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 14 #include <asm/pgtable.h> 15 #include <asm/processor.h> 16 #include <asm/system.h> 17 #include <asm/uaccess.h> 18 19 extern void 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() && kprobes_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 void __kprobes 76 ia64_do_page_fault (unsigned long address, unsigned long isr, struct pt_regs *regs) 77 { 78 int signal = SIGSEGV, code = SEGV_MAPERR; 79 struct vm_area_struct *vma, *prev_vma; 80 struct mm_struct *mm = current->mm; 81 struct siginfo si; 82 unsigned long mask; 83 int fault; 84 85 /* mmap_sem is performance critical.... */ 86 prefetchw(&mm->mmap_sem); 87 88 /* 89 * If we're in an interrupt or have no user context, we must not take the fault.. 90 */ 91 if (in_atomic() || !mm) 92 goto no_context; 93 94 #ifdef CONFIG_VIRTUAL_MEM_MAP 95 /* 96 * If fault is in region 5 and we are in the kernel, we may already 97 * have the mmap_sem (pfn_valid macro is called during mmap). There 98 * is no vma for region 5 addr's anyway, so skip getting the semaphore 99 * and go directly to the exception handling code. 100 */ 101 102 if ((REGION_NUMBER(address) == 5) && !user_mode(regs)) 103 goto bad_area_no_up; 104 #endif 105 106 /* 107 * This is to handle the kprobes on user space access instructions 108 */ 109 if (notify_page_fault(regs, TRAP_BRKPT)) 110 return; 111 112 down_read(&mm->mmap_sem); 113 114 vma = find_vma_prev(mm, address, &prev_vma); 115 if (!vma) 116 goto bad_area; 117 118 /* find_vma_prev() returns vma such that address < vma->vm_end or NULL */ 119 if (address < vma->vm_start) 120 goto check_expansion; 121 122 good_area: 123 code = SEGV_ACCERR; 124 125 /* OK, we've got a good vm_area for this memory area. Check the access permissions: */ 126 127 # define VM_READ_BIT 0 128 # define VM_WRITE_BIT 1 129 # define VM_EXEC_BIT 2 130 131 # 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 mask = ( (((isr >> IA64_ISR_X_BIT) & 1UL) << VM_EXEC_BIT) 140 | (((isr >> IA64_ISR_W_BIT) & 1UL) << VM_WRITE_BIT)); 141 142 if ((vma->vm_flags & mask) != mask) 143 goto bad_area; 144 145 survive: 146 /* 147 * If for any reason at all we couldn't handle the fault, make 148 * sure we exit gracefully rather than endlessly redo the 149 * fault. 150 */ 151 fault = handle_mm_fault(mm, vma, address, (mask & VM_WRITE) != 0); 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_SIGBUS) { 161 signal = SIGBUS; 162 goto bad_area; 163 } 164 BUG(); 165 } 166 if (fault & VM_FAULT_MAJOR) 167 current->maj_flt++; 168 else 169 current->min_flt++; 170 up_read(&mm->mmap_sem); 171 return; 172 173 check_expansion: 174 if (!(prev_vma && (prev_vma->vm_flags & VM_GROWSUP) && (address == prev_vma->vm_end))) { 175 if (!(vma->vm_flags & VM_GROWSDOWN)) 176 goto bad_area; 177 if (REGION_NUMBER(address) != REGION_NUMBER(vma->vm_start) 178 || REGION_OFFSET(address) >= RGN_MAP_LIMIT) 179 goto bad_area; 180 if (expand_stack(vma, address)) 181 goto bad_area; 182 } else { 183 vma = prev_vma; 184 if (REGION_NUMBER(address) != REGION_NUMBER(vma->vm_start) 185 || REGION_OFFSET(address) >= RGN_MAP_LIMIT) 186 goto bad_area; 187 /* 188 * Since the register backing store is accessed sequentially, 189 * we disallow growing it by more than a page at a time. 190 */ 191 if (address > vma->vm_end + PAGE_SIZE - sizeof(long)) 192 goto bad_area; 193 if (expand_upwards(vma, address)) 194 goto bad_area; 195 } 196 goto good_area; 197 198 bad_area: 199 up_read(&mm->mmap_sem); 200 #ifdef CONFIG_VIRTUAL_MEM_MAP 201 bad_area_no_up: 202 #endif 203 if ((isr & IA64_ISR_SP) 204 || ((isr & IA64_ISR_NA) && (isr & IA64_ISR_CODE_MASK) == IA64_ISR_CODE_LFETCH)) 205 { 206 /* 207 * This fault was due to a speculative load or lfetch.fault, set the "ed" 208 * bit in the psr to ensure forward progress. (Target register will get a 209 * NaT for ld.s, lfetch will be canceled.) 210 */ 211 ia64_psr(regs)->ed = 1; 212 return; 213 } 214 if (user_mode(regs)) { 215 si.si_signo = signal; 216 si.si_errno = 0; 217 si.si_code = code; 218 si.si_addr = (void __user *) address; 219 si.si_isr = isr; 220 si.si_flags = __ISR_VALID; 221 force_sig_info(signal, &si, current); 222 return; 223 } 224 225 no_context: 226 if ((isr & IA64_ISR_SP) 227 || ((isr & IA64_ISR_NA) && (isr & IA64_ISR_CODE_MASK) == IA64_ISR_CODE_LFETCH)) 228 { 229 /* 230 * This fault was due to a speculative load or lfetch.fault, set the "ed" 231 * bit in the psr to ensure forward progress. (Target register will get a 232 * NaT for ld.s, lfetch will be canceled.) 233 */ 234 ia64_psr(regs)->ed = 1; 235 return; 236 } 237 238 /* 239 * Since we have no vma's for region 5, we might get here even if the address is 240 * valid, due to the VHPT walker inserting a non present translation that becomes 241 * stale. If that happens, the non present fault handler already purged the stale 242 * translation, which fixed the problem. So, we check to see if the translation is 243 * valid, and return if it is. 244 */ 245 if (REGION_NUMBER(address) == 5 && mapped_kernel_page_is_present(address)) 246 return; 247 248 if (ia64_done_with_exception(regs)) 249 return; 250 251 /* 252 * Oops. The kernel tried to access some bad page. We'll have to terminate things 253 * with extreme prejudice. 254 */ 255 bust_spinlocks(1); 256 257 if (address < PAGE_SIZE) 258 printk(KERN_ALERT "Unable to handle kernel NULL pointer dereference (address %016lx)\n", address); 259 else 260 printk(KERN_ALERT "Unable to handle kernel paging request at " 261 "virtual address %016lx\n", address); 262 die("Oops", regs, isr); 263 bust_spinlocks(0); 264 do_exit(SIGKILL); 265 return; 266 267 out_of_memory: 268 up_read(&mm->mmap_sem); 269 if (is_init(current)) { 270 yield(); 271 down_read(&mm->mmap_sem); 272 goto survive; 273 } 274 printk(KERN_CRIT "VM: killing process %s\n", current->comm); 275 if (user_mode(regs)) 276 do_exit(SIGKILL); 277 goto no_context; 278 } 279