1 /* 2 * PowerPC version 3 * Copyright (C) 1995-1996 Gary Thomas (gdt@linuxppc.org) 4 * 5 * Derived from "arch/i386/mm/fault.c" 6 * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds 7 * 8 * Modified by Cort Dougan and Paul Mackerras. 9 * 10 * Modified for PPC64 by Dave Engebretsen (engebret@ibm.com) 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/signal.h> 19 #include <linux/sched.h> 20 #include <linux/kernel.h> 21 #include <linux/errno.h> 22 #include <linux/string.h> 23 #include <linux/types.h> 24 #include <linux/ptrace.h> 25 #include <linux/mman.h> 26 #include <linux/mm.h> 27 #include <linux/interrupt.h> 28 #include <linux/highmem.h> 29 #include <linux/module.h> 30 #include <linux/kprobes.h> 31 32 #include <asm/page.h> 33 #include <asm/pgtable.h> 34 #include <asm/mmu.h> 35 #include <asm/mmu_context.h> 36 #include <asm/system.h> 37 #include <asm/uaccess.h> 38 #include <asm/tlbflush.h> 39 #include <asm/kdebug.h> 40 #include <asm/siginfo.h> 41 42 #ifdef CONFIG_KPROBES 43 ATOMIC_NOTIFIER_HEAD(notify_page_fault_chain); 44 45 /* Hook to register for page fault notifications */ 46 int register_page_fault_notifier(struct notifier_block *nb) 47 { 48 return atomic_notifier_chain_register(¬ify_page_fault_chain, nb); 49 } 50 51 int unregister_page_fault_notifier(struct notifier_block *nb) 52 { 53 return atomic_notifier_chain_unregister(¬ify_page_fault_chain, nb); 54 } 55 56 static inline int notify_page_fault(enum die_val val, const char *str, 57 struct pt_regs *regs, long err, int trap, int sig) 58 { 59 struct die_args args = { 60 .regs = regs, 61 .str = str, 62 .err = err, 63 .trapnr = trap, 64 .signr = sig 65 }; 66 return atomic_notifier_call_chain(¬ify_page_fault_chain, val, &args); 67 } 68 #else 69 static inline int notify_page_fault(enum die_val val, const char *str, 70 struct pt_regs *regs, long err, int trap, int sig) 71 { 72 return NOTIFY_DONE; 73 } 74 #endif 75 76 /* 77 * Check whether the instruction at regs->nip is a store using 78 * an update addressing form which will update r1. 79 */ 80 static int store_updates_sp(struct pt_regs *regs) 81 { 82 unsigned int inst; 83 84 if (get_user(inst, (unsigned int __user *)regs->nip)) 85 return 0; 86 /* check for 1 in the rA field */ 87 if (((inst >> 16) & 0x1f) != 1) 88 return 0; 89 /* check major opcode */ 90 switch (inst >> 26) { 91 case 37: /* stwu */ 92 case 39: /* stbu */ 93 case 45: /* sthu */ 94 case 53: /* stfsu */ 95 case 55: /* stfdu */ 96 return 1; 97 case 62: /* std or stdu */ 98 return (inst & 3) == 1; 99 case 31: 100 /* check minor opcode */ 101 switch ((inst >> 1) & 0x3ff) { 102 case 181: /* stdux */ 103 case 183: /* stwux */ 104 case 247: /* stbux */ 105 case 439: /* sthux */ 106 case 695: /* stfsux */ 107 case 759: /* stfdux */ 108 return 1; 109 } 110 } 111 return 0; 112 } 113 114 #if !(defined(CONFIG_4xx) || defined(CONFIG_BOOKE)) 115 static void do_dabr(struct pt_regs *regs, unsigned long address, 116 unsigned long error_code) 117 { 118 siginfo_t info; 119 120 if (notify_die(DIE_DABR_MATCH, "dabr_match", regs, error_code, 121 11, SIGSEGV) == NOTIFY_STOP) 122 return; 123 124 if (debugger_dabr_match(regs)) 125 return; 126 127 /* Clear the DABR */ 128 set_dabr(0); 129 130 /* Deliver the signal to userspace */ 131 info.si_signo = SIGTRAP; 132 info.si_errno = 0; 133 info.si_code = TRAP_HWBKPT; 134 info.si_addr = (void __user *)address; 135 force_sig_info(SIGTRAP, &info, current); 136 } 137 #endif /* !