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/pgtable.h> 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_sem is performance critical.... */ 79 prefetchw(&mm->mmap_sem); 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_sem (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 retry: 110 down_read(&mm->mmap_sem); 111 112 vma = find_vma_prev(mm, address, &prev_vma); 113 if (!vma && !prev_vma ) 114 goto bad_area; 115 116 /* 117 * find_vma_prev() returns vma such that address < vma->vm_end or NULL 118 * 119 * May find no vma, but could be that the last vm area is the 120 * register backing store that needs to expand upwards, in 121 * this case vma will be null, but prev_vma will ne non-null 122 */ 123 if (( !vma && prev_vma ) || (address < vma->vm_start) ) 124 goto check_expansion; 125 126 good_area: 127 code = SEGV_ACCERR; 128 129 /* OK, we've got a good vm_area for this memory area. Check the access permissions: */ 130 131 # if (((1 << VM_READ_BIT) != VM_READ || (1 << VM_WRITE_BIT) != VM_WRITE) \ 132 || (1 << VM_EXEC_BIT) != VM_EXEC) 133 # error File is out of sync with <linux/mm.h>. Please update. 134 # endif 135 136 if (((isr >> IA64_ISR_R_BIT) & 1UL) && (!(vma->vm_flags & (VM_READ | VM_WRITE)))) 137 goto bad_area; 138 139 if ((vma->vm_flags & mask) != mask) 140 goto bad_area; 141 142 /* 143 * If for any reason at all we couldn't handle the fault, make 144 * sure we exit gracefully rather than endlessly redo the 145 * fault. 146 */ 147 fault = handle_mm_fault(vma, address, flags); 148 149 if (fault_signal_pending(fault, regs)) 150 return; 151 152 if (unlikely(fault & VM_FAULT_ERROR)) { 153 /* 154 * We ran out of memory, or some other thing happened 155 * to us that made us unable to handle the page fault 156 * gracefully. 157 */ 158 if (fault & VM_FAULT_OOM) { 159 goto out_of_memory; 160 } else if (fault & VM_FAULT_SIGSEGV) { 161 goto bad_area; 162 } else if (fault & VM_FAULT_SIGBUS) { 163 signal = SIGBUS; 164 goto bad_area; 165 } 166 BUG(); 167 } 168 169 if (flags & FAULT_FLAG_ALLOW_RETRY) { 170 if (fault & VM_FAULT_MAJOR) 171 current->maj_flt++; 172 else 173 current->min_flt++; 174 if (fault & VM_FAULT_RETRY) { 175 flags |= FAULT_FLAG_TRIED; 176 177 /* No need to up_read(&mm->mmap_sem) as we would 178 * have already released it in __lock_page_or_retry 179 * in mm/filemap.c. 180 */ 181 182 goto retry; 183 } 184 } 185 186 up_read(&mm->mmap_sem); 187 return; 188 189 check_expansion: 190 if (!(prev_vma && (prev_vma->vm_flags & VM_GROWSUP) && (address == prev_vma->vm_end))) { 191 if (!vma) 192 goto bad_area; 193 if (!(vma->vm_flags & VM_GROWSDOWN)) 194 goto bad_area; 195 if (REGION_NUMBER(address) != REGION_NUMBER(vma->vm_start) 196 || REGION_OFFSET(address) >= RGN_MAP_LIMIT) 197 goto bad_area; 198 if (expand_stack(vma, address)) 199 goto bad_area; 200 } else { 201 vma = prev_vma; 202 if (REGION_NUMBER(address) != REGION_NUMBER(vma->vm_start) 203 || REGION_OFFSET(address) >= RGN_MAP_LIMIT) 204 goto bad_area; 205 /* 206 * Since the register backing store is accessed sequentially, 207 * we disallow growing it by more than a page at a time. 208 */ 209 if (address > vma->vm_end + PAGE_SIZE - sizeof(long)) 210 goto bad_area; 211 if (expand_upwards(vma, address)) 212 goto bad_area; 213 } 214 goto good_area; 215 216 bad_area: 217 up_read(&mm->mmap_sem); 218 #ifdef CONFIG_VIRTUAL_MEM_MAP 219 bad_area_no_up: 220 #endif 221 if ((isr & IA64_ISR_SP) 222 || ((isr & IA64_ISR_NA) && (isr & IA64_ISR_CODE_MASK) == IA64_ISR_CODE_LFETCH)) 223 { 224 /* 225 * This fault was due to a speculative load or lfetch.fault, set the "ed" 226 * bit in the psr to ensure forward progress. (Target register will get a 227 * NaT for ld.s, lfetch will be canceled.) 228 */ 229 ia64_psr(regs)->ed = 1; 230 return; 231 } 232 if (user_mode(regs)) { 233 force_sig_fault(signal, code, (void __user *) address, 234 0, __ISR_VALID, isr); 235 return; 236 } 237 238 no_context: 239 if ((isr & IA64_ISR_SP) 240 || ((isr & IA64_ISR_NA) && (isr & IA64_ISR_CODE_MASK) == IA64_ISR_CODE_LFETCH)) 241 { 242 /* 243 * This fault was due to a speculative load or lfetch.fault, set the "ed" 244 * bit in the psr to ensure forward progress. (Target register will get a 245 * NaT for ld.s, lfetch will be canceled.) 246 */ 247 ia64_psr(regs)->ed = 1; 248 return; 249 } 250 251 /* 252 * Since we have no vma's for region 5, we might get here even if the address is 253 * valid, due to the VHPT walker inserting a non present translation that becomes 254 * stale. If that happens, the non present fault handler already purged the stale 255 * translation, which fixed the problem. So, we check to see if the translation is 256 * valid, and return if it is. 257 */ 258 if (REGION_NUMBER(address) == 5 && mapped_kernel_page_is_present(address)) 259 return; 260 261 if (ia64_done_with_exception(regs)) 262 return; 263 264 /* 265 * Oops. The kernel tried to access some bad page. We'll have to terminate things 266 * with extreme prejudice. 267 */ 268 bust_spinlocks(1); 269 270 if (address < PAGE_SIZE) 271 printk(KERN_ALERT "Unable to handle kernel NULL pointer dereference (address %016lx)\n", address); 272 else 273 printk(KERN_ALERT "Unable to handle kernel paging request at " 274 "virtual address %016lx\n", address); 275 if (die("Oops", regs, isr)) 276 regs = NULL; 277 bust_spinlocks(0); 278 if (regs) 279 do_exit(SIGKILL); 280 return; 281 282 out_of_memory: 283 up_read(&mm->mmap_sem); 284 if (!user_mode(regs)) 285 goto no_context; 286 pagefault_out_of_memory(); 287 } 288