1 // TODO VM_EXEC flag work-around, cache aliasing 2 /* 3 * arch/xtensa/mm/fault.c 4 * 5 * This file is subject to the terms and conditions of the GNU General Public 6 * License. See the file "COPYING" in the main directory of this archive 7 * for more details. 8 * 9 * Copyright (C) 2001 - 2010 Tensilica Inc. 10 * 11 * Chris Zankel <chris@zankel.net> 12 * Joe Taylor <joe@tensilica.com, joetylr@yahoo.com> 13 */ 14 15 #include <linux/mm.h> 16 #include <linux/extable.h> 17 #include <linux/hardirq.h> 18 #include <linux/perf_event.h> 19 #include <linux/uaccess.h> 20 #include <asm/mmu_context.h> 21 #include <asm/cacheflush.h> 22 #include <asm/hardirq.h> 23 #include <asm/pgalloc.h> 24 25 DEFINE_PER_CPU(unsigned long, asid_cache) = ASID_USER_FIRST; 26 void bad_page_fault(struct pt_regs*, unsigned long, int); 27 28 #undef DEBUG_PAGE_FAULT 29 30 /* 31 * This routine handles page faults. It determines the address, 32 * and the problem, and then passes it off to one of the appropriate 33 * routines. 34 * 35 * Note: does not handle Miss and MultiHit. 36 */ 37 38 void do_page_fault(struct pt_regs *regs) 39 { 40 struct vm_area_struct * vma; 41 struct mm_struct *mm = current->mm; 42 unsigned int exccause = regs->exccause; 43 unsigned int address = regs->excvaddr; 44 siginfo_t info; 45 46 int is_write, is_exec; 47 int fault; 48 unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE; 49 50 info.si_code = SEGV_MAPERR; 51 52 /* We fault-in kernel-space virtual memory on-demand. The 53 * 'reference' page table is init_mm.pgd. 54 */ 55 if (address >= TASK_SIZE && !user_mode(regs)) 56 goto vmalloc_fault; 57 58 /* If we're in an interrupt or have no user 59 * context, we must not take the fault.. 60 */ 61 if (faulthandler_disabled() || !mm) { 62 bad_page_fault(regs, address, SIGSEGV); 63 return; 64 } 65 66 is_write = (exccause == EXCCAUSE_STORE_CACHE_ATTRIBUTE) ? 1 : 0; 67 is_exec = (exccause == EXCCAUSE_ITLB_PRIVILEGE || 68 exccause == EXCCAUSE_ITLB_MISS || 69 exccause == EXCCAUSE_FETCH_CACHE_ATTRIBUTE) ? 1 : 0; 70 71 #ifdef DEBUG_PAGE_FAULT 72 printk("[%s:%d:%08x:%d:%08x:%s%s]\n", current->comm, current->pid, 73 address, exccause, regs->pc, is_write? "w":"", is_exec? "x":""); 74 #endif 75 76 if (user_mode(regs)) 77 flags |= FAULT_FLAG_USER; 78 retry: 79 down_read(&mm->mmap_sem); 80 vma = find_vma(mm, address); 81 82 if (!vma) 83 goto bad_area; 84 if (vma->vm_start <= address) 85 goto good_area; 86 if (!(vma->vm_flags & VM_GROWSDOWN)) 87 goto bad_area; 88 if (expand_stack(vma, address)) 89 goto bad_area; 90 91 /* Ok, we have a good vm_area for this memory access, so 92 * we can handle it.. 93 */ 94 95 good_area: 96 info.si_code = SEGV_ACCERR; 97 98 if (is_write) { 99 if (!(vma->vm_flags & VM_WRITE)) 100 goto bad_area; 101 flags |= FAULT_FLAG_WRITE; 102 } else if (is_exec) { 103 if (!(vma->vm_flags & VM_EXEC)) 104 goto bad_area; 105 } else /* Allow read even from write-only pages. */ 106 if (!(vma->vm_flags & (VM_READ | VM_WRITE))) 107 goto bad_area; 108 109 /* If for any reason at all we couldn't handle the fault, 110 * make sure we exit gracefully rather than endlessly redo 111 * the fault. 