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/system.h> 23 #include <asm/pgalloc.h> 24 25 unsigned long asid_cache = ASID_USER_FIRST; 26 void bad_page_fault(struct pt_regs*, unsigned long, int); 27 28 #undef DEBUG_PAGE_FAULT 29 30 /* 31 * This routine handles page faults. It determines the address, 32 * and the problem, and then passes it off to one of the appropriate 33 * routines. 34 * 35 * Note: does not handle Miss and MultiHit. 36 */ 37 38 void do_page_fault(struct pt_regs *regs) 39 { 40 struct vm_area_struct * vma; 41 struct mm_struct *mm = current->mm; 42 unsigned int exccause = regs->exccause; 43 unsigned int address = regs->excvaddr; 44 siginfo_t info; 45 46 int is_write, is_exec; 47 int fault; 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 down_read(&mm->mmap_sem); 76 vma = find_vma(mm, address); 77 78 if (!vma) 79 goto bad_area; 80 if (vma->vm_start <= address) 81 goto good_area; 82 if (!(vma->vm_flags & VM_GROWSDOWN)) 83 goto bad_area; 84 if (expand_stack(vma, address)) 85 goto bad_area; 86 87 /* Ok, we have a good vm_area for this memory access, so 88 * we can handle it.. 89 */ 90 91 good_area: 92 info.si_code = SEGV_ACCERR; 93 94 if (is_write) { 95 if (!(vma->vm_flags & VM_WRITE)) 96 goto bad_area; 97 } else if (is_exec) { 98 if (!(vma->vm_flags & VM_EXEC)) 99 goto bad_area; 100 } else /* Allow read even from write-only pages. */ 101 if (!(vma->vm_flags & (VM_READ | VM_WRITE))) 102 goto bad_area; 103 104 /* If for any reason at all we couldn't handle the fault, 105 * make sure we exit gracefully rather than endlessly redo 106 * the fault. 107 */ 108 survive: 109 fault = handle_mm_fault(mm, vma, address, is_write ? FAULT_FLAG_WRITE : 0); 110 if (unlikely(fault & VM_FAULT_ERROR)) { 111 if (fault & VM_FAULT_OOM) 112 goto out_of_memory; 113 else if (fault & VM_FAULT_SIGBUS) 114 goto do_sigbus; 115 BUG(); 116 } 117 if (fault & VM_FAULT_MAJOR) 118 current->maj_flt++; 119 else 120 current->min_flt++; 121 122 up_read(&mm->mmap_sem); 123 return; 124 125 /* Something tried to access memory that isn't in our memory map.. 126 * Fix it, but check if it's kernel or user first.. 127 */ 128 bad_area: 129 up_read(&mm->mmap_sem); 130 if (user_mode(regs)) { 131 current->thread.bad_vaddr = address; 132 current->thread.error_code = is_write; 133 info.si_signo = SIGSEGV; 134 info.si_errno = 0; 135 /* info.si_code has been set above */ 136 info.si_addr = (void *) address; 137 force_sig_info(SIGSEGV, &info, current); 138 return; 139 } 140 bad_page_fault(regs, address, SIGSEGV); 141 return; 142 143 144 /* We ran out of memory, or some other thing happened to us that made 145 * us unable to handle the page fault gracefully. 146 */ 147 out_of_memory: 148 up_read(&mm->mmap_sem); 149 if (is_global_init(current)) { 150 yield(); 151 down_read(&mm->mmap_sem); 152 goto survive; 153 } 154 printk("VM: killing process %s\n", current->comm); 155 if (user_mode(regs)) 156 do_group_exit(SIGKILL); 157 bad_page_fault(regs, address, SIGKILL); 158 return; 159 160 do_sigbus: 161 up_read(&mm->mmap_sem); 162 163 /* Send a sigbus, regardless of whether we were in kernel 164 * or user mode. 165 */ 166 current->thread.bad_vaddr = address; 167 info.si_code = SIGBUS; 168 info.si_errno = 0; 169 info.si_code = BUS_ADRERR; 170 info.si_addr = (void *) address; 171 force_sig_info(SIGBUS, &info, current); 172 173 /* Kernel mode? Handle exceptions or die */ 174 if (!user_mode(regs)) 175 bad_page_fault(regs, address, SIGBUS); 176 177 vmalloc_fault: 178 { 179 /* Synchronize this task's top level page-table 180 * with the 'reference' page table. 181 */ 182 struct mm_struct *act_mm = current->active_mm; 183 int index = pgd_index(address); 184 pgd_t *pgd, *pgd_k; 185 pmd_t *pmd, *pmd_k; 186 pte_t *pte_k; 187 188 if (act_mm == NULL) 189 goto bad_page_fault; 190 191 pgd = act_mm->pgd + index; 192 pgd_k = init_mm.pgd + index; 193 194 if (!pgd_present(*pgd_k)) 195 goto bad_page_fault; 196 197 pgd_val(*pgd) = pgd_val(*pgd_k); 198 199 pmd = pmd_offset(pgd, address); 200 pmd_k = pmd_offset(pgd_k, address); 201 if (!pmd_present(*pmd) || !pmd_present(*pmd_k)) 202 goto bad_page_fault; 203 204 pmd_val(*pmd) = pmd_val(*pmd_k); 205 pte_k = pte_offset_kernel(pmd_k, address); 206 207 if (!pte_present(*pte_k)) 208 goto bad_page_fault; 209 return; 210 } 211 bad_page_fault: 212 bad_page_fault(regs, address, SIGKILL); 213 return; 214 } 215 216 217 void 218 bad_page_fault(struct pt_regs *regs, unsigned long address, int sig) 219 { 220 extern void die(const char*, struct pt_regs*, long); 221 const struct exception_table_entry *entry; 222 223 /* Are we prepared to handle this kernel fault? */ 224 if ((entry = search_exception_tables(regs->pc)) != NULL) { 225 #ifdef DEBUG_PAGE_FAULT 226 printk(KERN_DEBUG "%s: Exception at pc=%#010lx (%lx)\n", 227 current->comm, regs->pc, entry->fixup); 228 #endif 229 current->thread.bad_uaddr = address; 230 regs->pc = entry->fixup; 231 return; 232 } 233 234 /* Oops. The kernel tried to access some bad page. We'll have to 235 * terminate things with extreme prejudice. 236 */ 237 printk(KERN_ALERT "Unable to handle kernel paging request at virtual " 238 "address %08lx\n pc = %08lx, ra = %08lx\n", 239 address, regs->pc, regs->areg[0]); 240 die("Oops", regs, sig); 241 do_exit(sig); 242 } 243 244