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/pagemap.h> 26 #include <linux/ptrace.h> 27 #include <linux/mman.h> 28 #include <linux/mm.h> 29 #include <linux/interrupt.h> 30 #include <linux/highmem.h> 31 #include <linux/extable.h> 32 #include <linux/kprobes.h> 33 #include <linux/kdebug.h> 34 #include <linux/perf_event.h> 35 #include <linux/ratelimit.h> 36 #include <linux/context_tracking.h> 37 #include <linux/hugetlb.h> 38 #include <linux/uaccess.h> 39 40 #include <asm/firmware.h> 41 #include <asm/page.h> 42 #include <asm/pgtable.h> 43 #include <asm/mmu.h> 44 #include <asm/mmu_context.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 inst is a store using 70 * an update addressing form which will update r1. 71 */ 72 static bool store_updates_sp(unsigned int inst) 73 { 74 /* check for 1 in the rA field */ 75 if (((inst >> 16) & 0x1f) != 1) 76 return false; 77 /* check major opcode */ 78 switch (inst >> 26) { 79 case OP_STWU: 80 case OP_STBU: 81 case OP_STHU: 82 case OP_STFSU: 83 case OP_STFDU: 84 return true; 85 case OP_STD: /* std or stdu */ 86 return (inst & 3) == 1; 87 case OP_31: 88 /* check minor opcode */ 89 switch ((inst >> 1) & 0x3ff) { 90 case OP_31_XOP_STDUX: 91 case OP_31_XOP_STWUX: 92 case OP_31_XOP_STBUX: 93 case OP_31_XOP_STHUX: 94 case OP_31_XOP_STFSUX: 95 case OP_31_XOP_STFDUX: 96 return true; 97 } 98 } 99 return false; 100 } 101 /* 102 * do_page_fault error handling helpers 103 */ 104 105 static int 106 __bad_area_nosemaphore(struct pt_regs *regs, unsigned long address, int si_code) 107 { 108 /* 109 * If we are in kernel mode, bail out with a SEGV, this will 110 * be caught by the assembly which will restore the non-volatile 111 * registers before calling bad_page_fault() 112 */ 113 if (!user_mode(regs)) 114 return SIGSEGV; 115 116 _exception(SIGSEGV, regs, si_code, address); 117 118 return 0; 119 } 120 121 static noinline int bad_area_nosemaphore(struct pt_regs *regs, unsigned long address) 122 { 123 return __bad_area_nosemaphore(regs, address, SEGV_MAPERR); 124 } 125 126 static int __bad_area(struct pt_regs *regs, unsigned long address, int si_code) 127 { 128 struct mm_struct *mm = current->mm; 129 130 /* 131 * Something tried to access memory that isn't in our memory map.. 132 * Fix it, but check if it's kernel or user first.. 133 */ 134 up_read(&mm->mmap_sem); 135 136 return __bad_area_nosemaphore(regs, address, si_code); 137 } 138 139 static noinline int bad_area(struct pt_regs *regs, unsigned long address) 140 { 141 return __bad_area(regs, address, SEGV_MAPERR); 142 } 143 144 static int bad_key_fault_exception(struct pt_regs *regs, unsigned long address, 145 int pkey) 146 { 147 /* 148 * If we are in kernel mode, bail out with a SEGV, this will 149 * be caught by the assembly which will restore the non-volatile 150 * registers before calling bad_page_fault() 151 */ 152 if (!user_mode(regs)) 153 return SIGSEGV; 154 155 _exception_pkey(regs, address, pkey); 156 157 return 0; 158 } 159 160 static noinline int bad_access(struct pt_regs *regs, unsigned long address) 161 { 162 return __bad_area(regs, address, SEGV_ACCERR); 163 } 164 165 static int do_sigbus(struct pt_regs *regs, unsigned long address, 166 vm_fault_t fault) 167 { 168 if (!user_mode(regs)) 169 return SIGBUS; 170 171 current->thread.trap_nr = BUS_ADRERR; 172 #ifdef