s390/mm: align swapper_pg_dir to 16k

The segment/region table that is part of the kernel image must be
properly aligned to 16k in order to make the crdte inline assembly
work.
Otherwise it will calculate a wrong segment/region table start address
and access incorrect memory locations if the swapper_pg_dir is not
aligned to 16k.

Therefore define BSS_FIRST_SECTIONS in order to put the swapper_pg_dir
at the beginning of the bss section and also align the bss section to
16k just like other architectures did.
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/include/asm/pgtable.h

@@ -32,7 +32,7 @@
 #include <asm/bug.h>
 #include <asm/page.h>
 
-extern pgd_t swapper_pg_dir[] __attribute__ ((aligned (4096)));
+extern pgd_t swapper_pg_dir[];
 extern void paging_init(void);
 extern void vmem_map_init(void);
 pmd_t *vmem_pmd_alloc(void);

arch/s390/kernel/vmlinux.lds.S

@@ -4,6 +4,13 @@
 
 #include <asm/thread_info.h>
 #include <asm/page.h>
+
+/*
+ * Put .bss..swapper_pg_dir as the first thing in .bss. This will
+ * make sure it has 16k alignment.
+ */
+#define BSS_FIRST_SECTIONS *(.bss..swapper_pg_dir)
+
 #include <asm-generic/vmlinux.lds.h>
 
 OUTPUT_FORMAT("elf64-s390", "elf64-s390", "elf64-s390")
@@ -81,7 +88,7 @@ SECTIONS
 	. = ALIGN(PAGE_SIZE);
 	__init_end = .;		/* freed after init ends here */
 
-	BSS_SECTION(0, 2, 0)
+	BSS_SECTION(PAGE_SIZE, 4 * PAGE_SIZE, PAGE_SIZE)
 
 	_end = . ;
 

arch/s390/mm/init.c

@@ -40,7 +40,7 @@
 #include <asm/ctl_reg.h>
 #include <asm/sclp.h>
 
-pgd_t swapper_pg_dir[PTRS_PER_PGD] __attribute__((__aligned__(PAGE_SIZE)));
+pgd_t swapper_pg_dir[PTRS_PER_PGD] __section(.bss..swapper_pg_dir);
 
 unsigned long empty_zero_page, zero_page_mask;
 EXPORT_SYMBOL(empty_zero_page);