1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * MMU fault handling support. 4 * 5 * Copyright (C) 1998-2002 Hewlett-Packard Co 6 * David Mosberger-Tang <davidm@hpl.hp.com> 7 */ 8 #include <linux/sched/signal.h> 9 #include <linux/kernel.h> 10 #include <linux/mm.h> 11 #include <linux/extable.h> 12 #include <linux/interrupt.h> 13 #include <linux/kprobes.h> 14 #include <linux/kdebug.h> 15 #include <linux/prefetch.h> 16 #include <linux/uaccess.h> 17 #include <linux/perf_event.h> 18 19 #include <asm/processor.h> 20 #include <asm/exception.h> 21 22 extern int die(char *, struct pt_regs *, long); 23 24 /* 25 * Return TRUE if ADDRESS points at a page in the kernel's mapped segment 26 * (inside region 5, on ia64) and that page is present. 27 */ 28 static int 29 mapped_kernel_page_is_present (unsigned long address) 30 { 31 pgd_t *pgd; 32 p4d_t *p4d; 33 pud_t *pud; 34 pmd_t *pmd; 35 pte_t *ptep, pte; 36 37 pgd = pgd_offset_k(address); 38 if (pgd_none(*pgd) || pgd_bad(*pgd)) 39 return 0; 40 41 p4d = p4d_offset(pgd, address); 42 if (p4d_none(*p4d) || p4d_bad(*p4d)) 43 return 0; 44 45 pud = pud_offset(p4d, address); 46 if (pud_none(*pud) || pud_bad(*pud)) 47 return 0; 48 49 pmd = pmd_offset(pud, address); 50 if (pmd_none(*pmd) || pmd_bad(*pmd)) 51 return 0; 52 53 ptep = pte_offset_kernel(pmd, address); 54 if (!ptep) 55 return 0; 56 57 pte = *ptep; 58 return pte_present(pte); 59 } 60 61 # define VM_READ_BIT 0 62 # define VM_WRITE_BIT 1 63 # define VM_EXEC_BIT 2 64 65 void __kprobes 66 ia64_do_page_fault (unsigned long address, unsigned long isr, struct pt_regs *regs) 67 { 68 int signal = SIGSEGV, code = SEGV_MAPERR; 69 struct vm_area_struct *vma, *prev_vma; 70 struct mm_struct *mm = current->mm; 71 unsigned long mask; 72 vm_fault_t fault; 73 unsigned int flags = FAULT_FLAG_DEFAULT; 74 75 mask = ((((isr >> IA64_ISR_X_BIT) & 1UL) << VM_EXEC_BIT) 76 | (((isr >> IA64_ISR_W_BIT) & 1UL) << VM_WRITE_BIT)); 77 78 /* mmap_lock is performance critical.... */ 79 prefetchw(&mm->mmap_lock); 80 81 /* 82 * If we're in an interrupt or have no user context, we must not take the fault.. 83 */ 84 if (faulthandler_disabled() || !mm) 85 goto no_context; 86 87 #ifdef CONFIG_VIRTUAL_MEM_MAP 88 /* 89 * If fault is in region 5 and we are in the kernel, we may already 90 * have the mmap_lock (pfn_valid macro is called during mmap). There 91 * is no vma for region 5 addr's anyway, so skip getting the semaphore 92 * and go directly to the exception handling code. 93 */ 94 95 if ((REGION_NUMBER(address) == 5) && !user_mode(regs)) 96 goto bad_area_no_up; 97 #endif 98 99 /* 100 * This is to handle the kprobes on user space access instructions 101 */ 102 if (kprobe_page_fault(regs, TRAP_BRKPT)) 103 return; 104 105 if (user_mode(regs)) 106 flags |= FAULT_FLAG_USER; 107 if (mask & VM_WRITE) 108 flags |= FAULT_FLAG_WRITE; 109 110 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address); 111 retry: 112 mmap_read_lock(mm); 113 114 vma = find_vma_prev(mm, address, &prev_vma); 115 if (!vma && !prev_vma ) 116 goto bad_area; 117 118 /* 119 * find_vma_prev() returns vma such that address < vma->vm_end or NULL 120 * 121 * May find no vma, but could be that the last vm area is the 122 * register backing store that needs to expand upwards, in 123 * this case vma will be null, but prev_vma will ne non-null 124 */ 125 if (( !vma && prev_vma ) || (address < vma->vm_start) ) 126 goto check_expansion; 127 128 good_area: 129 code = SEGV_ACCERR; 130 131 /* OK, we've got a good vm_area for this memory area. Check the access permissions: */ 132 133 # if (((1 << VM_READ_BIT) != VM_READ || (1 << VM_WRITE_BIT) != VM_WRITE) \ 134 || (1 << VM_EXEC_BIT) != VM_EXEC) 135 # error File is out of sync with <linux/mm.h>. Please update. 136 # endif 137 138 if (((isr >> IA64_ISR_R_BIT) & 1UL) && (!(vma->vm_flags & (VM_READ | VM_WRITE)))) 139 goto bad_area; 140 141 if ((vma->vm_flags & mask) != mask) 142 goto bad_area; 143 144 /* 145 * If for any reason at all we couldn't handle the fault, make 146 * sure we exit gracefully rather than endlessly redo the 147 * fault. 