CONFIG_MEMORY_FAILURE 173 if (fault & (VM_FAULT_HWPOISON|VM_FAULT_HWPOISON_LARGE)) { 174 unsigned int lsb = 0; /* shutup gcc */ 175 176 pr_err("MCE: Killing %s:%d due to hardware memory corruption fault at %lx\n", 177 current->comm, current->pid, address); 178 179 if (fault & VM_FAULT_HWPOISON_LARGE) 180 lsb = hstate_index_to_shift(VM_FAULT_GET_HINDEX(fault)); 181 if (fault & VM_FAULT_HWPOISON) 182 lsb = PAGE_SHIFT; 183 184 force_sig_mceerr(BUS_MCEERR_AR, (void __user *)address, lsb, 185 current); 186 return 0; 187 } 188 189 #endif 190 force_sig_fault(SIGBUS, BUS_ADRERR, (void __user *)address, current); 191 return 0; 192 } 193 194 static int mm_fault_error(struct pt_regs *regs, unsigned long addr, 195 vm_fault_t fault) 196 { 197 /* 198 * Kernel page fault interrupted by SIGKILL. We have no reason to 199 * continue processing. 200 */ 201 if (fatal_signal_pending(current) && !user_mode(regs)) 202 return SIGKILL; 203 204 /* Out of memory */ 205 if (fault & VM_FAULT_OOM) { 206 /* 207 * We ran out of memory, or some other thing happened to us that 208 * made us unable to handle the page fault gracefully. 209 */ 210 if (!user_mode(regs)) 211 return SIGSEGV; 212 pagefault_out_of_memory(); 213 } else { 214 if (fault & (VM_FAULT_SIGBUS|VM_FAULT_HWPOISON| 215 VM_FAULT_HWPOISON_LARGE)) 216 return do_sigbus(regs, addr, fault); 217 else if (fault & VM_FAULT_SIGSEGV) 218 return bad_area_nosemaphore(regs, addr); 219 else 220 BUG(); 221 } 222 return 0; 223 } 224 225 /* Is this a bad kernel fault ? */ 226 static bool bad_kernel_fault(bool is_exec, unsigned long error_code, 227 unsigned long address) 228 { 229 /* NX faults set DSISR_PROTFAULT on the 8xx, DSISR_NOEXEC_OR_G on others */ 230 if (is_exec && (error_code & (DSISR_NOEXEC_OR_G | DSISR_KEYFAULT | 231 DSISR_PROTFAULT))) { 232 printk_ratelimited(KERN_CRIT "kernel tried to execute" 233 " exec-protected page (%lx) -" 234 "exploit attempt? (uid: %d)\n", 235 address, from_kuid(&init_user_ns, 236 current_uid())); 237 } 238 return is_exec || (address >= TASK_SIZE); 239 } 240 241 static bool bad_stack_expansion(struct pt_regs *regs, unsigned long address, 242 struct vm_area_struct *vma, unsigned int flags, 243 bool *must_retry) 244 { 245 /* 246 * N.B. The POWER/Open ABI allows programs to access up to 247 * 288 bytes below the stack pointer. 248 * The kernel signal delivery code writes up to about 1.5kB 249 * below the stack pointer (r1) before decrementing it. 250 * The exec code can write slightly over 640kB to the stack 251 * before setting the user r1. Thus we allow the stack to 252 * expand to 1MB without further checks. 253 */ 254 if (address + 0x100000 < vma->vm_end) { 255 unsigned int __user *nip = (unsigned int __user *)regs->nip; 256 /* get user regs even if this fault is in kernel mode */ 257 struct pt_regs *uregs = current->thread.regs; 258 if (uregs == NULL) 259 return true; 260 261 /* 262 * A user-mode access to an address a long way below 263 * the stack pointer is only valid if the instruction 264 * is one which would update the stack pointer to the 265 * address accessed if the instruction completed, 266 * i.e. either stwu rs,n(r1) or stwux rs,r1,rb 267 * (or the byte, halfword, float or double forms). 268 * 269 * If we don't check this then any write to the area 270 * between the last mapped region and the stack will 271 * expand the stack rather than segfaulting. 