1 /* 2 * OpenRISC fault.c 3 * 4 * Linux architectural port borrowing liberally from similar works of 5 * others. All original copyrights apply as per the original source 6 * declaration. 7 * 8 * Modifications for the OpenRISC architecture: 9 * Copyright (C) 2003 Matjaz Breskvar <phoenix@bsemi.com> 10 * Copyright (C) 2010-2011 Jonas Bonn <jonas@southpole.se> 11 * 12 * This program is free software; you can redistribute it and/or 13 * modify it under the terms of the GNU General Public License 14 * as published by the Free Software Foundation; either version 15 * 2 of the License, or (at your option) any later version. 16 */ 17 18 #include <linux/mm.h> 19 #include <linux/interrupt.h> 20 #include <linux/module.h> 21 #include <linux/sched.h> 22 23 #include <asm/uaccess.h> 24 #include <asm/siginfo.h> 25 #include <asm/signal.h> 26 27 #define NUM_TLB_ENTRIES 64 28 #define TLB_OFFSET(add) (((add) >> PAGE_SHIFT) & (NUM_TLB_ENTRIES-1)) 29 30 unsigned long pte_misses; /* updated by do_page_fault() */ 31 unsigned long pte_errors; /* updated by do_page_fault() */ 32 33 /* __PHX__ :: - check the vmalloc_fault in do_page_fault() 34 * - also look into include/asm-or32/mmu_context.h 35 */ 36 volatile pgd_t *current_pgd; 37 38 extern void die(char *, struct pt_regs *, long); 39 40 /* 41 * This routine handles page faults. It determines the address, 42 * and the problem, and then passes it off to one of the appropriate 43 * routines. 44 * 45 * If this routine detects a bad access, it returns 1, otherwise it 46 * returns 0. 47 */ 48 49 asmlinkage void do_page_fault(struct pt_regs *regs, unsigned long address, 50 unsigned long vector, int write_acc) 51 { 52 struct task_struct *tsk; 53 struct mm_struct *mm; 54 struct vm_area_struct *vma; 55 siginfo_t info; 56 int fault; 57 unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE; 58 59 tsk = current; 60 61 /* 62 * We fault-in kernel-space virtual memory on-demand. The 63 * 'reference' page table is init_mm.pgd. 64 * 65 * NOTE! We MUST NOT take any locks for this case. We may 66 * be in an interrupt or a critical region, and should 67 * only copy the information from the master page table, 68 * nothing more. 69 * 70 * NOTE2: This is done so that, when updating the vmalloc 71 * mappings we don't have to walk all processes pgdirs and 72 * add the high mappings all at once. Instead we do it as they 73 * are used. However vmalloc'ed page entries have the PAGE_GLOBAL 74 * bit set so sometimes the TLB can use a lingering entry. 75 * 76 * This verifies that the fault happens in kernel space 77 * and that the fault was not a protection error. 78 */ 79 80 if (address >= VMALLOC_START && 81 (vector != 0x300 && vector != 0x400) && 82 !user_mode(regs)) 83 goto vmalloc_fault; 84 85 /* If exceptions were enabled, we can reenable them here */ 86 if (user_mode(regs)) { 87 /* Exception was in userspace: reenable interrupts */ 88 local_irq_enable(); 89 } else { 90 /* If exception was in a syscall, then IRQ's may have 91 * been enabled or disabled. If they were enabled, 92 * reenable them. 93 */ 94 if (regs->sr && (SPR_SR_IEE | SPR_SR_TEE)) 95 local_irq_enable(); 96 } 97 98 mm = tsk->mm; 99 info.si_code = SEGV_MAPERR; 100 101 /* 102 * If we're in an interrupt or have no user 103 * context, we must not take the fault.. 