From 0290c9e328e04052e317171953feb18177a34aed Mon Sep 17 00:00:00 2001 From: Heiko Carstens Date: Mon, 16 Nov 2020 08:06:41 +0100 Subject: 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 Reviewed-by: Alexander Gordeev Signed-off-by: Heiko Carstens --- arch/s390/include/asm/mmu_context.h | 2 +- arch/s390/include/asm/pgtable.h | 1 + arch/s390/kernel/smp.c | 2 +- arch/s390/kernel/vmlinux.lds.S | 3 ++- arch/s390/mm/init.c | 10 ++++++++-- 5 files changed, 13 insertions(+), 5 deletions(-) (limited to 'arch') 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 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; -- cgit v1.2.3