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 /* lockless_dereference synchronizes with smp_store_release */ 76 ldt = lockless_dereference(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 static inline void enter_lazy_tlb(struct mm_struct *mm, struct task_struct *tsk) 130 { 131 int cpu = smp_processor_id(); 132 133 if (cpumask_test_cpu(cpu, mm_cpumask(mm))) 134 cpumask_clear_cpu(cpu, mm_cpumask(mm)); 135 } 136 137 static inline int init_new_context(struct task_struct *tsk, 138 struct mm_struct *mm) 139 { 140 mm->context.ctx_id = atomic64_inc_return(&last_mm_ctx_id); 141 atomic64_set(&mm->context.tlb_gen, 0); 142 143 #ifdef CONFIG_X86_INTEL_MEMORY_PROTECTION_KEYS 144 if (cpu_feature_enabled(X86_FEATURE_OSPKE)) { 145 /* pkey 0 is the default and always allocated */ 146 mm->context.pkey_allocation_map = 0x1; 147 /* -1 means unallocated or invalid */ 148 mm->context.execute_only_pkey = -1; 149 } 150 #endif 151 return init_new_context_ldt(tsk, mm); 152 } 153 static inline void destroy_context(struct mm_struct *mm) 154 { 155 destroy_context_ldt(mm); 156 } 157 158 extern void switch_mm(struct mm_struct *prev, struct mm_struct *next, 159 struct task_struct *tsk); 160 161 extern void switch_mm_irqs_off(struct mm_struct *prev, struct mm_struct *next, 162 struct task_struct *tsk); 163 #define switch_mm_irqs_off switch_mm_irqs_off 164 165 #define activate_mm(prev, next) \ 166 do { \ 167 paravirt_activate_mm((prev), (next)); \ 168 switch_mm((prev), (next), NULL); \ 169 } while (0); 170 171 #ifdef CONFIG_X86_32 172 #define deactivate_mm(tsk, mm) \ 173 do { \ 174 lazy_load_gs(0); \ 175 } while (0) 176 #else 177 #define deactivate_mm(tsk, mm) \ 178 do { \ 179 load_gs_index(0); \ 180 loadsegment(fs, 0); \ 181 } while (0) 182 #endif 183 184 static inline void arch_dup_mmap(struct mm_struct *oldmm, 185 struct mm_struct *mm) 186 { 187 paravirt_arch_dup_mmap(oldmm, mm); 188 } 189 190 static inline void arch_exit_mmap(struct mm_struct *mm) 191 { 192 paravirt_arch_exit_mmap(mm); 193 } 194 195 #ifdef CONFIG_X86_64 196 static inline bool is_64bit_mm(struct mm_struct *mm) 197 { 198 return !IS_ENABLED(CONFIG_IA32_EMULATION) || 199 !(mm->context.ia32_compat == TIF_IA32); 200 } 201 #else 202 static inline bool is_64bit_mm(struct mm_struct *mm) 203 { 204 return false; 205 } 206 #endif 207 208 static inline void arch_bprm_mm_init(struct mm_struct *mm, 209 struct vm_area_struct *vma) 210 { 211 mpx_mm_init(mm); 212 } 213 214 static inline void arch_unmap(struct mm_struct *mm, struct vm_area_struct *vma, 215 unsigned long start, unsigned long end) 216 { 217 /* 218 * mpx_notify_unmap() goes and reads a rarely-hot 219 * cacheline in the mm_struct. That can be expensive 220 * enough to be seen in profiles. 221 * 222 * The mpx_notify_unmap() call and its contents have been 223 * observed to affect munmap() performance on hardware 224 * where MPX is not present. 225 * 226 * The unlikely() optimizes for the fast case: no MPX 227 * in the CPU, or no MPX use in the process. Even if 228 * we get this wrong (in the unlikely event that MPX 229 * is widely enabled on some system) the overhead of 230 * MPX itself (reading bounds tables) is expected to 231 * overwhelm the overhead of getting this unlikely() 232 * consistently wrong. 