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 /* 29 * This routine handles page faults. It determines the address, 30 * and the problem, and then passes it off to one of the appropriate 31 * routines. 32 * 33 * Note: does not handle Miss and MultiHit. 34 */ 35 36 void do_page_fault(struct pt_regs *regs) 37 { 38 struct vm_area_struct * vma; 39 struct mm_struct *mm = current->mm; 40 unsigned int exccause = regs->exccause; 41 unsigned int address = regs->excvaddr; 42 int code; 43 44 int is_write, is_exec; 45 vm_fault_t fault; 46 unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE; 47 48 code = SEGV_MAPERR; 49 50 /* We fault-in kernel-space virtual memory on-demand. The 51 * 'reference' page table is init_mm.pgd. 52 */ 53 if (address >= TASK_SIZE && !user_mode(regs)) 54 goto vmalloc_fault; 55 56 /* If we're in an interrupt or have no user 57 * context, we must not take the fault.. 58 */ 59 if (faulthandler_disabled() || !mm) { 60 bad_page_fault(regs, address, SIGSEGV); 61 return; 62 } 63 64 is_write = (exccause == EXCCAUSE_STORE_CACHE_ATTRIBUTE) ? 1 : 0; 65 is_exec = (exccause == EXCCAUSE_ITLB_PRIVILEGE || 66 exccause == EXCCAUSE_ITLB_MISS || 67 exccause == EXCCAUSE_FETCH_CACHE_ATTRIBUTE) ? 1 : 0; 68 69 pr_debug("[%s:%d:%08x:%d:%08lx:%s%s]\n", 70 current->comm, current->pid, 71 address, exccause, regs->pc, 72 is_write ? "w" : "", is_exec ? "x" : ""); 73 74 if (user_mode(regs)) 75 flags |= FAULT_FLAG_USER; 76 retry: 77 down_read(&mm->mmap_sem); 78 vma = find_vma(mm, address); 79 80 if (!vma) 81 goto bad_area; 82 if (vma->vm_start <= address) 83 goto good_area; 84 if (!(vma->vm_flags & VM_GROWSDOWN)) 85 goto bad_area; 86 if (expand_stack(vma, address)) 87 goto bad_area; 88 89 /* Ok, we have a good vm_area for this memory access, so 90 * we can handle it.. 91 */ 92 93 good_area: 94 code = SEGV_ACCERR; 95 96 if (is_write) { 97 if (!(vma->vm_flags & VM_WRITE)) 98 goto bad_area; 99 flags |= FAULT_FLAG_WRITE; 100 } else if (is_exec) { 101 if (!(vma->vm_flags & VM_EXEC)) 102 goto bad_area; 103 } else /* Allow read even from write-only pages. */ 104 if (!(vma->vm_flags & (VM_READ | VM_WRITE))) 105 goto bad_area; 106 107 /* If for any reason at all we couldn't handle the fault, 108 * make sure we exit gracefully rather than endlessly redo 109 * the fault. 110 */ 111 fault = handle_mm_fault(vma, address, flags); 112 113 if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current)) 114 return; 115 116 if (unlikely(fault & VM_FAULT_ERROR)) { 117 if (fault & VM_FAULT_OOM) 118 goto out_of_memory; 119 else if (fault & VM_FAULT_SIGSEGV) 120 goto bad_area; 121 else if (fault & VM_FAULT_SIGBUS) 122 goto do_sigbus; 123 BUG(); 124 } 125 if (flags & FAULT_FLAG_ALLOW_RETRY) { 126 if (fault & VM_FAULT_MAJOR) 127 current->maj_flt++; 128 else 129 current->min_flt++; 130 if (fault & VM_FAULT_RETRY) { 131 flags &= ~FAULT_FLAG_ALLOW_RETRY; 132 flags |= FAULT_FLAG_TRIED; 133 134 /* No need to up_read(&mm->mmap_sem) as we would 135 * have already released it in __lock_page_or_retry 136 * in mm/filemap.c. 137 */ 138 139 goto retry; 140 } 141 } 142 143 up_read(&mm->mmap_sem); 144 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address); 145 if (flags & VM_FAULT_MAJOR) 146 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, regs, address); 147 else 148 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, regs, address); 149 150 return; 151 152 /* Something tried to access memory that isn't in our memory map.. 153 * Fix it, but check if it's kernel or user first.. 