Hi Jason, On Sun, Apr 15, 2018 at 06:04:16PM +0200, Jason A. Donenfeld wrote: > Otherwise modules that use these arithmetic operations will fail to > link. We accomplish this with EXPORT_SYMBOL in the .S file, but because > of symbol versioning, we actually need to have a declaration of these > too in C. So, we introduce asm-prototypes.h, which is the same file name > and technique used for similar reasons in the m68k arch tree. > > While we're at it, we also fix this up to use SPDX, and I personally > choose to relicense this as GPL2||BSD so that these symbols don't need > to be export_symbol_gpl, so all modules can use the routines, since > these are important general purpose compiler-generated function calls. > > Signed-off-by: Jason A. Donenfeld <Jason@xxxxxxxxx> > Reported-by: PaX Team <pageexec@xxxxxxxxxxx> > Cc: stable@xxxxxxxxxxxxxxx > --- > arch/arm64/include/asm/asm-prototypes.h | 11 +++++++++++ > arch/arm64/lib/tishift.S | 19 ++++++------------- > 2 files changed, 17 insertions(+), 13 deletions(-) > create mode 100644 arch/arm64/include/asm/asm-prototypes.h I've not run into any build issues here -- is this specifically with some out-of-tree module? > diff --git a/arch/arm64/include/asm/asm-prototypes.h b/arch/arm64/include/asm/asm-prototypes.h > new file mode 100644 > index 000000000000..8f1919e44f51 > --- /dev/null > +++ b/arch/arm64/include/asm/asm-prototypes.h It would be better not to introduce a new header file just for this, I think. How about compiler.h instead? > @@ -0,0 +1,11 @@ > +/* SPDX-License-Identifier: (GPL-2.0 OR BSD-3-Clause) > + * > + * Copyright (C) 2017-2018 Jason A. Donenfeld <Jason@xxxxxxxxx>. All Rights Reserved. > + */ > + > +/* These functions are defined in lib/tishift.S, but need to be declared > + * here so that symbol versioning picks them up. > + */ > +extern long long __ashlti3(long long a, int b); > +extern long long __ashrti3(long long a, int b); > +extern long long __lshrti3(long long a, int b); > diff --git a/arch/arm64/lib/tishift.S b/arch/arm64/lib/tishift.S > index d3db9b2cd479..3bca433973cb 100644 > --- a/arch/arm64/lib/tishift.S > +++ b/arch/arm64/lib/tishift.S > @@ -1,20 +1,10 @@ > -/* > - * Copyright (C) 2017 Jason A. Donenfeld <Jason@xxxxxxxxx>. All Rights Reserved. > +/* SPDX-License-Identifier: (GPL-2.0 OR BSD-3-Clause) > * > - * This program is free software; you can redistribute it and/or modify > - * it under the terms of the GNU General Public License version 2 as > - * published by the Free Software Foundation. > - * > - * This program is distributed in the hope that it will be useful, > - * but WITHOUT ANY WARRANTY; without even the implied warranty of > - * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the > - * GNU General Public License for more details. > - * > - * You should have received a copy of the GNU General Public License > - * along with this program. If not, see <http://www.gnu.org/licenses/>. > + * Copyright (C) 2017-2018 Jason A. Donenfeld <Jason@xxxxxxxxx>. All Rights Reserved. > */ > > #include <linux/linkage.h> > +#include <asm-generic/export.h> > > ENTRY(__ashlti3) > cbz x2, 1f > @@ -36,6 +26,7 @@ ENTRY(__ashlti3) > mov x0, x2 > ret > ENDPROC(__ashlti3) > +EXPORT_SYMBOL(__ashlti3) We normally export asm symbols via arm64ksyms.c. In fact, would doing that remove the need for the explicit declarations completely? Will