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 #include <linux/pkeys.h>
   8
   9 #include <trace/events/tlb.h>
  10
  11 #include <asm/pgalloc.h>
  12 #include <asm/tlbflush.h>
  13 #include <asm/paravirt.h>
  14 #include <asm/mpx.h>
  15 #ifndef CONFIG_PARAVIRT
  16 static inline void paravirt_activate_mm(struct mm_struct *prev,
  17                                         struct mm_struct *next)
  18 {
  19 }
  20 #endif  /* !CONFIG_PARAVIRT */
  21
  22 #ifdef CONFIG_PERF_EVENTS
  23 extern struct static_key rdpmc_always_available;
  24
  25 static inline void load_mm_cr4(struct mm_struct *mm)
  26 {
  27         if (static_key_false(&rdpmc_always_available) ||
  28             atomic_read(&mm->context.perf_rdpmc_allowed))
  29                 cr4_set_bits(X86_CR4_PCE);
  30         else
  31                 cr4_clear_bits(X86_CR4_PCE);
  32 }
  33 #else
  34 static inline void load_mm_cr4(struct mm_struct *mm) {}
  35 #endif
  36
  37 #ifdef CONFIG_MODIFY_LDT_SYSCALL
  38 /*
  39  * ldt_structs can be allocated, used, and freed, but they are never
  40  * modified while live.
  41  */
  42 struct ldt_struct {
  43         /*
  44          * Xen requires page-aligned LDTs with special permissions.  This is
  45          * needed to prevent us from installing evil descriptors such as
  46          * call gates.  On native, we could merge the ldt_struct and LDT
  47          * allocations, but it's not worth trying to optimize.
  48          */
  49         struct desc_struct *entries;
  50         unsigned int nr_entries;
  51 };
  52
  53 /*
  54  * Used for LDT copy/destruction.
  55  */
  56 int init_new_context_ldt(struct task_struct *tsk, struct mm_struct *mm);
  57 void destroy_context_ldt(struct mm_struct *mm);
  58 #else   /* CONFIG_MODIFY_LDT_SYSCALL */
  59 static inline int init_new_context_ldt(struct task_struct *tsk,
  60                                        struct mm_struct *mm)
  61 {
  62         return 0;
  63 }
  64 static inline void destroy_context_ldt(struct mm_struct *mm) {}
  65 #endif
  66
  67 static inline void load_mm_ldt(struct mm_struct *mm)
  68 {
  69 #ifdef CONFIG_MODIFY_LDT_SYSCALL
  70         struct ldt_struct *ldt;
  71
  72         /* lockless_dereference synchronizes with smp_store_release */
  73         ldt = lockless_dereference(mm->context.ldt);
  74
  75         /*
  76          * Any change to mm->context.ldt is followed by an IPI to all
  77          * CPUs with the mm active.  The LDT will not be freed until
  78          * after the IPI is handled by all such CPUs.  This means that,
  79          * if the ldt_struct changes before we return, the values we see
  80          * will be safe, and the new values will be loaded before we run
  81          * any user code.
  82          *
  83          * NB: don't try to convert this to use RCU without extreme care.
  84          * We would still need IRQs off, because we don't want to change
  85          * the local LDT after an IPI loaded a newer value than the one
  86          * that we can see.
  87          */
  88
  89         if (unlikely(ldt))
  90                 set_ldt(ldt->entries, ldt->nr_entries);
  91         else
  92                 clear_LDT();
  93 #else
  94         clear_LDT();
  95 #endif
  96
  97         DEBUG_LOCKS_WARN_ON(preemptible());
  98 }
  99
 100 static inline void enter_lazy_tlb(struct mm_struct *mm, struct task_struct *tsk)
 101 {
 102         if (this_cpu_read(cpu_tlbstate.state) == TLBSTATE_OK)
 103                 this_cpu_write(cpu_tlbstate.state, TLBSTATE_LAZY);
 104 }
 105
 106 static inline int init_new_context(struct task_struct *tsk,
 107                                    struct mm_struct *mm)
 108 {
 109         #ifdef CONFIG_X86_INTEL_MEMORY_PROTECTION_KEYS
 110         if (cpu_feature_enabled(X86_FEATURE_OSPKE)) {
 111                 /* pkey 0 is the default and always allocated */
 112                 mm->context.pkey_allocation_map = 0x1;
 113                 /* -1 means unallocated or invalid */
 114                 mm->context.execute_only_pkey = -1;
 115         }
 116         #endif
 117         init_new_context_ldt(tsk, mm);
 118
 119         return 0;
 120 }
 121 static inline void destroy_context(struct mm_struct *mm)
 122 {
 123         destroy_context_ldt(mm);
