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Peter Anvin" , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Jennifer Miller , Tiffany Bao , Ruoyu Wang , Adam Doupe , Kyle Zeng , Yan Shoshitaishvili Subject: Re: [PATCH v2] mm/vmalloc: widen guard region to defeat ENTER-based stack pivot Message-ID: <20260701072747.GN48970@noisy.programming.kicks-ass.net> References: <20260629214712.1198680-1-xmei5@asu.edu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 6165F80005 X-Rspam-User: X-Stat-Signature: hsxsjt1ye91xucmi6mq8ys6ubw4r5ak3 X-HE-Tag: 1782890871-782962 X-HE-Meta: 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 V358RPlE QtgkpGWT5zL70Rc9liLsTaGyuyyjsepevmdoDWqMzxHFE+5yO/k1QayB6gaMJYRD92xHPLX0Ai2+WGVhak3mW0ZeHc3VnHFm48uaDfEaw77WAd7BSbjxGH+FzkfVF2szxYgbRamSqE1iq/PM0zyTEL9kbaFbzFr0XhYPteuopBMRgXz6wy5I5UttxBHE7cElPapRUaBBvCk76H4LDchYan/8/d1ruz2XvMH9PneTEIrlxPVc= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, Jun 29, 2026 at 03:29:50PM -0700, Dave Hansen wrote: > But, really, if ENTER is so evil and nobody uses it, shouldn't we just > have an MSR bit somewhere to tell the CPU to #UD for it rather than > playing these stack games? For supervisor mode only, I suppose. We can't ever get rid of userspace ENTER because legacy I suppose. But we can make sure the kernel is clean. So yeah, having a knob to make supervisor-ENTER trap would be useful I suppose.