272 */ 273 if (address + 2048 >= uregs->gpr[1]) 274 return false; 275 276 if ((flags & FAULT_FLAG_WRITE) && (flags & FAULT_FLAG_USER) && 277 access_ok(nip, sizeof(*nip))) { 278 unsigned int inst; 279 int res; 280 281 pagefault_disable(); 282 res = __get_user_inatomic(inst, nip); 283 pagefault_enable(); 284 if (!res) 285 return !store_updates_sp(inst); 286 *must_retry = true; 287 } 288 return true; 289 } 290 return false; 291 } 292 293 static bool access_error(bool is_write, bool is_exec, 294 struct vm_area_struct *vma) 295 { 296 /* 297 * Allow execution from readable areas if the MMU does not 298 * provide separate controls over reading and executing. 299 * 300 * Note: That code used to not be enabled for 4xx/BookE. 301 * It is now as I/D cache coherency for these is done at 302 * set_pte_at() time and I see no reason why the test 303 * below wouldn't be valid on those processors. This -may- 304 * break programs compiled with a really old ABI though. 305 */ 306 if (is_exec) { 307 return !(vma->vm_flags & VM_EXEC) && 308 (cpu_has_feature(CPU_FTR_NOEXECUTE) || 309 !(vma->vm_flags & (VM_READ | VM_WRITE))); 310 } 311 312 if (is_write) { 313 if (unlikely(!(vma->vm_flags & VM_WRITE))) 314 return true; 315 return false; 316 } 317 318 if (unlikely(!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)))) 319 return true; 320 /* 321 * We should ideally do the vma pkey access check here. But in the 322 * fault path, handle_mm_fault() also does the same check. To avoid 323 * these multiple checks, we skip it here and handle access error due 324 * to pkeys later. 325 */ 326 return false; 327 } 328 329 #ifdef CONFIG_PPC_SMLPAR 330 static inline void cmo_account_page_fault(void) 331 { 332 if (firmware_has_feature(FW_FEATURE_CMO)) { 333 u32 page_ins; 334 335 preempt_disable(); 336 page_ins = be32_to_cpu(get_lppaca()->page_ins); 337 page_ins += 1 << PAGE_FACTOR; 338 get_lppaca()->page_ins = cpu_to_be32(page_ins); 339 preempt_enable(); 340 } 341 } 342 #else 343 static inline void cmo_account_page_fault(void) { } 344 #endif /* CONFIG_PPC_SMLPAR */ 345 346 #ifdef CONFIG_PPC_BOOK3S 347 static void sanity_check_fault(bool is_write, bool is_user, 348 unsigned long error_code, unsigned long address) 349 { 350 /* 351 * Userspace trying to access kernel address, we get PROTFAULT for that. 352 */ 353 if (is_user && address >= TASK_SIZE) { 354 pr_crit_ratelimited("%s[%d]: User access of kernel address (%lx) - exploit attempt? (uid: %d)\n", 355 current->comm, current->pid, address, 356 from_kuid(&init_user_ns, current_uid())); 357 return; 358 } 359 360 /* 361 * For hash translation mode, we should never get a 362 * PROTFAULT. Any update to pte to reduce access will result in us 363 * removing the hash page table entry, thus resulting in a DSISR_NOHPTE 364 * fault instead of DSISR_PROTFAULT. 365 * 366 * A pte update to relax the access will not result in a hash page table 367 * entry invalidate and hence can result in DSISR_PROTFAULT. 368 * ptep_set_access_flags() doesn't do a hpte flush. This is why we have 369 * the special !is_write in the below conditional. 