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 20 static inline void paravirt_activate_mm(struct mm_struct *prev, 21 struct mm_struct *next) 22 { 23 } 24 #endif /* !CONFIG_PARAVIRT */ 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 static inline int init_new_context(struct task_struct *tsk, 182 struct mm_struct *mm) 183 { 184 mutex_init(&mm->context.lock); 185 186 mm->context.ctx_id = atomic64_inc_return(&last_mm_ctx_id); 187 atomic64_set(&mm->context.tlb_gen, 0); 188 189 #ifdef CONFIG_X86_INTEL_MEMORY_PROTECTION_KEYS 190 if (cpu_feature_enabled(X86_FEATURE_OSPKE)) { 191 /* pkey 0 is the default and allocated implicitly */ 192 mm->context.pkey_allocation_map = 0x1; 193 /* -1 means unallocated or invalid */ 194 mm->context.execute_only_pkey = -1; 195 } 196 #endif 197 init_new_context_ldt(mm); 198 return 0; 199 } 200 static inline void destroy_context(struct mm_struct *mm) 201 { 202 destroy_context_ldt(mm); 203 } 204 205 extern void switch_mm(struct mm_struct *prev, struct mm_struct *next, 206 struct task_struct *tsk); 207 208 extern void switch_mm_irqs_off(struct mm_struct *prev, struct mm_struct *next, 209 struct task_struct *tsk); 210 #define switch_mm_irqs_off switch_mm_irqs_off 211 212 #define activate_mm(prev, next) \ 213 do { \ 214 paravirt_activate_mm((prev), (next)); \ 215 switch_mm((prev), (next), NULL); \ 216 } while (0); 217 218 #ifdef CONFIG_X86_32 219 #define deactivate_mm(tsk, mm) \ 220 do { \ 221 lazy_load_gs(0); \ 222 } while (0) 223 #else 224 #define deactivate_mm(tsk, mm) \ 225 do { \ 226 load_gs_index(0); \ 227 loadsegment(fs, 0); \ 228 } while (0) 229 #endif 230 231 static inline int arch_dup_mmap(struct mm_struct *oldmm, struct mm_struct *mm) 232 { 233 paravirt_arch_dup_mmap(oldmm, mm); 234 return ldt_dup_context(oldmm, mm); 235 } 236 237 static inline void arch_exit_mmap(struct mm_struct *mm) 238 { 239 paravirt_arch_exit_mmap(mm); 240 ldt_arch_exit_mmap(mm); 241 } 242 243 #ifdef CONFIG_X86_64 244 static inline bool is_64bit_mm(struct mm_struct *mm) 245 { 246 return !IS_ENABLED(CONFIG_IA32_EMULATION) || 247 !(mm->context.ia32_compat == TIF_IA32); 248 } 249 #else 250 static inline bool is_64bit_mm(struct mm_struct *mm) 251 { 252 return false; 253 } 254 #endif 255 256 static inline void arch_bprm_mm_init(struct mm_struct *mm, 257 struct vm_area_struct *vma) 258 { 259 mpx_mm_init(mm); 260 } 261 262 static inline void arch_unmap(struct mm_struct *mm, struct vm_area_struct *vma, 263 unsigned long start, unsigned long end) 264 { 265 /* 266 * mpx_notify_unmap() goes and reads a rarely-hot 267 * cacheline in the mm_struct. That can be expensive 268 * enough to be seen in profiles. 269 * 270 * The mpx_notify_unmap() call and its contents have been 271 * observed to affect munmap() performance on hardware 272 * where MPX is not present. 273 * 274 * The unlikely() optimizes for the fast case: no MPX 275 * in the CPU, or no MPX use in the process. Even if 276 * we get this wrong (in the unlikely event that MPX 277 * is widely enabled on some system) the overhead of 278 * MPX itself (reading bounds tables) is expected to 279 * overwhelm the overhead of getting this unlikely() 280 * consistently wrong. 281 */ 282 if (unlikely(cpu_feature_enabled(X86_FEATURE_MPX))) 283 mpx_notify_unmap(mm, vma, start, end); 284 } 285 286 /* 287 * We only want to enforce protection keys on the current process 288 * because we effectively have no access to PKRU for other 289 * processes or any way to tell *which * PKRU in a threaded 290 * process we could use. 291 * 292 * So do not enforce things if the VMA is not from the current 293 * mm, or if we are in a kernel thread. 294 */ 295 static inline bool vma_is_foreign(struct vm_area_struct *vma) 296 { 297 if (!current->mm) 298 return true; 299 /* 300 * Should PKRU be enforced on the access to this VMA? If 301 * the VMA is from another process, then PKRU has no 302 * relevance and should not be enforced. 303 */ 304 if (current->mm != vma->vm_mm) 305 return true; 306 307 return false; 308 } 309 310 static inline bool arch_vma_access_permitted(struct vm_area_struct *vma, 311 bool write, bool execute, bool foreign) 312 { 313 /* pkeys never affect instruction fetches */ 314 if (execute) 315 return true; 316 /* allow access if the VMA is not one from this process */ 317 if (foreign || vma_is_foreign(vma)) 318 return true; 319 return __pkru_allows_pkey(vma_pkey(vma), write); 320 } 321 322 /* 323 * This can be used from process context to figure out what the value of 324 * CR3 is without needing to do a (slow) __read_cr3(). 325 * 326 * It's intended to be used for code like KVM that sneakily changes CR3 327 * and needs to restore it. It needs to be used very carefully. 328 */ 329 static inline unsigned long __get_current_cr3_fast(void) 330 { 331 unsigned long cr3 = build_cr3(this_cpu_read(cpu_tlbstate.loaded_mm)->pgd, 332 this_cpu_read(cpu_tlbstate.loaded_mm_asid)); 333 334 /* For now, be very restrictive about when this can be called. */ 335 VM_WARN_ON(in_nmi() || preemptible()); 336 337 VM_BUG_ON(cr3 != __read_cr3()); 338 return cr3; 339 } 340 341 #endif /* _ASM_X86_MMU_CONTEXT_H */ 342