1 /* SPDX-License-Identifier: GPL-2.0 */ 2 #ifndef _ASM_X86_MMU_CONTEXT_H 3 #define _ASM_X86_MMU_CONTEXT_H 4 5 #include <asm/desc.h> 6 #include <linux/atomic.h> 7 #include <linux/mm_types.h> 8 #include <linux/pkeys.h> 9 10 #include <trace/events/tlb.h> 11 12 #include <asm/pgalloc.h> 13 #include <asm/tlbflush.h> 14 #include <asm/paravirt.h> 15 #include <asm/mpx.h> 16 17 extern atomic64_t last_mm_ctx_id; 18 19 #ifndef CONFIG_PARAVIRT_XXL 20 static inline void paravirt_activate_mm(struct mm_struct *prev, 21 struct mm_struct *next) 22 { 23 } 24 #endif /* !CONFIG_PARAVIRT_XXL */ 25 26 #ifdef CONFIG_PERF_EVENTS 27 28 DECLARE_STATIC_KEY_FALSE(rdpmc_always_available_key); 29 30 static inline void load_mm_cr4(struct mm_struct *mm) 31 { 32 if (static_branch_unlikely(&rdpmc_always_available_key) || 33 atomic_read(&mm->context.perf_rdpmc_allowed)) 34 cr4_set_bits(X86_CR4_PCE); 35 else 36 cr4_clear_bits(X86_CR4_PCE); 37 } 38 #else 39 static inline void load_mm_cr4(struct mm_struct *mm) {} 40 #endif 41 42 #ifdef CONFIG_MODIFY_LDT_SYSCALL 43 /* 44 * ldt_structs can be allocated, used, and freed, but they are never 45 * modified while live. 46 */ 47 struct ldt_struct { 48 /* 49 * Xen requires page-aligned LDTs with special permissions. This is 50 * needed to prevent us from installing evil descriptors such as 51 * call gates. On native, we could merge the ldt_struct and LDT 52 * allocations, but it's not worth trying to optimize. 53 */ 54 struct desc_struct *entries; 55 unsigned int nr_entries; 56 57 /* 58 * If PTI is in use, then the entries array is not mapped while we're 59 * in user mode. The whole array will be aliased at the addressed 60 * given by ldt_slot_va(slot). We use two slots so that we can allocate 61 * and map, and enable a new LDT without invalidating the mapping 62 * of an older, still-in-use LDT. 63 * 64 * slot will be -1 if this LDT doesn't have an alias mapping. 65 */ 66 int slot; 67 }; 68 69 /* This is a multiple of PAGE_SIZE. */ 70 #define LDT_SLOT_STRIDE (LDT_ENTRIES * LDT_ENTRY_SIZE) 71 72 static inline void *ldt_slot_va(int slot) 73 { 74 return (void *)(LDT_BASE_ADDR + LDT_SLOT_STRIDE * slot); 75 } 76 77 /* 78 * Used for LDT copy/destruction. 79 */ 80 static inline void init_new_context_ldt(struct mm_struct *mm) 81 { 82 mm->context.ldt = NULL; 83 init_rwsem(&mm->context.ldt_usr_sem); 84 } 85 int ldt_dup_context(struct mm_struct *oldmm, struct mm_struct *mm); 86 void destroy_context_ldt(struct mm_struct *mm); 87 void ldt_arch_exit_mmap(struct mm_struct *mm); 88 #else /* CONFIG_MODIFY_LDT_SYSCALL */ 89 static inline void init_new_context_ldt(struct mm_struct *mm) { } 90 static inline int ldt_dup_context(struct mm_struct *oldmm, 91 struct mm_struct *mm) 92 { 93 return 0; 94 } 95 static inline void destroy_context_ldt(struct mm_struct *mm) { } 96 static inline void ldt_arch_exit_mmap(struct mm_struct *mm) { } 97 #endif 98 99 static inline void load_mm_ldt(struct mm_struct *mm) 100 { 101 #ifdef CONFIG_MODIFY_LDT_SYSCALL 102 struct ldt_struct *ldt; 103 104 /* READ_ONCE synchronizes with smp_store_release */ 105 ldt = READ_ONCE(mm->context.ldt); 106 107 /* 108 * Any change to mm->context.ldt is followed by an IPI to all 109 * CPUs with the mm active. The LDT will not be freed until 110 * after the IPI is handled by all such CPUs. This means that, 111 * if the ldt_struct changes before we return, the values we see 112 * will be safe, and the new values will be loaded before we run 113 * any user code. 114 * 115 * NB: don't try to convert this to use RCU without extreme care. 116 * We would still need IRQs off, because we don't want to change 117 * the local LDT after an IPI loaded a newer value than the one 118 * that we can see. 119 */ 120 121 if (unlikely(ldt)) { 122 if (static_cpu_has(X86_FEATURE_PTI)) { 123 if (WARN_ON_ONCE((unsigned long)ldt->slot > 1)) { 124 /* 125 * Whoops -- either the new LDT isn't mapped 126 * (if slot == -1) or is mapped into a bogus 127 * slot (if slot > 1). 