154 */ 155 bad_area: 156 up_read(&mm->mmap_sem); 157 if (user_mode(regs)) { 158 current->thread.bad_vaddr = address; 159 current->thread.error_code = is_write; 160 force_sig_fault(SIGSEGV, code, (void *) address); 161 return; 162 } 163 bad_page_fault(regs, address, SIGSEGV); 164 return; 165 166 167 /* We ran out of memory, or some other thing happened to us that made 168 * us unable to handle the page fault gracefully. 169 */ 170 out_of_memory: 171 up_read(&mm->mmap_sem); 172 if (!user_mode(regs)) 173 bad_page_fault(regs, address, SIGKILL); 174 else 175 pagefault_out_of_memory(); 176 return; 177 178 do_sigbus: 179 up_read(&mm->mmap_sem); 180 181 /* Send a sigbus, regardless of whether we were in kernel 182 * or user mode. 183 */ 184 current->thread.bad_vaddr = address; 185 force_sig_fault(SIGBUS, BUS_ADRERR, (void *) address); 186 187 /* Kernel mode? Handle exceptions or die */ 188 if (!user_mode(regs)) 189 bad_page_fault(regs, address, SIGBUS); 190 return; 191 192 vmalloc_fault: 193 { 194 /* Synchronize this task's top level page-table 195 * with the 'reference' page table. 196 */ 197 struct mm_struct *act_mm = current->active_mm; 198 int index = pgd_index(address); 199 pgd_t *pgd, *pgd_k; 200 p4d_t *p4d, *p4d_k; 201 pud_t *pud, *pud_k; 202 pmd_t *pmd, *pmd_k; 203 pte_t *pte_k; 204 205 if (act_mm == NULL) 206 goto bad_page_fault; 207 208 pgd = act_mm->pgd + index; 209 pgd_k = init_mm.pgd + index; 210 211 if (!pgd_present(*pgd_k)) 212 goto bad_page_fault; 213 214 pgd_val(*pgd) = pgd_val(*pgd_k); 215 216 p4d = p4d_offset(pgd, address); 217 p4d_k = p4d_offset(pgd_k, address); 218 if (!p4d_present(*p4d) || !p4d_present(*p4d_k)) 219 goto bad_page_fault; 220 221 pud = pud_offset(p4d, address); 222 pud_k = pud_offset(p4d_k, address); 223 if (!pud_present(*pud) || !pud_present(*pud_k)) 224 goto bad_page_fault; 225 226 pmd = pmd_offset(pud, address); 227 pmd_k = pmd_offset(pud_k, address); 228 if (!pmd_present(*pmd) || !pmd_present(*pmd_k)) 229 goto bad_page_fault; 230 231 pmd_val(*pmd) = pmd_val(*pmd_k); 232 pte_k = pte_offset_kernel(pmd_k, address); 233 234 if (!pte_present(*pte_k)) 235 goto bad_page_fault; 236 return; 237 } 238 bad_page_fault: 239 bad_page_fault(regs, address, SIGKILL); 240 return; 241 } 242 243 244 void 245 bad_page_fault(struct pt_regs *regs, unsigned long address, int sig) 246 { 247 extern void die(const char*, struct pt_regs*, long); 248 const struct exception_table_entry *entry; 249 250 /* Are we prepared to handle this kernel fault? */ 251 if ((entry = search_exception_tables(regs->pc)) != NULL) { 252 pr_debug("%s: Exception at pc=%#010lx (%lx)\n", 253 current->comm, regs->pc, entry->fixup); 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 pr_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