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 - 2005 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; 129 130 /* No need to up_read(&mm->mmap_sem) as we would 131 * have already released it in __lock_page_or_retry 132 * in mm/filemap.c. 133 */ 134 135 goto retry; 136 } 137 } 138 139 up_read(&mm->mmap_sem); 140 return; 141 142 /* Something tried to access memory that isn't in our memory map.. 143 * Fix it, but check if it's kernel or user first.. 144 */ 145 bad_area: 146 up_read(&mm->mmap_sem); 147 if (user_mode(regs)) { 148 current->thread.bad_vaddr = address; 149 current->thread.error_code = is_write; 150 info.si_signo = SIGSEGV; 151 info.si_errno = 0; 152 /* info.si_code has been set above */ 153 info.si_addr = (void *) address; 154 force_sig_info(SIGSEGV, &info, current); 155 return; 156 } 157 bad_page_fault(regs, address, SIGSEGV); 158 return; 159 160 161 /* We ran out of memory, or some other thing happened to us that made 162 * us unable to handle the page fault gracefully. 163 */ 164 out_of_memory: 165 up_read(&mm->mmap_sem); 166 if (!user_mode(regs)) 167 bad_page_fault(regs, address, SIGKILL); 168 else 169 pagefault_out_of_memory(); 170 return; 171 172 do_sigbus: 173 up_read(&mm->mmap_sem); 174 175 /* Send a sigbus, regardless of whether we were in kernel 176 * or user mode. 177 */ 178 current->thread.bad_vaddr = address; 179 info.si_code = SIGBUS; 180 info.si_errno = 0; 181 info.si_code = BUS_ADRERR; 182 info.si_addr = (void *) address; 183 force_sig_info(SIGBUS, &info, current); 184 185 /* Kernel mode? Handle exceptions or die */ 186 if (!user_mode(regs)) 187 bad_page_fault(regs, address, SIGBUS); 188 189 vmalloc_fault: 190 { 191 /* Synchronize this task's top level page-table 192 * with the 'reference' page table. 193 */ 194 struct mm_struct *act_mm = current->active_mm; 195 int index = pgd_index(address); 196 pgd_t *pgd, *pgd_k; 197 pmd_t *pmd, *pmd_k; 198 pte_t *pte_k; 199 200 if (act_mm == NULL) 201 goto bad_page_fault; 202 203 pgd = act_mm->pgd + index; 204 pgd_k = init_mm.pgd + index; 205 206 if (!pgd_present(*pgd_k)) 207 goto bad_page_fault; 208 209 pgd_val(*pgd) = pgd_val(*pgd_k); 210 211 pmd = pmd_offset(pgd, address); 212 pmd_k = pmd_offset(pgd_k, address); 213 if (!pmd_present(*pmd) || !pmd_present(*pmd_k)) 214 goto bad_page_fault; 215 216 pmd_val(*pmd) = pmd_val(*pmd_k); 217 pte_k = pte_offset_kernel(pmd_k, address); 218 219 if (!pte_present(*pte_k)) 220 goto bad_page_fault; 221 return; 222 } 223 bad_page_fault: 224 bad_page_fault(regs, address, SIGKILL); 225 return; 226 } 227 228 229 void 230 bad_page_fault(struct pt_regs *regs, unsigned long address, int sig) 231 { 232 extern void die(const char*, struct pt_regs*, long); 233 const struct exception_table_entry *entry; 234 235 /* Are we prepared to handle this kernel fault? */ 236 if ((entry = search_exception_tables(regs->pc)) != NULL) { 237 #ifdef DEBUG_PAGE_FAULT 238 printk(KERN_DEBUG "%s: Exception at pc=%#010lx (%lx)\n", 239 current->comm, regs->pc, entry->fixup); 240 #endif 241 current->thread.bad_uaddr = address; 242 regs->pc = entry->fixup; 243 return; 244 } 245 246 /* Oops. The kernel tried to access some bad page. We'll have to 247 * terminate things with extreme prejudice. 248 */ 249 printk(KERN_ALERT "Unable to handle kernel paging request at virtual " 250 "address %08lx\n pc = %08lx, ra = %08lx\n", 251 address, regs->pc, regs->areg[0]); 252 die("Oops", regs, sig); 253 do_exit(sig); 254 } 255 256