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/extable.h> 17#include <linux/hardirq.h> 18#include <linux/perf_event.h> 19#include <linux/uaccess.h> 20#include <asm/mmu_context.h> 21#include <asm/cacheflush.h> 22#include <asm/hardirq.h> 23 24DEFINE_PER_CPU(unsigned long, asid_cache) = ASID_USER_FIRST; 25void bad_page_fault(struct pt_regs*, unsigned long, int); 26 27/* 28 * This routine handles page faults. It determines the address, 29 * and the problem, and then passes it off to one of the appropriate 30 * routines. 31 * 32 * Note: does not handle Miss and MultiHit. 33 */ 34 35void do_page_fault(struct pt_regs *regs) 36{ 37 struct vm_area_struct * vma; 38 struct mm_struct *mm = current->mm; 39 unsigned int exccause = regs->exccause; 40 unsigned int address = regs->excvaddr; 41 int code; 42 43 int is_write, is_exec; 44 vm_fault_t fault; 45 unsigned int flags = FAULT_FLAG_DEFAULT; 46 47 code = SEGV_MAPERR; 48 49 /* We fault-in kernel-space virtual memory on-demand. The 50 * 'reference' page table is init_mm.pgd. 51 */ 52 if (address >= TASK_SIZE && !user_mode(regs)) 53 goto vmalloc_fault; 54 55 /* If we're in an interrupt or have no user 56 * context, we must not take the fault.. 57 */ 58 if (faulthandler_disabled() || !mm) { 59 bad_page_fault(regs, address, SIGSEGV); 60 return; 61 } 62 63 is_write = (exccause == EXCCAUSE_STORE_CACHE_ATTRIBUTE) ? 1 : 0; 64 is_exec = (exccause == EXCCAUSE_ITLB_PRIVILEGE || 65 exccause == EXCCAUSE_ITLB_MISS || 66 exccause == EXCCAUSE_FETCH_CACHE_ATTRIBUTE) ? 1 : 0; 67 68 pr_debug("[%s:%d:%08x:%d:%08lx:%s%s]\n", 69 current->comm, current->pid, 70 address, exccause, regs->pc, 71 is_write ? "w" : "", is_exec ? "x" : ""); 72 73 if (user_mode(regs)) 74 flags |= FAULT_FLAG_USER; 75 76 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address); 77 78retry: 79 mmap_read_lock(mm); 80 vma = find_vma(mm, address); 81 82 if (!vma) 83 goto bad_area; 84 if (vma->vm_start <= address) 85 goto good_area; 86 if (!(vma->vm_flags & VM_GROWSDOWN)) 87 goto bad_area; 88 if (expand_stack(vma, address)) 89 goto bad_area; 90 91 /* Ok, we have a good vm_area for this memory access, so 92 * we can handle it.. 93 */ 94 95good_area: 96 code = SEGV_ACCERR; 97 98 if (is_write) { 99 if (!(vma->vm_flags & VM_WRITE)) 100 goto bad_area; 101 flags |= FAULT_FLAG_WRITE; 102 } else if (is_exec) { 103 if (!(vma->vm_flags & VM_EXEC)) 104 goto bad_area; 105 } else /* Allow read even from write-only pages. */ 106 if (!(vma->vm_flags & (VM_READ | VM_WRITE))) 107 goto bad_area; 108 109 /* If for any reason at all we couldn't handle the fault, 110 * make sure we exit gracefully rather than endlessly redo 111 * the fault. 112 */ 113 fault = handle_mm_fault(vma, address, flags, regs); 114 115 if (fault_signal_pending(fault, regs)) { 116 if (!user_mode(regs)) 117 goto bad_page_fault; 118 return; 119 } 120 121 if (unlikely(fault & VM_FAULT_ERROR)) { 122 if (fault & VM_FAULT_OOM) 123 goto out_of_memory; 124 else if (fault & VM_FAULT_SIGSEGV) 125 goto bad_area; 126 else if (fault & VM_FAULT_SIGBUS) 127 goto do_sigbus; 128 BUG(); 129 } 130 if (flags & FAULT_FLAG_ALLOW_RETRY) { 131 if (fault & VM_FAULT_RETRY) { 132 flags |= FAULT_FLAG_TRIED; 133 134 /* No need to mmap_read_unlock(mm) as we would 135 * have already released it in __lock_page_or_retry 136 * in mm/filemap.c. 137 */ 138 139 goto retry; 140 } 141 } 142 143 mmap_read_unlock(mm); 144 return; 145 146 /* Something tried to access memory that isn't in our memory map.. 147 * Fix it, but check if it's kernel or user first.. 