1 /* SPDX-License-Identifier: GPL-2.0 */ 2 #ifndef _ASM_X86_PGTABLE_3LEVEL_H 3 #define _ASM_X86_PGTABLE_3LEVEL_H 4 5 #include <asm/atomic64_32.h> 6 7 /* 8 * Intel Physical Address Extension (PAE) Mode - three-level page 9 * tables on PPro+ CPUs. 10 * 11 * Copyright (C) 1999 Ingo Molnar <mingo@redhat.com> 12 */ 13 14 #define pte_ERROR(e) \ 15 pr_err("%s:%d: bad pte %p(%08lx%08lx)\n", \ 16 __FILE__, __LINE__, &(e), (e).pte_high, (e).pte_low) 17 #define pmd_ERROR(e) \ 18 pr_err("%s:%d: bad pmd %p(%016Lx)\n", \ 19 __FILE__, __LINE__, &(e), pmd_val(e)) 20 #define pgd_ERROR(e) \ 21 pr_err("%s:%d: bad pgd %p(%016Lx)\n", \ 22 __FILE__, __LINE__, &(e), pgd_val(e)) 23 24 /* Rules for using set_pte: the pte being assigned *must* be 25 * either not present or in a state where the hardware will 26 * not attempt to update the pte. In places where this is 27 * not possible, use pte_get_and_clear to obtain the old pte 28 * value and then use set_pte to update it. -ben 29 */ 30 static inline void native_set_pte(pte_t *ptep, pte_t pte) 31 { 32 ptep->pte_high = pte.pte_high; 33 smp_wmb(); 34 ptep->pte_low = pte.pte_low; 35 } 36 37 #define pmd_read_atomic pmd_read_atomic 38 /* 39 * pte_offset_map_lock() on 32-bit PAE kernels was reading the pmd_t with 40 * a "*pmdp" dereference done by GCC. Problem is, in certain places 41 * where pte_offset_map_lock() is called, concurrent page faults are 42 * allowed, if the mmap_sem is hold for reading. An example is mincore 43 * vs page faults vs MADV_DONTNEED. On the page fault side 44 * pmd_populate() rightfully does a set_64bit(), but if we're reading the 45 * pmd_t with a "*pmdp" on the mincore side, a SMP race can happen 46 * because GCC will not read the 64-bit value of the pmd atomically. 47 * 48 * To fix this all places running pte_offset_map_lock() while holding the 49 * mmap_sem in read mode, shall read the pmdp pointer using this 50 * function to know if the pmd is null or not, and in turn to know if 51 * they can run pte_offset_map_lock() or pmd_trans_huge() or other pmd 52 * operations. 53 * 54 * Without THP if the mmap_sem is held for reading, the pmd can only 55 * transition from null to not null while pmd_read_atomic() runs. So 56 * we can always return atomic pmd values with this function. 57 * 58 * With THP if the mmap_sem is held for reading, the pmd can become 59 * trans_huge or none or point to a pte (and in turn become "stable") 60 * at any time under pmd_read_atomic(). We could read it truly 61 * atomically here with an atomic64_read() for the THP enabled case (and 62 * it would be a whole lot simpler), but to avoid using cmpxchg8b we 63 * only return an atomic pmdval if the low part of the pmdval is later 64 * found to be stable (i.e. pointing to a pte). We are also returning a 65 * 'none' (zero) pmdval if the low part of the pmd is zero. 66 * 67 * In some cases the high and low part of the pmdval returned may not be 68 * consistent if THP is enabled (the low part may point to previously 69 * mapped hugepage, while the high part may point to a more recently 70 * mapped hugepage), but pmd_none_or_trans_huge_or_clear_bad() only 71 * needs the low part of the pmd to be read atomically to decide if the 72 * pmd is unstable or not, with the