PATCH v2 05/13] mm/vmalloc: Add a get_vm_area_node() and vmap_pages_range() public functions David Stevens
2026-04-24 19:14 ` [PATCH v2 06/13] fork: Move vmap stack freeing to work queue David Stevens
2026-04-24 19:14 ` [PATCH v2 07/13] fork: Dynamic Kernel Stacks David Stevens
2026-04-24 19:14 ` [PATCH v2 08/13] task_stack.h: Add stack_not_used() support for dynamic stack David Stevens
2026-04-24 19:14 ` [PATCH v2 09/13] fork: Dynamic Kernel Stack accounting David Stevens
2026-04-24 19:14 ` [PATCH v2 10/13] fork: Store task pointer in unpopulated stack ptes David Stevens
2026-06-26 22:46 ` Thomas Gleixner
2026-06-27 23:11 ` Thomas Gleixner
2026-04-24 19:14 ` [PATCH v2 11/13] x86/entry/fred: encode frame pointer on entry David Stevens
2026-04-24 19:14 ` [PATCH v2 12/13] x86: Add support for dynamic kernel stacks via FRED David Stevens
2026-06-26 22:39 ` Thomas Gleixner
2026-06-27 4:05 ` David Stevens
2026-06-28 16:46 ` Thomas Gleixner
2026-06-28 20:33 ` H. Peter Anvin
2026-06-29 8:41 ` Thomas Gleixner
2026-06-29 14:52 ` H. Peter Anvin
2026-04-24 19:14 ` [PATCH v2 13/13] x86: Add support for dynamic kernel stacks via IST David Stevens
2026-04-24 19:41 ` [PATCH v2 00/13] Dynamic Kernel Stacks Dave Hansen
2026-04-24 21:35 ` Pasha Tatashin
2026-04-24 22:21 ` Dave Hansen
2026-04-24 22:49 ` David Stevens
2026-04-24 22:26 ` David Laight
2026-04-24 23:06 ` Pasha Tatashin
2026-06-19 0:29 ` Dave Hansen
2026-06-19 19:56 ` Zach O'Keefe
2026-06-20 5:25 ` David Stevens
2026-06-20 23:22 ` Dave Hansen
2026-04-25 9:19 ` H. Peter Anvin
2026-04-27 16:17 ` Dave Hansen
2026-06-18 14:50 ` Zach O'Keefe
2026-06-18 18:53 ` Dave Hansen
2026-06-18 22:28 ` H. Peter Anvin
2026-06-19 0:40 ` David Stevens
2026-06-19 0:44 ` H. Peter Anvin
2026-06-19 12:45 ` Thomas Gleixner
2026-06-19 19:20 ` Zach O'Keefe
2026-06-19 21:59 ` Thomas Gleixner
2026-06-20 5:02 ` David Stevens
2026-06-20 21:59 ` Thomas Gleixner
2026-06-20 19:33 ` Zach O'Keefe
2026-06-20 19:44 ` H. Peter Anvin
2026-06-20 20:01 ` Zach O'Keefe
2026-06-20 23:34 ` Thomas Gleixner
2026-06-22 23:00 ` Zach O'Keefe
2026-06-23 7:50 ` David Hildenbrand (Arm)
2026-06-23 9:10 ` David Laight
2026-06-23 9:19 ` David Hildenbrand (Arm)
2026-06-23 21:58 ` Thomas Gleixner
2026-06-29 16:02 ` Dave Hansen [this message]
2026-06-29 16:12 ` H. Peter Anvin
2026-06-29 16:18 ` Vlastimil Babka (SUSE)
2026-06-29 16:21 ` H. Peter Anvin
2026-06-29 17:29 ` Zach O'Keefe
2026-06-29 17:38 ` Dave Hansen
2026-06-29 19:43 ` David Laight
2026-06-29 20:17 ` Matthew Wilcox
2026-06-29 20:28 ` David Laight
2026-06-25 11:56 ` Andrew Cooper
2026-06-25 21:38 ` H. Peter Anvin
2026-06-26 8:16 ` David Laight
2026-04-27 16:31 ` Pasha Tatashin
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