148 */ 149 fault = handle_mm_fault(vma, address, flags, regs); 150 151 if (fault_signal_pending(fault, regs)) 152 return; 153 154 if (unlikely(fault & VM_FAULT_ERROR)) { 155 /* 156 * We ran out of memory, or some other thing happened 157 * to us that made us unable to handle the page fault 158 * gracefully. 159 */ 160 if (fault & VM_FAULT_OOM) { 161 goto out_of_memory; 162 } else if (fault & VM_FAULT_SIGSEGV) { 163 goto bad_area; 164 } else if (fault & VM_FAULT_SIGBUS) { 165 signal = SIGBUS; 166 goto bad_area; 167 } 168 BUG(); 169 } 170 171 if (flags & FAULT_FLAG_ALLOW_RETRY) { 172 if (fault & VM_FAULT_RETRY) { 173 flags |= FAULT_FLAG_TRIED; 174 175 /* No need to mmap_read_unlock(mm) as we would 176 * have already released it in __lock_page_or_retry 177 * in mm/filemap.c. 178 */ 179 180 goto retry; 181 } 182 } 183 184 mmap_read_unlock(mm); 185 return; 186 187 check_expansion: 188 if (!(prev_vma && (prev_vma->vm_flags & VM_GROWSUP) && (address == prev_vma->vm_end))) { 189 if (!vma) 190 goto bad_area; 191 if (!(vma->vm_flags & VM_GROWSDOWN)) 192 goto bad_area; 193 if (REGION_NUMBER(address) != REGION_NUMBER(vma->vm_start) 194 || REGION_OFFSET(address) >= RGN_MAP_LIMIT) 195 goto bad_area; 196 if (expand_stack(vma, address)) 197 goto bad_area; 198 } else { 199 vma = prev_vma; 200 if (REGION_NUMBER(address) != REGION_NUMBER(vma->vm_start) 201 || REGION_OFFSET(address) >= RGN_MAP_LIMIT) 202 goto bad_area; 203 /* 204 * Since the register backing store is accessed sequentially, 205 * we disallow growing it by more than a page at a time. 206 */ 207 if (address > vma->vm_end + PAGE_SIZE - sizeof(long)) 208 goto bad_area; 209 if (expand_upwards(vma, address)) 210 goto bad_area; 211 } 212 goto good_area; 213 214 bad_area: 215 mmap_read_unlock(mm); 216 #ifdef CONFIG_VIRTUAL_MEM_MAP 217 bad_area_no_up: 218 #endif 219 if ((isr & IA64_ISR_SP) 220 || ((isr & IA64_ISR_NA) && (isr & IA64_ISR_CODE_MASK) == IA64_ISR_CODE_LFETCH)) 221 { 222 /* 223 * This fault was due to a speculative load or lfetch.fault, set the "ed" 224 * bit in the psr to ensure forward progress. (Target register will get a 225 * NaT for ld.s, lfetch will be canceled.) 226 */ 227 ia64_psr(regs)->ed = 1; 228 return; 229 } 230 if (user_mode(regs)) { 231 force_sig_fault(signal, code, (void __user *) address, 232 0, __ISR_VALID, isr); 233 return; 234 } 235 236 no_context: 237 if ((isr & IA64_ISR_SP) 238 || ((isr & IA64_ISR_NA) && (isr & IA64_ISR_CODE_MASK) == IA64_ISR_CODE_LFETCH)) 239 { 240 /* 241 * This fault was due to a speculative load or lfetch.fault, set the "ed" 242 * bit in the psr to ensure forward progress. (Target register will get a 243 * NaT for ld.s, lfetch will be canceled.) 244 */ 245 ia64_psr(regs)->ed = 1; 246 return; 247 } 248 249 /* 250 * Since we have no vma's for region 5, we might get here even if the address is 251 * valid, due to the VHPT walker inserting a non present translation that becomes 252 * stale. If that happens, the non present fault handler already purged the stale 253 * translation, which fixed the problem. So, we check to see if the translation is 254 * valid, and return if it is. 255 */ 256 if (REGION_NUMBER(address) == 5 && mapped_kernel_page_is_present(address)) 257 return; 258 259 if (ia64_done_with_exception(regs)) 260 return; 261 262 /* 263 * Oops. The kernel tried to access some bad page. We'll have to terminate things 264 * with extreme prejudice. 265 */ 266 bust_spinlocks(1); 267 268 if (address < PAGE_SIZE) 269 printk(KERN_ALERT "Unable to handle kernel NULL pointer dereference (address %016lx)\n", address); 270 else 271 printk(KERN_ALERT "Unable to handle kernel paging request at " 272 "virtual address %016lx\n", address); 273 if (die("Oops", regs, isr)) 274 regs = NULL; 275 bust_spinlocks(0); 276 if (regs) 277 do_exit(SIGKILL); 278 return; 279 280 out_of_memory: 281 mmap_read_unlock(mm); 282 if (!user_mode(regs)) 283 goto no_context; 284 pagefault_out_of_memory(); 285 } 286