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_DEFAULT; 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 mmap_read_lock(mm); 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_signal_pending(fault, regs)) 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_TRIED; 132 133 /* No need to mmap_read_unlock(mm) as we would 134 * have already released it in __lock_page_or_retry 135 * in mm/filemap.c. 136 */ 137 138 goto retry; 139 } 140 } 141 142 mmap_read_unlock(mm); 143 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address); 144 if (flags & VM_FAULT_MAJOR) 145 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, regs, address); 146 else 147 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, regs, address); 148 149 return; 150 151 /* Something tried to access memory that isn't in our memory map.. 152 * Fix it, but check if it's kernel or user first.. 153 */ 154 bad_area: 155 mmap_read_unlock(mm); 156 if (user_mode(regs)) { 157 current->thread.bad_vaddr = address; 158 current->thread.error_code = is_write; 159 force_sig_fault(SIGSEGV, code, (void *) address); 160 return; 161 } 162 bad_page_fault(regs, address, SIGSEGV); 163 return; 164 165 166 /* We ran out of memory, or some other thing happened to us that made 167 * us unable to handle the page fault gracefully. 168 */ 169 out_of_memory: 170 mmap_read_unlock(mm); 171 if (!user_mode(regs)) 172 bad_page_fault(regs, address, SIGKILL); 173 else 174 pagefault_out_of_memory(); 175 return; 176 177 do_sigbus: 178 mmap_read_unlock(mm); 179 180 /* Send a sigbus, regardless of whether we were in kernel 181 * or user mode. 182 */ 183 current->thread.bad_vaddr = address; 184 force_sig_fault(SIGBUS, BUS_ADRERR, (void *) address); 185 186 /* Kernel mode? Handle exceptions or die */ 187 if (!user_mode(regs)) 188 bad_page_fault(regs, address, SIGBUS); 189 return; 190 191 vmalloc_fault: 192 { 193 /* Synchronize this task's top level page-table 194 * with the 'reference' page table. 195 */ 196 struct mm_struct *act_mm = current->active_mm; 197 int index = pgd_index(address); 198 pgd_t *pgd, *pgd_k; 199 p4d_t *p4d, *p4d_k; 200 pud_t *pud, *pud_k; 201 pmd_t *pmd, *pmd_k; 202 pte_t *pte_k; 203 204 if (act_mm == NULL) 205 goto bad_page_fault; 206 207 pgd = act_mm->pgd + index; 208 pgd_k = init_mm.pgd + index; 209 210 if (!pgd_present(*pgd_k)) 211 goto bad_page_fault; 212 213 pgd_val(*pgd) = pgd_val(*pgd_k); 214 215 p4d = p4d_offset(pgd, address); 216 p4d_k = p4d_offset(pgd_k, address); 217 if (!p4d_present(*p4d) || !p4d_present(*p4d_k)) 218 goto bad_page_fault; 219 220 pud = pud_offset(p4d, address); 221 pud_k = pud_offset(p4d_k, address); 222 if (!pud_present(*pud) || !pud_present(*pud_k)) 223 goto bad_page_fault; 224 225 pmd = pmd_offset(pud, address); 226 pmd_k = pmd_offset(pud_k, address); 227 if (!pmd_present(*pmd) || !pmd_present(*pmd_k)) 228 goto bad_page_fault; 229 230 pmd_val(*pmd) = pmd_val(*pmd_k); 231 pte_k = pte_offset_kernel(pmd_k, address); 232 233 if (!pte_present(*pte_k)) 234 goto bad_page_fault; 235 return; 236 } 237 bad_page_fault: 238 bad_page_fault(regs, address, SIGKILL); 239 return; 240 } 241 242 243 void 244 bad_page_fault(struct pt_regs *regs, unsigned long address, int sig) 245 { 246 extern void die(const char*, struct pt_regs*, long); 247 const struct exception_table_entry *entry; 248 249 /* Are we prepared to handle this kernel fault? */ 250 if ((entry = search_exception_tables(regs->pc)) != NULL) { 251 pr_debug("%s: Exception at pc=%#010lx (%lx)\n", 252 current->comm, regs->pc, entry->fixup); 253 current->thread.bad_uaddr = address; 254 regs->pc = entry->fixup; 255 return; 256 } 257 258 /* Oops. The kernel tried to access some bad page. We'll have to 259 * terminate things with extreme prejudice. 260 */ 261 pr_alert("Unable to handle kernel paging request at virtual " 262 "address %08lx\n pc = %08lx, ra = %08lx\n", 263 address, regs->pc, regs->areg[0]); 264 die("Oops", regs, sig); 265 do_exit(sig); 266 } 267