1 /* 2 * MMU fault handling support. 3 * 4 * Copyright (C) 1998-2002 Hewlett-Packard Co 5 * David Mosberger-Tang <davidm@hpl.hp.com> 6 */ 7 #include <linux/sched.h> 8 #include <linux/kernel.h> 9 #include <linux/mm.h> 10 #include <linux/smp_lock.h> 11 #include <linux/interrupt.h> 12 #include <linux/kprobes.h> 13 #include <linux/kdebug.h> 14 15 #include <asm/pgtable.h> 16 #include <asm/processor.h> 17 #include <asm/system.h> 18 #include <asm/uaccess.h> 19 20 extern void die (char *, struct pt_regs *, long); 21 22 #ifdef CONFIG_KPROBES 23 ATOMIC_NOTIFIER_HEAD(notify_page_fault_chain); 24 25 /* Hook to register for page fault notifications */ 26 int register_page_fault_notifier(struct notifier_block *nb) 27 { 28 return atomic_notifier_chain_register(¬ify_page_fault_chain, nb); 29 } 30 31 int unregister_page_fault_notifier(struct notifier_block *nb) 32 { 33 return atomic_notifier_chain_unregister(¬ify_page_fault_chain, nb); 34 } 35 36 static inline int notify_page_fault(enum die_val val, const char *str, 37 struct pt_regs *regs, long err, int trap, int sig) 38 { 39 struct die_args args = { 40 .regs = regs, 41 .str = str, 42 .err = err, 43 .trapnr = trap, 44 .signr = sig 45 }; 46 return atomic_notifier_call_chain(¬ify_page_fault_chain, val, &args); 47 } 48 #else 49 static inline int notify_page_fault(enum die_val val, const char *str, 50 struct pt_regs *regs, long err, int trap, int sig) 51 { 52 return NOTIFY_DONE; 53 } 54 #endif 55 56 /* 57 * Return TRUE if ADDRESS points at a page in the kernel's mapped segment 58 * (inside region 5, on ia64) and that page is present. 59 */ 60 static int 61 mapped_kernel_page_is_present (unsigned long address) 62 { 63 pgd_t *pgd; 64 pud_t *pud; 65 pmd_t *pmd; 66 pte_t *ptep, pte; 67 68 pgd = pgd_offset_k(address); 69 if (pgd_none(*pgd) || pgd_bad(*pgd)) 70 return 0; 71 72 pud = pud_offset(pgd, address); 73 if (pud_none(*pud) || pud_bad(*pud)) 74 return 0; 75 76 pmd = pmd_offset(pud, address); 77 if (pmd_none(*pmd) || pmd_bad(*pmd)) 78 return 0; 79 80 ptep = pte_offset_kernel(pmd, address); 81 if (!ptep) 82 return 0; 83 84 pte = *ptep; 85 return pte_present(pte); 86 } 87 88 void __kprobes 89 ia64_do_page_fault (unsigned long address, unsigned long isr, struct pt_regs *regs) 90 { 91 int signal = SIGSEGV, code = SEGV_MAPERR; 92 struct vm_area_struct *vma, *prev_vma; 93 struct mm_struct *mm = current->mm; 94 struct siginfo si; 95 unsigned long mask; 96 97 /* mmap_sem is performance critical.... */ 98 prefetchw(&mm->mmap_sem); 99 100 /* 101 * If we're in an interrupt or have no user context, we must not take the fault.. 102 */ 103 if (in_atomic() || !mm) 104 goto no_context; 105 106 #ifdef CONFIG_VIRTUAL_MEM_MAP 107 /* 108 * If fault is in region 5 and we are in the kernel, we may already 109 * have the mmap_sem (pfn_valid macro is called during mmap). There 110 * is no vma for region 5 addr's anyway, so skip getting the semaphore 111 * and go directly to the exception handling code. 112 */ 113 114 if ((REGION_NUMBER(address) == 5) && !user_mode(regs)) 115 goto bad_area_no_up; 116 #endif 117 118 /* 119 * This is to handle the kprobes on user space access instructions 120 */ 121 if (notify_page_fault(DIE_PAGE_FAULT, "page fault", regs, code, TRAP_BRKPT, 122 SIGSEGV) == NOTIFY_STOP) 123 return; 124 125 down_read(&mm->mmap_sem); 126 127 vma = find_vma_prev(mm, address, &prev_vma); 128 if (!vma) 129 goto bad_area; 130 131 /* find_vma_prev() returns vma such that address < vma->vm_end or NULL */ 132 if (address < vma->vm_start) 133 goto check_expansion; 134 135 good_area: 136 code = SEGV_ACCERR; 137 138 /* OK, we've got a good vm_area for this memory area. Check the access permissions: */ 139 140 # define VM_READ_BIT 0 141 # define VM_WRITE_BIT 1 142 # define VM_EXEC_BIT 2 143 144 # if (((1 << VM_READ_BIT) != VM_READ || (1 << VM_WRITE_BIT) != VM_WRITE) \ 145 || (1 << VM_EXEC_BIT) != VM_EXEC) 146 # error File is out of sync with <linux/mm.h>. Please update. 147 # endif 148 149 if (((isr >> IA64_ISR_R_BIT) & 1UL) && (!