104 */ 105 106 if (in_interrupt() || !mm) 107 goto no_context; 108 109 retry: 110 down_read(&mm->mmap_sem); 111 vma = find_vma(mm, address); 112 113 if (!vma) 114 goto bad_area; 115 116 if (vma->vm_start <= address) 117 goto good_area; 118 119 if (!(vma->vm_flags & VM_GROWSDOWN)) 120 goto bad_area; 121 122 if (user_mode(regs)) { 123 /* 124 * accessing the stack below usp is always a bug. 125 * we get page-aligned addresses so we can only check 126 * if we're within a page from usp, but that might be 127 * enough to catch brutal errors at least. 128 */ 129 if (address + PAGE_SIZE < regs->sp) 130 goto bad_area; 131 } 132 if (expand_stack(vma, address)) 133 goto bad_area; 134 135 /* 136 * Ok, we have a good vm_area for this memory access, so 137 * we can handle it.. 138 */ 139 140 good_area: 141 info.si_code = SEGV_ACCERR; 142 143 /* first do some preliminary protection checks */ 144 145 if (write_acc) { 146 if (!(vma->vm_flags & VM_WRITE)) 147 goto bad_area; 148 flags |= FAULT_FLAG_WRITE; 149 } else { 150 /* not present */ 151 if (!(vma->vm_flags & (VM_READ | VM_EXEC))) 152 goto bad_area; 153 } 154 155 /* are we trying to execute nonexecutable area */ 156 if ((vector == 0x400) && !(vma->vm_page_prot.pgprot & _PAGE_EXEC)) 157 goto bad_area; 158 159 /* 160 * If for any reason at all we couldn't handle the fault, 161 * make sure we exit gracefully rather than endlessly redo 162 * the fault. 163 */ 164 165 fault = handle_mm_fault(mm, vma, address, flags); 166 167 if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current)) 168 return; 169 170 if (unlikely(fault & VM_FAULT_ERROR)) { 171 if (fault & VM_FAULT_OOM) 172 goto out_of_memory; 173 else if (fault & VM_FAULT_SIGBUS) 174 goto do_sigbus; 175 BUG(); 176 } 177 178 if (flags & FAULT_FLAG_ALLOW_RETRY) { 179 /*RGD modeled on Cris */ 180 if (fault & VM_FAULT_MAJOR) 181 tsk->maj_flt++; 182 else 183 tsk->min_flt++; 184 if (fault & VM_FAULT_RETRY) { 185 flags &= ~FAULT_FLAG_ALLOW_RETRY; 186 flags |= FAULT_FLAG_TRIED; 187 188 /* No need to up_read(&mm->mmap_sem) as we would 189 * have already released it in __lock_page_or_retry 190 * in mm/filemap.c. 191 */ 192 193 goto retry; 194 } 195 } 196 197 up_read(&mm->mmap_sem); 198 return; 199 200 /* 201 * Something tried to access memory that isn't in our memory map.. 202 * Fix it, but check if it's kernel or user first.. 203 */ 204 205 bad_area: 206 up_read(&mm->mmap_sem); 207 208 bad_area_nosemaphore: 209 210 /* User mode accesses just cause a SIGSEGV */ 211 212 if (user_mode(regs)) { 213 info.si_signo = SIGSEGV; 214 info.si_errno = 0; 215 /* info.si_code has been set above */ 216 info.si_addr = (void *)address; 217 force_sig_info(SIGSEGV, &info, tsk); 218 return; 219 } 220 221 no_context: 222 223 /* Are we prepared to handle this kernel fault? 224 * 225 * (The kernel has valid exception-points in the source 226 * when it acesses user-memory. When it fails in one 227 * of those points, we find it in a table and do a jump 228 * to some fixup code that loads an appropriate error 229 * code) 230 */ 231 232 { 233 const struct exception_table_entry *entry; 234 235 __asm__ __volatile__("l.nop 42"); 236 237 if ((entry = search_exception_tables(regs->pc)) != NULL) { 238 /* Adjust the instruction pointer in the stackframe */ 239 regs->pc = entry->fixup; 240 return; 241 } 242 } 243 244 /* 245 * Oops. The kernel tried to access some bad page. We'll have to 246 * terminate things with extreme prejudice. 