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[82.69.66.36]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3912bfdfcb8sm8137332f8f.33.2025.03.08.00.15.33 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 08 Mar 2025 00:15:33 -0800 (PST) Date: Sat, 8 Mar 2025 08:15:30 +0000 From: David Laight To: Josh Poimboeuf Cc: "H. Peter Anvin" , Ingo Molnar , linux-kernel@vger.kernel.org, tip-bot2 for Josh Poimboeuf , linux-tip-commits@vger.kernel.org, "Peter Zijlstra (Intel)" , Linus Torvalds , Brian Gerst , x86@kernel.org Subject: Re: [tip: x86/asm] x86/asm: Make ASM_CALL_CONSTRAINT conditional on frame pointers Message-ID: <20250308081530.7c7e4f94@pumpkin> In-Reply-To: <20250308013814.sa745d25m3ddlu2b@jpoimboe> References: <174108458405.14745.4864877018394987266.tip-bot2@tip-bot2> <90B1074B-E7D4-4CE0-8A82-ADEB7BAED7AD@zytor.com> <20250307232157.comm4lycebr7zmre@jpoimboe> <20250308013814.sa745d25m3ddlu2b@jpoimboe> 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 Fri, 7 Mar 2025 17:38:14 -0800 Josh Poimboeuf wrote: ... > We hopefully won't need those hacks much longer anyway, as I'll have > another series to propose removing frame pointers for x86-64. > > x86-32 can keep frame pointers, but doesn't need the constraints. It's > not supported for livepatch so it doesn't need to be 100% reliable. > Worst case, an unwind skips a frame, but the call address still shows up > on stack trace dumps prepended with '?'. Doesn't 'user copy hardening' also do stack following? That needs to find all the stack frames (that have locals) and I think is is more reliable with frame pointers. David