1 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 25unsigned long asid_cache = ASID_USER_FIRST; 26void 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 38void 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 91good_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 fault = handle_mm_fault(mm, vma, address, is_write ? FAULT_FLAG_WRITE : 0); 109 if (unlikely(fault & VM_FAULT_ERROR)) { 110 if (fault & VM_FAULT_OOM) 111 goto out_of_memory; 112 else if (fault & VM_FAULT_SIGBUS) 113 goto do_sigbus; 114 BUG(); 115 } 116 if (fault & VM_FAULT_MAJOR) 117 current->maj_flt++; 118 else 119 current->min_flt++; 120 121 up_read(&mm->mmap_sem); 122 return; 123 124 /* Something tried to access memory that isn't in our memory map.. 125 * Fix it, but check if it's kernel or user first.. 126 */ 127bad_area: 128 up_read(&mm->mmap_sem); 129 if (user_mode(regs)) { 130 current->thread.bad_vaddr = address; 131 current->thread.error_code = is_write; 132 info.si_signo = SIGSEGV; 133 info.si_errno = 0; 134 /* info.si_code has been set above */ 135 info.si_addr = (void *) address; 136 force_sig_info(SIGSEGV, &info, current); 137 return; 138 } 139 bad_page_fault(regs, address, SIGSEGV); 140 return; 141 142 143 /* We ran out of memory, or some other thing happened to us that made 144 * us unable to handle the page fault gracefully. 145 */ 146out_of_memory: 147 up_read(&mm->mmap_sem); 148 if (!user_mode(regs)) 149 bad_page_fault(regs, address, SIGKILL); 150 else 151 pagefault_out_of_memory(); 152 return; 153 154do_sigbus: 155 up_read(&mm->mmap_sem); 156 157 /* Send a sigbus, regardless of whether we were in kernel 158 * or user mode. 159 */ 160 current->thread.bad_vaddr = address; 161 info.si_code = SIGBUS; 162 info.si_errno = 0; 163 info.si_code = BUS_ADRERR; 164 info.si_addr = (void *) address; 165 force_sig_info(SIGBUS, &info, current); 166 167 /* Kernel mode? Handle exceptions or die */ 168 if (!user_mode(regs)) 169 bad_page_fault(regs, address, SIGBUS); 170 171vmalloc_fault: 172 { 173 /* Synchronize this task's top level page-table 174 * with the 'reference' page table. 175 */ 176 struct mm_struct *act_mm = current->active_mm; 177 int index = pgd_index(address); 178 pgd_t *pgd, *pgd_k; 179 pmd_t *pmd, *pmd_k; 180 pte_t *pte_k; 181 182 if (act_mm == NULL) 183 goto bad_page_fault; 184 185 pgd = act_mm->pgd + index; 186 pgd_k = init_mm.pgd + index; 187 188 if (!pgd_present(*pgd_k)) 189 goto bad_page_fault; 190 191 pgd_val(*pgd) = pgd_val(*pgd_k); 192 193 pmd = pmd_offset(pgd, address); 194 pmd_k = pmd_offset(pgd_k, address); 195 if (!pmd_present(*pmd) || !pmd_present(*pmd_k)) 196 goto bad_page_fault; 197 198 pmd_val(*pmd) = pmd_val(*pmd_k); 199 pte_k = pte_offset_kernel(pmd_k, address); 200 201 if (!pte_present(*pte_k)) 202 goto bad_page_fault; 203 return; 204 } 205bad_page_fault: 206 bad_page_fault(regs, address, SIGKILL); 207 return; 208} 209 210 211void 212bad_page_fault(struct pt_regs *regs, unsigned long address, int sig) 213{ 214 extern void die(const char*, struct pt_regs*, long); 215 const struct exception_table_entry *entry; 216 217 /* Are we prepared to handle this kernel fault? */ 218 if ((entry = search_exception_tables(regs->pc)) != NULL) { 219#ifdef DEBUG_PAGE_FAULT 220 printk(KERN_DEBUG "%s: Exception at pc=%#010lx (%lx)\n", 221 current->comm, regs->pc, entry->fixup); 222#endif 223 current->thread.bad_uaddr = address; 224 regs->pc = entry->fixup; 225 return; 226 } 227 228 /* Oops. The kernel tried to access some bad page. We'll have to 229 * terminate things with extreme prejudice. 230 */ 231 printk(KERN_ALERT "Unable to handle kernel paging request at virtual " 232 "address %08lx\n pc = %08lx, ra = %08lx\n", 233 address, regs->pc, regs->areg[0]); 234 die("Oops", regs, sig); 235 do_exit(sig); 236} 237