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s390/kasan: remove 3-level paging support

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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: Heiko Carstens <hca@linux.ibm.com>
Reviewed-by: Alexander Gordeev <agordeev@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
This commit is contained in:
Vasily Gorbik 2020-10-15 10:01:42 +02:00 committed by Heiko Carstens
parent f38b0a7439
commit a3453d923e
4 changed files with 11 additions and 58 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
arch/s390/Kconfig
View File

@ -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

5
arch/s390/include/asm/kasan.h
View File

@ -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)

52
arch/s390/mm/kasan_init.c
View File

@ -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);
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;
}
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);
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);
/* 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));
memcpy(p4_dir_dst, p4_dir_src,
(KASAN_SHADOW_SIZE >> P4D_SHIFT) * sizeof(p4d_t));
}
void __init kasan_free_early_identity(void)

9
lib/Kconfig.kasan
View File

@ -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