(CONFIG_4xx || CONFIG_BOOKE)*/ 138 139 /* 140 * For 600- and 800-family processors, the error_code parameter is DSISR 141 * for a data fault, SRR1 for an instruction fault. For 400-family processors 142 * the error_code parameter is ESR for a data fault, 0 for an instruction 143 * fault. 144 * For 64-bit processors, the error_code parameter is 145 * - DSISR for a non-SLB data access fault, 146 * - SRR1 & 0x08000000 for a non-SLB instruction access fault 147 * - 0 any SLB fault. 148 * 149 * The return value is 0 if the fault was handled, or the signal 150 * number if this is a kernel fault that can't be handled here. 151 */ 152 int __kprobes do_page_fault(struct pt_regs *regs, unsigned long address, 153 unsigned long error_code) 154 { 155 struct vm_area_struct * vma; 156 struct mm_struct *mm = current->mm; 157 siginfo_t info; 158 int code = SEGV_MAPERR; 159 int is_write = 0; 160 int trap = TRAP(regs); 161 int is_exec = trap == 0x400; 162 163 #if !(defined(CONFIG_4xx) || defined(CONFIG_BOOKE)) 164 /* 165 * Fortunately the bit assignments in SRR1 for an instruction 166 * fault and DSISR for a data fault are mostly the same for the 167 * bits we are interested in. But there are some bits which 168 * indicate errors in DSISR but can validly be set in SRR1. 169 */ 170 if (trap == 0x400) 171 error_code &= 0x48200000; 172 else 173 is_write = error_code & DSISR_ISSTORE; 174 #else 175 is_write = error_code & ESR_DST; 176 #endif /* CONFIG_4xx || CONFIG_BOOKE */ 177 178 if (notify_page_fault(DIE_PAGE_FAULT, "page_fault", regs, error_code, 179 11, SIGSEGV) == NOTIFY_STOP) 180 return 0; 181 182 if (trap == 0x300) { 183 if (debugger_fault_handler(regs)) 184 return 0; 185 } 186 187 /* On a kernel SLB miss we can only check for a valid exception entry */ 188 if (!user_mode(regs) && (address >= TASK_SIZE)) 189 return SIGSEGV; 190 191 #if !(defined(CONFIG_4xx) || defined(CONFIG_BOOKE)) 192 if (error_code & DSISR_DABRMATCH) { 193 /* DABR match */ 194 do_dabr(regs, address, error_code); 195 return 0; 196 } 197 #endif /* !(CONFIG_4xx || CONFIG_BOOKE)*/ 198 199 if (in_atomic() || mm == NULL) { 200 if (!user_mode(regs)) 201 return SIGSEGV; 202 /* in_atomic() in user mode is really bad, 203 as is current->mm == NULL. */ 204 printk(KERN_EMERG "Page fault in user mode with" 205 "in_atomic() = %d mm = %p\n", in_atomic(), mm); 206 printk(KERN_EMERG "NIP = %lx MSR = %lx\n", 207 regs->nip, regs->msr); 208 die("Weird page fault", regs, SIGSEGV); 209 } 210 211 /* When running in the kernel we expect faults to occur only to 212 * addresses in user space. All other faults represent errors in the 213 * kernel and should generate an OOPS. Unfortunately, in the case of an 214 * erroneous fault occurring in a code path which already holds mmap_sem 215 * we will deadlock attempting to validate the fault against the 216 * address space. Luckily the kernel only validly references user 217 * space from well defined areas of code, which are listed in the 218 * exceptions table. 