arch/x86/include/asm/mmu_context.h

   1 #ifndef _ASM_X86_MMU_CONTEXT_H
   2 #define _ASM_X86_MMU_CONTEXT_H
   3
   4 #include <asm/desc.h>
   5 #include <linux/atomic.h>
   6 #include <linux/mm_types.h>
   7
   8 #include <trace/events/tlb.h>
   9
  10 #include <asm/pgalloc.h>
  11 #include <asm/tlbflush.h>
  12 #include <asm/paravirt.h>
  13 #include <asm/mpx.h>
  14 #ifndef CONFIG_PARAVIRT
  15 static inline void paravirt_activate_mm(struct mm_struct *prev,
  16                                         struct mm_struct *next)
  17 {
  18 }
  19 #endif  /* !CONFIG_PARAVIRT */
  20
  21 #ifdef CONFIG_PERF_EVENTS
  22 extern struct static_key rdpmc_always_available;
  23
  24 static inline void load_mm_cr4(struct mm_struct *mm)
  25 {
  26         if (static_key_false(&rdpmc_always_available) ||
  27             atomic_read(&mm->context.perf_rdpmc_allowed))
  28                 cr4_set_bits(X86_CR4_PCE);
  29         else
  30                 cr4_clear_bits(X86_CR4_PCE);
  31 }
  32 #else
  33 static inline void load_mm_cr4(struct mm_struct *mm) {}
  34 #endif
  35
  36 #ifdef CONFIG_MODIFY_LDT_SYSCALL
  37 /*
  38  * ldt_structs can be allocated, used, and freed, but they are never
  39  * modified while live.
  40  */
  41 struct ldt_struct {
  42         /*
  43          * Xen requires page-aligned LDTs with special permissions.  This is
  44          * needed to prevent us from installing evil descriptors such as
  45          * call gates.  On native, we could merge the ldt_struct and LDT
  46          * allocations, but it's not worth trying to optimize.
  47          */
  48         struct desc_struct *entries;
  49         int size;
  50 };
  51
  52 /*
  53  * Used for LDT copy/destruction.
  54  */
  55 int init_new_context_ldt(struct task_struct *tsk, struct mm_struct *mm);
  56 void destroy_context_ldt(struct mm_struct *mm);
  57 #else   /* CONFIG_MODIFY_LDT_SYSCALL */
  58 static inline int init_new_context_ldt(struct task_struct *tsk,
  59                                        struct mm_struct *mm)
  60 {
  61         return 0;
  62 }
  63 static inline void destroy_context_ldt(struct mm_struct *mm) {}
  64 #endif
  65
  66 static inline void load_mm_ldt(struct mm_struct *mm)
  67 {
  68 #ifdef CONFIG_MODIFY_LDT_SYSCALL
  69         struct ldt_struct *ldt;
  70
  71         /* lockless_dereference synchronizes with smp_store_release */
  72         ldt = lockless_dereference(mm->context.ldt);
  73
  74         /*
  75          * Any change to mm->context.ldt is followed by an IPI to all
  76          * CPUs with the mm active.  The LDT will not be freed until
  77          * after the IPI is handled by all such CPUs.  This means that,
  78          * if the ldt_struct changes before we return, the values we see
  79          * will be safe, and the new values will be loaded before we run
  80          * any user code.
  81          *
  82          * NB: don't try to convert this to use RCU without extreme care.
  83          * We would still need IRQs off, because we don't want to change
  84          * the local LDT after an IPI loaded a newer value than the one
  85          * that we can see.
  86          */
  87
  88         if (unlikely(ldt))
  89                 set_ldt(ldt->entries, ldt->size);
  90         else
  91                 clear_LDT();
  92 #else
  93         clear_LDT();
  94 #endif
  95
  96         DEBUG_LOCKS_WARN_ON(preemptible());
  97 }
  98
  99 static inline void enter_lazy_tlb(struct mm_struct *mm, struct task_struct *tsk)
 100 {
 101 #ifdef CONFIG_SMP
 102         if (this_cpu_read(cpu_tlbstate.state) == TLBSTATE_OK)
 103                 this_cpu_write(cpu_tlbstate.state, TLBSTATE_LAZY);
 104 #endif
 105 }
 106
 107 static inline int init_new_context(struct task_struct *tsk,
 108                                    struct mm_struct *mm)
 109 {
 110         init_new_context_ldt(tsk, mm);
 111         return 0;
 112 }
 113 static inline void destroy_context(struct mm_struct *mm)
 114 {
 115         destroy_context_ldt(mm);
 116 }
 117
 118 extern void switch_mm(struct mm_struct *prev, struct mm_struct *next,
 119                       struct task_struct *tsk);
 120
 121 extern void switch_mm_irqs_off(struct mm_struct *prev, struct mm_struct *next,
 122                                struct task_struct *tsk);
 123 #define switch_mm_irqs_off switch_mm_irqs_off
 124
 125 #define activate_mm(prev, next)                 \
 126 do {                                            \
 127         paravirt_activate_mm((prev), (next));   \
 128         switch_mm((prev), (next), NULL);        \
 129 } while (0);
 130
 131 #ifdef CONFIG_X86_32
 132 #define deactivate_mm(tsk, mm)                  \