370 * 371 * For platforms that doesn't supports coherent icache and do support 372 * per page noexec bit, we do setup things such that we do the 373 * sync between D/I cache via fault. But that is handled via low level 374 * hash fault code (hash_page_do_lazy_icache()) and we should not reach 375 * here in such case. 376 * 377 * For wrong access that can result in PROTFAULT, the above vma->vm_flags 378 * check should handle those and hence we should fall to the bad_area 379 * handling correctly. 380 * 381 * For embedded with per page exec support that doesn't support coherent 382 * icache we do get PROTFAULT and we handle that D/I cache sync in 383 * set_pte_at while taking the noexec/prot fault. Hence this is WARN_ON 384 * is conditional for server MMU. 385 * 386 * For radix, we can get prot fault for autonuma case, because radix 387 * page table will have them marked noaccess for user. 388 */ 389 if (radix_enabled() || is_write) 390 return; 391 392 WARN_ON_ONCE(error_code & DSISR_PROTFAULT); 393 } 394 #else 395 static void sanity_check_fault(bool is_write, bool is_user, 396 unsigned long error_code, unsigned long address) { } 397 #endif /* CONFIG_PPC_BOOK3S */ 398 399 /* 400 * Define the correct "is_write" bit in error_code based 401 * on the processor family 402 */ 403 #if (defined(CONFIG_4xx) || defined(CONFIG_BOOKE)) 404 #define page_fault_is_write(__err) ((__err) & ESR_DST) 405 #define page_fault_is_bad(__err) (0) 406 #else 407 #define page_fault_is_write(__err) ((__err) & DSISR_ISSTORE) 408 #if defined(CONFIG_PPC_8xx) 409 #define page_fault_is_bad(__err) ((__err) & DSISR_NOEXEC_OR_G) 410 #elif defined(CONFIG_PPC64) 411 #define page_fault_is_bad(__err) ((__err) & DSISR_BAD_FAULT_64S) 412 #else 413 #define page_fault_is_bad(__err) ((__err) & DSISR_BAD_FAULT_32S) 414 #endif 415 #endif 416 417 /* 418 * For 600- and 800-family processors, the error_code parameter is DSISR 419 * for a data fault, SRR1 for an instruction fault. For 400-family processors 420 * the error_code parameter is ESR for a data fault, 0 for an instruction 421 * fault. 422 * For 64-bit processors, the error_code parameter is 423 * - DSISR for a non-SLB data access fault, 424 * - SRR1 & 0x08000000 for a non-SLB instruction access fault 425 * - 0 any SLB fault. 426 * 427 * The return value is 0 if the fault was handled, or the signal 428 * number if this is a kernel fault that can't be handled here. 429 */ 430 static int __do_page_fault(struct pt_regs *regs, unsigned long address, 431 unsigned long error_code) 432 { 433 struct vm_area_struct * vma; 434 struct mm_struct *mm = current->mm; 435 unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE; 436 int is_exec = TRAP(regs) == 0x400; 437 int is_user = user_mode(regs); 438 int is_write = page_fault_is_write(error_code); 439 vm_fault_t fault, major = 0; 440 bool must_retry = false; 441 442 if (notify_page_fault(regs)) 443 return 0; 444 445 if (unlikely(page_fault_is_bad(error_code))) { 446 if (is_user) { 447 _exception(SIGBUS, regs, BUS_OBJERR, address); 448 return 0; 449 } 450 return SIGBUS; 451 } 452 453 /* Additional sanity check(s) */ 454 sanity_check_fault(is_write, is_user, error_code, address); 455 456 /* 457 * The kernel should never take an execute fault nor should it 458 * take a page fault to a kernel address. 