arch/arm/include/asm/mmu_context.h

   1 /*
   2  *  arch/arm/include/asm/mmu_context.h
   3  *
   4  *  Copyright (C) 1996 Russell King.
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License version 2 as
   8  * published by the Free Software Foundation.
   9  *
  10  *  Changelog:
  11  *   27-06-1996 RMK     Created
  12  */
  13 #ifndef __ASM_ARM_MMU_CONTEXT_H
  14 #define __ASM_ARM_MMU_CONTEXT_H
  15
  16 #include <linux/compiler.h>
  17 #include <linux/sched.h>
  18 #include <asm/cacheflush.h>
  19 #include <asm/cachetype.h>
  20 #include <asm/proc-fns.h>
  21
  22 void __check_kvm_seq(struct mm_struct *mm);
  23
  24 #ifdef CONFIG_CPU_HAS_ASID
  25
  26 /*
  27  * On ARMv6, we have the following structure in the Context ID:
  28  *
  29  * 31                         7          0
  30  * +-------------------------+-----------+
  31  * |      process ID         |   ASID    |
  32  * +-------------------------+-----------+
  33  * |              context ID             |
  34  * +-------------------------------------+
  35  *
  36  * The ASID is used to tag entries in the CPU caches and TLBs.
  37  * The context ID is used by debuggers and trace logic, and
  38  * should be unique within all running processes.
  39  */
  40 #define ASID_BITS               8
  41 #define ASID_MASK               ((~0) << ASID_BITS)
  42 #define ASID_FIRST_VERSION      (1 << ASID_BITS)
  43
  44 extern unsigned int cpu_last_asid;
  45 #ifdef CONFIG_SMP
  46 DECLARE_PER_CPU(struct mm_struct *, current_mm);
  47 #endif
  48
  49 void __init_new_context(struct task_struct *tsk, struct mm_struct *mm);
  50 void __new_context(struct mm_struct *mm);
  51
  52 static inline void check_context(struct mm_struct *mm)
  53 {
  54         /*
  55          * This code is executed with interrupts enabled. Therefore,
  56          * mm->context.id cannot be updated to the latest ASID version
  57          * on a different CPU (and condition below not triggered)
  58          * without first getting an IPI to reset the context. The
  59          * alternative is to take a read_lock on mm->context.id_lock
  60          * (after changing its type to rwlock_t).
  61          */
  62         if (unlikely((mm->context.id ^ cpu_last_asid) >> ASID_BITS))
  63                 __new_context(mm);
  64
  65         if (unlikely(mm->context.kvm_seq != init_mm.context.kvm_seq))
  66                 __check_kvm_seq(mm);
  67 }
  68
  69 #define init_new_context(tsk,mm)        (__init_new_context(tsk,mm),0)
  70
  71 #else
  72
  73 static inline void check_context(struct mm_struct *mm)
  74 {
  75 #ifdef CONFIG_MMU
  76         if (unlikely(mm->context.kvm_seq != init_mm.context.kvm_seq))
  77                 __check_kvm_seq(mm);
  78 #endif
  79 }
  80
  81 #define init_new_context(tsk,mm)        0
  82
  83 #endif
  84
  85 #define destroy_context(mm)             do { } while(0)
  86
  87 /*
  88  * This is called when "tsk" is about to enter lazy TLB mode.
  89  *
  90  * mm:  describes the currently active mm context
  91  * tsk: task which is entering lazy tlb
  92  * cpu: cpu number which is entering lazy tlb
  93  *
  94  * tsk->mm will be NULL
  95  */
  96 static inline void
  97 enter_lazy_tlb(struct mm_struct *mm, struct task_struct *tsk)
  98 {
  99 }
 100
 101 /*
 102  * This is the actual mm switch as far as the scheduler
 103  * is concerned.  No registers are touched.  We avoid
 104  * calling the CPU specific function when the mm hasn't
 105  * actually changed.
 106  */
 107 static inline void
 108 switch_mm(struct mm_struct *prev, struct mm_struct *next,
 109           struct task_struct *tsk)
 110 {
 111 #ifdef CONFIG_MMU
 112         unsigned int cpu = smp_processor_id();
 113
 114 #ifdef CONFIG_SMP
 115         /* check for possible thread migration */
 116         if (!cpumask_empty(mm_cpumask(next)) &&
 117             !cpumask_test_cpu(cpu, mm_cpumask(next)))
 118                 __flush_icache_all();
 119 #endif
 120         if (!cpumask_test_and_set_cpu(cpu, mm_cpumask(next)) || prev != next) {
 121 #ifdef CONFIG_SMP
 122                 struct mm_struct **crt_mm = &per_cpu(current_mm, cpu);
 123                 *crt_mm = next;
 124 #endif
 125                 check_context(next);
 126                 cpu_switch_mm(next->pgd, next);
 127                 if (cache_is_vivt())
 128                         cpumask_clear_cpu(cpu, mm_cpumask(prev));
 129         }
 130 #endif
 131 }
 132
 133 #define deactivate_mm(tsk,mm)   do { } while (0)
 134 #define activate_mm(prev,next)  switch_mm(prev, next, NULL)
 135
 136 /*
 137  * We are inserting a "fake" vma for the user-accessible vector page so
 138  * gdb and friends can get to it through ptrace and /proc/<pid>/mem.
 139  * But we also want to remove it before the generic code gets to see it
 140  * during process exit or the unmapping of it would  cause total havoc.
 141  * (the macro is used as remove_vma() is static to mm/mmap.c)
 142  */
 143 #define arch_exit_mmap(mm) \
 144 do { \
 145         struct vm_area_struct *high_vma = find_vma(mm, 0xffff0000); \
 146         if (high_vma) { \
 147                 BUG_ON(high_vma->vm_next);  /* it should be last */ \
 148                 if (high_vma->vm_prev) \
 149                         high_vma->vm_prev->vm_next = NULL; \
 150                 else \
 151                         mm->mmap = NULL; \
 152                 rb_erase(&high_vma->vm_rb, &mm->mm_rb); \
 153                 mm->mmap_cache = NULL; \
 154                 mm->map_count--; \
 155                 remove_vma(high_vma); \
 156         } \
 157 } while (0)
 158
 159 static inline void arch_dup_mmap(struct mm_struct *oldmm,
 160                                  struct mm_struct *mm)
 161 {
 162 }
 163
 164 #endif