arm64: fix COMPAT_SHMLBA definition for large pages

BugLink: https://bugs.launchpad.net/bugs/1826212

[ Upstream commit b9b7aebb ]

ARM glibc uses (4 * __getpagesize()) for SHMLBA, which is correct for
4KB pages and works fine for 64KB pages, but the kernel uses a hardcoded
16KB that is too small for 64KB page based kernels. This changes the
definition to what user space sees when using 64KB pages.
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Yury Norov <ynorov@caviumnetworks.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

arch/arm64/include/asm/shmparam.h

@@ -21,7 +21,7 @@
  * alignment value. Since we don't have aliasing D-caches, the rest of
  * the time we can safely use PAGE_SIZE.
  */
-#define COMPAT_SHMLBA	0x4000
+#define COMPAT_SHMLBA	(4 * PAGE_SIZE)
 
 #include <asm-generic/shmparam.h>