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/sched/task_stack.h> 21 #include <linux/kernel.h> 22 #include <linux/errno.h> 23 #include <linux/string.h> 24 #include <linux/types.h> 25 #include <linux/ptrace.h> 26 #include <linux/mman.h> 27 #include <linux/mm.h> 28 #include <linux/interrupt.h> 29 #include <linux/highmem.h> 30 #include <linux/extable.h> 31 #include <linux/kprobes.h> 32 #include <linux/kdebug.h> 33 #include <linux/perf_event.h> 34 #include <linux/ratelimit.h> 35 #include <linux/context_tracking.h> 36 #include <linux/hugetlb.h> 37 #include <linux/uaccess.h> 38 39 #include <asm/firmware.h> 40 #include <asm/page.h> 41 #include <asm/pgtable.h> 42 #include <asm/mmu.h> 43 #include <asm/mmu_context.h> 44 #include <asm/tlbflush.h> 45 #include <asm/siginfo.h> 46 #include <asm/debug.h> 47 48 static inline bool notify_page_fault(struct pt_regs *regs) 49 { 50 bool ret = false; 51 52 #ifdef CONFIG_KPROBES 53 /* kprobe_running() needs smp_processor_id() */ 54 if (!user_mode(regs)) { 55 preempt_disable(); 56 if (kprobe_running() && kprobe_fault_handler(regs, 11)) 57 ret = true; 58 preempt_enable(); 59 } 60 #endif /* CONFIG_KPROBES */ 61 62 if (unlikely(debugger_fault_handler(regs))) 63 ret = true; 64 65 return ret; 66 } 67 68 /* 69 * Check whether the instruction at regs->nip is a store using 70 * an update addressing form which will update r1. 71 */ 72 static bool store_updates_sp(struct pt_regs *regs) 73 { 74 unsigned int inst; 75 76 if (get_user(inst, (unsigned int __user *)regs->nip)) 77 return false; 78 /* check for 1 in the rA field */ 79 if (((inst >> 16) & 0x1f) != 1) 80 return false; 81 /* check major opcode */ 82 switch (inst >> 26) { 83 case 37: /* stwu */ 84 case 39: /* stbu */ 85 case 45: /* sthu */ 86 case 53: /* stfsu */ 87 case 55: /* stfdu */ 88 return true; 89 case 62: /* std or stdu */ 90 return (inst & 3) == 1; 91 case 31: 92 /* check minor opcode */ 93 switch ((inst >> 1) & 0x3ff) { 94 case 181: /* stdux */ 95 case 183: /* stwux */ 96 case 247: /* stbux */ 97 case 439: /* sthux */ 98 case 695: /* stfsux */ 99 case 759: /* stfdux */ 100 return true; 101 } 102 } 103 return false; 104 } 105 /* 106 * do_page_fault error handling helpers 107 */ 108 109 static int 110 __bad_area_nosemaphore(struct pt_regs *regs, unsigned long address, int si_code) 111 { 112 /* 113 * If we are in kernel mode, bail out with a SEGV, this will 114 * be caught by the assembly which will restore the non-volatile 115 * registers before calling bad_page_fault() 116 */ 117 if (!user_mode(regs)) 118 return SIGSEGV; 119 120 _exception(SIGSEGV, regs, si_code, address); 121 122 return 0; 123 } 124 125 static noinline int bad_area_nosemaphore(struct pt_regs *regs, unsigned long address) 126 { 127 return __bad_area_nosemaphore(regs, address, SEGV_MAPERR); 128 } 129 130 static int __bad_area(struct pt_regs *regs, unsigned long address, int si_code) 131 { 132 struct mm_struct *mm = current->mm; 133 134 /* 135 * Something tried to access memory that isn't in our memory map.. 136 * Fix it, but check if it's kernel or user first.. 137 */ 138 up_read(&mm->mmap_sem); 139 140 return __bad_area_nosemaphore(regs, address, si_code); 141 } 142 143 static noinline int bad_area(struct pt_regs *regs, unsigned long address) 144 { 145 return __bad_area(regs, address, SEGV_MAPERR); 146 } 147 148 static noinline int bad_access(struct pt_regs *regs, unsigned long address) 149 { 150 return __bad_area(regs, address, SEGV_ACCERR); 151 } 152 153 static int do_sigbus(struct pt_regs *regs, unsigned long address, 154 unsigned int fault) 155 { 156 siginfo_t info; 157 unsigned int lsb = 0; 158 159 if (!user_mode(regs)) 160 return SIGBUS; 161 162 