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/extable.h> 21 #include <linux/sched/signal.h> 22 23 #include <linux/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[NR_CPUS]; 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 int si_code; 56 vm_fault_t 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 flags |= FAULT_FLAG_USER; 90 } else { 91 /* If exception was in a syscall, then IRQ's may have 92 * been enabled or disabled. If they were enabled, 93 * reenable them. 94 */ 95 if (regs->sr && (SPR_SR_IEE | SPR_SR_TEE)) 96 local_irq_enable(); 97 } 98 99 mm = tsk->mm; 100 si_code = SEGV_MAPERR; 101 102 /* 103 * If we're in an interrupt or have no user 104 * context, we must not take the fault.. 105 */ 106 107 if (in_interrupt() || !mm) 108 goto no_context; 109 110 retry: 111 down_read(&mm->mmap_sem); 112 vma = find_vma(mm, address); 113 114 if (!vma) 115 goto bad_area; 116 117 if (vma->vm_start <= address) 118 goto good_area; 119 120 if (!(vma->vm_flags & VM_GROWSDOWN)) 121 goto bad_area; 122 123 if (user_mode(regs)) { 124 /* 125 * accessing the stack below usp is always a bug. 126 * we get page-aligned addresses so we can only check 127 * if we're within a page from usp, but that might be 128 * enough to catch brutal errors at least. 129 */ 130 if (address + PAGE_SIZE < regs->sp) 131 goto bad_area; 132 } 133 if (expand_stack(vma, address)) 134 goto bad_area; 135 136 /* 137 * Ok, we have a good vm_area for this memory access, so 138 * we can handle it.. 139 */ 140 141 good_area: 142 si_code = SEGV_ACCERR; 143 144 /* first do some preliminary protection checks */ 145 146 if (write_acc) { 147 if (!(vma->vm_flags & VM_WRITE)) 148 goto bad_area; 149 flags |= FAULT_FLAG_WRITE; 150 } else { 151 /* not present */ 152 if (!(vma->vm_flags & (VM_READ | VM_EXEC))) 153 goto bad_area; 154 } 155 156 /* are we trying to execute nonexecutable area */ 157 if ((vector == 0x400) && !(vma->vm_page_prot.pgprot & _PAGE_EXEC)) 158 goto bad_area; 159 160 /* 161 * If for any reason at all we couldn't handle the fault, 162 * make sure we exit gracefully rather than endlessly redo 163 * the fault. 164 */ 165 166 fault = handle_mm_fault(vma, address, flags); 167 168 if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current)) 169 return; 170 171 if (unlikely(fault & VM_FAULT_ERROR)) { 172 if (fault & VM_FAULT_OOM) 173 goto out_of_memory; 174 else if (fault & VM_FAULT_SIGSEGV) 175 goto bad_area; 176 else if (fault & VM_FAULT_SIGBUS) 177 goto do_sigbus; 178 BUG(); 179 } 180 181 if (flags & FAULT_FLAG_ALLOW_RETRY) { 182 /*RGD modeled on Cris */ 183 if (fault & VM_FAULT_MAJOR) 184 tsk->maj_flt++; 185 else 186 tsk->min_flt++; 187 if (fault & VM_FAULT_RETRY) { 188 flags &= ~FAULT_FLAG_ALLOW_RETRY; 189 flags |= FAULT_FLAG_TRIED; 190 191 /* No need to up_read(&mm->mmap_sem) as we would 192 * have already released it in __lock_page_or_retry 193 * in mm/filemap.c. 194 */ 195 196 goto retry; 197 } 198 } 199 200 up_read(&mm->mmap_sem); 201 return; 202 203 /* 204 * Something tried to access memory that isn't in our memory map.. 205 * Fix it, but check if it's kernel or user first.. 206 */ 207 208 bad_area: 209 up_read(&mm->mmap_sem); 210 211 bad_area_nosemaphore: 212 213 /* User mode accesses just cause a SIGSEGV */ 214 215 if (user_mode(regs)) { 216 force_sig_fault(SIGSEGV, si_code, (void __user *)address, tsk); 217 return; 218 } 219 220 no_context: 221 222 /* Are we prepared to handle this kernel fault? 