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[82.69.66.36]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-48fffb9aac4sm234496915e9.9.2026.05.18.03.28.43 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 18 May 2026 03:28:43 -0700 (PDT) Date: Mon, 18 May 2026 11:28:42 +0100 From: David Laight To: Zong Li Cc: pjw@kernel.org, palmer@dabbelt.com, aou@eecs.berkeley.edu, alex@ghiti.fr, debug@rivosinc.com, linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3] riscv: cif: reduce shadow stack size limit from 4GB to 2GB Message-ID: <20260518112842.07f0f2af@pumpkin> In-Reply-To: <20260518105725.7afe7a4c@pumpkin> References: <20260514075036.1432352-1-zong.li@sifive.com> <20260514095605.2c7d8761@pumpkin> <20260515102411.4d3e868a@pumpkin> <20260515201613.243ea49b@pumpkin> <20260518105725.7afe7a4c@pumpkin> X-Mailer: Claws Mail 4.1.1 (GTK 3.24.38; arm-unknown-linux-gnueabihf) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Mon, 18 May 2026 10:57:25 +0100 David Laight wrote: .. > Actually would it be possible to initially just allocate one page? > If you get an overflow fault on the shadow stack I think you can > safely reallocate it at an entirely different user virtual address. > That would remove all the problems over committing a lot of swap. > Most threads will never do the 512 nested calls needed to blow the stack. Forget that - probably breaks setjmp(). -- David