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 16 extern atomic64_t last_mm_ctx_id; 17 18 #ifndef CONFIG_PARAVIRT 19 static inline void paravirt_activate_mm(struct mm_struct *prev, 20 struct mm_struct *next) 21 { 22 } 23 #endif /* !CONFIG_PARAVIRT */ 24 25 #ifdef CONFIG_PERF_EVENTS 26 extern struct static_key rdpmc_always_available; 27 28 static inline void load_mm_cr4(struct mm_struct *mm) 29 { 30 if (static_key_false(&rdpmc_always_available) || 31 atomic_read(&mm->context.perf_rdpmc_allowed)) 32 cr4_set_bits(X86_CR4_PCE); 33 else 34 cr4_clear_bits(X86_CR4_PCE); 35 } 36 #else 37 static inline void load_mm_cr4(struct mm_struct *mm) {} 38 #endif 39 40 #ifdef CONFIG_MODIFY_LDT_SYSCALL 41 /* 42 * ldt_structs can be allocated, used, and freed, but they are never 43 * modified while live. 44 */ 45 struct ldt_struct { 46 /* 47 * Xen requires page-aligned LDTs with special permissions. This is 48 * needed to prevent us from installing evil descriptors such as 49 * call gates. On native, we could merge the ldt_struct and LDT 50 * allocations, but it's not worth trying to optimize. 51 */ 52 struct desc_struct *entries; 53 unsigned int nr_entries; 54 }; 55 56 /* 57 * Used for LDT copy/destruction. 58 */ 59 int init_new_context_ldt(struct task_struct *tsk, struct mm_struct *mm); 60 void destroy_context_ldt(struct mm_struct *mm); 61 #else /* CONFIG_MODIFY_LDT_SYSCALL */ 62 static inline int init_new_context_ldt(struct task_struct *tsk, 63 struct mm_struct *mm) 64 { 65 return 0; 66 } 67 static inline void destroy_context_ldt(struct mm_struct *mm) {} 68 #endif 69 70 static inline void load_mm_ldt(struct mm_struct *mm) 71 { 72 #ifdef CONFIG_MODIFY_LDT_SYSCALL 73 struct ldt_struct *ldt; 74 75 /* READ_ONCE synchronizes with smp_store_release */ 76 ldt = READ_ONCE(mm->context.ldt); 77 78 /* 79 * Any change to mm->context.ldt is followed by an IPI to all 80 * CPUs with the mm active. The LDT will not be freed until 81 * after the IPI is handled by all such CPUs. This means that, 82 * if the ldt_struct changes before we return, the values we see 83 * will be safe, and the new values will be loaded before we run 84 * any user code. 85 * 86 * NB: don't try to convert this to use RCU without extreme care. 87 * We would still need IRQs off, because we don't want to change 88 * the local LDT after an IPI loaded a newer value than the one 89 * that we can see. 90 */ 91 92 if (unlikely(ldt)) 93 set_ldt(ldt->entries, ldt->nr_entries); 94 else 95 clear_LDT(); 96 #else 97 clear_LDT(); 98 #endif 99 } 100 101 static inline void switch_ldt(struct mm_struct *prev, struct mm_struct *next) 102 { 103 #ifdef CONFIG_MODIFY_LDT_SYSCALL 104 /* 105 * Load the LDT if either the old or new mm had an LDT. 106 * 107 * An mm will never go from having an LDT to not having an LDT. Two 108 * mms never share an LDT, so we don't gain anything by checking to 109 * see whether the LDT changed. There's also no guarantee that 110 * prev->context.ldt actually matches LDTR, but, if LDTR is non-NULL, 111 * then prev->context.ldt will also be non-NULL. 112 * 113 * If we really cared, we could optimize the case where prev == next 114 * and we're exiting lazy mode. Most of the time, if this happens, 115 * we don't actually need to reload LDTR, but modify_ldt() is mostly 116 * used by legacy code and emulators where we don't need this level of 117 * performance. 