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 24DEFINE_PER_CPU(unsigned long, asid_cache) = ASID_USER_FIRST; 25void 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 37void 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 if (user_mode(regs)) 76 flags |= FAULT_FLAG_USER; 77retry: 78 down_read(&mm->mmap_sem); 79 vma = find_vma(mm, address); 80 81 if (!vma) 82 goto bad_area; 83 if (vma->vm_start <= address) 84 goto good_area; 85 if (!(vma->vm_flags & VM_GROWSDOWN)) 86 goto bad_area; 87 if (expand_stack(vma, address)) 88 goto bad_area; 89 90 /* Ok, we have a good vm_area for this memory access, so 91 * we can handle it.. 92 */ 93 94good_area: 95 info.si_code = SEGV_ACCERR; 96 97 if (is_write) { 98 if (!(vma->vm_flags & VM_WRITE)) 99 goto bad_area; 100 flags |= FAULT_FLAG_WRITE; 101 } else if (is_exec) { 102 if (!(vma->vm_flags & VM_EXEC)) 103 goto bad_area; 104 } else /* Allow read even from write-only pages. */ 105 if (!(vma->vm_flags & (VM_READ | VM_WRITE))) 106 goto bad_area; 107 108 /* If for any reason at all we couldn't handle the fault, 109 * make sure we exit gracefully rather than endlessly redo 110 * the fault. 111 */ 112 fault = handle_mm_fault(mm, vma, address, flags); 113 114 if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current)) 115 return; 116 117 if (unlikely(fault & VM_FAULT_ERROR)) { 118 if (fault & VM_FAULT_OOM) 119 goto out_of_memory; 120 else if (fault & VM_FAULT_SIGSEGV) 121 goto bad_area; 122 else if (fault & VM_FAULT_SIGBUS) 123 goto do_sigbus; 124 BUG(); 125 } 126 if (flags & FAULT_FLAG_ALLOW_RETRY) { 127 if (fault & VM_FAULT_MAJOR) 128 current->maj_flt++; 129 else 130 current->min_flt++; 131 if (fault & VM_FAULT_RETRY) { 132 flags &= ~FAULT_FLAG_ALLOW_RETRY; 133 flags |= FAULT_FLAG_TRIED; 134 135 /* No need to up_read(&mm->mmap_sem) as we would 136 * have already released it in __lock_page_or_retry 137 * in mm/filemap.c. 138 */ 139 140 goto retry; 141 } 142 } 143 144 up_read(&mm->mmap_sem); 145 return; 146 147 /* Something tried to access memory that isn't in our memory map.. 148 * Fix it, but check if it's kernel or user first.. 149 */ 150bad_area: 151 up_read(&mm->mmap_sem); 152 if (user_mode(regs)) { 153 current->thread.bad_vaddr = address; 154 current->thread.error_code = is_write; 155 info.si_signo = SIGSEGV; 156 info.si_errno = 0; 157 /* info.si_code has been set above */ 158 info.si_addr = (void *) address; 159 force_sig_info(SIGSEGV, &info, current); 160 return; 161 } 162 bad_page_fault(regs, address, SIGSEGV); 163 return; 164 165 166 /* We ran out of memory, or some other thing happened to us that made 167 * us unable to handle the page fault gracefully. 168 */ 169out_of_memory: 170 up_read(&mm->mmap_sem); 171 if (!user_mode(regs)) 172 bad_page_fault(regs, address, SIGKILL); 173 else 174 pagefault_out_of_memory(); 175 return; 176 177do_sigbus: 178 up_read(&mm->mmap_sem); 179 180 /* Send a sigbus, regardless of whether we were in kernel 181 * or user mode. 182 */ 183 current->thread.bad_vaddr = address; 184 info.si_code = SIGBUS; 185 info.si_errno = 0; 186 info.si_code = BUS_ADRERR; 187 info.si_addr = (void *) address; 188 force_sig_info(SIGBUS, &info, current); 189 190 /* Kernel mode? Handle exceptions or die */ 191 if (!user_mode(regs)) 192 bad_page_fault(regs, address, SIGBUS); 193 return; 194 195vmalloc_fault: 196 { 197 /* Synchronize this task's top level page-table 198 * with the 'reference' page table. 199 */ 200 struct mm_struct *act_mm = current->active_mm; 201 int index = pgd_index(address); 202 pgd_t *pgd, *pgd_k; 203 pmd_t *pmd, *pmd_k; 204 pte_t *pte_k; 205 206 if (act_mm == NULL) 207 goto bad_page_fault; 208 209 pgd = act_mm->pgd + index; 210 pgd_k = init_mm.pgd + index; 211 212 if (!pgd_present(*pgd_k)) 213 goto bad_page_fault; 214 215 pgd_val(*pgd) = pgd_val(*pgd_k); 216 217 pmd = pmd_offset(pgd, address); 218 pmd_k = pmd_offset(pgd_k, address); 219 if (!pmd_present(*pmd) || !pmd_present(*pmd_k)) 220 goto bad_page_fault; 221 222 pmd_val(*pmd) = pmd_val(*pmd_k); 223 pte_k = pte_offset_kernel(pmd_k, address); 224 225 if (!pte_present(*pte_k)) 226 goto bad_page_fault; 227 return; 228 } 229bad_page_fault: 230 bad_page_fault(regs, address, SIGKILL); 231 return; 232} 233 234 235void 236bad_page_fault(struct pt_regs *regs, unsigned long address, int sig) 237{ 238 extern void die(const char*, struct pt_regs*, long); 239 const struct exception_table_entry *entry; 240 241 /* Are we prepared to handle this kernel fault? */ 242 if ((entry = search_exception_tables(regs->pc)) != NULL) { 243#ifdef DEBUG_PAGE_FAULT 244 printk(KERN_DEBUG "%s: Exception at pc=%#010lx (%lx)\n", 245 current->comm, regs->pc, entry->fixup); 246#endif 247 current->thread.bad_uaddr = address; 248 regs->pc = entry->fixup; 249 return; 250 } 251 252 /* Oops. The kernel tried to access some bad page. We'll have to 253 * terminate things with extreme prejudice. 254 */ 255 printk(KERN_ALERT "Unable to handle kernel paging request at virtual " 256 "address %08lx\n pc = %08lx, ra = %08lx\n", 257 address, regs->pc, regs->areg[0]); 258 die("Oops", regs, sig); 259 do_exit(sig); 260} 261