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