current->thread.trap_nr = BUS_ADRERR; 163 info.si_signo = SIGBUS; 164 info.si_errno = 0; 165 info.si_code = BUS_ADRERR; 166 info.si_addr = (void __user *)address; 167 #ifdef CONFIG_MEMORY_FAILURE 168 if (fault & (VM_FAULT_HWPOISON|VM_FAULT_HWPOISON_LARGE)) { 169 pr_err("MCE: Killing %s:%d due to hardware memory corruption fault at %lx\n", 170 current->comm, current->pid, address); 171 info.si_code = BUS_MCEERR_AR; 172 } 173 174 if (fault & VM_FAULT_HWPOISON_LARGE) 175 lsb = hstate_index_to_shift(VM_FAULT_GET_HINDEX(fault)); 176 if (fault & VM_FAULT_HWPOISON) 177 lsb = PAGE_SHIFT; 178 #endif 179 info.si_addr_lsb = lsb; 180 force_sig_info(SIGBUS, &info, current); 181 return 0; 182 } 183 184 static int mm_fault_error(struct pt_regs *regs, unsigned long addr, int fault) 185 { 186 /* 187 * Kernel page fault interrupted by SIGKILL. We have no reason to 188 * continue processing. 189 */ 190 if (fatal_signal_pending(current) && !user_mode(regs)) 191 return SIGKILL; 192 193 /* Out of memory */ 194 if (fault & VM_FAULT_OOM) { 195 /* 196 * We ran out of memory, or some other thing happened to us that 197 * made us unable to handle the page fault gracefully. 198 */ 199 if (!user_mode(regs)) 200 return SIGSEGV; 201 pagefault_out_of_memory(); 202 } else { 203 if (fault & (VM_FAULT_SIGBUS|VM_FAULT_HWPOISON| 204 VM_FAULT_HWPOISON_LARGE)) 205 return do_sigbus(regs, addr, fault); 206 else if (fault & VM_FAULT_SIGSEGV) 207 return bad_area_nosemaphore(regs, addr); 208 else 209 BUG(); 210 } 211 return 0; 212 } 213 214 /* Is this a bad kernel fault ? */ 215 static bool bad_kernel_fault(bool is_exec, unsigned long error_code, 216 unsigned long address) 217 { 218 if (is_exec && (error_code & (DSISR_NOEXEC_OR_G | DSISR_KEYFAULT))) { 219 printk_ratelimited(KERN_CRIT "kernel tried to execute" 220 " exec-protected page (%lx) -" 221 "exploit attempt? (uid: %d)\n", 222 address, from_kuid(&init_user_ns, 223 current_uid())); 224 } 225 return is_exec || (address >= TASK_SIZE); 226 } 227 228 static bool bad_stack_expansion(struct pt_regs *regs, unsigned long address, 229 struct vm_area_struct *vma, 230 bool store_update_sp) 231 { 232 /* 233 * N.B. The POWER/Open ABI allows programs to access up to 234 * 288 bytes below the stack pointer. 235 * The kernel signal delivery code writes up to about 1.5kB 236 * below the stack pointer (r1) before decrementing it. 237 * The exec code can write slightly over 640kB to the stack 238 * before setting the user r1. Thus we allow the stack to 239 * expand to 1MB without further checks. 240 */ 241 if (address + 0x100000 < vma->vm_end) { 242 /* get user regs even if this fault is in kernel mode */ 243 struct pt_regs *uregs = current->thread.regs; 244 if (uregs == NULL) 245 return true; 246 247 /* 248 * A user-mode access to an address a long way below 249 * the stack pointer is only valid if the instruction 250 * is one which would update the stack pointer to the 251 * address accessed if the instruction completed, 252 * i.e. either stwu rs,n(r1) or stwux rs,r1,rb 253 * (or the byte, halfword, float or double forms). 254 * 255 * If we don't check this then any write to the area 256 * between the last mapped region and the stack will 257 * expand the stack rather than segfaulting. 258 */ 259 if (address + 2048 < uregs->gpr[1] && !store_update_sp) 260 return true; 261 } 262 return false; 263 } 264 265 static bool access_error(bool is_write, bool is_exec, 266 struct vm_area_struct *vma) 267 { 268 /* 269 * Allow execution from readable areas if the MMU does not 270 * provide separate controls over reading and executing. 271 * 272 * Note: That code used to not be enabled for 4xx/BookE. 