(vma->vm_flags & (VM_READ | VM_WRITE)))) 150 goto bad_area; 151 152 mask = ( (((isr >> IA64_ISR_X_BIT) & 1UL) << VM_EXEC_BIT) 153 | (((isr >> IA64_ISR_W_BIT) & 1UL) << VM_WRITE_BIT)); 154 155 if ((vma->vm_flags & mask) != mask) 156 goto bad_area; 157 158 survive: 159 /* 160 * If for any reason at all we couldn't handle the fault, make 161 * sure we exit gracefully rather than endlessly redo the 162 * fault. 163 */ 164 switch (handle_mm_fault(mm, vma, address, (mask & VM_WRITE) != 0)) { 165 case VM_FAULT_MINOR: 166 ++current->min_flt; 167 break; 168 case VM_FAULT_MAJOR: 169 ++current->maj_flt; 170 break; 171 case VM_FAULT_SIGBUS: 172 /* 173 * We ran out of memory, or some other thing happened 174 * to us that made us unable to handle the page fault 175 * gracefully. 176 */ 177 signal = SIGBUS; 178 goto bad_area; 179 case VM_FAULT_OOM: 180 goto out_of_memory; 181 default: 182 BUG(); 183 } 184 up_read(&mm->mmap_sem); 185 return; 186 187 check_expansion: 188 if (!(prev_vma && (prev_vma->vm_flags & VM_GROWSUP) && (address == prev_vma->vm_end))) { 189 if (!(vma->vm_flags & VM_GROWSDOWN)) 190 goto bad_area; 191 if (REGION_NUMBER(address) != REGION_NUMBER(vma->vm_start) 192 || REGION_OFFSET(address) >= RGN_MAP_LIMIT) 193 goto bad_area; 194 if (expand_stack(vma, address)) 195 goto bad_area; 196 } else { 197 vma = prev_vma; 198 if (REGION_NUMBER(address) != REGION_NUMBER(vma->vm_start) 199 || REGION_OFFSET(address) >= RGN_MAP_LIMIT) 200 goto bad_area; 201 /* 202 * Since the register backing store is accessed sequentially, 203 * we disallow growing it by more than a page at a time. 204 */ 205 if (address > vma->vm_end + PAGE_SIZE - sizeof(long)) 206 goto bad_area; 207 if (expand_upwards(vma, address)) 208 goto bad_area; 209 } 210 goto good_area; 211 212 bad_area: 213 up_read(&mm->mmap_sem); 214 #ifdef CONFIG_VIRTUAL_MEM_MAP 215 bad_area_no_up: 216 #endif 217 if ((isr & IA64_ISR_SP) 218 || ((isr & IA64_ISR_NA) && (isr & IA64_ISR_CODE_MASK) == IA64_ISR_CODE_LFETCH)) 219 { 220 /* 221 * This fault was due to a speculative load or lfetch.fault, set the "ed" 222 * bit in the psr to ensure forward progress. (Target register will get a 223 * NaT for ld.s, lfetch will be canceled.) 224 */ 225 ia64_psr(regs)->ed = 1; 226 return; 227 } 228 if (user_mode(regs)) { 229 si.si_signo = signal; 230 si.si_errno = 0; 231 si.si_code = code; 232 si.si_addr = (void __user *) address; 233 si.si_isr = isr; 234 si.si_flags = __ISR_VALID; 235 force_sig_info(signal, &si, current); 236 return; 237 } 238 239 no_context: 240 if ((isr & IA64_ISR_SP) 241 || ((isr & IA64_ISR_NA) && (isr & IA64_ISR_CODE_MASK) == IA64_ISR_CODE_LFETCH)) 242 { 243 /* 244 * This fault was due to a speculative load or lfetch.fault, set the "ed" 245 * bit in the psr to ensure forward progress. (Target register will get a 246 * NaT for ld.s, lfetch will be canceled.) 247 */ 248 ia64_psr(regs)->ed = 1; 249 return; 250 } 251 252 /* 253 * Since we have no vma's for region 5, we might get here even if the address is 254 * valid, due to the VHPT walker inserting a non present translation that becomes 255 * stale. If that happens, the non present fault handler already purged the stale 256 * translation, which fixed the problem. So, we check to see if the translation is 257 * valid, and return if it is. 258 */ 259 if (REGION_NUMBER(address) == 5 && mapped_kernel_page_is_present(address)) 260 return; 261 262 if (ia64_done_with_exception(regs)) 263 return; 264 265 /* 266 * Oops. The kernel tried to access some bad page. We'll have to terminate things 267 * with extreme prejudice. 268 */ 269 bust_spinlocks(1); 270 271 if (address < PAGE_SIZE) 272 printk(KERN_ALERT "Unable to handle kernel NULL pointer dereference (address %016lx)\n", address); 273 else 274 printk(KERN_ALERT "Unable to handle kernel paging request at " 275 "virtual address %016lx\n", address); 276 die("Oops", regs, isr); 277 bust_spinlocks(0); 278 do_exit(SIGKILL); 279 return; 280 281 out_of_memory: 282 up_read(&mm->mmap_sem); 283 if (is_init(current)) { 284 yield(); 285 down_read(&mm->mmap_sem); 286 goto survive; 287 } 288 printk(KERN_CRIT "VM: killing process %s\n", current->comm); 289 if (user_mode(regs)) 290 do_exit(SIGKILL); 291 goto no_context; 292 } 293