Commit 26ced812 authored by Vasily Gorbik's avatar Vasily Gorbik Committed by Heiko Carstens
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s390/kasan: avoid mapping KASAN shadow for standby memory 



KASAN common code is able to handle memory hotplug and create KASAN shadow
memory on a fly. Online memory ranges are available from mem_detect,
use this information to avoid mapping KASAN shadow for standby memory.

Reviewed-by: default avatarAlexander Gordeev <agordeev@linux.ibm.com>
Signed-off-by: default avatarVasily Gorbik <gor@linux.ibm.com>
Signed-off-by: default avatarHeiko Carstens <hca@linux.ibm.com>
parent 8382c963

arch/s390/boot/kaslr.c

+1 −1
Original line number Diff line number Diff line
@@ -182,7 +182,7 @@ unsigned long get_random_base(unsigned long safe_addr) 
	 * which vmem and kasan code will use for shadow memory and

	 * pgtable mapping allocations.

	 */

	memory_limit -= kasan_estimate_memory_needs(memory_limit);

	memory_limit -= kasan_estimate_memory_needs(online_mem_total);

	memory_limit -= vmem_estimate_memory_needs(online_mem_total);



	safe_addr = ALIGN(safe_addr, THREAD_SIZE);

arch/s390/mm/kasan_init.c

+5 −21
Original line number Diff line number Diff line
@@ -227,26 +227,13 @@ void __init kasan_early_init(void) 
	p4d_t p4d_z = __p4d(__pa(kasan_early_shadow_pud) | _REGION2_ENTRY);

	unsigned long untracked_end = MODULES_VADDR;

	unsigned long shadow_alloc_size;

	unsigned long memsize;

	unsigned long start, end;

	int i;



	kasan_early_detect_facilities();

	if (!has_nx)

		pte_z = clear_pte_bit(pte_z, __pgprot(_PAGE_NOEXEC));



	memsize = get_mem_detect_end();

	if (!memsize)

		kasan_early_panic("cannot detect physical memory size\n");

	/*

	 * Kasan currently supports standby memory but only if it follows

	 * online memory (default allocation), i.e. no memory holes.

	 * - memsize represents end of online memory

	 * - ident_map_size represents online + standby and memory limits

	 *   accounted.

	 * Kasan maps "memsize" right away.

	 * [__sha(0), __sha(memsize)]	- shadow memory for identity mapping

	 * The rest [memsize, ident_map_size] if memsize < ident_map_size

	 * could be mapped/unmapped dynamically later during memory hotplug.

	 */

	BUILD_BUG_ON(!IS_ALIGNED(KASAN_SHADOW_START, P4D_SIZE));

	BUILD_BUG_ON(!IS_ALIGNED(KASAN_SHADOW_END, P4D_SIZE));
@@ -256,12 +243,8 @@ void __init kasan_early_init(void) 
	crst_table_init((unsigned long *)kasan_early_shadow_pmd, pmd_val(pmd_z));

	memset64((u64 *)kasan_early_shadow_pte, pte_val(pte_z), PTRS_PER_PTE);



	shadow_alloc_size = memsize >> KASAN_SHADOW_SCALE_SHIFT;



	if (pgalloc_low + shadow_alloc_size > memsize)

		kasan_early_panic("out of memory during initialisation\n");



	if (has_edat) {

		shadow_alloc_size = get_mem_detect_online_total() >> KASAN_SHADOW_SCALE_SHIFT;

		segment_pos = round_down(pgalloc_pos, _SEGMENT_SIZE);

		segment_low = segment_pos - shadow_alloc_size;

		segment_low = round_down(segment_low, _SEGMENT_SIZE);
@@ -299,7 +282,8 @@ void __init kasan_early_init(void) 
	 * +- shadow end ----+---------+- shadow end ---+

	 */

	/* populate kasan shadow (for identity mapping and zero page mapping) */

	kasan_early_pgtable_populate(__sha(0), __sha(memsize), POPULATE_MAP);

	for_each_mem_detect_block(i, &start, &end)

		kasan_early_pgtable_populate(__sha(start), __sha(end), POPULATE_MAP);

	if (IS_ENABLED(CONFIG_KASAN_VMALLOC)) {

		untracked_end = VMALLOC_START;

		/* shallowly populate kasan shadow for vmalloc and modules */