273 * It is now as I/D cache coherency for these is done at 274 * set_pte_at() time and I see no reason why the test 275 * below wouldn't be valid on those processors. This -may- 276 * break programs compiled with a really old ABI though. 277 */ 278 if (is_exec) { 279 return !(vma->vm_flags & VM_EXEC) && 280 (cpu_has_feature(CPU_FTR_NOEXECUTE) || 281 !(vma->vm_flags & (VM_READ | VM_WRITE))); 282 } 283 284 if (is_write) { 285 if (unlikely(!(vma->vm_flags & VM_WRITE))) 286 return true; 287 return false; 288 } 289 290 if (unlikely(!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)))) 291 return true; 292 293 return false; 294 } 295 296 #ifdef CONFIG_PPC_SMLPAR 297 static inline void cmo_account_page_fault(void) 298 { 299 if (firmware_has_feature(FW_FEATURE_CMO)) { 300 u32 page_ins; 301 302 preempt_disable(); 303 page_ins = be32_to_cpu(get_lppaca()->page_ins); 304 page_ins += 1 << PAGE_FACTOR; 305 get_lppaca()->page_ins = cpu_to_be32(page_ins); 306 preempt_enable(); 307 } 308 } 309 #else 310 static inline void cmo_account_page_fault(void) { } 311 #endif /* CONFIG_PPC_SMLPAR */ 312 313 #ifdef CONFIG_PPC_STD_MMU 314 static void sanity_check_fault(bool is_write, unsigned long error_code) 315 { 316 /* 317 * For hash translation mode, we should never get a 318 * PROTFAULT. Any update to pte to reduce access will result in us 319 * removing the hash page table entry, thus resulting in a DSISR_NOHPTE 320 * fault instead of DSISR_PROTFAULT. 321 * 322 * A pte update to relax the access will not result in a hash page table 323 * entry invalidate and hence can result in DSISR_PROTFAULT. 324 * ptep_set_access_flags() doesn't do a hpte flush. This is why we have 325 * the special !is_write in the below conditional. 326 * 327 * For platforms that doesn't supports coherent icache and do support 328 * per page noexec bit, we do setup things such that we do the 329 * sync between D/I cache via fault. But that is handled via low level 330 * hash fault code (hash_page_do_lazy_icache()) and we should not reach 331 * here in such case. 332 * 333 * For wrong access that can result in PROTFAULT, the above vma->vm_flags 334 * check should handle those and hence we should fall to the bad_area 335 * handling correctly. 336 * 337 * For embedded with per page exec support that doesn't support coherent 338 * icache we do get PROTFAULT and we handle that D/I cache sync in 339 * set_pte_at while taking the noexec/prot fault. Hence this is WARN_ON 340 * is conditional for server MMU. 341 * 342 * For radix, we can get prot fault for autonuma case, because radix 343 * page table will have them marked noaccess for user. 344 */ 345 if (!radix_enabled() && !is_write) 346 WARN_ON_ONCE(error_code & DSISR_PROTFAULT); 347 } 348 #else 349 static void sanity_check_fault(bool is_write, unsigned long error_code) { } 350 #endif /* CONFIG_PPC_STD_MMU */ 351 352 /* 353 * Define the correct "is_write" bit in error_code based 354 * on the processor family 355 */ 356 #if (defined(CONFIG_4xx) || defined(CONFIG_BOOKE)) 357 #define page_fault_is_write(__err) ((__err) & ESR_DST) 358 #define page_fault_is_bad(__err) (0) 359 #else 360 #define page_fault_is_write(__err) ((__err) & DSISR_ISSTORE) 361 #if defined(CONFIG_PPC_8xx) 362 #define page_fault_is_bad(__err) ((__err) & DSISR_NOEXEC_OR_G) 363 #elif defined(CONFIG_PPC64) 364 #define page_fault_is_bad(__err) ((__err) & DSISR_BAD_FAULT_64S) 365 #else 366 #define page_fault_is_bad(__err) ((__err) & DSISR_BAD_FAULT_32S) 367 #endif 368 #endif 369 370 /* 371 * For 600- and 800-family processors, the error_code parameter is DSISR 372 * for a data fault, SRR1 for an instruction fault. For 400-family processors 373 * the error_code parameter is ESR for a data fault, 0 for an instruction 374 * fault. 