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 size;
  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->size);
  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 #ifdef CONFIG_SMP
 103         if (this_cpu_read(cpu_tlbstate.state) == TLBSTATE_OK)
 104                 this_cpu_write(cpu_tlbstate.state, TLBSTATE_LAZY);
 105 #endif
 106 }
 107
 108 static inline int init_new_context(struct task_struct *tsk,
 109                                    struct mm_struct *mm)
 110 {
 111         #ifdef CONFIG_X86_INTEL_MEMORY_PROTECTION_KEYS
 112         if (cpu_feature_enabled(X86_FEATURE_OSPKE)) {
 113                 /* pkey 0 is the default and always allocated */
 114                 mm->context.pkey_allocation_map = 0x1;
 115                 /* -1 means unallocated or invalid */
 116                 mm->context.execute_only_pkey = -1;
 117         }
 118         #endif
 119         init_new_context_ldt(tsk, mm);
 120
 121         return 0;
 122 }
 123 static inline void destroy_context(struct mm_struct *mm)
 124 {
 125         destroy_context_ldt(mm);
 126 }
 127
 128 extern void switch_mm(struct mm_struct *prev, struct mm_struct *next,
 129                       struct task_struct *tsk);
 130
 131 extern void switch_mm_irqs_off(struct mm_struct *prev, struct mm_struct *next,
 132                                struct task_struct *tsk);
 133 #define switch_mm_irqs_off switch_mm_irqs_off
 134
 135 #define activate_mm(prev, next)                 \
 136 do {                                            \
 137         paravirt_activate_mm((prev), (next));   \
 138         switch_mm((prev), (next), NULL);        \
 139 } while (0);
 140
 141 #ifdef CONFIG_X86_32
 142 #define deactivate_mm(tsk, mm)                  \
 143 do {                                            \
 144         lazy_load_gs(0);                        \
 145 } while (0)
 146 #else
 147 #define deactivate_mm(tsk, mm)                  \
 148 do {                                            \
 149         load_gs_index(0);                       \
 150         loadsegment(fs, 0);                     \
 151 } while (0)
 152 #endif
 153
 154 static inline void arch_dup_mmap(struct mm_struct *oldmm,
 155                                  struct mm_struct *mm)
 156 {
 157         paravirt_arch_dup_mmap(oldmm, mm);
 158 }
 159
 160 static inline void arch_exit_mmap(struct mm_struct *mm)
 161 {
 162         paravirt_arch_exit_mmap(mm);
 163 }
 164
 165 #ifdef CONFIG_X86_64
 166 static inline bool is_64bit_mm(struct mm_struct *mm)
 167 {
 168         return  !IS_ENABLED(CONFIG_IA32_EMULATION) ||
 169                 !(mm->context.ia32_compat == TIF_IA32);
 170 }
 171 #else
 172 static inline bool is_64bit_mm(struct mm_struct *mm)
 173 {
 174         return false;
 175 }
 176 #endif
 177
 178 static inline void arch_bprm_mm_init(struct mm_struct *mm,
 179                 struct vm_area_struct *vma)
 180 {
 181         mpx_mm_init(mm);
 182 }
 183
 184 static inline void arch_unmap(struct mm_struct *mm, struct vm_area_struct *vma,
 185                               unsigned long start, unsigned long end)
 186 {
 187         /*
 188          * mpx_notify_unmap() goes and reads a rarely-hot
 189          * cacheline in the mm_struct.  That can be expensive
 190          * enough to be seen in profiles.
 191          *
 192          * The mpx_notify_unmap() call and its contents have been
 193          * observed to affect munmap() performance on hardware
 194          * where MPX is not present.
 195          *
 196          * The unlikely() optimizes for the fast case: no MPX
 197          * in the CPU, or no MPX use in the process.  Even if
 198          * we get this wrong (in the unlikely event that MPX
 199          * is widely enabled on some system) the overhead of
 200          * MPX itself (reading bounds tables) is expected to
 201          * overwhelm the overhead of getting this unlikely()
 202          * consistently wrong.
 203          */
 204         if (unlikely(cpu_feature_enabled(X86_FEATURE_MPX)))
 205                 mpx_notify_unmap(mm, vma, start, end);
 206 }
 207
 208 #ifdef CONFIG_X86_INTEL_MEMORY_PROTECTION_KEYS
 209 static inline int vma_pkey(struct vm_area_struct *vma)
 210 {
 211         unsigned long vma_pkey_mask = VM_PKEY_BIT0 | VM_PKEY_BIT1 |
 212                                       VM_PKEY_BIT2 | VM_PKEY_BIT3;
 213
 214         return (vma->vm_flags & vma_pkey_mask) >> VM_PKEY_SHIFT;
 215 }
 216 #else
 217 static inline int vma_pkey(struct vm_area_struct *vma)
 218 {
 219         return 0;
 220 }
 221 #endif
 222
 223 static inline bool __pkru_allows_pkey(u16 pkey, bool write)
 224 {
 225         u32 pkru = read_pkru();
 226
 227         if (!__pkru_allows_read(pkru, pkey))
 228                 return false;
 229         if (write && !__pkru_allows_write(pkru, pkey))
 230                 return false;
 231
 232         return true;
 233 }
 234
 235 /*
 236  * We only want to enforce protection keys on the current process
 237  * because we effectively have no access to PKRU for other
 238  * processes or any way to tell *which * PKRU in a threaded
 239  * process we could use.
 240  *
 241  * So do not enforce things if the VMA is not from the current
 242  * mm, or if we are in a kernel thread.
 243  */
 244 static inline bool vma_is_foreign(struct vm_area_struct *vma)
 245 {
 246         if (!current->mm)
 247                 return true;
 248         /*
 249          * Should PKRU be enforced on the access to this VMA?  If
 250          * the VMA is from another process, then PKRU has no
 251          * relevance and should not be enforced.
 252          */
 253         if (current->mm != vma->vm_mm)
 254                 return true;
 255
 256         return false;
 257 }
 258
 259 static inline bool arch_vma_access_permitted(struct vm_area_struct *vma,
 260                 bool write, bool execute, bool foreign)
 261 {
 262         /* pkeys never affect instruction fetches */
 263         if (execute)
 264                 return true;
 265         /* allow access if the VMA is not one from this process */
 266         if (foreign || vma_is_foreign(vma))
 267                 return true;
 268         return __pkru_allows_pkey(vma_pkey(vma), write);
 269 }
 270
 271 static inline bool arch_pte_access_permitted(pte_t pte, bool write)
 272 {
 273         return __pkru_allows_pkey(pte_flags_pkey(pte_flags(pte)), write);
 274 }
 275 #endif /* _ASM_X86_MMU_CONTEXT_H */