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 18 #include <asm/processor.h> 19 #include <asm/exception.h> 20 21 extern int die(char *, struct pt_regs *, long); 22 23 /* 24 * Return TRUE if ADDRESS points at a page in the kernel's mapped segment 25 * (inside region 5, on ia64) and that page is present. 26 */ 27 static int 28 mapped_kernel_page_is_present (unsigned long address) 29 { 30 pgd_t *pgd; 31 p4d_t *p4d; 32 pud_t *pud; 33 pmd_t *pmd; 34 pte_t *ptep, pte; 35 36 pgd = pgd_offset_k(address); 37 if (pgd_none(*pgd) || pgd_bad(*pgd)) 38 return 0; 39 40 p4d = p4d_offset(pgd, address); 41 if (p4d_none(*p4d) || p4d_bad(*p4d)) 42 return 0; 43 44 pud = pud_offset(p4d, address); 45 if (pud_none(*pud) || pud_bad(*pud)) 46 return 0; 47 48 pmd = pmd_offset(pud, address); 49 if (pmd_none(*pmd) || pmd_bad(*pmd)) 50 return 0; 51 52 ptep = pte_offset_kernel(pmd, address); 53 if (!ptep) 54 return 0; 55 56 pte = *ptep; 57 return pte_present(pte); 58 } 59 60 # define VM_READ_BIT 0 61 # define VM_WRITE_BIT 1 62 # define VM_EXEC_BIT 2 63 64 void __kprobes 65 ia64_do_page_fault (unsigned long address, unsigned long isr, struct pt_regs *regs) 66 { 67 int signal = SIGSEGV, code = SEGV_MAPERR; 68 struct vm_area_struct *vma, *prev_vma; 69 struct mm_struct *mm = current->mm; 70 unsigned long mask; 71 vm_fault_t fault; 72 unsigned int flags = FAULT_FLAG_DEFAULT; 73 74 mask = ((((isr >> IA64_ISR_X_BIT) & 1UL) << VM_EXEC_BIT) 75 | (((isr >> IA64_ISR_W_BIT) & 1UL) << VM_WRITE_BIT)); 76 77 /* mmap_lock is performance critical.... */ 78 prefetchw(&mm->mmap_lock); 79 80 /* 81 * If we're in an interrupt or have no user context, we must not take the fault.. 82 */ 83 if (faulthandler_disabled() || !mm) 84 goto no_context; 85 86 #ifdef CONFIG_VIRTUAL_MEM_MAP 87 /* 88 * If fault is in region 5 and we are in the kernel, we may already 89 * have the mmap_lock (pfn_valid macro is called during mmap). There 90 * is no vma for region 5 addr's anyway, so skip getting the semaphore 91 * and go directly to the exception handling code. 92 */ 93 94 if ((REGION_NUMBER(address) == 5) && !user_mode(regs)) 95 goto bad_area_no_up; 96 #endif 97 98 /* 99 * This is to handle the kprobes on user space access instructions 100 */ 101 if (kprobe_page_fault(regs, TRAP_BRKPT)) 102 return; 103 104 if (user_mode(regs)) 105 flags |= FAULT_FLAG_USER; 106 if (mask & VM_WRITE) 107 flags |= FAULT_FLAG_WRITE; 108 retry: 109 mmap_read_lock(mm); 110 111 vma = find_vma_prev(mm, address, &prev_vma); 112 if (!vma && !prev_vma ) 113 goto bad_area; 114 115 /* 116 * find_vma_prev() returns vma such that address < vma->vm_end or NULL 117 * 118 * May find no vma, but could be that the last vm area is the 119 * register backing store that needs to expand upwards, in 120 * this case vma will be null, but prev_vma will ne non-null 121 */ 122 if (( !vma && prev_vma ) || (address < vma->vm_start) ) 123 goto check_expansion; 124 125 good_area: 126 code = SEGV_ACCERR; 127 128 /* OK, we've got a good vm_area for this memory area. Check the access permissions: */ 129 130 # if (((1 << VM_READ_BIT) != VM_READ || (1 << VM_WRITE_BIT) != VM_WRITE) \ 131 || (1 << VM_EXEC_BIT) != VM_EXEC) 132 # error File is out of sync with <linux/mm.h>. Please update. 133 # endif 134 135 if (((isr >> IA64_ISR_R_BIT) & 1UL) && (!(vma->vm_flags & (VM_READ | VM_WRITE)))) 136 goto bad_area; 137 138 if ((vma->vm_flags & mask) != mask) 139 goto bad_area; 140 141 /* 142 * If for any reason at all we couldn't handle the fault, make 143 * sure we exit gracefully rather than endlessly redo the 144 * fault. 145 */ 146 fault = handle_mm_fault(vma, address, flags); 147 148 if (fault_signal_pending(fault, regs)) 149 return; 150 151 if (unlikely(fault & VM_FAULT_ERROR)) { 152 /* 153 * We ran out of memory, or some other thing happened 154 * to us that made us unable to handle the page fault 155 * gracefully. 