219 * 220 * As the vast majority of faults will be valid we will only perform 221 * the source reference check when there is a possibility of a deadlock. 222 * Attempt to lock the address space, if we cannot we then validate the 223 * source. If this is invalid we can skip the address space check, 224 * thus avoiding the deadlock. 225 */ 226 if (!down_read_trylock(&mm->mmap_sem)) { 227 if (!user_mode(regs) && !search_exception_tables(regs->nip)) 228 goto bad_area_nosemaphore; 229 230 down_read(&mm->mmap_sem); 231 } 232 233 vma = find_vma(mm, address); 234 if (!vma) 235 goto bad_area; 236 if (vma->vm_start <= address) 237 goto good_area; 238 if (!(vma->vm_flags & VM_GROWSDOWN)) 239 goto bad_area; 240 241 /* 242 * N.B. The POWER/Open ABI allows programs to access up to 243 * 288 bytes below the stack pointer. 244 * The kernel signal delivery code writes up to about 1.5kB 245 * below the stack pointer (r1) before decrementing it. 246 * The exec code can write slightly over 640kB to the stack 247 * before setting the user r1. Thus we allow the stack to 248 * expand to 1MB without further checks. 249 */ 250 if (address + 0x100000 < vma->vm_end) { 251 /* get user regs even if this fault is in kernel mode */ 252 struct pt_regs *uregs = current->thread.regs; 253 if (uregs == NULL) 254 goto bad_area; 255 256 /* 257 * A user-mode access to an address a long way below 258 * the stack pointer is only valid if the instruction 259 * is one which would update the stack pointer to the 260 * address accessed if the instruction completed, 261 * i.e. either stwu rs,n(r1) or stwux rs,r1,rb 262 * (or the byte, halfword, float or double forms). 263 * 264 * If we don't check this then any write to the area 265 * between the last mapped region and the stack will 266 * expand the stack rather than segfaulting. 267 */ 268 if (address + 2048 < uregs->gpr[1] 269 && (!user_mode(regs) || !store_updates_sp(regs))) 270 goto bad_area; 271 } 272 if (expand_stack(vma, address)) 273 goto bad_area; 274 275 good_area: 276 code = SEGV_ACCERR; 277 #if defined(CONFIG_6xx) 278 if (error_code & 0x95700000) 279 /* an error such as lwarx to I/O controller space, 280 address matching DABR, eciwx, etc. */ 281 goto bad_area; 282 #endif /* CONFIG_6xx */ 283 #if defined(CONFIG_8xx) 284 /* The MPC8xx seems to always set 0x80000000, which is 285 * "undefined". Of those that can be set, this is the only 286 * one which seems bad. 287 */ 288 if (error_code & 0x10000000) 289 /* Guarded storage error. */ 290 goto bad_area; 291 #endif /* CONFIG_8xx */ 292 293 if (is_exec) { 294 #ifdef CONFIG_PPC64 295 /* protection fault */ 296 if (error_code & DSISR_PROTFAULT) 297 goto bad_area; 298 if (!(vma->vm_flags & VM_EXEC)) 299 goto bad_area; 300 #endif 301 #if defined(CONFIG_4xx) || defined(CONFIG_BOOKE) 302 pte_t *ptep; 303 pmd_t *pmdp; 304 305 /* Since 4xx/Book-E supports per-page execute permission, 306 * we lazily flush dcache to icache. */ 307 ptep = NULL; 308 if (get_pteptr(mm, address, &ptep, &pmdp)) { 309 spinlock_t *ptl = pte_lockptr(mm, pmdp); 310 spin_lock(ptl); 311 if (pte_present(*ptep)) { 312 struct page *page = pte_page(*ptep); 313 314 if (!test_bit(PG_arch_1, &page->flags)) { 315 flush_dcache_icache_page(page); 316 set_bit(PG_arch_1, &page->flags); 317 } 318 pte_update(ptep, 0, _PAGE_HWEXEC); 319 _tlbie(address); 320 pte_unmap_unlock(ptep, ptl); 321 up_read(&mm->mmap_sem); 322 return 0; 323 } 324 pte_unmap_unlock(ptep, ptl); 325 } 326 #endif 327 /* a write */ 328 } else if (is_write) { 329 if (!