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