112 */ 113 fault = handle_mm_fault(vma, address, flags); 114 115 if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current)) 116 return; 117 118 if (unlikely(fault & VM_FAULT_ERROR)) { 119 if (fault & VM_FAULT_OOM) 120 goto out_of_memory; 121 else if (fault & VM_FAULT_SIGSEGV) 122 goto bad_area; 123 else if (fault & VM_FAULT_SIGBUS) 124 goto do_sigbus; 125 BUG(); 126 } 127 if (flags & FAULT_FLAG_ALLOW_RETRY) { 128 if (fault & VM_FAULT_MAJOR) 129 current->maj_flt++; 130 else 131 current->min_flt++; 132 if (fault & VM_FAULT_RETRY) { 133 flags &= ~FAULT_FLAG_ALLOW_RETRY; 134 flags |= FAULT_FLAG_TRIED; 135 136 /* No need to up_read(&mm->mmap_sem) as we would 137 * have already released it in __lock_page_or_retry 138 * in mm/filemap.c. 139 */ 140 141 goto retry; 142 } 143 } 144 145 up_read(&mm->mmap_sem); 146 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address); 147 if (flags & VM_FAULT_MAJOR) 148 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, regs, address); 149 else 150 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, regs, address); 151 152 return; 153 154 /* Something tried to access memory that isn't in our memory map.. 155 * Fix it, but check if it's kernel or user first.. 156 */ 157 bad_area: 158 up_read(&mm->mmap_sem); 159 if (user_mode(regs)) { 160 current->thread.bad_vaddr = address; 161 current->thread.error_code = is_write; 162 info.si_signo = SIGSEGV; 163 info.si_errno = 0; 164 /* info.si_code has been set above */ 165 info.si_addr = (void *) address; 166 force_sig_info(SIGSEGV, &info, current); 167 return; 168 } 169 bad_page_fault(regs, address, SIGSEGV); 170 return; 171 172 173 /* We ran out of memory, or some other thing happened to us that made 174 * us unable to handle the page fault gracefully. 175 */ 176 out_of_memory: 177 up_read(&mm->mmap_sem); 178 if (!user_mode(regs)) 179 bad_page_fault(regs, address, SIGKILL); 180 else 181 pagefault_out_of_memory(); 182 return; 183 184 do_sigbus: 185 up_read(&mm->mmap_sem); 186 187 /* Send a sigbus, regardless of whether we were in kernel 188 * or user mode. 189 */ 190 current->thread.bad_vaddr = address; 191 info.si_code = SIGBUS; 192 info.si_errno = 0; 193 info.si_code = BUS_ADRERR; 194 info.si_addr = (void *) address; 195 force_sig_info(SIGBUS, &info, current); 196 197 /* Kernel mode? Handle exceptions or die */ 198 if (!user_mode(regs)) 199 bad_page_fault(regs, address, SIGBUS); 200 return; 201 202 vmalloc_fault: 203 { 204 /* Synchronize this task's top level page-table 205 * with the 'reference' page table. 206 */ 207 struct mm_struct *act_mm = current->active_mm; 208 int index = pgd_index(address); 209 pgd_t *pgd, *pgd_k; 210 pmd_t *pmd, *pmd_k; 211 pte_t *pte_k; 212 213 if (act_mm == NULL) 214 goto bad_page_fault; 215 216 pgd = act_mm->pgd + index; 217 pgd_k = init_mm.pgd + index; 218 219 if (!pgd_present(*pgd_k)) 220 goto bad_page_fault; 221 222 pgd_val(*pgd) = pgd_val(*pgd_k); 223 224 pmd = pmd_offset(pgd, address); 225 pmd_k = pmd_offset(pgd_k, address); 226 if (!pmd_present(*pmd) || !pmd_present(*pmd_k)) 227 goto bad_page_fault; 228 229 pmd_val(*pmd) = pmd_val(*pmd_k); 230 pte_k = pte_offset_kernel(pmd_k, address); 231 232 if (!pte_present(*pte_k)) 233 goto bad_page_fault; 234 return; 235 } 236 bad_page_fault: 237 bad_page_fault(regs, address, SIGKILL); 238 return; 239 } 240 241 242 void 243 bad_page_fault(struct pt_regs *regs, unsigned long address, int sig) 244 { 245 extern void die(const char*, struct pt_regs*, long); 246 const struct exception_table_entry *entry; 247 248 /* Are we prepared to handle this kernel fault? */ 249 if ((entry = search_exception_tables(regs->pc)) != NULL) { 250 #ifdef DEBUG_PAGE_FAULT 251 printk(KERN_DEBUG "%s: Exception at pc=%#010lx (%lx)\n", 252 current->comm, regs->pc, entry->fixup); 253 #endif 254 current->thread.bad_uaddr = address; 255 regs->pc = entry->fixup; 256 return; 257 } 258 259 /* Oops. The kernel tried to access some bad page. We'll have to 260 * terminate things with extreme prejudice. 261 */ 262 printk(KERN_ALERT "Unable to handle kernel paging request at virtual " 263 "address %08lx\n pc = %08lx, ra = %08lx\n", 264 address, regs->pc, regs->areg[0]); 265 die("Oops", regs, sig); 266 do_exit(sig); 267 } 268