Commit 8ddccc8a authored by Alexander Gordeev's avatar Alexander Gordeev Committed by Heiko Carstens
Browse files

s390/boot: cleanup number of page table levels setup 



The separate vmalloc area size check against _REGION2_SIZE
is needed in case user provided insanely large value using
vmalloc= kernel command line parameter. That could lead to
overflow and selecting 3 page table levels instead of 4.

Use size_add() for the overflow check and get rid of the
extra vmalloc area check.

With the current values of CONFIG_MAX_PHYSMEM_BITS and
PAGES_PER_SECTION the sum of maximal possible size of
identity mapping and vmemmap area (derived from these
macros) plus modules area size MODULES_LEN can not
overflow. Thus, that sum is used as first addend while
vmalloc area size is second addend for size_add().

Suggested-by: default avatarHeiko Carstens <hca@linux.ibm.com>
Acked-by: default avatarHeiko Carstens <hca@linux.ibm.com>
Signed-off-by: default avatarAlexander Gordeev <agordeev@linux.ibm.com>
Signed-off-by: default avatarHeiko Carstens <hca@linux.ibm.com>
parent ee4ac527

arch/s390/boot/startup.c

+4 −5
Original line number Diff line number Diff line
@@ -177,6 +177,7 @@ static unsigned long setup_kernel_memory_layout(void) 
	unsigned long asce_limit;

	unsigned long rte_size;

	unsigned long pages;

	unsigned long vsize;

	unsigned long vmax;



	pages = ident_map_size / PAGE_SIZE;
@@ -184,11 +185,9 @@ static unsigned long setup_kernel_memory_layout(void) 
	vmemmap_size = SECTION_ALIGN_UP(pages) * sizeof(struct page);



	/* choose kernel address space layout: 4 or 3 levels. */

	vmemmap_start = round_up(ident_map_size, _REGION3_SIZE);

	if (IS_ENABLED(CONFIG_KASAN) ||

	    vmalloc_size > _REGION2_SIZE ||

	    vmemmap_start + vmemmap_size + vmalloc_size + MODULES_LEN >

		    _REGION2_SIZE) {

	vsize = round_up(ident_map_size, _REGION3_SIZE) + vmemmap_size + MODULES_LEN;

	vsize = size_add(vsize, vmalloc_size);

	if (IS_ENABLED(CONFIG_KASAN) || (vsize > _REGION2_SIZE)) {

		asce_limit = _REGION1_SIZE;

		rte_size = _REGION2_SIZE;

	} else {