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[82.69.66.36]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-477184ff5a0sm41654325e9.6.2025.10.29.02.56.39 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 29 Oct 2025 02:56:39 -0700 (PDT) Date: Wed, 29 Oct 2025 09:56:38 +0000 From: David Laight To: Linus Torvalds Cc: Josh Poimboeuf , Peter Zijlstra , Linux Kernel Mailing List Subject: Re: odd objtool 'unreachable instruction' warning Message-ID: <20251029095638.06cce7c7@pumpkin> In-Reply-To: References: 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 Tue, 28 Oct 2025 12:29:11 -0700 Linus Torvalds wrote: > Josh, Peter, > due to another entirely unrelated discussion, I ended up resurrecting > my "make asm readable" patch that I have had in my local tree when I > want to look at the actual generated code for user accesses. > > That is a local hack that just removes the alternative noise for the > common ops, so that I actually see the fences and clac/stac > instructions as such, instead of seeing them as nops in the object > file or as horrible noise in the assembler output. I've toyed with using explicit nop sequences that would be identifiable as stac, clac and lfence. At least that would tell you which is which. Since the flags can be trashed there are plenty to choose from. (eg all the cmpb $n,%reg if you don't mind a false dependency.) David