arch/powerpc/mm/fault.c

   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 #include <linux/kdebug.h>
  32 #include <linux/perf_event.h>
  33 #include <linux/ratelimit.h>
  34 #include <linux/context_tracking.h>
  35 #include <linux/hugetlb.h>
  36 #include <linux/uaccess.h>
  37
  38 #include <asm/firmware.h>
  39 #include <asm/page.h>
  40 #include <asm/pgtable.h>
  41 #include <asm/mmu.h>
  42 #include <asm/mmu_context.h>
  43 #include <asm/tlbflush.h>
  44 #include <asm/siginfo.h>
  45 #include <asm/debug.h>
  46
  47 #include "icswx.h"
  48
  49 #ifdef CONFIG_KPROBES
  50 static inline int notify_page_fault(struct pt_regs *regs)
  51 {
  52         int ret = 0;
  53
  54         /* kprobe_running() needs smp_processor_id() */
  55         if (!user_mode(regs)) {
  56                 preempt_disable();
  57                 if (kprobe_running() && kprobe_fault_handler(regs, 11))
  58                         ret = 1;
  59                 preempt_enable();
  60         }
  61
  62         return ret;
  63 }
  64 #else
  65 static inline int notify_page_fault(struct pt_regs *regs)
  66 {
  67         return 0;
  68 }
  69 #endif
  70
  71 /*
  72  * Check whether the instruction at regs->nip is a store using
  73  * an update addressing form which will update r1.
  74  */
  75 static int store_updates_sp(struct pt_regs *regs)
  76 {
  77         unsigned int inst;
  78
  79         if (get_user(inst, (unsigned int __user *)regs->nip))
  80                 return 0;
  81         /* check for 1 in the rA field */
  82         if (((inst >> 16) & 0x1f) != 1)
  83                 return 0;
  84         /* check major opcode */
  85         switch (inst >> 26) {
  86         case 37:        /* stwu */
  87         case 39:        /* stbu */
  88         case 45:        /* sthu */
  89         case 53:        /* stfsu */
  90         case 55:        /* stfdu */
  91                 return 1;
  92         case 62:        /* std or stdu */
  93                 return (inst & 3) == 1;
  94         case 31:
  95                 /* check minor opcode */
  96                 switch ((inst >> 1) & 0x3ff) {
  97                 case 181:       /* stdux */
  98                 case 183:       /* stwux */
  99                 case 247:       /* stbux */
 100                 case 439:       /* sthux */
 101                 case 695:       /* stfsux */
 102                 case 759:       /* stfdux */
 103                         return 1;
 104                 }
 105         }
 106         return 0;
 107 }
 108 /*
 109  * do_page_fault error handling helpers
 110  */
 111
 112 #define MM_FAULT_RETURN         0
 113 #define MM_FAULT_CONTINUE       -1
 114 #define MM_FAULT_ERR(sig)       (sig)
 115
 116 static int do_sigbus(struct pt_regs *regs, unsigned long address,
 117                      unsigned int fault)
 118 {
 119         siginfo_t info;
 120         unsigned int lsb = 0;
 121
 122         up_read(&current->mm->mmap_sem);
 123
 124         if (!user_mode(regs))
 125                 return MM_FAULT_ERR(SIGBUS);
 126
 127         current->thread.trap_nr = BUS_ADRERR;
 128         info.si_signo = SIGBUS;
 129         info.si_errno = 0;
 130         info.si_code = BUS_ADRERR;
 131         info.si_addr = (void __user *)address;
 132 #ifdef CONFIG_MEMORY_FAILURE
 133         if (fault & (VM_FAULT_HWPOISON|VM_FAULT_HWPOISON_LARGE)) {
 134                 pr_err("MCE: Killing %s:%d due to hardware memory corruption fault at %lx\n",
 135                         current->comm, current->pid, address);
 136                 info.si_code = BUS_MCEERR_AR;
 137         }
 138
 139         if (fault & VM_FAULT_HWPOISON_LARGE)
 140                 lsb = hstate_index_to_shift(VM_FAULT_GET_HINDEX(fault));
 141         if (fault & VM_FAULT_HWPOISON)
 142                 lsb = PAGE_SHIFT;
 143 #endif
 144         info.si_addr_lsb = lsb;
 145         force_sig_info(SIGBUS, &info, current);
 146         return MM_FAULT_RETURN;
 147 }
 148
 149 static int mm_fault_error(struct pt_regs *regs, unsigned long addr, int fault)
 150 {
 151         /*
 152          * Pagefault was interrupted by SIGKILL. We have no reason to
 153          * continue the pagefault.
