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