118 * 119 * This uses | instead of || because it generates better code. 120 */ 121 if (unlikely((unsigned long)prev->context.ldt | 122 (unsigned long)next->context.ldt)) 123 load_mm_ldt(next); 124 #endif 125 126 DEBUG_LOCKS_WARN_ON(preemptible()); 127 } 128 129 void enter_lazy_tlb(struct mm_struct *mm, struct task_struct *tsk); 130 131 static inline int init_new_context(struct task_struct *tsk, 132 struct mm_struct *mm) 133 { 134 mm->context.ctx_id = atomic64_inc_return(&last_mm_ctx_id); 135 atomic64_set(&mm->context.tlb_gen, 0); 136 137 #ifdef CONFIG_X86_INTEL_MEMORY_PROTECTION_KEYS 138 if (cpu_feature_enabled(X86_FEATURE_OSPKE)) { 139 /* pkey 0 is the default and always allocated */ 140 mm->context.pkey_allocation_map = 0x1; 141 /* -1 means unallocated or invalid */ 142 mm->context.execute_only_pkey = -1; 143 } 144 #endif 145 return init_new_context_ldt(tsk, mm); 146 } 147 static inline void destroy_context(struct mm_struct *mm) 148 { 149 destroy_context_ldt(mm); 150 } 151 152 extern void switch_mm(struct mm_struct *prev, struct mm_struct *next, 153 struct task_struct *tsk); 154 155 extern void switch_mm_irqs_off(struct mm_struct *prev, struct mm_struct *next, 156 struct task_struct *tsk); 157 #define switch_mm_irqs_off switch_mm_irqs_off 158 159 #define activate_mm(prev, next) \ 160 do { \ 161 paravirt_activate_mm((prev), (next)); \ 162 switch_mm((prev), (next), NULL); \ 163 } while (0); 164 165 #ifdef CONFIG_X86_32 166 #define deactivate_mm(tsk, mm) \ 167 do { \ 168 lazy_load_gs(0); \ 169 } while (0) 170 #else 171 #define deactivate_mm(tsk, mm) \ 172 do { \ 173 load_gs_index(0); \ 174 loadsegment(fs, 0); \ 175 } while (0) 176 #endif 177 178 static inline void arch_dup_mmap(struct mm_struct *oldmm, 179 struct mm_struct *mm) 180 { 181 paravirt_arch_dup_mmap(oldmm, mm); 182 } 183 184 static inline void arch_exit_mmap(struct mm_struct *mm) 185 { 186 paravirt_arch_exit_mmap(mm); 187 } 188 189 #ifdef CONFIG_X86_64 190 static inline bool is_64bit_mm(struct mm_struct *mm) 191 { 192 return !IS_ENABLED(CONFIG_IA32_EMULATION) || 193 !(mm->context.ia32_compat == TIF_IA32); 194 } 195 #else 196 static inline bool is_64bit_mm(struct mm_struct *mm) 197 { 198 return false; 199 } 200 #endif 201 202 static inline void arch_bprm_mm_init(struct mm_struct *mm, 203 struct vm_area_struct *vma) 204 { 205 mpx_mm_init(mm); 206 } 207 208 static inline void arch_unmap(struct mm_struct *mm, struct vm_area_struct *vma, 209 unsigned long start, unsigned long end) 210 { 211 /* 212 * mpx_notify_unmap() goes and reads a rarely-hot 213 * cacheline in the mm_struct. That can be expensive 214 * enough to be seen in profiles. 215 * 216 * The mpx_notify_unmap() call and its contents have been 217 * observed to affect munmap() performance on hardware 218 * where MPX is not present. 219 * 220 * The unlikely() optimizes for the fast case: no MPX 221 * in the CPU, or no MPX use in the process. Even if 222 * we get this wrong (in the unlikely event that MPX 223 * is widely enabled on some system) the overhead of 224 * MPX itself (reading bounds tables) is expected to 225 * overwhelm the overhead of getting this unlikely() 226 * consistently wrong. 