247 */ 248 249 if ((unsigned long)(address) < PAGE_SIZE) 250 printk(KERN_ALERT 251 "Unable to handle kernel NULL pointer dereference"); 252 else 253 printk(KERN_ALERT "Unable to handle kernel access"); 254 printk(" at virtual address 0x%08lx\n", address); 255 256 die("Oops", regs, write_acc); 257 258 do_exit(SIGKILL); 259 260 /* 261 * We ran out of memory, or some other thing happened to us that made 262 * us unable to handle the page fault gracefully. 263 */ 264 265 out_of_memory: 266 __asm__ __volatile__("l.nop 42"); 267 __asm__ __volatile__("l.nop 1"); 268 269 up_read(&mm->mmap_sem); 270 printk("VM: killing process %s\n", tsk->comm); 271 if (user_mode(regs)) 272 do_exit(SIGKILL); 273 goto no_context; 274 275 do_sigbus: 276 up_read(&mm->mmap_sem); 277 278 /* 279 * Send a sigbus, regardless of whether we were in kernel 280 * or user mode. 281 */ 282 info.si_signo = SIGBUS; 283 info.si_errno = 0; 284 info.si_code = BUS_ADRERR; 285 info.si_addr = (void *)address; 286 force_sig_info(SIGBUS, &info, tsk); 287 288 /* Kernel mode? Handle exceptions or die */ 289 if (!user_mode(regs)) 290 goto no_context; 291 return; 292 293 vmalloc_fault: 294 { 295 /* 296 * Synchronize this task's top level page-table 297 * with the 'reference' page table. 298 * 299 * Use current_pgd instead of tsk->active_mm->pgd 300 * since the latter might be unavailable if this 301 * code is executed in a misfortunately run irq 302 * (like inside schedule() between switch_mm and 303 * switch_to...). 304 */ 305 306 int offset = pgd_index(address); 307 pgd_t *pgd, *pgd_k; 308 pud_t *pud, *pud_k; 309 pmd_t *pmd, *pmd_k; 310 pte_t *pte_k; 311 312 /* 313 phx_warn("do_page_fault(): vmalloc_fault will not work, " 314 "since current_pgd assign a proper value somewhere\n" 315 "anyhow we don't need this at the moment\n"); 316 317 phx_mmu("vmalloc_fault"); 318 */ 319 pgd = (pgd_t *)current_pgd + offset; 320 pgd_k = init_mm.pgd + offset; 321 322 /* Since we're two-level, we don't need to do both 323 * set_pgd and set_pmd (they do the same thing). If 324 * we go three-level at some point, do the right thing 325 * with pgd_present and set_pgd here. 326 * 327 * Also, since the vmalloc area is global, we don't 328 * need to copy individual PTE's, it is enough to 329 * copy the pgd pointer into the pte page of the 330 * root task. If that is there, we'll find our pte if 331 * it exists. 332 */ 333 334 pud = pud_offset(pgd, address); 335 pud_k = pud_offset(pgd_k, address); 336 if (!pud_present(*pud_k)) 337 goto no_context; 338 339 pmd = pmd_offset(pud, address); 340 pmd_k = pmd_offset(pud_k, address); 341 342 if (!pmd_present(*pmd_k)) 343 goto bad_area_nosemaphore; 344 345 set_pmd(pmd, *pmd_k); 346 347 /* Make sure the actual PTE exists as well to 348 * catch kernel vmalloc-area accesses to non-mapped 349 * addresses. If we don't do this, this will just 350 * silently loop forever. 351 */ 352 353 pte_k = pte_offset_kernel(pmd_k, address); 354 if (!pte_present(*pte_k)) 355 goto no_context; 356 357 return; 358 } 359 } 360