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/interrupt.h> 11 #include <linux/kprobes.h> 12 #include <linux/kdebug.h> 13 #include <linux/prefetch.h> 14 15 #include <asm/pgtable.h> 16 #include <asm/processor.h> 17 #include <asm/uaccess.h> 18 19 extern int die(char *, struct pt_regs *, long); 20 21 #ifdef CONFIG_KPROBES 22 static inline int notify_page_fault(struct pt_regs *regs, int trap) 23 { 24 int ret = 0; 25 26 if (!user_mode(regs)) { 27 /* kprobe_running() needs smp_processor_id() */ 28 preempt_disable(); 29 if (kprobe_running() && kprobe_fault_handler(regs, trap)) 30 ret = 1; 31 preempt_enable(); 32 } 33 34 return ret; 35 } 36 #else 37 static inline int notify_page_fault(struct pt_regs *regs, int trap) 38 { 39 return 0; 40 } 41 #endif 42 43 /* 44 * Return TRUE if ADDRESS points at a page in the kernel's mapped segment 45 * (inside region 5, on ia64) and that page is present. 46 */ 47 static int 48 mapped_kernel_page_is_present (unsigned long address) 49 { 50 pgd_t *pgd; 51 pud_t *pud; 52 pmd_t *pmd; 53 pte_t *ptep, pte; 54 55 pgd = pgd_offset_k(address); 56 if (pgd_none(*pgd) || pgd_bad(*pgd)) 57 return 0; 58 59 pud = pud_offset(pgd, address); 60 if (pud_none(*pud) || pud_bad(*pud)) 61 return 0; 62 63 pmd = pmd_offset(pud, address); 64 if (pmd_none(*pmd) || pmd_bad(*pmd)) 65 return 0; 66 67 ptep = pte_offset_kernel(pmd, address); 68 if (!ptep) 69 return 0; 70 71 pte = *ptep; 72 return pte_present(pte); 73 } 74 75 # define VM_READ_BIT 0 76 # define VM_WRITE_BIT 1 77 # define VM_EXEC_BIT 2 78 79 void __kprobes 80 ia64_do_page_fault (unsigned long address, unsigned long isr, struct pt_regs *regs) 81 { 82 int signal = SIGSEGV, code = SEGV_MAPERR; 83 struct vm_area_struct *vma, *prev_vma; 84 struct mm_struct *mm = current->mm; 85 struct siginfo si; 86 unsigned long mask; 87 int fault; 88 unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE; 89 90 mask = ((((isr >> IA64_ISR_X_BIT) & 1UL) << VM_EXEC_BIT) 91 | (((isr >> IA64_ISR_W_BIT) & 1UL) << VM_WRITE_BIT)); 92 93 flags |= ((mask & VM_WRITE) ? FAULT_FLAG_WRITE : 0); 94 95 /* mmap_sem is performance critical.... */ 96 prefetchw(&mm->mmap_sem); 97 98 /* 99 * If we're in an interrupt or have no user context, we must not take the fault.. 100 */ 101 if (in_atomic() || !mm) 102 goto no_context; 103 104 #ifdef CONFIG_VIRTUAL_MEM_MAP 105 /* 106 * If fault is in region 5 and we are in the kernel, we may already 107 * have the mmap_sem (pfn_valid macro is called during mmap). There 108 * is no vma for region 5 addr's anyway, so skip getting the semaphore 109 * and go directly to the exception handling code. 110 */ 111 112 if ((REGION_NUMBER(address) == 5) && !user_mode(regs)) 113 goto bad_area_no_up; 114 #endif 115 116 /* 117 * This is to handle the kprobes on user space access instructions 118 */ 119 if (notify_page_fault(regs, TRAP_BRKPT)) 120 return; 121 122 retry: 123 down_read(&mm->mmap_sem); 124 125 vma = find_vma_prev(mm, address, &prev_vma); 126 if (!vma && !prev_vma ) 127 goto bad_area; 128 129 /* 130 * find_vma_prev() returns vma such that address < vma->vm_end or NULL 131 * 132 * May find no vma, but could be that the last vm area is the 133 * register backing store that needs to expand upwards, in 134 * this case vma will be null, but prev_vma will ne non-null 135 */ 136 if (( !vma && prev_vma ) || (address < vma->vm_start) ) 137 goto check_expansion; 138 139 good_area: 140 code = SEGV_ACCERR; 141 142 /* OK, we've got a good vm_area for this memory area. Check the access permissions: */ 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 if ((vma->vm_flags & mask) != mask) 153 goto bad_area; 154 155 /* 156 * If for any reason at all we couldn't handle the fault, make 157 * sure we exit gracefully rather than endlessly redo the 158 * fault. 159 */ 160 fault = handle_mm_fault(mm, vma, address, flags); 161 162 if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current)) 163 return; 164 165 if (unlikely(fault & VM_FAULT_ERROR)) { 166 /* 167 * We ran out of memory, or some other thing happened 168 * to us that made us unable to handle the page fault 169 * gracefully. 