 133 do {                                            \
 134         lazy_load_gs(0);                        \
 135 } while (0)
 136 #else
 137 #define deactivate_mm(tsk, mm)                  \
 138 do {                                            \
 139         load_gs_index(0);                       \
 140         loadsegment(fs, 0);                     \
 141 } while (0)
 142 #endif
 143
 144 static inline void arch_dup_mmap(struct mm_struct *oldmm,
 145                                  struct mm_struct *mm)
 146 {
 147         paravirt_arch_dup_mmap(oldmm, mm);
 148 }
 149
 150 static inline void arch_exit_mmap(struct mm_struct *mm)
 151 {
 152         paravirt_arch_exit_mmap(mm);
 153 }
 154
 155 #ifdef CONFIG_X86_64
 156 static inline bool is_64bit_mm(struct mm_struct *mm)
 157 {
 158         return  !IS_ENABLED(CONFIG_IA32_EMULATION) ||
 159                 !(mm->context.ia32_compat == TIF_IA32);
 160 }
 161 #else
 162 static inline bool is_64bit_mm(struct mm_struct *mm)
 163 {
 164         return false;
 165 }
 166 #endif
 167
 168 static inline void arch_bprm_mm_init(struct mm_struct *mm,
 169                 struct vm_area_struct *vma)
 170 {
 171         mpx_mm_init(mm);
 172 }
 173
 174 static inline void arch_unmap(struct mm_struct *mm, struct vm_area_struct *vma,
 175                               unsigned long start, unsigned long end)
 176 {
 177         /*
 178          * mpx_notify_unmap() goes and reads a rarely-hot
 179          * cacheline in the mm_struct.  That can be expensive
 180          * enough to be seen in profiles.
 181          *
 182          * The mpx_notify_unmap() call and its contents have been
 183          * observed to affect munmap() performance on hardware
 184          * where MPX is not present.
 185          *
 186          * The unlikely() optimizes for the fast case: no MPX
 187          * in the CPU, or no MPX use in the process.  Even if
 188          * we get this wrong (in the unlikely event that MPX
 189          * is widely enabled on some system) the overhead of
 190          * MPX itself (reading bounds tables) is expected to
 191          * overwhelm the overhead of getting this unlikely()
 192          * consistently wrong.
 193          */
 194         if (unlikely(cpu_feature_enabled(X86_FEATURE_MPX)))
 195                 mpx_notify_unmap(mm, vma, start, end);
 196 }
 197
 198 static inline int vma_pkey(struct vm_area_struct *vma)
 199 {
 200         u16 pkey = 0;
 201 #ifdef CONFIG_X86_INTEL_MEMORY_PROTECTION_KEYS
 202         unsigned long vma_pkey_mask = VM_PKEY_BIT0 | VM_PKEY_BIT1 |
 203                                       VM_PKEY_BIT2 | VM_PKEY_BIT3;
 204         pkey = (vma->vm_flags & vma_pkey_mask) >> VM_PKEY_SHIFT;
 205 #endif
 206         return pkey;
 207 }
 208
 209 static inline bool __pkru_allows_pkey(u16 pkey, bool write)
 210 {
 211         u32 pkru = read_pkru();
 212
 213         if (!__pkru_allows_read(pkru, pkey))
 214                 return false;
 215         if (write && !__pkru_allows_write(pkru, pkey))
 216                 return false;
 217
 218         return true;
 219 }
 220
 221 /*
 222  * We only want to enforce protection keys on the current process
 223  * because we effectively have no access to PKRU for other
 224  * processes or any way to tell *which * PKRU in a threaded
 225  * process we could use.
 226  *
 227  * So do not enforce things if the VMA is not from the current
 228  * mm, or if we are in a kernel thread.
 229  */
 230 static inline bool vma_is_foreign(struct vm_area_struct *vma)
 231 {
 232         if (!current->mm)
 233                 return true;
 234         /*
 235          * Should PKRU be enforced on the access to this VMA?  If
 236          * the VMA is from another process, then PKRU has no
 237          * relevance and should not be enforced.
 238          */
 239         if (current->mm != vma->vm_mm)
 240                 return true;
 241
 242         return false;
 243 }
 244
 245 static inline bool arch_vma_access_permitted(struct vm_area_struct *vma,
 246                 bool write, bool execute, bool foreign)
 247 {
 248         /* pkeys never affect instruction fetches */
 249         if (execute)
 250                 return true;
 251         /* allow access if the VMA is not one from this process */
 252         if (foreign || vma_is_foreign(vma))
 253                 return true;
 254         return __pkru_allows_pkey(vma_pkey(vma), write);
 255 }
 256
 257 static inline bool arch_pte_access_permitted(pte_t pte, bool write)
 258 {
 259         return __pkru_allows_pkey(pte_flags_pkey(pte_flags(pte)), write);
 260 }
 261
 262 #endif /* _ASM_X86_MMU_CONTEXT_H */