only exception when the low part 73 * of the pmd is zero, in which case we return a 'none' pmd. 74 */ 75 static inline pmd_t pmd_read_atomic(pmd_t *pmdp) 76 { 77 pmdval_t ret; 78 u32 *tmp = (u32 *)pmdp; 79 80 ret = (pmdval_t) (*tmp); 81 if (ret) { 82 /* 83 * If the low part is null, we must not read the high part 84 * or we can end up with a partial pmd. 85 */ 86 smp_rmb(); 87 ret |= ((pmdval_t)*(tmp + 1)) << 32; 88 } 89 90 return (pmd_t) { ret }; 91 } 92 93 static inline void native_set_pte_atomic(pte_t *ptep, pte_t pte) 94 { 95 set_64bit((unsigned long long *)(ptep), native_pte_val(pte)); 96 } 97 98 static inline void native_set_pmd(pmd_t *pmdp, pmd_t pmd) 99 { 100 set_64bit((unsigned long long *)(pmdp), native_pmd_val(pmd)); 101 } 102 103 static inline void native_set_pud(pud_t *pudp, pud_t pud) 104 { 105 #ifdef CONFIG_PAGE_TABLE_ISOLATION 106 pud.p4d.pgd = pti_set_user_pgtbl(&pudp->p4d.pgd, pud.p4d.pgd); 107 #endif 108 set_64bit((unsigned long long *)(pudp), native_pud_val(pud)); 109 } 110 111 /* 112 * For PTEs and PDEs, we must clear the P-bit first when clearing a page table 113 * entry, so clear the bottom half first and enforce ordering with a compiler 114 * barrier. 115 */ 116 static inline void native_pte_clear(struct mm_struct *mm, unsigned long addr, 117 pte_t *ptep) 118 { 119 ptep->pte_low = 0; 120 smp_wmb(); 121 ptep->pte_high = 0; 122 } 123 124 static inline void native_pmd_clear(pmd_t *pmd) 125 { 126 u32 *tmp = (u32 *)pmd; 127 *tmp = 0; 128 smp_wmb(); 129 *(tmp + 1) = 0; 130 } 131 132 static inline void native_pud_clear(pud_t *pudp) 133 { 134 } 135 136 static inline void pud_clear(pud_t *pudp) 137 { 138 set_pud(pudp, __pud(0)); 139 140 /* 141 * According to Intel App note "TLBs, Paging-Structure Caches, 142 * and Their Invalidation", April 2007, document 317080-001, 143 * section 8.1: in PAE mode we explicitly have to flush the 144 * TLB via cr3 if the top-level pgd is changed... 145 * 146 * Currently all places where pud_clear() is called either have 147 * flush_tlb_mm() followed or don't need TLB flush (x86_64 code or 148 * pud_clear_bad()), so we don't need TLB flush here. 149 */ 150 } 151 152 #ifdef CONFIG_SMP 153 static inline pte_t native_ptep_get_and_clear(pte_t *ptep) 154 { 155 pte_t res; 156 157 res.pte = (pteval_t)arch_atomic64_xchg((atomic64_t *)ptep, 0); 158 159 return res; 160 } 161 #else 162 #define native_ptep_get_and_clear(xp) native_local_ptep_get_and_clear(xp) 163 #endif 164 165 union split_pmd { 166 struct { 167 u32 pmd_low; 168 u32 pmd_high; 169 }; 170 pmd_t pmd; 171 }; 172 173 #ifdef CONFIG_SMP 174 static inline pmd_t native_pmdp_get_and_clear(pmd_t *pmdp) 175 { 176 union split_pmd res, *orig = (union split_pmd *)pmdp; 177 178 /* xchg acts as a barrier before setting of the high bits */ 179 res.pmd_low = xchg(&orig->pmd_low, 0); 180 res.pmd_high = orig->pmd_high; 181 orig->pmd_high = 0; 182 183 return res.pmd; 184 } 185 #else 186 #define native_pmdp_get_and_clear(xp) native_local_pmdp_get_and_clear(xp) 187 #endif 188 189 #ifndef pmdp_establish 190 #define pmdp_establish pmdp_establish 191 static inline pmd_t pmdp_establish(struct vm_area_struct *vma, 192 unsigned long address, pmd_t *pmdp, pmd_t pmd) 193 { 194 pmd_t old; 195 196 /* 197 * If pmd has present bit cleared we can get away without expensive 198 * cmpxchg64: we can update pmdp half-by-half without racing with 199 * anybody. 