Commit a3453d92 authored by Vasily Gorbik's avatar Vasily Gorbik Committed by Heiko Carstens
Browse files

s390/kasan: remove 3-level paging support 



Compiling the kernel with Kasan disables automatic 3-level vs 4-level
kernel space paging selection, because the shadow memory offset has
to be known at compile time and there is no such offset which would be
acceptable for both 3 and 4-level paging. Instead S390_4_LEVEL_PAGING
option was introduced which allowed to pick how many paging levels to
use under Kasan.

With the introduction of protected virtualization, kernel memory layout
may be affected due to ultravisor secure storage limit. This adds
additional complexity into how memory layout would look like in
combination with Kasan predefined shadow memory offsets. To simplify
this make Kasan 4-level paging default and remove Kasan 3-level paging
support.

Suggested-by: default avatarHeiko Carstens <hca@linux.ibm.com>
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 f38b0a74

arch/s390/Kconfig

+1 −2
Original line number Diff line number Diff line
@@ -53,8 +53,7 @@ config ARCH_SUPPORTS_UPROBES 
config KASAN_SHADOW_OFFSET

	hex

	depends on KASAN

	default 0x18000000000000 if KASAN_S390_4_LEVEL_PAGING

	default 0x30000000000

	default 0x18000000000000



config S390

	def_bool y

arch/s390/include/asm/kasan.h

+0 −5
Original line number Diff line number Diff line
@@ -5,13 +5,8 @@ 
#ifdef CONFIG_KASAN



#define KASAN_SHADOW_SCALE_SHIFT 3

#ifdef CONFIG_KASAN_S390_4_LEVEL_PAGING

#define KASAN_SHADOW_SIZE						       \

	(_AC(1, UL) << (_REGION1_SHIFT - KASAN_SHADOW_SCALE_SHIFT))

#else

#define KASAN_SHADOW_SIZE						       \

	(_AC(1, UL) << (_REGION2_SHIFT - KASAN_SHADOW_SCALE_SHIFT))

#endif

#define KASAN_SHADOW_OFFSET	_AC(CONFIG_KASAN_SHADOW_OFFSET, UL)

#define KASAN_SHADOW_START	KASAN_SHADOW_OFFSET

#define KASAN_SHADOW_END	(KASAN_SHADOW_START + KASAN_SHADOW_SIZE)

arch/s390/mm/kasan_init.c

+10 −42
Original line number Diff line number Diff line
@@ -123,8 +123,7 @@ static void __init kasan_early_vmemmap_populate(unsigned long address, 
			pgd_populate(&init_mm, pg_dir, p4_dir);

		}



		if (IS_ENABLED(CONFIG_KASAN_S390_4_LEVEL_PAGING) &&

		    mode == POPULATE_SHALLOW) {

		if (mode == POPULATE_SHALLOW) {

			address = (address + P4D_SIZE) & P4D_MASK;

			continue;

		}
@@ -143,12 +142,6 @@ static void __init kasan_early_vmemmap_populate(unsigned long address, 
			p4d_populate(&init_mm, p4_dir, pu_dir);

		}



		if (!IS_ENABLED(CONFIG_KASAN_S390_4_LEVEL_PAGING) &&

		    mode == POPULATE_SHALLOW) {

			address = (address + PUD_SIZE) & PUD_MASK;

			continue;

		}



		pu_dir = pud_offset(p4_dir, address);

		if (pud_none(*pu_dir)) {

			if (mode == POPULATE_ZERO_SHADOW &&
@@ -281,7 +274,6 @@ void __init kasan_early_init(void) 
	unsigned long shadow_alloc_size;

	unsigned long vmax_unlimited;

	unsigned long initrd_end;

	unsigned long asce_type;

	unsigned long memsize;

	unsigned long pgt_prot = pgprot_val(PAGE_KERNEL_RO);

	pte_t pte_z;
@@ -304,25 +296,12 @@ void __init kasan_early_init(void) 
		memsize = min(memsize, OLDMEM_SIZE);

	memsize = min(memsize, KASAN_SHADOW_START);



	if (IS_ENABLED(CONFIG_KASAN_S390_4_LEVEL_PAGING)) {

		/* 4 level paging */

	BUILD_BUG_ON(!IS_ALIGNED(KASAN_SHADOW_START, P4D_SIZE));