223 * 224 * (The kernel has valid exception-points in the source 225 * when it acesses user-memory. When it fails in one 226 * of those points, we find it in a table and do a jump 227 * to some fixup code that loads an appropriate error 228 * code) 229 */ 230 231 { 232 const struct exception_table_entry *entry; 233 234 __asm__ __volatile__("l.nop 42"); 235 236 if ((entry = search_exception_tables(regs->pc)) != NULL) { 237 /* Adjust the instruction pointer in the stackframe */ 238 regs->pc = entry->fixup; 239 return; 240 } 241 } 242 243 /* 244 * Oops. The kernel tried to access some bad page. We'll have to 245 * terminate things with extreme prejudice. 246 */ 247 248 if ((unsigned long)(address) < PAGE_SIZE) 249 printk(KERN_ALERT 250 "Unable to handle kernel NULL pointer dereference"); 251 else 252 printk(KERN_ALERT "Unable to handle kernel access"); 253 printk(" at virtual address 0x%08lx\n", address); 254 255 die("Oops", regs, write_acc); 256 257 do_exit(SIGKILL); 258 259 /* 260 * We ran out of memory, or some other thing happened to us that made 261 * us unable to handle the page fault gracefully. 262 */ 263 264 out_of_memory: 265 __asm__ __volatile__("l.nop 42"); 266 __asm__ __volatile__("l.nop 1"); 267 268 up_read(&mm->mmap_sem); 269 if (!user_mode(regs)) 270 goto no_context; 271 pagefault_out_of_memory(); 272 return; 273 274 do_sigbus: 275 up_read(&mm->mmap_sem); 276 277 /* 278 * Send a sigbus, regardless of whether we were in kernel 279 * or user mode. 280 */ 281 force_sig_fault(SIGBUS, BUS_ADRERR, (void __user *)address, tsk); 282 283 /* Kernel mode? Handle exceptions or die */ 284 if (!user_mode(regs)) 285 goto no_context; 286 return; 287 288 vmalloc_fault: 289 { 290 /* 291 * Synchronize this task's top level page-table 292 * with the 'reference' page table. 293 * 294 * Use current_pgd instead of tsk->active_mm->pgd 295 * since the latter might be unavailable if this 296 * code is executed in a misfortunately run irq 297 * (like inside schedule() between switch_mm and 298 * switch_to...). 299 */ 300 301 int offset = pgd_index(address); 302 pgd_t *pgd, *pgd_k; 303 pud_t *pud, *pud_k; 304 pmd_t *pmd, *pmd_k; 305 pte_t *pte_k; 306 307 /* 308 phx_warn("do_page_fault(): vmalloc_fault will not work, " 309 "since current_pgd assign a proper value somewhere\n" 310 "anyhow we don't need this at the moment\n"); 311 312 phx_mmu("vmalloc_fault"); 313 */ 314 pgd = (pgd_t *)current_pgd[smp_processor_id()] + offset; 315 pgd_k = init_mm.pgd + offset; 316 317 /* Since we're two-level, we don't need to do both 318 * set_pgd and set_pmd (they do the same thing). If 319 * we go three-level at some point, do the right thing 320 * with pgd_present and set_pgd here. 321 * 322 * Also, since the vmalloc area is global, we don't 323 * need to copy individual PTE's, it is enough to 324 * copy the pgd pointer into the pte page of the 325 * root task. If that is there, we'll find our pte if 326 * it exists. 327 */ 328 329 pud = pud_offset(pgd, address); 330 pud_k = pud_offset(pgd_k, address); 331 if (!pud_present(*pud_k)) 332 goto no_context; 333 334 pmd = pmd_offset(pud, address); 335 pmd_k = pmd_offset(pud_k, address); 336 337 if (!pmd_present(*pmd_k)) 338 goto bad_area_nosemaphore; 339 340 set_pmd(pmd, *pmd_k); 341 342 /* Make sure the actual PTE exists as well to 343 * catch kernel vmalloc-area accesses to non-mapped 344 * addresses. If we don't do this, this will just 345 * silently loop forever. 346 */ 347 348 pte_k = pte_offset_kernel(pmd_k, address); 349 if (!pte_present(*pte_k)) 350 goto no_context; 351 352 return; 353 } 354 } 355