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 extern struct static_key rdpmc_always_available; 28 29 static inline void load_mm_cr4(struct mm_struct *mm) 30 { 31 if (static_key_false(&rdpmc_always_available) || 32 atomic_read(&mm->context.perf_rdpmc_allowed)) 33 cr4_set_bits(X86_CR4_PCE); 34 else 35 cr4_clear_bits(X86_CR4_PCE); 36 } 37 #else 38 static inline void load_mm_cr4(struct mm_struct *mm) {} 39 #endif 40 41 #ifdef CONFIG_MODIFY_LDT_SYSCALL 42 /* 43 * ldt_structs can be allocated, used, and freed, but they are never 44 * modified while live. 45 */ 46 struct ldt_struct { 47 /* 48 * Xen requires page-aligned LDTs with special permissions. This is 49 * needed to prevent us from installing evil descriptors such as 50 * call gates. On native, we could merge the ldt_struct and LDT 51 * allocations, but it's not worth trying to optimize. 52 */ 53 struct desc_struct *entries; 54 unsigned int nr_entries; 55 }; 56 57 /* 58 * Used for LDT copy/destruction. 59 */ 60 int init_new_context_ldt(struct task_struct *tsk, struct mm_struct *mm); 61 void destroy_context_ldt(struct mm_struct *mm); 62 #else /* CONFIG_MODIFY_LDT_SYSCALL */ 63 static inline int init_new_context_ldt(struct task_struct *tsk, 64 struct mm_struct *mm) 65 { 66 return 0; 67 } 68 static inline void destroy_context_ldt(struct mm_struct *mm) {} 69 #endif 70 71 static inline void load_mm_ldt(struct mm_struct *mm) 72 { 73 #ifdef CONFIG_MODIFY_LDT_SYSCALL 74 struct ldt_struct *ldt; 75 76 /* READ_ONCE synchronizes with smp_store_release */ 77 ldt = READ_ONCE(mm->context.ldt); 78 79 /* 80 * Any change to mm->context.ldt is followed by an IPI to all 81 * CPUs with the mm active. The LDT will not be freed until 82 * after the IPI is handled by all such CPUs. This means that, 83 * if the ldt_struct changes before we return, the values we see 84 * will be safe, and the new values will be loaded before we run 85 * any user code. 86 * 87 * NB: don't try to convert this to use RCU without extreme care. 88 * We would still need IRQs off, because we don't want to change 89 * the local LDT after an IPI loaded a newer value than the one 90 * that we can see. 91 */ 92 93 if (unlikely(ldt)) 94 set_ldt(ldt->entries, ldt->nr_entries); 95 else 96 clear_LDT(); 97 #else 98 clear_LDT(); 99 #endif 100 } 101 102 static inline void switch_ldt(struct mm_struct *prev, struct mm_struct *next) 103 { 104 #ifdef CONFIG_MODIFY_LDT_SYSCALL 105 /* 106 * Load the LDT if either the old or new mm had an LDT. 107 * 108 * An mm will never go from having an LDT to not having an LDT. Two 109 * mms never share an LDT, so we don't gain anything by checking to 110 * see whether the LDT changed. There's also no guarantee that 111 * prev->context.ldt actually matches LDTR, but, if LDTR is non-NULL, 112 * then prev->context.ldt will also be non-NULL. 113 * 114 * If we really cared, we could optimize the case where prev == next 115 * and we're exiting lazy mode. Most of the time, if this happens, 116 * we don't actually need to reload LDTR, but modify_ldt() is mostly 117 * used by legacy code and emulators where we don't need this level of 118 * performance. 119 * 120 * This uses | instead of || because it generates better code. 121 */ 122 if (unlikely((unsigned long)prev->context.ldt | 123 (unsigned long)next->context.ldt)) 124 load_mm_ldt(next); 125 #endif 126 127 DEBUG_LOCKS_WARN_ON(preemptible()); 128 } 129 130 void enter_lazy_tlb(struct mm_struct *mm, struct task_struct *tsk); 131 132 static inline int init_new_context(struct task_struct *tsk, 133 struct mm_struct *mm) 134 { 135 mm->context.ctx_id = atomic64_inc_return(&last_mm_ctx_id); 136 atomic64_set(&mm->context.tlb_gen, 0); 137 138 #ifdef CONFIG_X86_INTEL_MEMORY_PROTECTION_KEYS 139 if (cpu_feature_enabled(X86_FEATURE_OSPKE)) { 140 /* pkey 0 is the default and always allocated */ 141 mm->context.pkey_allocation_map = 0x1; 142 /* -1 means unallocated or invalid */ 143 mm->context.execute_only_pkey = -1; 144 } 145 #endif 146 return init_new_context_ldt(tsk, mm); 147 } 148 static inline void destroy_context(struct mm_struct *mm) 149 { 150 destroy_context_ldt(mm); 151 } 152 153 extern void switch_mm(struct mm_struct *prev, struct mm_struct *next, 154 struct task_struct *tsk); 155 156 extern void switch_mm_irqs_off(struct mm_struct *prev, struct mm_struct *next, 157 struct task_struct *tsk); 158 #define switch_mm_irqs_off switch_mm_irqs_off 159 160 #define activate_mm(prev, next) \ 161 do { \ 162 paravirt_activate_mm((prev), (next)); \ 163 switch_mm((prev), (next), NULL); \ 164 } while (0); 165 166 #ifdef CONFIG_X86_32 167 #define deactivate_mm(tsk, mm) \ 168 do { \ 169 lazy_load_gs(0); \ 170 } while (0) 171 #else 172 #define deactivate_mm(tsk, mm) \ 173 do { \ 174 load_gs_index(0); \ 175 loadsegment(fs, 0); \ 176 } while (0) 177 #endif 178 179 static inline void arch_dup_mmap(struct mm_struct *oldmm, 180 struct mm_struct *mm) 181 { 182 paravirt_arch_dup_mmap(oldmm, mm); 183 } 184 185 static inline void arch_exit_mmap(struct mm_struct *mm) 186 { 187 paravirt_arch_exit_mmap(mm); 188 } 189 190 #ifdef CONFIG_X86_64 191 static inline bool is_64bit_mm(struct mm_struct *mm) 192 { 193 return !IS_ENABLED(CONFIG_IA32_EMULATION) || 194 !