modules: Ensure 64-bit alignment on __ksymtab_* sections

On 64-bit architectures without CONFIG_HAVE_ARCH_PREL32_RELOCATIONS
(e.g. ppc64, ppc64le, parisc, s390x,...) the __KSYM_REF() macro stores
64-bit pointers into the __ksymtab* sections.
Make sure that those sections will be correctly aligned at module link time,
otherwise unaligned memory accesses may happen at runtime.

As per unaligned-memory-access [0] "unaligned memory accesses [...]
will not work correctly on certain platforms and will cause performance
problems on others", so fix this.

The __kcrctab* sections store 32-bit entities, so use ALIGN(4) for those.

Signed-off-by: Helge Deller <[email protected]>
[mcgrof: added unaligned-memory-access justification]
Link: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/core-api/unaligned-memory-access.rst # [0]
Signed-off-by: Luis Chamberlain <[email protected]>

Author: hdeller

scripts/module.lds.S

@@ -18,10 +18,10 @@ SECTIONS {
 		*(.export_symbol)
 	}
 
-	__ksymtab		0 : { *(SORT(___ksymtab+*)) }
-	__ksymtab_gpl		0 : { *(SORT(___ksymtab_gpl+*)) }
-	__kcrctab		0 : { *(SORT(___kcrctab+*)) }
-	__kcrctab_gpl		0 : { *(SORT(___kcrctab_gpl+*)) }
+	__ksymtab		0 : ALIGN(8) { *(SORT(___ksymtab+*)) }
+	__ksymtab_gpl		0 : ALIGN(8) { *(SORT(___ksymtab_gpl+*)) }
+	__kcrctab		0 : ALIGN(4) { *(SORT(___kcrctab+*)) }
+	__kcrctab_gpl		0 : ALIGN(4) { *(SORT(___kcrctab_gpl+*)) }
 
 	.ctors			0 : ALIGN(8) { *(SORT(.ctors.*)) *(.ctors) }
 	.init_array		0 : ALIGN(8) { *(SORT(.init_array.*)) *(.init_array) }