From: Matthew Wilcox <willy@infradead.org>
To: "H. Peter Anvin" <hpa@zytor.com>
Cc: Xiang Mei <xmei5@asu.edu>, Pedro Falcato <pfalcato@suse.de>,
Kees Cook <kees@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Thomas Gleixner <tglx@kernel.org>, Ingo Molnar <mingo@redhat.com>,
Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
x86@kernel.org, linux-hardening@vger.kernel.org,
Uladzislau Rezki <urezki@gmail.com>,
"Gustavo A . R . Silva" <gustavoars@kernel.org>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
Jennifer Miller <jmill@asu.edu>, Tiffany Bao <tbao@asu.edu>,
Ruoyu Wang <fishw@asu.edu>, Adam Doupe <doupe@asu.edu>,
Kyle Zeng <zengyhkyle@asu.edu>,
Yan Shoshitaishvili <yans@asu.edu>
Subject: Re: [PATCH] mm/vmalloc: widen guard region to defeat ENTER-based stack pivot
Date: Mon, 29 Jun 2026 05:43:15 +0100 [thread overview]
Message-ID: <akH34ycu5-q2Yc_D@casper.infradead.org> (raw)
In-Reply-To: <499a4e15-34a4-421b-946a-c855199fdbf9@zytor.com>
On Sun, Jun 28, 2026 at 07:09:37PM -0700, H. Peter Anvin wrote:
> On 2026-06-26 13:05, Xiang Mei wrote:
> >
> > Thanks for your questions and attention.
> >
> > 1) `enter` can do big enough stack pivoting (where we can't find many
> > `add/sub/adc/sbb rsp, ` doing so)
>
> Say what?
>
> Using add/sub/lea on %rsp is probably more common than enter, because enter is
> considered kind of slow.
>
> gcc, I believe, will generate "leave" but not "enter" as a result.
>
>
> > 2) `enter` is not rare since we can take part in the instruction.
>
> This sentence doesn't parse.
They mean that we can jump into the middle of an instruction, and it is
not rare to see a 'c8' byte in the instruction stream.
next prev parent reply other threads:[~2026-06-29 4:43 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-06-26 17:34 [PATCH] mm/vmalloc: widen guard region to defeat ENTER-based stack pivot Xiang Mei
2026-06-26 17:46 ` Xiang Mei
2026-06-26 17:48 ` Xiang Mei
2026-06-30 7:12 ` Peter Zijlstra
2026-06-30 8:09 ` Xiang Mei
2026-06-26 19:39 ` Pedro Falcato
2026-06-26 20:05 ` Xiang Mei
2026-06-29 2:09 ` H. Peter Anvin
2026-06-29 4:43 ` Matthew Wilcox [this message]
2026-06-29 12:50 ` H. Peter Anvin
2026-06-29 17:21 ` Xiang Mei
2026-06-29 21:50 ` Xiang Mei
2026-06-29 21:51 ` Xiang Mei
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