459 */ 460 if (unlikely(!is_user && bad_kernel_fault(is_exec, error_code, address))) 461 return SIGSEGV; 462 463 /* 464 * If we're in an interrupt, have no user context or are running 465 * in a region with pagefaults disabled then we must not take the fault 466 */ 467 if (unlikely(faulthandler_disabled() || !mm)) { 468 if (is_user) 469 printk_ratelimited(KERN_ERR "Page fault in user mode" 470 " with faulthandler_disabled()=%d" 471 " mm=%p\n", 472 faulthandler_disabled(), mm); 473 return bad_area_nosemaphore(regs, address); 474 } 475 476 /* We restore the interrupt state now */ 477 if (!arch_irq_disabled_regs(regs)) 478 local_irq_enable(); 479 480 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address); 481 482 if (error_code & DSISR_KEYFAULT) 483 return bad_key_fault_exception(regs, address, 484 get_mm_addr_key(mm, address)); 485 486 /* 487 * We want to do this outside mmap_sem, because reading code around nip 488 * can result in fault, which will cause a deadlock when called with 489 * mmap_sem held 490 */ 491 if (is_user) 492 flags |= FAULT_FLAG_USER; 493 if (is_write) 494 flags |= FAULT_FLAG_WRITE; 495 if (is_exec) 496 flags |= FAULT_FLAG_INSTRUCTION; 497 498 /* When running in the kernel we expect faults to occur only to 499 * addresses in user space. All other faults represent errors in the 500 * kernel and should generate an OOPS. Unfortunately, in the case of an 501 * erroneous fault occurring in a code path which already holds mmap_sem 502 * we will deadlock attempting to validate the fault against the 503 * address space. Luckily the kernel only validly references user 504 * space from well defined areas of code, which are listed in the 505 * exceptions table. 506 * 507 * As the vast majority of faults will be valid we will only perform 508 * the source reference check when there is a possibility of a deadlock. 509 * Attempt to lock the address space, if we cannot we then validate the 510 * source. If this is invalid we can skip the address space check, 511 * thus avoiding the deadlock. 512 */ 513 if (unlikely(!down_read_trylock(&mm->mmap_sem))) { 514 if (!is_user && !search_exception_tables(regs->nip)) 515 return bad_area_nosemaphore(regs, address); 516 517 retry: 518 down_read(&mm->mmap_sem); 519 } else { 520 /* 521 * The above down_read_trylock() might have succeeded in 522 * which case we'll have missed the might_sleep() from 523 * down_read(): 524 */ 525 might_sleep(); 526 } 527 528 vma = find_vma(mm, address); 529 if (unlikely(!vma)) 530 return bad_area(regs, address); 531 if (likely(vma->vm_start <= address)) 532 goto good_area; 533 if (unlikely(!(vma->vm_flags & VM_GROWSDOWN))) 534 return bad_area(regs, address); 535 536 /* The stack is being expanded, check if it's valid */ 537 if (unlikely(bad_stack_expansion(regs, address, vma, flags, 538 &must_retry))) { 539 if (!must_retry) 540 return bad_area(regs, address); 541 542 up_read(&mm->mmap_sem); 543 if (fault_in_pages_readable((const char __user *)regs->nip, 544 sizeof(unsigned int))) 545 return bad_area_nosemaphore(regs, address); 546 goto retry; 547 } 548 549 /* Try to expand it */ 550 if (unlikely(expand_stack(vma, address))) 551 return bad_area(regs, address); 552 553 good_area: 554 if (unlikely(access_error(is_write, is_exec, vma))) 555 return bad_access(regs, address); 556 557 /* 558 * If for any reason at all we couldn't handle the fault, 559 * make sure we exit gracefully rather than endlessly redo 560 * the fault. 561 */ 562 fault = handle_mm_fault(vma, address, flags); 563 564 #ifdef CONFIG_PPC_MEM_KEYS 565 /* 566 * we skipped checking for access error due to key earlier. 