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Processes started with kernel_execve from a kernel thread will have current->mm==NULL. Reading current->mm->context.alloc_pgste will read a more or less random bit from lowcore in this case. If the bit turns out to be set the whole process tree started this way will allocate page table extensions although they have no need for it. Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
100 lines
2.9 KiB
C
100 lines
2.9 KiB
C
/*
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* include/asm-s390/mmu_context.h
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*
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* S390 version
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*
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* Derived from "include/asm-i386/mmu_context.h"
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*/
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#ifndef __S390_MMU_CONTEXT_H
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#define __S390_MMU_CONTEXT_H
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#include <asm/pgalloc.h>
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#include <asm/uaccess.h>
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#include <asm/tlbflush.h>
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#include <asm-generic/mm_hooks.h>
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static inline int init_new_context(struct task_struct *tsk,
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struct mm_struct *mm)
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{
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atomic_set(&mm->context.attach_count, 0);
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mm->context.flush_mm = 0;
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mm->context.asce_bits = _ASCE_TABLE_LENGTH | _ASCE_USER_BITS;
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#ifdef CONFIG_64BIT
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mm->context.asce_bits |= _ASCE_TYPE_REGION3;
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#endif
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if (current->mm && current->mm->context.alloc_pgste) {
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/*
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* alloc_pgste indicates, that any NEW context will be created
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* with extended page tables. The old context is unchanged. The
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* page table allocation and the page table operations will
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* look at has_pgste to distinguish normal and extended page
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* tables. The only way to create extended page tables is to
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* set alloc_pgste and then create a new context (e.g. dup_mm).
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* The page table allocation is called after init_new_context
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* and if has_pgste is set, it will create extended page
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* tables.
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*/
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mm->context.noexec = 0;
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mm->context.has_pgste = 1;
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mm->context.alloc_pgste = 1;
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} else {
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mm->context.noexec = (user_mode == SECONDARY_SPACE_MODE);
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mm->context.has_pgste = 0;
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mm->context.alloc_pgste = 0;
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}
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mm->context.asce_limit = STACK_TOP_MAX;
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crst_table_init((unsigned long *) mm->pgd, pgd_entry_type(mm));
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return 0;
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}
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#define destroy_context(mm) do { } while (0)
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#ifndef __s390x__
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#define LCTL_OPCODE "lctl"
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#else
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#define LCTL_OPCODE "lctlg"
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#endif
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static inline void update_mm(struct mm_struct *mm, struct task_struct *tsk)
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{
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pgd_t *pgd = mm->pgd;
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S390_lowcore.user_asce = mm->context.asce_bits | __pa(pgd);
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if (user_mode != HOME_SPACE_MODE) {
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/* Load primary space page table origin. */
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pgd = mm->context.noexec ? get_shadow_table(pgd) : pgd;
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S390_lowcore.user_exec_asce = mm->context.asce_bits | __pa(pgd);
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asm volatile(LCTL_OPCODE" 1,1,%0\n"
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: : "m" (S390_lowcore.user_exec_asce) );
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} else
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/* Load home space page table origin. */
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asm volatile(LCTL_OPCODE" 13,13,%0"
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: : "m" (S390_lowcore.user_asce) );
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set_fs(current->thread.mm_segment);
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}
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static inline void switch_mm(struct mm_struct *prev, struct mm_struct *next,
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struct task_struct *tsk)
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{
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cpumask_set_cpu(smp_processor_id(), mm_cpumask(next));
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update_mm(next, tsk);
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atomic_dec(&prev->context.attach_count);
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WARN_ON(atomic_read(&prev->context.attach_count) < 0);
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atomic_inc(&next->context.attach_count);
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/* Check for TLBs not flushed yet */
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if (next->context.flush_mm)
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__tlb_flush_mm(next);
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}
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#define enter_lazy_tlb(mm,tsk) do { } while (0)
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#define deactivate_mm(tsk,mm) do { } while (0)
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static inline void activate_mm(struct mm_struct *prev,
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struct mm_struct *next)
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{
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switch_mm(prev, next, current);
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}
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#endif /* __S390_MMU_CONTEXT_H */
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