170 */ 171 if (fault & VM_FAULT_OOM) { 172 goto out_of_memory; 173 } else if (fault & VM_FAULT_SIGBUS) { 174 signal = SIGBUS; 175 goto bad_area; 176 } 177 BUG(); 178 } 179 180 if (flags & FAULT_FLAG_ALLOW_RETRY) { 181 if (fault & VM_FAULT_MAJOR) 182 current->maj_flt++; 183 else 184 current->min_flt++; 185 if (fault & VM_FAULT_RETRY) { 186 flags &= ~FAULT_FLAG_ALLOW_RETRY; 187 flags |= FAULT_FLAG_TRIED; 188 189 /* No need to up_read(&mm->mmap_sem) as we would 190 * have already released it in __lock_page_or_retry 191 * in mm/filemap.c. 192 */ 193 194 goto retry; 195 } 196 } 197 198 up_read(&mm->mmap_sem); 199 return; 200 201 check_expansion: 202 if (!(prev_vma && (prev_vma->vm_flags & VM_GROWSUP) && (address == prev_vma->vm_end))) { 203 if (!vma) 204 goto bad_area; 205 if (!(vma->vm_flags & VM_GROWSDOWN)) 206 goto bad_area; 207 if (REGION_NUMBER(address) != REGION_NUMBER(vma->vm_start) 208 || REGION_OFFSET(address) >= RGN_MAP_LIMIT) 209 goto bad_area; 210 if (expand_stack(vma, address)) 211 goto bad_area; 212 } else { 213 vma = prev_vma; 214 if (REGION_NUMBER(address) != REGION_NUMBER(vma->vm_start) 215 || REGION_OFFSET(address) >= RGN_MAP_LIMIT) 216 goto bad_area; 217 /* 218 * Since the register backing store is accessed sequentially, 219 * we disallow growing it by more than a page at a time. 220 */ 221 if (address > vma->vm_end + PAGE_SIZE - sizeof(long)) 222 goto bad_area; 223 if (expand_upwards(vma, address)) 224 goto bad_area; 225 } 226 goto good_area; 227 228 bad_area: 229 up_read(&mm->mmap_sem); 230 #ifdef CONFIG_VIRTUAL_MEM_MAP 231 bad_area_no_up: 232 #endif 233 if ((isr & IA64_ISR_SP) 234 || ((isr & IA64_ISR_NA) && (isr & IA64_ISR_CODE_MASK) == IA64_ISR_CODE_LFETCH)) 235 { 236 /* 237 * This fault was due to a speculative load or lfetch.fault, set the "ed" 238 * bit in the psr to ensure forward progress. (Target register will get a 239 * NaT for ld.s, lfetch will be canceled.) 240 */ 241 ia64_psr(regs)->ed = 1; 242 return; 243 } 244 if (user_mode(regs)) { 245 si.si_signo = signal; 246 si.si_errno = 0; 247 si.si_code = code; 248 si.si_addr = (void __user *) address; 249 si.si_isr = isr; 250 si.si_flags = __ISR_VALID; 251 force_sig_info(signal, &si, current); 252 return; 253 } 254 255 no_context: 256 if ((isr & IA64_ISR_SP) 257 || ((isr & IA64_ISR_NA) && (isr & IA64_ISR_CODE_MASK) == IA64_ISR_CODE_LFETCH)) 258 { 259 /* 260 * This fault was due to a speculative load or lfetch.fault, set the "ed" 261 * bit in the psr to ensure forward progress. (Target register will get a 262 * NaT for ld.s, lfetch will be canceled.) 263 */ 264 ia64_psr(regs)->ed = 1; 265 return; 266 } 267 268 /* 269 * Since we have no vma's for region 5, we might get here even if the address is 270 * valid, due to the VHPT walker inserting a non present translation that becomes 271 * stale. If that happens, the non present fault handler already purged the stale 272 * translation, which fixed the problem. So, we check to see if the translation is 273 * valid, and return if it is. 274 */ 275 if (REGION_NUMBER(address) == 5 && mapped_kernel_page_is_present(address)) 276 return; 277 278 if (ia64_done_with_exception(regs)) 279 return; 280 281 /* 282 * Oops. The kernel tried to access some bad page. We'll have to terminate things 283 * with extreme prejudice. 284 */ 285 bust_spinlocks(1); 286 287 if (address < PAGE_SIZE) 288 printk(KERN_ALERT "Unable to handle kernel NULL pointer dereference (address %016lx)\n", address); 289 else 290 printk(KERN_ALERT "Unable to handle kernel paging request at " 291 "virtual address %016lx\n", address); 292 if (die("Oops", regs, isr)) 293 regs = NULL; 294 bust_spinlocks(0); 295 if (regs) 296 do_exit(SIGKILL); 297 return; 298 299 out_of_memory: 300 up_read(&mm->mmap_sem); 301 if (!user_mode(regs)) 302 goto no_context; 303 pagefault_out_of_memory(); 304 } 305