[PATCH] arm64: export tishift functions to modules

[Jason A. Donenfeld]

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

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
@@ -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)
 
 ENTRY(__ashrti3)
 	cbz	x2, 1f
@@ -57,6 +48,7 @@ ENTRY(__ashrti3)
 	mov	x1, x2
 	ret
 ENDPROC(__ashrti3)
+EXPORT_SYMBOL(__ashrti3)
 
 ENTRY(__lshrti3)
 	cbz	x2, 1f
@@ -78,3 +70,4 @@ ENTRY(__lshrti3)
 	mov	x1, x2
 	ret
 ENDPROC(__lshrti3)
+EXPORT_SYMBOL(__lshrti3)
-- 
2.17.0