375 * For 64-bit processors, the error_code parameter is 376 * - DSISR for a non-SLB data access fault, 377 * - SRR1 & 0x08000000 for a non-SLB instruction access fault 378 * - 0 any SLB fault. 379 * 380 * The return value is 0 if the fault was handled, or the signal 381 * number if this is a kernel fault that can't be handled here. 382 */ 383 static int __do_page_fault(struct pt_regs *regs, unsigned long address, 384 unsigned long error_code) 385 { 386 struct vm_area_struct * vma; 387 struct mm_struct *mm = current->mm; 388 unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE; 389 int is_exec = TRAP(regs) == 0x400; 390 int is_user = user_mode(regs); 391 int is_write = page_fault_is_write(error_code); 392 int fault, major = 0; 393 bool store_update_sp = false; 394 395 if (notify_page_fault(regs)) 396 return 0; 397 398 if (unlikely(page_fault_is_bad(error_code))) { 399 if (is_user) { 400 _exception(SIGBUS, regs, BUS_OBJERR, address); 401 return 0; 402 } 403 return SIGBUS; 404 } 405 406 /* Additional sanity check(s) */ 407 sanity_check_fault(is_write, error_code); 408 409 /* 410 * The kernel should never take an execute fault nor should it 411 * take a page fault to a kernel address. 412 */ 413 if (unlikely(!is_user && bad_kernel_fault(is_exec, error_code, address))) 414 return SIGSEGV; 415 416 /* 417 * If we're in an interrupt, have no user context or are running 418 * in a region with pagefaults disabled then we must not take the fault 419 */ 420 if (unlikely(faulthandler_disabled() || !mm)) { 421 if (is_user) 422 printk_ratelimited(KERN_ERR "Page fault in user mode" 423 " with faulthandler_disabled()=%d" 424 " mm=%p\n", 425 faulthandler_disabled(), mm); 426 return bad_area_nosemaphore(regs, address); 427 } 428 429 /* We restore the interrupt state now */ 430 if (!arch_irq_disabled_regs(regs)) 431 local_irq_enable(); 432 433 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address); 434 435 /* 436 * We want to do this outside mmap_sem, because reading code around nip 437 * can result in fault, which will cause a deadlock when called with 438 * mmap_sem held 439 */ 440 if (is_write && is_user) 441 store_update_sp = store_updates_sp(regs); 442 443 if (is_user) 444 flags |= FAULT_FLAG_USER; 445 if (is_write) 446 flags |= FAULT_FLAG_WRITE; 447 if (is_exec) 448 flags |= FAULT_FLAG_INSTRUCTION; 449 450 /* When running in the kernel we expect faults to occur only to 451 * addresses in user space. All other faults represent errors in the 452 * kernel and should generate an OOPS. Unfortunately, in the case of an 453 * erroneous fault occurring in a code path which already holds mmap_sem 454 * we will deadlock attempting to validate the fault against the 455 * address space. Luckily the kernel only validly references user 456 * space from well defined areas of code, which are listed in the 457 * exceptions table. 458 * 459 * As the vast majority of faults will be valid we will only perform 460 * the source reference check when there is a possibility of a deadlock. 461 * Attempt to lock the address space, if we cannot we then validate the 462 * source. If this is invalid we can skip the address space check, 463 * thus avoiding the deadlock. 464 */ 465 if (unlikely(!down_read_trylock(&mm->mmap_sem))) { 466 if (!is_user && !search_exception_tables(regs->nip)) 467 return bad_area_nosemaphore(regs, address); 468 469 retry: 470 down_read(&mm->mmap_sem); 471 } else { 472 /* 473 * The above down_read_trylock() might have succeeded in 474 * which case we'll have missed the might_sleep() from 475 * down_read(): 476 */ 477 might_sleep(); 478 } 479 480 vma = find_vma(mm, address); 481 if (unlikely(!vma)) 482 return bad_area(regs, address); 483 if (likely(vma->vm_start <= address)) 484 goto good_area; 485 if (unlikely(!