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authorHeiko Carstens <hca@linux.ibm.com>2020-11-16 10:06:41 +0300
committerHeiko Carstens <hca@linux.ibm.com>2020-11-23 14:01:12 +0300
commit0290c9e328e04052e317171953feb18177a34aed (patch)
tree9ba70533fc8727ef2d664542b62f90180d44819c /arch/s390/mm/init.c
parent87d5986345219a7e4f204726d9085ea87f3e22d0 (diff)
downloadlinux-0290c9e328e04052e317171953feb18177a34aed.tar.xz
s390/mm: use invalid asce instead of kernel asce
Create a region 3 page table which contains only invalid entries, and use that via "s390_invalid_asce" instead of the kernel ASCE whenever there is either - no user address space available, e.g. during early startup - as an intermediate ASCE when address spaces are switched This makes sure that user space accesses in such situations are guaranteed to fail. Reviewed-by: Sven Schnelle <svens@linux.ibm.com> Reviewed-by: Alexander Gordeev <agordeev@linux.ibm.com> Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Diffstat (limited to 'arch/s390/mm/init.c')
-rw-r--r--arch/s390/mm/init.c10
1 files changed, 8 insertions, 2 deletions
diff --git a/arch/s390/mm/init.c b/arch/s390/mm/init.c
index 69e6e2a5072e..73a163065b95 100644
--- a/arch/s390/mm/init.c
+++ b/arch/s390/mm/init.c
@@ -49,6 +49,9 @@
#include <linux/virtio_config.h>
pgd_t swapper_pg_dir[PTRS_PER_PGD] __section(".bss..swapper_pg_dir");
+static pgd_t invalid_pg_dir[PTRS_PER_PGD] __section(".bss..invalid_pg_dir");
+
+unsigned long s390_invalid_asce;
unsigned long empty_zero_page, zero_page_mask;
EXPORT_SYMBOL(empty_zero_page);
@@ -92,6 +95,9 @@ void __init paging_init(void)
unsigned long pgd_type, asce_bits;
psw_t psw;
+ s390_invalid_asce = (unsigned long)invalid_pg_dir;
+ s390_invalid_asce |= _ASCE_TYPE_REGION3 | _ASCE_TABLE_LENGTH;
+ crst_table_init((unsigned long *)invalid_pg_dir, _REGION3_ENTRY_EMPTY);
init_mm.pgd = swapper_pg_dir;
if (VMALLOC_END > _REGION2_SIZE) {
asce_bits = _ASCE_TYPE_REGION2 | _ASCE_TABLE_LENGTH;
@@ -102,14 +108,14 @@ void __init paging_init(void)
}
init_mm.context.asce = (__pa(init_mm.pgd) & PAGE_MASK) | asce_bits;
S390_lowcore.kernel_asce = init_mm.context.asce;
- S390_lowcore.user_asce = S390_lowcore.kernel_asce;
+ S390_lowcore.user_asce = s390_invalid_asce;
crst_table_init((unsigned long *) init_mm.pgd, pgd_type);
vmem_map_init();
kasan_copy_shadow_mapping();
/* enable virtual mapping in kernel mode */
__ctl_load(S390_lowcore.kernel_asce, 1, 1);
- __ctl_load(S390_lowcore.kernel_asce, 7, 7);
+ __ctl_load(S390_lowcore.user_asce, 7, 7);
__ctl_load(S390_lowcore.kernel_asce, 13, 13);
psw.mask = __extract_psw();
psw_bits(psw).dat = 1;