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 48 info.si_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 (in_atomic() || !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 #ifdef DEBUG_PAGE_FAULT 70 printk("[%s:%d:%08x:%d:%08x:%s%s]\n", current->comm, current->pid, 71 address, exccause, regs->pc, is_write? "w":"", is_exec? "x":""); 72 #endif 73 74 down_read(&mm->mmap_sem); 75 vma = find_vma(mm, address); 76 77 if (!vma) 78 goto bad_area; 79 if (vma->vm_start <= address) 80 goto good_area; 81 if (!(vma->vm_flags & VM_GROWSDOWN)) 82 goto bad_area; 83 if (expand_stack(vma, address)) 84 goto bad_area; 85 86 /* Ok, we have a good vm_area for this memory access, so 87 * we can handle it.. 88 */ 89 90 good_area: 91 info.si_code = SEGV_ACCERR; 92 93 if (is_write) { 94 if (!(vma->vm_flags & VM_WRITE)) 95 goto bad_area; 96 } else if (is_exec) { 97 if (!(vma->vm_flags & VM_EXEC)) 98 goto bad_area; 99 } else /* Allow read even from write-only pages. */ 100 if (!(vma->vm_flags & (VM_READ | VM_WRITE))) 101 goto bad_area; 102 103 /* If for any reason at all we couldn't handle the fault, 104 * make sure we exit gracefully rather than endlessly redo 105 * the fault. 106 */ 107 fault = handle_mm_fault(mm, vma, address, is_write ? FAULT_FLAG_WRITE : 0); 108 if (unlikely(fault & VM_FAULT_ERROR)) { 109 if (fault & VM_FAULT_OOM) 110 goto out_of_memory; 111 else if (fault & VM_FAULT_SIGBUS) 112 goto do_sigbus; 113 BUG(); 114 } 115 if (fault & VM_FAULT_MAJOR) 116 current->maj_flt++; 117 else 118 current->min_flt++; 119 120 up_read(&mm->mmap_sem); 121 return; 122 123 /* Something tried to access memory that isn't in our memory map.. 124 * Fix it, but check if it's kernel or user first.. 125 */ 126 bad_area: 127 up_read(&mm->mmap_sem); 128 if (user_mode(regs)) { 129 current->thread.bad_vaddr = address; 130 current->thread.error_code = is_write; 131 info.si_signo = SIGSEGV; 132 info.si_errno = 0; 133 /* info.si_code has been set above */ 134 info.si_addr = (void *) address; 135 force_sig_info(SIGSEGV, &info, current); 136 return; 137 } 138 bad_page_fault(regs, address, SIGSEGV); 139 return; 140 141 142 /* We ran out of memory, or some other thing happened to us that made 143 * us unable to handle the page fault gracefully. 144 */ 145 out_of_memory: 146 up_read(&mm->mmap_sem); 147 if (!user_mode(regs)) 148 bad_page_fault(regs, address, SIGKILL); 149 else 150 pagefault_out_of_memory(); 151 return; 152 153 do_sigbus: 154 up_read(&mm->mmap_sem); 155 156 /* Send a sigbus, regardless of whether we were in kernel 157 * or user mode. 158 */ 159 current->thread.bad_vaddr = address; 160 info.si_code = SIGBUS; 161 info.si_errno = 0; 162 info.si_code = BUS_ADRERR; 163 info.si_addr = (void *) address; 164 force_sig_info(SIGBUS, &info, current); 165 166 /* Kernel mode? Handle exceptions or die */ 167 if (!user_mode(regs)) 168 bad_page_fault(regs, address, SIGBUS); 169 170 vmalloc_fault: 171 { 172 /* Synchronize this task's top level page-table 173 * with the 'reference' page table. 174 */ 175 struct mm_struct *act_mm = current->active_mm; 176 int index = pgd_index(address); 177 pgd_t *pgd, *pgd_k; 178 pmd_t *pmd, *pmd_k; 179 pte_t *pte_k; 180 181 if (act_mm == NULL) 182 goto bad_page_fault; 183 184 pgd = act_mm->pgd + index; 185 pgd_k = init_mm.pgd + index; 186 187 if (!pgd_present(*pgd_k)) 188 goto bad_page_fault; 189 190 pgd_val(*pgd) = pgd_val(*pgd_k); 191 192 pmd = pmd_offset(pgd, address); 193 pmd_k = pmd_offset(pgd_k, address); 194 if (!pmd_present(*pmd) || !pmd_present(*pmd_k)) 195 goto bad_page_fault; 196 197 pmd_val(*pmd) = pmd_val(*pmd_k); 198 pte_k = pte_offset_kernel(pmd_k, address); 199 200 if (!pte_present(*pte_k)) 201 goto bad_page_fault; 202 return; 203 } 204 bad_page_fault: 205 bad_page_fault(regs, address, SIGKILL); 206 return; 207 } 208 209 210 void 211 bad_page_fault(struct pt_regs *regs, unsigned long address, int sig) 212 { 213 extern void die(const char*, struct pt_regs*, long); 214 const struct exception_table_entry *entry; 215 216 /* Are we prepared to handle this kernel fault? */ 217 if ((entry = search_exception_tables(regs->pc)) != NULL) { 218 #ifdef DEBUG_PAGE_FAULT 219 printk(KERN_DEBUG "%s: Exception at pc=%#010lx (%lx)\n", 220 current->comm, regs->pc, entry->fixup); 221 #endif 222 current->thread.bad_uaddr = address; 223 regs->pc = entry->fixup; 224 return; 225 } 226 227 /* Oops. The kernel tried to access some bad page. We'll have to 228 * terminate things with extreme prejudice. 229 */ 230 printk(KERN_ALERT "Unable to handle kernel paging request at virtual " 231 "address %08lx\n pc = %08lx, ra = %08lx\n", 232 address, regs->pc, regs->areg[0]); 233 die("Oops", regs, sig); 234 do_exit(sig); 235 } 236 237