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