(mm->context.ia32_compat == TIF_IA32); 195 } 196 #else 197 static inline bool is_64bit_mm(struct mm_struct *mm) 198 { 199 return false; 200 } 201 #endif 202 203 static inline void arch_bprm_mm_init(struct mm_struct *mm, 204 struct vm_area_struct *vma) 205 { 206 mpx_mm_init(mm); 207 } 208 209 static inline void arch_unmap(struct mm_struct *mm, struct vm_area_struct *vma, 210 unsigned long start, unsigned long end) 211 { 212 /* 213 * mpx_notify_unmap() goes and reads a rarely-hot 214 * cacheline in the mm_struct. That can be expensive 215 * enough to be seen in profiles. 216 * 217 * The mpx_notify_unmap() call and its contents have been 218 * observed to affect munmap() performance on hardware 219 * where MPX is not present. 220 * 221 * The unlikely() optimizes for the fast case: no MPX 222 * in the CPU, or no MPX use in the process. Even if 223 * we get this wrong (in the unlikely event that MPX 224 * is widely enabled on some system) the overhead of 225 * MPX itself (reading bounds tables) is expected to 226 * overwhelm the overhead of getting this unlikely() 227 * consistently wrong. 228 */ 229 if (unlikely(cpu_feature_enabled(X86_FEATURE_MPX))) 230 mpx_notify_unmap(mm, vma, start, end); 231 } 232 233 #ifdef CONFIG_X86_INTEL_MEMORY_PROTECTION_KEYS 234 static inline int vma_pkey(struct vm_area_struct *vma) 235 { 236 unsigned long vma_pkey_mask = VM_PKEY_BIT0 | VM_PKEY_BIT1 | 237 VM_PKEY_BIT2 | VM_PKEY_BIT3; 238 239 return (vma->vm_flags & vma_pkey_mask) >> VM_PKEY_SHIFT; 240 } 241 #else 242 static inline int vma_pkey(struct vm_area_struct *vma) 243 { 244 return 0; 245 } 246 #endif 247 248 /* 249 * We only want to enforce protection keys on the current process 250 * because we effectively have no access to PKRU for other 251 * processes or any way to tell *which * PKRU in a threaded 252 * process we could use. 253 * 254 * So do not enforce things if the VMA is not from the current 255 * mm, or if we are in a kernel thread. 256 */ 257 static inline bool vma_is_foreign(struct vm_area_struct *vma) 258 { 259 if (!current->mm) 260 return true; 261 /* 262 * Should PKRU be enforced on the access to this VMA? If 263 * the VMA is from another process, then PKRU has no 264 * relevance and should not be enforced. 265 */ 266 if (current->mm != vma->vm_mm) 267 return true; 268 269 return false; 270 } 271 272 static inline bool arch_vma_access_permitted(struct vm_area_struct *vma, 273 bool write, bool execute, bool foreign) 274 { 275 /* pkeys never affect instruction fetches */ 276 if (execute) 277 return true; 278 /* allow access if the VMA is not one from this process */ 279 if (foreign || vma_is_foreign(vma)) 280 return true; 281 return __pkru_allows_pkey(vma_pkey(vma), write); 282 } 283 284 /* 285 * If PCID is on, ASID-aware code paths put the ASID+1 into the PCID 286 * bits. This serves two purposes. It prevents a nasty situation in 287 * which PCID-unaware code saves CR3, loads some other value (with PCID 288 * == 0), and then restores CR3, thus corrupting the TLB for ASID 0 if 289 * the saved ASID was nonzero. It also means that any bugs involving 290 * loading a PCID-enabled CR3 with CR4.PCIDE off will trigger 291 * deterministically. 292 */ 293 294 static inline unsigned long build_cr3(struct mm_struct *mm, u16 asid) 295 { 296 if (static_cpu_has(X86_FEATURE_PCID)) { 297 VM_WARN_ON_ONCE(asid > 4094); 298 return __sme_pa(mm->pgd) | (asid + 1); 299 } else { 300 VM_WARN_ON_ONCE(asid != 0); 301 return __sme_pa(mm->pgd); 302 } 303 } 304 305 static inline unsigned long build_cr3_noflush(struct mm_struct *mm, u16 asid) 306 { 307 VM_WARN_ON_ONCE(asid > 4094); 308 return __sme_pa(mm->pgd) | (asid + 1) | CR3_NOFLUSH; 309 } 310 311 /* 312 * This can be used from process context to figure out what the value of 313 * CR3 is without needing to do a (slow) __read_cr3(). 314 * 315 * It's intended to be used for code like KVM that sneakily changes CR3 316 * and needs to restore it. It needs to be used very carefully. 317 */ 318 static inline unsigned long __get_current_cr3_fast(void) 319 { 320 unsigned long cr3 = build_cr3(this_cpu_read(cpu_tlbstate.loaded_mm), 321 this_cpu_read(cpu_tlbstate.loaded_mm_asid)); 322 323 /* For now, be very restrictive about when this can be called. */ 324 VM_WARN_ON(in_nmi() || preemptible()); 325 326 VM_BUG_ON(cr3 != __read_cr3()); 327 return cr3; 328 } 329 330 #endif /* _ASM_X86_MMU_CONTEXT_H */ 331