128 */ 129 clear_LDT(); 130 return; 131 } 132 133 /* 134 * If page table isolation is enabled, ldt->entries 135 * will not be mapped in the userspace pagetables. 136 * Tell the CPU to access the LDT through the alias 137 * at ldt_slot_va(ldt->slot). 138 */ 139 set_ldt(ldt_slot_va(ldt->slot), ldt->nr_entries); 140 } else { 141 set_ldt(ldt->entries, ldt->nr_entries); 142 } 143 } else { 144 clear_LDT(); 145 } 146 #else 147 clear_LDT(); 148 #endif 149 } 150 151 static inline void switch_ldt(struct mm_struct *prev, struct mm_struct *next) 152 { 153 #ifdef CONFIG_MODIFY_LDT_SYSCALL 154 /* 155 * Load the LDT if either the old or new mm had an LDT. 156 * 157 * An mm will never go from having an LDT to not having an LDT. Two 158 * mms never share an LDT, so we don't gain anything by checking to 159 * see whether the LDT changed. There's also no guarantee that 160 * prev->context.ldt actually matches LDTR, but, if LDTR is non-NULL, 161 * then prev->context.ldt will also be non-NULL. 162 * 163 * If we really cared, we could optimize the case where prev == next 164 * and we're exiting lazy mode. Most of the time, if this happens, 165 * we don't actually need to reload LDTR, but modify_ldt() is mostly 166 * used by legacy code and emulators where we don't need this level of 167 * performance. 168 * 169 * This uses | instead of || because it generates better code. 170 */ 171 if (unlikely((unsigned long)prev->context.ldt | 172 (unsigned long)next->context.ldt)) 173 load_mm_ldt(next); 174 #endif 175 176 DEBUG_LOCKS_WARN_ON(preemptible()); 177 } 178 179 void enter_lazy_tlb(struct mm_struct *mm, struct task_struct *tsk); 180 181 /* 182 * Init a new mm. Used on mm copies, like at fork() 183 * and on mm's that are brand-new, like at execve(). 184 */ 185 static inline int init_new_context(struct task_struct *tsk, 186 struct mm_struct *mm) 187 { 188 mutex_init(&mm->context.lock); 189 190 mm->context.ctx_id = atomic64_inc_return(&last_mm_ctx_id); 191 atomic64_set(&mm->context.tlb_gen, 0); 192 193 #ifdef CONFIG_X86_INTEL_MEMORY_PROTECTION_KEYS 194 if (cpu_feature_enabled(X86_FEATURE_OSPKE)) { 195 /* pkey 0 is the default and allocated implicitly */ 196 mm->context.pkey_allocation_map = 0x1; 197 /* -1 means unallocated or invalid */ 198 mm->context.execute_only_pkey = -1; 199 } 200 #endif 201 init_new_context_ldt(mm); 202 return 0; 203 } 204 static inline void destroy_context(struct mm_struct *mm) 205 { 206 destroy_context_ldt(mm); 207 } 208 209 extern void switch_mm(struct mm_struct *prev, struct mm_struct *next, 210 struct task_struct *tsk); 211 212 extern void switch_mm_irqs_off(struct mm_struct *prev, struct mm_struct *next, 213 struct task_struct *tsk); 214 #define switch_mm_irqs_off switch_mm_irqs_off 215 216 #define activate_mm(prev, next) \ 217 do { \ 218 paravirt_activate_mm((prev), (next)); \ 219 switch_mm((prev), (next), NULL); \ 220 } while (0); 221 222 #ifdef CONFIG_X86_32 223 #define deactivate_mm(tsk, mm) \ 224 do { \ 225 lazy_load_gs(0); \ 226 } while (0) 227 #else 228 #define deactivate_mm(tsk, mm) \ 229 do { \ 230 load_gs_index(0); \ 231 loadsegment(fs, 0); \ 232 } while (0) 233 #endif 234 235 static inline void arch_dup_pkeys(struct mm_struct *oldmm, 236 struct mm_struct *mm) 237 { 238 #ifdef CONFIG_X86_INTEL_MEMORY_PROTECTION_KEYS 239 if (!cpu_feature_enabled(X86_FEATURE_OSPKE)) 240 return; 241 242 /* Duplicate the oldmm pkey state in mm: */ 243 