	BUILD_BUG_ON(!IS_ALIGNED(KASAN_SHADOW_END, P4D_SIZE));

		crst_table_init((unsigned long *)early_pg_dir,

				_REGION2_ENTRY_EMPTY);

	crst_table_init((unsigned long *)early_pg_dir, _REGION2_ENTRY_EMPTY);

	untracked_mem_end = kasan_vmax = vmax_unlimited = _REGION1_SIZE;

	if (has_uv_sec_stor_limit())

		kasan_vmax = min(vmax_unlimited, uv_info.max_sec_stor_addr);

		asce_type = _ASCE_TYPE_REGION2;

	} else {

		/* 3 level paging */

		BUILD_BUG_ON(!IS_ALIGNED(KASAN_SHADOW_START, PUD_SIZE));

		BUILD_BUG_ON(!IS_ALIGNED(KASAN_SHADOW_END, PUD_SIZE));

		crst_table_init((unsigned long *)early_pg_dir,

				_REGION3_ENTRY_EMPTY);

		untracked_mem_end = kasan_vmax = vmax_unlimited = _REGION2_SIZE;

		asce_type = _ASCE_TYPE_REGION3;

	}



	/* init kasan zero shadow */

	crst_table_init((unsigned long *)kasan_early_shadow_p4d,
@@ -408,7 +387,7 @@ void __init kasan_early_init(void) 
	pgalloc_freeable = pgalloc_pos;

	/* populate identity mapping */

	kasan_early_vmemmap_populate(0, memsize, POPULATE_ONE2ONE);

	kasan_set_pgd(early_pg_dir, asce_type);

	kasan_set_pgd(early_pg_dir, _ASCE_TYPE_REGION2);

	kasan_enable_dat();

	/* enable kasan */

	init_task.kasan_depth = 0;
@@ -428,24 +407,13 @@ void __init kasan_copy_shadow(pgd_t *pg_dir) 
	pgd_t *pg_dir_dst;

	p4d_t *p4_dir_src;

	p4d_t *p4_dir_dst;

	pud_t *pu_dir_src;

	pud_t *pu_dir_dst;



	pg_dir_src = pgd_offset_raw(early_pg_dir, KASAN_SHADOW_START);

	pg_dir_dst = pgd_offset_raw(pg_dir, KASAN_SHADOW_START);

	p4_dir_src = p4d_offset(pg_dir_src, KASAN_SHADOW_START);

	p4_dir_dst = p4d_offset(pg_dir_dst, KASAN_SHADOW_START);

	if (!p4d_folded(*p4_dir_src)) {

		/* 4 level paging */

	memcpy(p4_dir_dst, p4_dir_src,

	       (KASAN_SHADOW_SIZE >> P4D_SHIFT) * sizeof(p4d_t));

		return;

	}

	/* 3 level paging */

	pu_dir_src = pud_offset(p4_dir_src, KASAN_SHADOW_START);

	pu_dir_dst = pud_offset(p4_dir_dst, KASAN_SHADOW_START);

	memcpy(pu_dir_dst, pu_dir_src,

	       (KASAN_SHADOW_SIZE >> PUD_SHIFT) * sizeof(pud_t));

}



void __init kasan_free_early_identity(void)

lib/Kconfig.kasan

+0 −9
Original line number Diff line number Diff line
@@ -136,15 +136,6 @@ config KASAN_STACK 
	default 1 if KASAN_STACK_ENABLE || CC_IS_GCC

	default 0



config KASAN_S390_4_LEVEL_PAGING

	bool "KASan: use 4-level paging"

	depends on S390

	help

	  Compiling the kernel with KASan disables automatic 3-level vs

	  4-level paging selection. 3-level paging is used by default (up

	  to 3TB of RAM with KASan enabled). This options allows to force

	  4-level paging instead.



config KASAN_SW_TAGS_IDENTIFY

	bool "Enable memory corruption identification"

	depends on KASAN_SW_TAGS