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[82.69.66.36]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4908098f782sm15483015e9.17.2026.05.27.05.02.08 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 27 May 2026 05:02:09 -0700 (PDT) Date: Wed, 27 May 2026 13:02:04 +0100 From: David Laight To: "H. Peter Anvin" Cc: Sebastian Andrzej Siewior , linux-kernel@vger.kernel.org, x86@kernel.org, Borislav Petkov , Dave Hansen , Ingo Molnar , Jonathan Corbet , Thomas Gleixner Subject: Re: [PATCH] x86: Start removing X86_X32_ABI Message-ID: <20260527130204.1f38710f@pumpkin> In-Reply-To: <5FC3AA08-47C8-46CE-9758-20ECDE6CE018@zytor.com> References: <20260523093734.A3AR7reJ@linutronix.de> <10BF3F18-4709-43D6-979C-49067707F1C1@zytor.com> <20260526104051.MmQQ03a8@linutronix.de> <5FC3AA08-47C8-46CE-9758-20ECDE6CE018@zytor.com> 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, 26 May 2026 08:54:56 -0700 "H. Peter Anvin" wrote: > On May 26, 2026 3:40:51 AM PDT, Sebastian Andrzej Siewior wrote: > >On 2026-05-23 14:43:52 [-0700], H. Peter Anvin wrote: > >> However, we can not recycle the syscall numbers. The x32 flag in the > >> syscall number was advisory originally; it was introduced late in the > >> game to work around a design bug in the input subsystem (*). > > > >If x32 is removed/ not supported why can't the 32/64 bit ABI use syscall > >numbers 512+? It is an ELF32 with EM_X86_64 which should be rejected. > >Shouldn't this free the space because there are no users anymore? > > > >> -hpa > > > >Sebastian > > System call numbers or even mechanisms are in no wise tied to the ELF type. > An x86-64 binary can issue x86-64, x32 or i386 system calls, even from 64-bit mode! > I suspect a 32bit binary can also switch to 64bit mode and issue any of them as well. -- David