 154          */
 155         if (fatal_signal_pending(current)) {
 156                 /*
 157                  * If we have retry set, the mmap semaphore will have
 158                  * alrady been released in __lock_page_or_retry(). Else
 159                  * we release it now.
 160                  */
 161                 if (!(fault & VM_FAULT_RETRY))
 162                         up_read(&current->mm->mmap_sem);
 163                 /* Coming from kernel, we need to deal with uaccess fixups */
 164                 if (user_mode(regs))
 165                         return MM_FAULT_RETURN;
 166                 return MM_FAULT_ERR(SIGKILL);
 167         }
 168
 169         /* No fault: be happy */
 170         if (!(fault & VM_FAULT_ERROR))
 171                 return MM_FAULT_CONTINUE;
 172
 173         /* Out of memory */
 174         if (fault & VM_FAULT_OOM) {
 175                 up_read(&current->mm->mmap_sem);
 176
 177                 /*
 178                  * We ran out of memory, or some other thing happened to us that
 179                  * made us unable to handle the page fault gracefully.
 180                  */
 181                 if (!user_mode(regs))
 182                         return MM_FAULT_ERR(SIGKILL);
 183                 pagefault_out_of_memory();
 184                 return MM_FAULT_RETURN;
 185         }
 186
 187         if (fault & (VM_FAULT_SIGBUS|VM_FAULT_HWPOISON|VM_FAULT_HWPOISON_LARGE))
 188                 return do_sigbus(regs, addr, fault);
 189
 190         /* We don't understand the fault code, this is fatal */
 191         BUG();
 192         return MM_FAULT_CONTINUE;
 193 }
 194
 195 /*
 196  * For 600- and 800-family processors, the error_code parameter is DSISR
 197  * for a data fault, SRR1 for an instruction fault. For 400-family processors
 198  * the error_code parameter is ESR for a data fault, 0 for an instruction
 199  * fault.
 200  * For 64-bit processors, the error_code parameter is
 201  *  - DSISR for a non-SLB data access fault,
 202  *  - SRR1 & 0x08000000 for a non-SLB instruction access fault
 203  *  - 0 any SLB fault.
 204  *
 205  * The return value is 0 if the fault was handled, or the signal
 206  * number if this is a kernel fault that can't be handled here.
 207  */
 208 int __kprobes do_page_fault(struct pt_regs *regs, unsigned long address,
 209                             unsigned long error_code)
 210 {
 211         enum ctx_state prev_state = exception_enter();
 212         struct vm_area_struct * vma;
 213         struct mm_struct *mm = current->mm;
 214         unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
 215         int code = SEGV_MAPERR;
 216         int is_write = 0;
 217         int trap = TRAP(regs);
 218         int is_exec = trap == 0x400;
 219         int fault;
 220         int rc = 0, store_update_sp = 0;
 221
 222 #if !(defined(CONFIG_4xx) || defined(CONFIG_BOOKE))
 223         /*
 224          * Fortunately the bit assignments in SRR1 for an instruction
 225          * fault and DSISR for a data fault are mostly the same for the
 226          * bits we are interested in.  But there are some bits which
 227          * indicate errors in DSISR but can validly be set in SRR1.
 228          */
 229         if (trap == 0x400)
 230                 error_code &= 0x48200000;
 231         else
 232                 is_write = error_code & DSISR_ISSTORE;
 233 #else
 234         is_write = error_code & ESR_DST;
 235 #endif /* CONFIG_4xx || CONFIG_BOOKE */
 236
 237 #ifdef CONFIG_PPC_ICSWX
 238         /*
 239          * we need to do this early because this "data storage
 240          * interrupt" does not update the DAR/DEAR so we don't want to
 241          * look at it
 242          */
 243         if (error_code & ICSWX_DSI_UCT) {
 244                 rc = acop_handle_fault(regs, address, error_code);
 245                 if (rc)
 246                         goto bail;
 247         }
 248 #endif /* CONFIG_PPC_ICSWX */
 249
 250         if (notify_page_fault(regs))
 251                 goto bail;
 252
 253         if (unlikely(debugger_fault_handler(regs)))
 254                 goto bail;
 255
 256         /* On a kernel SLB miss we can only check for a valid exception entry */
 257         if (!user_mode(regs) && (address >= TASK_SIZE)) {
 258                 rc = SIGSEGV;
 259                 goto bail;
 260         }
 261
 262 #if !(defined(CONFIG_4xx) || defined(CONFIG_BOOKE) || \
 263                              defined(CONFIG_PPC_BOOK3S_64))
 264         if (error_code & DSISR_DABRMATCH) {
 265                 /* breakpoint match */
 266                 do_break(regs, address, error_code);
 267                 goto bail;
 268         }
 269 #endif
 270
 271         /* We restore the interrupt state now */
 272         if (!arch_irq_disabled_regs(regs))
 273                 local_irq_enable();
 274
 275         if (faulthandler_disabled() || mm == NULL) {
 276                 if (!user_mode(regs)) {
