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authorHeiko Carstens <hca@linux.ibm.com>2020-11-16 08:06:41 +0100
committerHeiko Carstens <hca@linux.ibm.com>2020-11-23 12:01:12 +0100
commit0290c9e328e04052e317171953feb18177a34aed (patch)
tree9ba70533fc8727ef2d664542b62f90180d44819c
parent87d5986345219a7e4f204726d9085ea87f3e22d0 (diff)
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>
-rw-r--r--arch/s390/include/asm/mmu_context.h2
-rw-r--r--arch/s390/include/asm/pgtable.h1
-rw-r--r--arch/s390/kernel/smp.c2
-rw-r--r--arch/s390/kernel/vmlinux.lds.S3
-rw-r--r--arch/s390/mm/init.c10
5 files changed, 13 insertions, 5 deletions
diff --git a/arch/s390/include/asm/mmu_context.h b/arch/s390/include/asm/mmu_context.h
index 51def960a3dd..87a84fc59fc3 100644
--- a/arch/s390/include/asm/mmu_context.h
+++ b/arch/s390/include/asm/mmu_context.h
@@ -79,7 +79,7 @@ static inline void switch_mm(struct mm_struct *prev, struct mm_struct *next,
S390_lowcore.user_asce = next->context.asce;
cpumask_set_cpu(cpu, &next->context.cpu_attach_mask);
/* Clear previous user-ASCE from CR7 */
- __ctl_load(S390_lowcore.kernel_asce, 7, 7);
+ __ctl_load(s390_invalid_asce, 7, 7);
if (prev != next)
cpumask_clear_cpu(cpu, &prev->context.cpu_attach_mask);
}
diff --git a/arch/s390/include/asm/pgtable.h b/arch/s390/include/asm/pgtable.h
index a8edd96b2103..794746a32806 100644
--- a/arch/s390/include/asm/pgtable.h
+++ b/arch/s390/include/asm/pgtable.h
@@ -23,6 +23,7 @@
extern pgd_t swapper_pg_dir[];
extern void paging_init(void);
+extern unsigned long s390_invalid_asce;
enum {
PG_DIRECT_MAP_4K = 0,
diff --git a/arch/s390/kernel/smp.c b/arch/s390/kernel/smp.c
index cac96f240dd8..7f7d81f19292 100644
--- a/arch/s390/kernel/smp.c
+++ b/arch/s390/kernel/smp.c
@@ -259,7 +259,7 @@ static void pcpu_prepare_secondary(struct pcpu *pcpu, int cpu)
lc->spinlock_index = 0;
lc->percpu_offset = __per_cpu_offset[cpu];
lc->kernel_asce = S390_lowcore.kernel_asce;
- lc->user_asce = S390_lowcore.kernel_asce;
+ lc->user_asce = s390_invalid_asce;
lc->machine_flags = S390_lowcore.machine_flags;
lc->user_timer = lc->system_timer =
lc->steal_timer = lc->avg_steal_timer = 0;
diff --git a/arch/s390/kernel/vmlinux.lds.S b/arch/s390/kernel/vmlinux.lds.S
index 177ccfbda40a..4c0e19145cc6 100644
--- a/arch/s390/kernel/vmlinux.lds.S
+++ b/arch/s390/kernel/vmlinux.lds.S
@@ -10,7 +10,8 @@
* Put .bss..swapper_pg_dir as the first thing in .bss. This will
* make sure it has 16k alignment.
*/
-#define BSS_FIRST_SECTIONS *(.bss..swapper_pg_dir)
+#define BSS_FIRST_SECTIONS *(.bss..swapper_pg_dir) \
+ *(.bss..invalid_pg_dir)
/* Handle ro_after_init data on our own. */
#define RO_AFTER_INIT_DATA
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;