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Tue, 31 Mar 2026 07:44:25 -0400 (EDT) X-Mailer: MessagingEngine.com Webmail Interface MIME-Version: 1.0 X-ThreadId: AUJnWW6OA6Vc Date: Tue, 31 Mar 2026 13:44:04 +0200 From: "Arnd Bergmann" To: "Christian Schrefl" , "Miguel Ojeda" , "Russell King" , "Alice Ryhl" Cc: "Ard Biesheuvel" , "Jamie Cunliffe" , "Will Deacon" , "Catalin Marinas" , "Miguel Ojeda" , "Andreas Hindborg" , acourbot@nvidia.com, "Andrew Morton" , "Anton Ivanov" , =?UTF-8?Q?Bj=C3=B6rn_Roy_Baron?= , "Boqun Feng" , "Danilo Krummrich" , "David Gow" , "Gary Guo" , "Johannes Berg" , "Justin Stitt" , linux-arm-kernel@lists.infradead.org, linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-um@lists.infradead.org, llvm@lists.linux.dev, "Benno Lossin" , "Mark Rutland" , mmaurer@google.com, "Bill Wendling" , "Nathan Chancellor" , "Nick Desaulniers" , "Nicolas Schier" , "Nicolas Schier" , "Peter Zijlstra" , "Richard Weinberger" , rust-for-linux@vger.kernel.org, "Trevor Gross" , "Uladzislau Rezki (Sony)" Message-Id: In-Reply-To: References: <20260322192159.88138-1-ojeda@kernel.org> <20260323000327.111235-1-ojeda@kernel.org> <9cf5a94c-0f37-446c-b63d-ddac5674d220@gmail.com> Subject: Re: [PATCH v2 0/3] Inline helpers into Rust without full LTO Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-Rspam-User: X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: A9E1F40002 X-Stat-Signature: a8ez5r5nmtk8icsqgty5deddredp6b6c X-HE-Tag: 1774957467-180926 X-HE-Meta: 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 7xS+wzXO D8mdYMkn55nlzplPv8yW8FSJZBdoAieytjq9ceu43ff3mZehWhZ7dCkbdWUPr4vh5t9u1mC5ba+r8S+WPa1DMtUGd3Z6FxaB0tvNk+Pe6oh0J0IBMGjtywbGwQLDjmS8HMTO4t9QAL1METzDtmUItStZT+Y/Nm08DpWWq6y44PCBqYPrqztinKDIWPwIjz78O66NyB2FPLVMzIRBB9fWog+tMoaAvRy7Smbx/IP8HjZqYQG7x+ZgEYyDTYEUWDb/SxtgsTT2XDuCKFKM/owoOA/L/cUvqolDobrjUlOLOEk86/aEFRbOmjtde0DgfFOWMlkpckHuCB+XemnnWuMenr9ONyodx4KMQ9imcqzeF1CCmqLb/FCWBi1/iM/cQ9iCGj0k+lHlOSQx3KDdr4GFF3/Sbzm68yECit1IS Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, Mar 30, 2026, at 23:09, Christian Schrefl wrote: > On 3/26/26 6:30 PM, Miguel Ojeda wrote: >> On Thu, Mar 26, 2026 at 4:18=E2=80=AFPM Russell King (Oracle) >> wrote: >>> >>> I'm not sure if this is still true, but I believe it used to be the = case >>> that the -linux-gnueabi target has one behaviour for enums (fixed si= ze) >>> whereas -none-eabi, the size of the type depends on the range of val= ues >>> included in the enum. >>> >>> Certianly, when Arm Ltd were proposing EABI, EABI had the latter >>> behaviour, and I think there were cases where Linux used "enum" in >>> its UAPI. >>=20 >> Short enums? I see `c-enum-min-bits` in the armv7a-none-eabi built-in >> `rustc` target, and indeed: >>=20 >> #![no_std] >>=20 >> #[repr(C)] >> enum T { >> A, >> B, >> } >>=20 >> pub static S: usize =3D core::mem::size_of::(); >>=20 >> is 1 for that one, and 4 for the other. > > I guess we could use a custom target spec, but I'm not > sure if that is worth the hassle of adding another one. The kernel Makefile forces the Linux enum behavior using arch/arm/Makefile:CFLAGS_ABI :=3D-mabi=3Daapcs-linux -mfpu=3Dvfp ifeq ($(CONFIG_CC_IS_CLANG),y) CFLAGS_ABI +=3D -meabi gnu endif KBUILD_RUSTFLAGS +=3D --target=3Darm-unknown-linux-gnueabi regardless of the compiler. I think this should be safe for any combination of C and rust compilers. Arnd