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 24 DEFINE_PER_CPU(unsigned long, asid_cache) = ASID_USER_FIRST; 25 void bad_page_fault(struct pt_regs*, unsigned long, int); 26 27 /* 28 * This routine handles page faults. It determines the address, 29 * and the problem, and then passes it off to one of the appropriate 30 * routines. 31 * 32 * Note: does not handle Miss and MultiHit. 33 */ 34 35 void do_page_fault(struct pt_regs *regs) 36 { 37 struct vm_area_struct * vma; 38 struct mm_struct *mm = current->mm; 39 unsigned int exccause = regs->exccause; 40 unsigned int address = regs->excvaddr; 41 int code; 42 43 int is_write, is_exec; 44 vm_fault_t fault; 45 unsigned int flags = FAULT_FLAG_DEFAULT; 46 47 code = SEGV_MAPERR; 48 49 /* We fault-in kernel-space virtual memory on-demand. The 50 * 'reference' page table is init_mm.pgd. 51 */ 52 if (address >= TASK_SIZE && !user_mode(regs)) 53 goto vmalloc_fault; 54 55 /* If we're in an interrupt or have no user 56 * context, we must not take the fault.. 57 */ 58 if (faulthandler_disabled() || !mm) { 59 bad_page_fault(regs, address, SIGSEGV); 60 return; 61 } 62 63 is_write = (exccause == EXCCAUSE_STORE_CACHE_ATTRIBUTE) ? 1 : 0; 64 is_exec = (exccause == EXCCAUSE_ITLB_PRIVILEGE || 65 exccause == EXCCAUSE_ITLB_MISS || 66 exccause == EXCCAUSE_FETCH_CACHE_ATTRIBUTE) ? 1 : 0; 67 68 pr_debug("[%s:%d:%08x:%d:%08lx:%s%s]\n", 69 current->comm, current->pid, 70 address, exccause, regs->pc, 71 is_write ? "w" : "", is_exec ? "x" : ""); 72 73 if (user_mode(regs)) 74 flags |= FAULT_FLAG_USER; 75 76 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address); 77 78 retry: 79 mmap_read_lock(mm); 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 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, regs); 114 115 if (fault_signal_pending(fault, regs)) { 116 if (!user_mode(regs)) 117 goto bad_page_fault; 118 return; 119 } 120 121 if (unlikely(fault & VM_FAULT_ERROR)) { 122 if (fault & VM_FAULT_OOM) 123 goto out_of_memory; 124 else if (fault & VM_FAULT_SIGSEGV) 125 goto bad_area; 126 else if (fault & VM_FAULT_SIGBUS) 127 goto do_sigbus; 128 BUG(); 129 } 130 131 if (fault & VM_FAULT_RETRY) { 132 flags |= FAULT_FLAG_TRIED; 133 134 /* No need to mmap_read_unlock(mm) 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 mmap_read_unlock(mm); 143 return; 144 145 /* Something tried to access memory that isn't in our memory map.. 146 * Fix it, but check if it's kernel or user first.. 147 */ 148 bad_area: 149 mmap_read_unlock(mm); 150 if (user_mode(regs)) { 151 current->thread.bad_vaddr = address; 152 current->thread.error_code = is_write; 153 force_sig_fault(SIGSEGV, code, (void *) address); 154 return; 155 } 156 bad_page_fault(regs, address, SIGSEGV); 157 return; 158 159 160 /* We ran out of memory, or some other thing happened to us that made 161 * us unable to handle the page fault gracefully. 162 */ 163 out_of_memory: 164 mmap_read_unlock(mm); 165 if (!user_mode(regs)) 166 bad_page_fault(regs, address, SIGKILL); 167 else 168 pagefault_out_of_memory(); 169 return; 170 171 do_sigbus: 172 mmap_read_unlock(mm); 173 174 /* Send a sigbus, regardless of whether we were in kernel 175 * or user mode. 176 */ 177 current->thread.bad_vaddr = address; 178 force_sig_fault(SIGBUS, BUS_ADRERR, (void *) address); 179 180 /* Kernel mode? Handle exceptions or die */ 181 if (!user_mode(regs)) 182 bad_page_fault(regs, address, SIGBUS); 183 return; 184 185 vmalloc_fault: 186 { 187 /* Synchronize this task's top level page-table 188 * with the 'reference' page table. 189 */ 190 struct mm_struct *act_mm = current->active_mm; 191 int index = pgd_index(address); 192 pgd_t *pgd, *pgd_k; 193 p4d_t *p4d, *p4d_k; 194 pud_t *pud, *pud_k; 195 pmd_t *pmd, *pmd_k; 196 pte_t *pte_k; 197 198 if (act_mm == NULL) 199 goto bad_page_fault; 200 201 pgd = act_mm->pgd + index; 202 pgd_k = init_mm.pgd + index; 203 204 if (!pgd_present(*pgd_k)) 205 goto bad_page_fault; 206 207 pgd_val(*pgd) = pgd_val(*pgd_k); 208 209 p4d = p4d_offset(pgd, address); 210 p4d_k = p4d_offset(pgd_k, address); 211 if (!p4d_present(*p4d) || !p4d_present(*p4d_k)) 212 goto bad_page_fault; 213 214 pud = pud_offset(p4d, address); 215 pud_k = pud_offset(p4d_k, address); 216 if (!pud_present(*pud) || !pud_present(*pud_k)) 217 goto bad_page_fault; 218 219 pmd = pmd_offset(pud, address); 220 pmd_k = pmd_offset(pud_k, address); 221 if (!pmd_present(*pmd) || !pmd_present(*pmd_k)) 222 goto bad_page_fault; 223 224 pmd_val(*pmd) = pmd_val(*pmd_k); 225 pte_k = pte_offset_kernel(pmd_k, address); 226 227 if (!pte_present(*pte_k)) 228 goto bad_page_fault; 229 return; 230 } 231 bad_page_fault: 232 bad_page_fault(regs, address, SIGKILL); 233 return; 234 } 235 236 237 void 238 bad_page_fault(struct pt_regs *regs, unsigned long address, int sig) 239 { 240 extern void __noreturn die(const char*, struct pt_regs*, long); 241 const struct exception_table_entry *entry; 242 243 /* Are we prepared to handle this kernel fault? */ 244 if ((entry = search_exception_tables(regs->pc)) != NULL) { 245 pr_debug("%s: Exception at pc=%#010lx (%lx)\n", 246 current->comm, regs->pc, entry->fixup); 247 current->thread.bad_uaddr = address; 248 regs->pc = entry->fixup; 249 return; 250 } 251 252 /* Oops. The kernel tried to access some bad page. We'll have to 253 * terminate things with extreme prejudice. 254 */ 255 pr_alert("Unable to handle kernel paging request at virtual " 256 "address %08lx\n pc = %08lx, ra = %08lx\n", 257 address, regs->pc, regs->areg[0]); 258 die("Oops", regs, sig); 259 } 260