(vma->vm_flags & VM_GROWSDOWN))) 486 return bad_area(regs, address); 487 488 /* The stack is being expanded, check if it's valid */ 489 if (unlikely(bad_stack_expansion(regs, address, vma, store_update_sp))) 490 return bad_area(regs, address); 491 492 /* Try to expand it */ 493 if (unlikely(expand_stack(vma, address))) 494 return bad_area(regs, address); 495 496 good_area: 497 if (unlikely(access_error(is_write, is_exec, vma))) 498 return bad_access(regs, address); 499 500 /* 501 * If for any reason at all we couldn't handle the fault, 502 * make sure we exit gracefully rather than endlessly redo 503 * the fault. 504 */ 505 fault = handle_mm_fault(vma, address, flags); 506 major |= fault & VM_FAULT_MAJOR; 507 508 /* 509 * Handle the retry right now, the mmap_sem has been released in that 510 * case. 511 */ 512 if (unlikely(fault & VM_FAULT_RETRY)) { 513 /* We retry only once */ 514 if (flags & FAULT_FLAG_ALLOW_RETRY) { 515 /* 516 * Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk 517 * of starvation. 518 */ 519 flags &= ~FAULT_FLAG_ALLOW_RETRY; 520 flags |= FAULT_FLAG_TRIED; 521 if (!fatal_signal_pending(current)) 522 goto retry; 523 } 524 525 /* 526 * User mode? Just return to handle the fatal exception otherwise 527 * return to bad_page_fault 528 */ 529 return is_user ? 0 : SIGBUS; 530 } 531 532 up_read(¤t->mm->mmap_sem); 533 534 if (unlikely(fault & VM_FAULT_ERROR)) 535 return mm_fault_error(regs, address, fault); 536 537 /* 538 * Major/minor page fault accounting. 539 */ 540 if (major) { 541 current->maj_flt++; 542 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, regs, address); 543 cmo_account_page_fault(); 544 } else { 545 current->min_flt++; 546 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, regs, address); 547 } 548 return 0; 549 } 550 NOKPROBE_SYMBOL(__do_page_fault); 551 552 int do_page_fault(struct pt_regs *regs, unsigned long address, 553 unsigned long error_code) 554 { 555 enum ctx_state prev_state = exception_enter(); 556 int rc = __do_page_fault(regs, address, error_code); 557 exception_exit(prev_state); 558 return rc; 559 } 560 NOKPROBE_SYMBOL(do_page_fault); 561 562 /* 563 * bad_page_fault is called when we have a bad access from the kernel. 564 * It is called from the DSI and ISI handlers in head.S and from some 565 * of the procedures in traps.c. 566 */ 567 void bad_page_fault(struct pt_regs *regs, unsigned long address, int sig) 568 { 569 const struct exception_table_entry *entry; 570 571 /* Are we prepared to handle this fault? */ 572 if ((entry = search_exception_tables(regs->nip)) != NULL) { 573 regs->nip = extable_fixup(entry); 574 return; 575 } 576 577 /* kernel has accessed a bad area */ 578 579 switch (regs->trap) { 580 case 0x300: 581 case 0x380: 582 printk(KERN_ALERT "Unable to handle kernel paging request for " 583 "data at address 0x%08lx\n", regs->dar); 584 break; 585 case 0x400: 586 case 0x480: 587 printk(KERN_ALERT "Unable to handle kernel paging request for " 588 "instruction fetch\n"); 589 break; 590 case 0x600: 591 printk(KERN_ALERT "Unable to handle kernel paging request for " 592 "unaligned access at address 0x%08lx\n", regs->dar); 593 break; 594 default: 595 printk(KERN_ALERT "Unable to handle kernel paging request for " 596 "unknown fault\n"); 597 break; 598 } 599 printk(KERN_ALERT "Faulting instruction address: 0x%08lx\n", 600 regs->nip); 601 602 if (task_stack_end_corrupted(current)) 603 printk(KERN_ALERT "Thread overran stack, or stack corrupted\n"); 604 605 die("Kernel access of bad area", regs, sig); 606 } 607