233 */ 234 if (unlikely(cpu_feature_enabled(X86_FEATURE_MPX))) 235 mpx_notify_unmap(mm, vma, start, end); 236 } 237 238 #ifdef CONFIG_X86_INTEL_MEMORY_PROTECTION_KEYS 239 static inline int vma_pkey(struct vm_area_struct *vma) 240 { 241 unsigned long vma_pkey_mask = VM_PKEY_BIT0 | VM_PKEY_BIT1 | 242 VM_PKEY_BIT2 | VM_PKEY_BIT3; 243 244 return (vma->vm_flags & vma_pkey_mask) >> VM_PKEY_SHIFT; 245 } 246 #else 247 static inline int vma_pkey(struct vm_area_struct *vma) 248 { 249 return 0; 250 } 251 #endif 252 253 /* 254 * We only want to enforce protection keys on the current process 255 * because we effectively have no access to PKRU for other 256 * processes or any way to tell *which * PKRU in a threaded 257 * process we could use. 258 * 259 * So do not enforce things if the VMA is not from the current 260 * mm, or if we are in a kernel thread. 261 */ 262 static inline bool vma_is_foreign(struct vm_area_struct *vma) 263 { 264 if (!current->mm) 265 return true; 266 /* 267 * Should PKRU be enforced on the access to this VMA? If 268 * the VMA is from another process, then PKRU has no 269 * relevance and should not be enforced. 270 */ 271 if (current->mm != vma->vm_mm) 272 return true; 273 274 return false; 275 } 276 277 static inline bool arch_vma_access_permitted(struct vm_area_struct *vma, 278 bool write, bool execute, bool foreign) 279 { 280 /* pkeys never affect instruction fetches */ 281 if (execute) 282 return true; 283 /* allow access if the VMA is not one from this process */ 284 if (foreign || vma_is_foreign(vma)) 285 return true; 286 return __pkru_allows_pkey(vma_pkey(vma), write); 287 } 288 289 /* 290 * If PCID is on, ASID-aware code paths put the ASID+1 into the PCID 291 * bits. This serves two purposes. It prevents a nasty situation in 292 * which PCID-unaware code saves CR3, loads some other value (with PCID 293 * == 0), and then restores CR3, thus corrupting the TLB for ASID 0 if 294 * the saved ASID was nonzero. It also means that any bugs involving 295 * loading a PCID-enabled CR3 with CR4.PCIDE off will trigger 296 * deterministically. 297 */ 298 299 static inline unsigned long build_cr3(struct mm_struct *mm, u16 asid) 300 { 301 if (static_cpu_has(X86_FEATURE_PCID)) { 302 VM_WARN_ON_ONCE(asid > 4094); 303 return __sme_pa(mm->pgd) | (asid + 1); 304 } else { 305 VM_WARN_ON_ONCE(asid != 0); 306 return __sme_pa(mm->pgd); 307 } 308 } 309 310 static inline unsigned long build_cr3_noflush(struct mm_struct *mm, u16 asid) 311 { 312 VM_WARN_ON_ONCE(asid > 4094); 313 return __sme_pa(mm->pgd) | (asid + 1) | CR3_NOFLUSH; 314 } 315 316 /* 317 * This can be used from process context to figure out what the value of 318 * CR3 is without needing to do a (slow) __read_cr3(). 319 * 320 * It's intended to be used for code like KVM that sneakily changes CR3 321 * and needs to restore it. It needs to be used very carefully. 322 */ 323 static inline unsigned long __get_current_cr3_fast(void) 324 { 325 unsigned long cr3 = build_cr3(this_cpu_read(cpu_tlbstate.loaded_mm), 326 this_cpu_read(cpu_tlbstate.loaded_mm_asid)); 327 328 /* For now, be very restrictive about when this can be called. */ 329 VM_WARN_ON(in_nmi() || preemptible()); 330 331 VM_BUG_ON(cr3 != __read_cr3()); 332 return cr3; 333 } 334 335 #endif /* _ASM_X86_MMU_CONTEXT_H */ 336