567 * Check that using handle_mm_fault error return. 568 */ 569 if (unlikely(fault & VM_FAULT_SIGSEGV) && 570 !arch_vma_access_permitted(vma, is_write, is_exec, 0)) { 571 572 int pkey = vma_pkey(vma); 573 574 up_read(&mm->mmap_sem); 575 return bad_key_fault_exception(regs, address, pkey); 576 } 577 #endif /* CONFIG_PPC_MEM_KEYS */ 578 579 major |= fault & VM_FAULT_MAJOR; 580 581 /* 582 * Handle the retry right now, the mmap_sem has been released in that 583 * case. 584 */ 585 if (unlikely(fault & VM_FAULT_RETRY)) { 586 /* We retry only once */ 587 if (flags & FAULT_FLAG_ALLOW_RETRY) { 588 /* 589 * Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk 590 * of starvation. 591 */ 592 flags &= ~FAULT_FLAG_ALLOW_RETRY; 593 flags |= FAULT_FLAG_TRIED; 594 if (!fatal_signal_pending(current)) 595 goto retry; 596 } 597 598 /* 599 * User mode? Just return to handle the fatal exception otherwise 600 * return to bad_page_fault 601 */ 602 return is_user ? 0 : SIGBUS; 603 } 604 605 up_read(¤t->mm->mmap_sem); 606 607 if (unlikely(fault & VM_FAULT_ERROR)) 608 return mm_fault_error(regs, address, fault); 609 610 /* 611 * Major/minor page fault accounting. 612 */ 613 if (major) { 614 current->maj_flt++; 615 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, regs, address); 616 cmo_account_page_fault(); 617 } else { 618 current->min_flt++; 619 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, regs, address); 620 } 621 return 0; 622 } 623 NOKPROBE_SYMBOL(__do_page_fault); 624 625 int do_page_fault(struct pt_regs *regs, unsigned long address, 626 unsigned long error_code) 627 { 628 enum ctx_state prev_state = exception_enter(); 629 int rc = __do_page_fault(regs, address, error_code); 630 exception_exit(prev_state); 631 return rc; 632 } 633 NOKPROBE_SYMBOL(do_page_fault); 634 635 /* 636 * bad_page_fault is called when we have a bad access from the kernel. 637 * It is called from the DSI and ISI handlers in head.S and from some 638 * of the procedures in traps.c. 639 */ 640 void bad_page_fault(struct pt_regs *regs, unsigned long address, int sig) 641 { 642 const struct exception_table_entry *entry; 643 644 /* Are we prepared to handle this fault? */ 645 if ((entry = search_exception_tables(regs->nip)) != NULL) { 646 regs->nip = extable_fixup(entry); 647 return; 648 } 649 650 /* kernel has accessed a bad area */ 651 652 switch (TRAP(regs)) { 653 case 0x300: 654 case 0x380: 655 case 0xe00: 656 pr_alert("BUG: %s at 0x%08lx\n", 657 regs->dar < PAGE_SIZE ? "Kernel NULL pointer dereference" : 658 "Unable to handle kernel data access", regs->dar); 659 break; 660 case 0x400: 661 case 0x480: 662 pr_alert("BUG: Unable to handle kernel instruction fetch%s", 663 regs->nip < PAGE_SIZE ? " (NULL pointer?)\n" : "\n"); 664 break; 665 case 0x600: 666 pr_alert("BUG: Unable to handle kernel unaligned access at 0x%08lx\n", 667 regs->dar); 668 break; 669 default: 670 pr_alert("BUG: Unable to handle unknown paging fault at 0x%08lx\n", 671 regs->dar); 672 break; 673 } 674 printk(KERN_ALERT "Faulting instruction address: 0x%08lx\n", 675 regs->nip); 676 677 if (task_stack_end_corrupted(current)) 678 printk(KERN_ALERT "Thread overran stack, or stack corrupted\n"); 679 680 die("Kernel access of bad area", regs, sig); 681 } 682