227 */ 228 if (unlikely(cpu_feature_enabled(X86_FEATURE_MPX))) 229 mpx_notify_unmap(mm, vma, start, end); 230 } 231 232 #ifdef CONFIG_X86_INTEL_MEMORY_PROTECTION_KEYS 233 static inline int vma_pkey(struct vm_area_struct *vma) 234 { 235 unsigned long vma_pkey_mask = VM_PKEY_BIT0 | VM_PKEY_BIT1 | 236 VM_PKEY_BIT2 | VM_PKEY_BIT3; 237 238 return (vma->vm_flags & vma_pkey_mask) >> VM_PKEY_SHIFT; 239 } 240 #else 241 static inline int vma_pkey(struct vm_area_struct *vma) 242 { 243 return 0; 244 } 245 #endif 246 247 /* 248 * We only want to enforce protection keys on the current process 249 * because we effectively have no access to PKRU for other 250 * processes or any way to tell *which * PKRU in a threaded 251 * process we could use. 252 * 253 * So do not enforce things if the VMA is not from the current 254 * mm, or if we are in a kernel thread. 255 */ 256 static inline bool vma_is_foreign(struct vm_area_struct *vma) 257 { 258 if (!current->mm) 259 return true; 260 /* 261 * Should PKRU be enforced on the access to this VMA? If 262 * the VMA is from another process, then PKRU has no 263 * relevance and should not be enforced. 264 */ 265 if (current->mm != vma->vm_mm) 266 return true; 267 268 return false; 269 } 270 271 static inline bool arch_vma_access_permitted(struct vm_area_struct *vma, 272 bool write, bool execute, bool foreign) 273 { 274 /* pkeys never affect instruction fetches */ 275 if (execute) 276 return true; 277 /* allow access if the VMA is not one from this process */ 278 if (foreign || vma_is_foreign(vma)) 279 return true; 280 return __pkru_allows_pkey(vma_pkey(vma), write); 281 } 282 283 /* 284 * If PCID is on, ASID-aware code paths put the ASID+1 into the PCID 285 * bits. This serves two purposes. It prevents a nasty situation in 286 * which PCID-unaware code saves CR3, loads some other value (with PCID 287 * == 0), and then restores CR3, thus corrupting the TLB for ASID 0 if 288 * the saved ASID was nonzero. It also means that any bugs involving 289 * loading a PCID-enabled CR3 with CR4.PCIDE off will trigger 290 * deterministically. 291 */ 292 293 static inline unsigned long build_cr3(struct mm_struct *mm, u16 asid) 294 { 295 if (static_cpu_has(X86_FEATURE_PCID)) { 296 VM_WARN_ON_ONCE(asid > 4094); 297 return __sme_pa(mm->pgd) | (asid + 1); 298 } else { 299 VM_WARN_ON_ONCE(asid != 0); 300 return __sme_pa(mm->pgd); 301 } 302 } 303 304 static inline unsigned long build_cr3_noflush(struct mm_struct *mm, u16 asid) 305 { 306 VM_WARN_ON_ONCE(asid > 4094); 307 return __sme_pa(mm->pgd) | (asid + 1) | CR3_NOFLUSH; 308 } 309 310 /* 311 * This can be used from process context to figure out what the value of 312 * CR3 is without needing to do a (slow) __read_cr3(). 313 * 314 * It's intended to be used for code like KVM that sneakily changes CR3 315 * and needs to restore it. It needs to be used very carefully. 316 */ 317 static inline unsigned long __get_current_cr3_fast(void) 318 { 319 unsigned long cr3 = build_cr3(this_cpu_read(cpu_tlbstate.loaded_mm), 320 this_cpu_read(cpu_tlbstate.loaded_mm_asid)); 321 322 /* For now, be very restrictive about when this can be called. */ 323 VM_WARN_ON(in_nmi() || preemptible()); 324 325 VM_BUG_ON(cr3 != __read_cr3()); 326 return cr3; 327 } 328 329 #endif /* _ASM_X86_MMU_CONTEXT_H */ 330