mm->context.pkey_allocation_map = oldmm->context.pkey_allocation_map; 244 mm->context.execute_only_pkey = oldmm->context.execute_only_pkey; 245 #endif 246 } 247 248 static inline int arch_dup_mmap(struct mm_struct *oldmm, struct mm_struct *mm) 249 { 250 arch_dup_pkeys(oldmm, mm); 251 paravirt_arch_dup_mmap(oldmm, mm); 252 return ldt_dup_context(oldmm, mm); 253 } 254 255 static inline void arch_exit_mmap(struct mm_struct *mm) 256 { 257 paravirt_arch_exit_mmap(mm); 258 ldt_arch_exit_mmap(mm); 259 } 260 261 #ifdef CONFIG_X86_64 262 static inline bool is_64bit_mm(struct mm_struct *mm) 263 { 264 return !IS_ENABLED(CONFIG_IA32_EMULATION) || 265 !(mm->context.ia32_compat == TIF_IA32); 266 } 267 #else 268 static inline bool is_64bit_mm(struct mm_struct *mm) 269 { 270 return false; 271 } 272 #endif 273 274 static inline void arch_bprm_mm_init(struct mm_struct *mm, 275 struct vm_area_struct *vma) 276 { 277 mpx_mm_init(mm); 278 } 279 280 static inline void arch_unmap(struct mm_struct *mm, struct vm_area_struct *vma, 281 unsigned long start, unsigned long end) 282 { 283 /* 284 * mpx_notify_unmap() goes and reads a rarely-hot 285 * cacheline in the mm_struct. That can be expensive 286 * enough to be seen in profiles. 287 * 288 * The mpx_notify_unmap() call and its contents have been 289 * observed to affect munmap() performance on hardware 290 * where MPX is not present. 291 * 292 * The unlikely() optimizes for the fast case: no MPX 293 * in the CPU, or no MPX use in the process. Even if 294 * we get this wrong (in the unlikely event that MPX 295 * is widely enabled on some system) the overhead of 296 * MPX itself (reading bounds tables) is expected to 297 * overwhelm the overhead of getting this unlikely() 298 * consistently wrong. 299 */ 300 if (unlikely(cpu_feature_enabled(X86_FEATURE_MPX))) 301 mpx_notify_unmap(mm, vma, start, end); 302 } 303 304 /* 305 * We only want to enforce protection keys on the current process 306 * because we effectively have no access to PKRU for other 307 * processes or any way to tell *which * PKRU in a threaded 308 * process we could use. 309 * 310 * So do not enforce things if the VMA is not from the current 311 * mm, or if we are in a kernel thread. 312 */ 313 static inline bool vma_is_foreign(struct vm_area_struct *vma) 314 { 315 if (!current->mm) 316 return true; 317 /* 318 * Should PKRU be enforced on the access to this VMA? If 319 * the VMA is from another process, then PKRU has no 320 * relevance and should not be enforced. 321 */ 322 if (current->mm != vma->vm_mm) 323 return true; 324 325 return false; 326 } 327 328 static inline bool arch_vma_access_permitted(struct vm_area_struct *vma, 329 bool write, bool execute, bool foreign) 330 { 331 /* pkeys never affect instruction fetches */ 332 if (execute) 333 return true; 334 /* allow access if the VMA is not one from this process */ 335 if (foreign || vma_is_foreign(vma)) 336 return true; 337 return __pkru_allows_pkey(vma_pkey(vma), write); 338 } 339 340 /* 341 * This can be used from process context to figure out what the value of 342 * CR3 is without needing to do a (slow) __read_cr3(). 343 * 344 * It's intended to be used for code like KVM that sneakily changes CR3 345 * and needs to restore it. It needs to be used very carefully. 346 */ 347 static inline unsigned long __get_current_cr3_fast(void) 348 { 349 unsigned long cr3 = build_cr3(this_cpu_read(cpu_tlbstate.loaded_mm)->pgd, 350 this_cpu_read(cpu_tlbstate.loaded_mm_asid)); 351 352 /* For now, be very restrictive about when this can be called. */ 353 VM_WARN_ON(in_nmi() || preemptible()); 354 355 VM_BUG_ON(cr3 != __read_cr3()); 356 return cr3; 357 } 358 359 #endif /* _ASM_X86_MMU_CONTEXT_H */ 360