 124 }
 125
 126 extern void switch_mm(struct mm_struct *prev, struct mm_struct *next,
 127                       struct task_struct *tsk);
 128
 129 extern void switch_mm_irqs_off(struct mm_struct *prev, struct mm_struct *next,
 130                                struct task_struct *tsk);
 131 #define switch_mm_irqs_off switch_mm_irqs_off
 132
 133 #define activate_mm(prev, next)                 \
 134 do {                                            \
 135         paravirt_activate_mm((prev), (next));   \
 136         switch_mm((prev), (next), NULL);        \
 137 } while (0);
 138
 139 #ifdef CONFIG_X86_32
 140 #define deactivate_mm(tsk, mm)                  \
 141 do {                                            \
 142         lazy_load_gs(0);                        \
 143 } while (0)
 144 #else
 145 #define deactivate_mm(tsk, mm)                  \
 146 do {                                            \
 147         load_gs_index(0);                       \
 148         loadsegment(fs, 0);                     \
 149 } while (0)
 150 #endif
 151
 152 static inline void arch_dup_mmap(struct mm_struct *oldmm,
 153                                  struct mm_struct *mm)
 154 {
 155         paravirt_arch_dup_mmap(oldmm, mm);
 156 }
 157
 158 static inline void arch_exit_mmap(struct mm_struct *mm)
 159 {
 160         paravirt_arch_exit_mmap(mm);
 161 }
 162
 163 #ifdef CONFIG_X86_64
 164 static inline bool is_64bit_mm(struct mm_struct *mm)
 165 {
 166         return  !IS_ENABLED(CONFIG_IA32_EMULATION) ||
 167                 !(mm->context.ia32_compat == TIF_IA32);
 168 }
 169 #else
 170 static inline bool is_64bit_mm(struct mm_struct *mm)
 171 {
 172         return false;
 173 }
 174 #endif
 175
 176 static inline void arch_bprm_mm_init(struct mm_struct *mm,
 177                 struct vm_area_struct *vma)
 178 {
 179         mpx_mm_init(mm);
 180 }
 181
 182 static inline void arch_unmap(struct mm_struct *mm, struct vm_area_struct *vma,
 183                               unsigned long start, unsigned long end)
 184 {
 185         /*
 186          * mpx_notify_unmap() goes and reads a rarely-hot
 187          * cacheline in the mm_struct.  That can be expensive
 188          * enough to be seen in profiles.
 189          *
 190          * The mpx_notify_unmap() call and its contents have been
 191          * observed to affect munmap() performance on hardware
 192          * where MPX is not present.
 193          *
 194          * The unlikely() optimizes for the fast case: no MPX
 195          * in the CPU, or no MPX use in the process.  Even if
 196          * we get this wrong (in the unlikely event that MPX
 197          * is widely enabled on some system) the overhead of
 198          * MPX itself (reading bounds tables) is expected to
 199          * overwhelm the overhead of getting this unlikely()
 200          * consistently wrong.
 201          */
 202         if (unlikely(cpu_feature_enabled(X86_FEATURE_MPX)))
 203                 mpx_notify_unmap(mm, vma, start, end);
 204 }
 205
 206 #ifdef CONFIG_X86_INTEL_MEMORY_PROTECTION_KEYS
 207 static inline int vma_pkey(struct vm_area_struct *vma)
 208 {
 209         unsigned long vma_pkey_mask = VM_PKEY_BIT0 | VM_PKEY_BIT1 |
 210                                       VM_PKEY_BIT2 | VM_PKEY_BIT3;
 211
 212         return (vma->vm_flags & vma_pkey_mask) >> VM_PKEY_SHIFT;
 213 }
 214 #else
 215 static inline int vma_pkey(struct vm_area_struct *vma)
 216 {
 217         return 0;
 218 }
 219 #endif
 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
 258 /*
 259  * This can be used from process context to figure out what the value of
 260  * CR3 is without needing to do a (slow) __read_cr3().
 261  *
 262  * It's intended to be used for code like KVM that sneakily changes CR3
 263  * and needs to restore it.  It needs to be used very carefully.
 264  */
 265 static inline unsigned long __get_current_cr3_fast(void)
 266 {
 267         unsigned long cr3 = __pa(this_cpu_read(cpu_tlbstate.loaded_mm)->pgd);
 268
 269         /* For now, be very restrictive about when this can be called. */
 270         VM_WARN_ON(in_nmi() || !in_atomic());
 271
 272         VM_BUG_ON(cr3 != __read_cr3());
 273         return cr3;
 274 }
 275
 276 #endif /* _ASM_X86_MMU_CONTEXT_H */