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Thu, 9 Jan 2025 15:54:11 -0500 (EST) X-Mailer: MessagingEngine.com Webmail Interface Precedence: bulk X-Mailing-List: linux-alpha@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Date: Thu, 09 Jan 2025 21:53:51 +0100 From: "Arnd Bergmann" To: "Maciej W. Rozycki" , "Eric W. Biederman" Cc: "John Paul Adrian Glaubitz" , "Richard Henderson" , "Matt Turner" , "Kees Cook" , "Paul E. McKenney" , linux-alpha@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, "Michael Cree" , "Sam James" , "Geert Uytterhoeven" , "Michael Karcher" , "Chris Hofstaedtler" , util-linux@vger.kernel.org, linux-mips@vger.kernel.org, loongarch@lists.linux.dev Message-Id: In-Reply-To: References: <20250103140148.370368-1-glaubitz@physik.fu-berlin.de> <24f03227-1b55-4e50-b6e9-7ac74fda2602@app.fastmail.com> <678ee681-12c3-4e79-a04b-495daf343846@app.fastmail.com> <82d33a2d-dffe-4268-a175-4536b3f9c07f@app.fastmail.com> <87ed1cufj1.fsf@email.froward.int.ebiederm.org> Subject: Re: [PATCH] alpha: Fix personality flag propagation across an exec Content-Type: text/plain Content-Transfer-Encoding: 7bit On Thu, Jan 9, 2025, at 21:10, Maciej W. Rozycki wrote: > On Thu, 9 Jan 2025, Eric W. Biederman wrote: > >> > So, this would be the 100% correct for alpha then which would not loose >> > any functionality even for 32-bit binaries? >> >> I don't think it is correct to think about 32-bit binaries on alpha. >> >> Alpha never had a 32bit instruction set. But at some point it looks >> like binaries that could not handle more than 31 bits of address >> space got ported and someone implemented a work-around. I guess this >> is the --taso option that Arnd mentioned. > > This also saves some code space in non-PIE and plain static executables > as it takes fewer machine instructions to load a 64-bit address that is > known beforehand to be a sign-extended 32-bit value. > > This is similar to the MIPS n32 ABI, which also implies a 32-bit address > space while still using 64-bit registers for everything, starting from > stack slots (it's also ILP32 with the `long long' C data type only making > proper use of the full width of the CPU registers, while Alpha's --taso > ABI is I believe IP32 (?) with the plain `long' C data type still 64-bit, > just as with the regular LP64 ABI). I'm pretty sure it's still LP64 on Alpha Linux with gcc. There is an -mpointer-size=32 option in gcc for VMS, but I don't see anything like that in Linux. The only thing that is implemented here is the option for the linker that sets the EF_ALPHA_32BIT bit, but none of the code generation takes advantage of the upper bits being zero. Arnd