(vma->vm_flags & VM_WRITE)) 330 goto bad_area; 331 /* a read */ 332 } else { 333 /* protection fault */ 334 if (error_code & 0x08000000) 335 goto bad_area; 336 if (!(vma->vm_flags & (VM_READ | VM_EXEC))) 337 goto bad_area; 338 } 339 340 /* 341 * If for any reason at all we couldn't handle the fault, 342 * make sure we exit gracefully rather than endlessly redo 343 * the fault. 344 */ 345 survive: 346 switch (handle_mm_fault(mm, vma, address, is_write)) { 347 348 case VM_FAULT_MINOR: 349 current->min_flt++; 350 break; 351 case VM_FAULT_MAJOR: 352 current->maj_flt++; 353 break; 354 case VM_FAULT_SIGBUS: 355 goto do_sigbus; 356 case VM_FAULT_OOM: 357 goto out_of_memory; 358 default: 359 BUG(); 360 } 361 362 up_read(&mm->mmap_sem); 363 return 0; 364 365 bad_area: 366 up_read(&mm->mmap_sem); 367 368 bad_area_nosemaphore: 369 /* User mode accesses cause a SIGSEGV */ 370 if (user_mode(regs)) { 371 _exception(SIGSEGV, regs, code, address); 372 return 0; 373 } 374 375 if (is_exec && (error_code & DSISR_PROTFAULT) 376 && printk_ratelimit()) 377 printk(KERN_CRIT "kernel tried to execute NX-protected" 378 " page (%lx) - exploit attempt? (uid: %d)\n", 379 address, current->uid); 380 381 return SIGSEGV; 382 383 /* 384 * We ran out of memory, or some other thing happened to us that made 385 * us unable to handle the page fault gracefully. 386 */ 387 out_of_memory: 388 up_read(&mm->mmap_sem); 389 if (current->pid == 1) { 390 yield(); 391 down_read(&mm->mmap_sem); 392 goto survive; 393 } 394 printk("VM: killing process %s\n", current->comm); 395 if (user_mode(regs)) 396 do_exit(SIGKILL); 397 return SIGKILL; 398 399 do_sigbus: 400 up_read(&mm->mmap_sem); 401 if (user_mode(regs)) { 402 info.si_signo = SIGBUS; 403 info.si_errno = 0; 404 info.si_code = BUS_ADRERR; 405 info.si_addr = (void __user *)address; 406 force_sig_info(SIGBUS, &info, current); 407 return 0; 408 } 409 return SIGBUS; 410 } 411 412 /* 413 * bad_page_fault is called when we have a bad access from the kernel. 414 * It is called from the DSI and ISI handlers in head.S and from some 415 * of the procedures in traps.c. 416 */ 417 void bad_page_fault(struct pt_regs *regs, unsigned long address, int sig) 418 { 419 const struct exception_table_entry *entry; 420 421 /* Are we prepared to handle this fault? */ 422 if ((entry = search_exception_tables(regs->nip)) != NULL) { 423 regs->nip = entry->fixup; 424 return; 425 } 426 427 /* kernel has accessed a bad area */ 428 429 printk(KERN_ALERT "Unable to handle kernel paging request for "); 430 switch (regs->trap) { 431 case 0x300: 432 case 0x380: 433 printk("data at address 0x%08lx\n", regs->dar); 434 break; 435 case 0x400: 436 case 0x480: 437 printk("instruction fetch\n"); 438 break; 439 default: 440 printk("unknown fault\n"); 441 } 442 printk(KERN_ALERT "Faulting instruction address: 0x%08lx\n", 443 regs->nip); 444 445 die("Kernel access of bad area", regs, sig); 446 } 447