148 */ 149bad_area: 150 mmap_read_unlock(mm); 151 if (user_mode(regs)) { 152 current->thread.bad_vaddr = address; 153 current->thread.error_code = is_write; 154 force_sig_fault(SIGSEGV, code, (void *) address); 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 */ 164out_of_memory: 165 mmap_read_unlock(mm); 166 if (!user_mode(regs)) 167 bad_page_fault(regs, address, SIGKILL); 168 else 169 pagefault_out_of_memory(); 170 return; 171 172do_sigbus: 173 mmap_read_unlock(mm); 174 175 /* Send a sigbus, regardless of whether we were in kernel 176 * or user mode. 177 */ 178 current->thread.bad_vaddr = address; 179 force_sig_fault(SIGBUS, BUS_ADRERR, (void *) address); 180 181 /* Kernel mode? Handle exceptions or die */ 182 if (!user_mode(regs)) 183 bad_page_fault(regs, address, SIGBUS); 184 return; 185 186vmalloc_fault: 187 { 188 /* Synchronize this task's top level page-table 189 * with the 'reference' page table. 190 */ 191 struct mm_struct *act_mm = current->active_mm; 192 int index = pgd_index(address); 193 pgd_t *pgd, *pgd_k; 194 p4d_t *p4d, *p4d_k; 195 pud_t *pud, *pud_k; 196 pmd_t *pmd, *pmd_k; 197 pte_t *pte_k; 198 199 if (act_mm == NULL) 200 goto bad_page_fault; 201 202 pgd = act_mm->pgd + index; 203 pgd_k = init_mm.pgd + index; 204 205 if (!pgd_present(*pgd_k)) 206 goto bad_page_fault; 207 208 pgd_val(*pgd) = pgd_val(*pgd_k); 209 210 p4d = p4d_offset(pgd, address); 211 p4d_k = p4d_offset(pgd_k, address); 212 if (!p4d_present(*p4d) || !p4d_present(*p4d_k)) 213 goto bad_page_fault; 214 215 pud = pud_offset(p4d, address); 216 pud_k = pud_offset(p4d_k, address); 217 if (!pud_present(*pud) || !pud_present(*pud_k)) 218 goto bad_page_fault; 219 220 pmd = pmd_offset(pud, address); 221 pmd_k = pmd_offset(pud_k, address); 222 if (!pmd_present(*pmd) || !pmd_present(*pmd_k)) 223 goto bad_page_fault; 224 225 pmd_val(*pmd) = pmd_val(*pmd_k); 226 pte_k = pte_offset_kernel(pmd_k, address); 227 228 if (!pte_present(*pte_k)) 229 goto bad_page_fault; 230 return; 231 } 232bad_page_fault: 233 bad_page_fault(regs, address, SIGKILL); 234 return; 235} 236 237 238void 239bad_page_fault(struct pt_regs *regs, unsigned long address, int sig) 240{ 241 extern void die(const char*, struct pt_regs*, long); 242 const struct exception_table_entry *entry; 243 244 /* Are we prepared to handle this kernel fault? */ 245 if ((entry = search_exception_tables(regs->pc)) != NULL) { 246 pr_debug("%s: Exception at pc=%#010lx (%lx)\n", 247 current->comm, regs->pc, entry->fixup); 248 current->thread.bad_uaddr = address; 249 regs->pc = entry->fixup; 250 return; 251 } 252 253 /* Oops. The kernel tried to access some bad page. We'll have to 254 * terminate things with extreme prejudice. 255 */ 256 pr_alert("Unable to handle kernel paging request at virtual " 257 "address %08lx\n pc = %08lx, ra = %08lx\n", 258 address, regs->pc, regs->areg[0]); 259 die("Oops", regs, sig); 260 do_exit(sig); 261} 262