156 */ 157 if (fault & VM_FAULT_OOM) { 158 goto out_of_memory; 159 } else if (fault & VM_FAULT_SIGSEGV) { 160 goto bad_area; 161 } else if (fault & VM_FAULT_SIGBUS) { 162 signal = SIGBUS; 163 goto bad_area; 164 } 165 BUG(); 166 } 167 168 if (flags & FAULT_FLAG_ALLOW_RETRY) { 169 if (fault & VM_FAULT_MAJOR) 170 current->maj_flt++; 171 else 172 current->min_flt++; 173 if (fault & VM_FAULT_RETRY) { 174 flags |= FAULT_FLAG_TRIED; 175 176 /* No need to mmap_read_unlock(mm) as we would 177 * have already released it in __lock_page_or_retry 178 * in mm/filemap.c. 179 */ 180 181 goto retry; 182 } 183 } 184 185 mmap_read_unlock(mm); 186 return; 187 188 check_expansion: 189 if (!(prev_vma && (prev_vma->vm_flags & VM_GROWSUP) && (address == prev_vma->vm_end))) { 190 if (!vma) 191 goto bad_area; 192 if (!(vma->vm_flags & VM_GROWSDOWN)) 193 goto bad_area; 194 if (REGION_NUMBER(address) != REGION_NUMBER(vma->vm_start) 195 || REGION_OFFSET(address) >= RGN_MAP_LIMIT) 196 goto bad_area; 197 if (expand_stack(vma, address)) 198 goto bad_area; 199 } else { 200 vma = prev_vma; 201 if (REGION_NUMBER(address) != REGION_NUMBER(vma->vm_start) 202 || REGION_OFFSET(address) >= RGN_MAP_LIMIT) 203 goto bad_area; 204 /* 205 * Since the register backing store is accessed sequentially, 206 * we disallow growing it by more than a page at a time. 207 */ 208 if (address > vma->vm_end + PAGE_SIZE - sizeof(long)) 209 goto bad_area; 210 if (expand_upwards(vma, address)) 211 goto bad_area; 212 } 213 goto good_area; 214 215 bad_area: 216 mmap_read_unlock(mm); 217 #ifdef CONFIG_VIRTUAL_MEM_MAP 218 bad_area_no_up: 219 #endif 220 if ((isr & IA64_ISR_SP) 221 || ((isr & IA64_ISR_NA) && (isr & IA64_ISR_CODE_MASK) == IA64_ISR_CODE_LFETCH)) 222 { 223 /* 224 * This fault was due to a speculative load or lfetch.fault, set the "ed" 225 * bit in the psr to ensure forward progress. (Target register will get a 226 * NaT for ld.s, lfetch will be canceled.) 227 */ 228 ia64_psr(regs)->ed = 1; 229 return; 230 } 231 if (user_mode(regs)) { 232 force_sig_fault(signal, code, (void __user *) address, 233 0, __ISR_VALID, isr); 234 return; 235 } 236 237 no_context: 238 if ((isr & IA64_ISR_SP) 239 || ((isr & IA64_ISR_NA) && (isr & IA64_ISR_CODE_MASK) == IA64_ISR_CODE_LFETCH)) 240 { 241 /* 242 * This fault was due to a speculative load or lfetch.fault, set the "ed" 243 * bit in the psr to ensure forward progress. (Target register will get a 244 * NaT for ld.s, lfetch will be canceled.) 245 */ 246 ia64_psr(regs)->ed = 1; 247 return; 248 } 249 250 /* 251 * Since we have no vma's for region 5, we might get here even if the address is 252 * valid, due to the VHPT walker inserting a non present translation that becomes 253 * stale. If that happens, the non present fault handler already purged the stale 254 * translation, which fixed the problem. So, we check to see if the translation is 255 * valid, and return if it is. 256 */ 257 if (REGION_NUMBER(address) == 5 && mapped_kernel_page_is_present(address)) 258 return; 259 260 if (ia64_done_with_exception(regs)) 261 return; 262 263 /* 264 * Oops. The kernel tried to access some bad page. We'll have to terminate things 265 * with extreme prejudice. 266 */ 267 bust_spinlocks(1); 268 269 if (address < PAGE_SIZE) 270 printk(KERN_ALERT "Unable to handle kernel NULL pointer dereference (address %016lx)\n", address); 271 else 272 printk(KERN_ALERT "Unable to handle kernel paging request at " 273 "virtual address %016lx\n", address); 274 if (die("Oops", regs, isr)) 275 regs = NULL; 276 bust_spinlocks(0); 277 if (regs) 278 do_exit(SIGKILL); 279 return; 280 281 out_of_memory: 282 mmap_read_unlock(mm); 283 if (!user_mode(regs)) 284 goto no_context; 285 pagefault_out_of_memory(); 286 } 287