200 */ 201 if (!(pmd_val(pmd) & _PAGE_PRESENT)) { 202 union split_pmd old, new, *ptr; 203 204 ptr = (union split_pmd *)pmdp; 205 206 new.pmd = pmd; 207 208 /* xchg acts as a barrier before setting of the high bits */ 209 old.pmd_low = xchg(&ptr->pmd_low, new.pmd_low); 210 old.pmd_high = ptr->pmd_high; 211 ptr->pmd_high = new.pmd_high; 212 return old.pmd; 213 } 214 215 do { 216 old = *pmdp; 217 } while (cmpxchg64(&pmdp->pmd, old.pmd, pmd.pmd) != old.pmd); 218 219 return old; 220 } 221 #endif 222 223 #ifdef CONFIG_SMP 224 union split_pud { 225 struct { 226 u32 pud_low; 227 u32 pud_high; 228 }; 229 pud_t pud; 230 }; 231 232 static inline pud_t native_pudp_get_and_clear(pud_t *pudp) 233 { 234 union split_pud res, *orig = (union split_pud *)pudp; 235 236 #ifdef CONFIG_PAGE_TABLE_ISOLATION 237 pti_set_user_pgtbl(&pudp->p4d.pgd, __pgd(0)); 238 #endif 239 240 /* xchg acts as a barrier before setting of the high bits */ 241 res.pud_low = xchg(&orig->pud_low, 0); 242 res.pud_high = orig->pud_high; 243 orig->pud_high = 0; 244 245 return res.pud; 246 } 247 #else 248 #define native_pudp_get_and_clear(xp) native_local_pudp_get_and_clear(xp) 249 #endif 250 251 /* Encode and de-code a swap entry */ 252 #define SWP_TYPE_BITS 5 253 254 #define SWP_OFFSET_FIRST_BIT (_PAGE_BIT_PROTNONE + 1) 255 256 /* We always extract/encode the offset by shifting it all the way up, and then down again */ 257 #define SWP_OFFSET_SHIFT (SWP_OFFSET_FIRST_BIT + SWP_TYPE_BITS) 258 259 #define MAX_SWAPFILES_CHECK() BUILD_BUG_ON(MAX_SWAPFILES_SHIFT > 5) 260 #define __swp_type(x) (((x).val) & 0x1f) 261 #define __swp_offset(x) ((x).val >> 5) 262 #define __swp_entry(type, offset) ((swp_entry_t){(type) | (offset) << 5}) 263 264 /* 265 * Normally, __swp_entry() converts from arch-independent swp_entry_t to 266 * arch-dependent swp_entry_t, and __swp_entry_to_pte() just stores the result 267 * to pte. But here we have 32bit swp_entry_t and 64bit pte, and need to use the 268 * whole 64 bits. Thus, we shift the "real" arch-dependent conversion to 269 * __swp_entry_to_pte() through the following helper macro based on 64bit 270 * __swp_entry(). 271 */ 272 #define __swp_pteval_entry(type, offset) ((pteval_t) { \ 273 (~(pteval_t)(offset) << SWP_OFFSET_SHIFT >> SWP_TYPE_BITS) \ 274 | ((pteval_t)(type) << (64 - SWP_TYPE_BITS)) }) 275 276 #define __swp_entry_to_pte(x) ((pte_t){ .pte = \ 277 __swp_pteval_entry(__swp_type(x), __swp_offset(x)) }) 278 /* 279 * Analogically, __pte_to_swp_entry() doesn't just extract the arch-dependent 280 * swp_entry_t, but also has to convert it from 64bit to the 32bit 281 * intermediate representation, using the following macros based on 64bit 282 * __swp_type() and __swp_offset(). 283 */ 284 #define __pteval_swp_type(x) ((unsigned long)((x).pte >> (64 - SWP_TYPE_BITS))) 285 #define __pteval_swp_offset(x) ((unsigned long)(~((x).pte) << SWP_TYPE_BITS >> SWP_OFFSET_SHIFT)) 286 287 #define __pte_to_swp_entry(pte) (__swp_entry(__pteval_swp_type(pte), \ 288 __pteval_swp_offset(pte))) 289 290 #include <asm/pgtable-invert.h> 291 292 #endif /* _ASM_X86_PGTABLE_3LEVEL_H */ 293