 277                         rc = SIGSEGV;
 278                         goto bail;
 279                 }
 280                 /* faulthandler_disabled() in user mode is really bad,
 281                    as is current->mm == NULL. */
 282                 printk(KERN_EMERG "Page fault in user mode with "
 283                        "faulthandler_disabled() = %d mm = %p\n",
 284                        faulthandler_disabled(), mm);
 285                 printk(KERN_EMERG "NIP = %lx  MSR = %lx\n",
 286                        regs->nip, regs->msr);
 287                 die("Weird page fault", regs, SIGSEGV);
 288         }
 289
 290         perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
 291
 292         /*
 293          * We want to do this outside mmap_sem, because reading code around nip
 294          * can result in fault, which will cause a deadlock when called with
 295          * mmap_sem held
 296          */
 297         if (user_mode(regs))
 298                 store_update_sp = store_updates_sp(regs);
 299
 300         if (user_mode(regs))
 301                 flags |= FAULT_FLAG_USER;
 302
 303         /* When running in the kernel we expect faults to occur only to
 304          * addresses in user space.  All other faults represent errors in the
 305          * kernel and should generate an OOPS.  Unfortunately, in the case of an
 306          * erroneous fault occurring in a code path which already holds mmap_sem
 307          * we will deadlock attempting to validate the fault against the
 308          * address space.  Luckily the kernel only validly references user
 309          * space from well defined areas of code, which are listed in the
 310          * exceptions table.
 311          *
 312          * As the vast majority of faults will be valid we will only perform
 313          * the source reference check when there is a possibility of a deadlock.
 314          * Attempt to lock the address space, if we cannot we then validate the
 315          * source.  If this is invalid we can skip the address space check,
 316          * thus avoiding the deadlock.
 317          */
 318         if (!down_read_trylock(&mm->mmap_sem)) {
 319                 if (!user_mode(regs) && !search_exception_tables(regs->nip))
 320                         goto bad_area_nosemaphore;
 321
 322 retry:
 323                 down_read(&mm->mmap_sem);
 324         } else {
 325                 /*
 326                  * The above down_read_trylock() might have succeeded in
 327                  * which case we'll have missed the might_sleep() from
 328                  * down_read():
 329                  */
 330                 might_sleep();
 331         }
 332
 333         vma = find_vma(mm, address);
 334         if (!vma)
 335                 goto bad_area;
 336         if (vma->vm_start <= address)
 337                 goto good_area;
 338         if (!(vma->vm_flags & VM_GROWSDOWN))
 339                 goto bad_area;
 340
 341         /*
 342          * N.B. The POWER/Open ABI allows programs to access up to
 343          * 288 bytes below the stack pointer.
 344          * The kernel signal delivery code writes up to about 1.5kB
 345          * below the stack pointer (r1) before decrementing it.
 346          * The exec code can write slightly over 640kB to the stack
 347          * before setting the user r1.  Thus we allow the stack to
 348          * expand to 1MB without further checks.
 349          */
 350         if (address + 0x100000 < vma->vm_end) {
 351                 /* get user regs even if this fault is in kernel mode */
 352                 struct pt_regs *uregs = current->thread.regs;
 353                 if (uregs == NULL)
 354                         goto bad_area;
 355
 356                 /*
 357                  * A user-mode access to an address a long way below
 358                  * the stack pointer is only valid if the instruction
 359                  * is one which would update the stack pointer to the
 360                  * address accessed if the instruction completed,
 361                  * i.e. either stwu rs,n(r1) or stwux rs,r1,rb
 362                  * (or the byte, halfword, float or double forms).
 363                  *
 364                  * If we don't check this then any write to the area
 365                  * between the last mapped region and the stack will
 366                  * expand the stack rather than segfaulting.
 367                  */
 368                 if (address + 2048 < uregs->gpr[1] && !store_update_sp)
 369                         goto bad_area;
 370         }
 371         if (expand_stack(vma, address))
 372                 goto bad_area;
 373
 374 good_area:
 375         code = SEGV_ACCERR;
 376 #if defined(CONFIG_6xx)
 377         if (error_code & 0x95700000)
 378                 /* an error such as lwarx to I/O controller space,
 379                    address matching DABR, eciwx, etc. */
 380                 goto bad_area;
 381 #endif /* CONFIG_6xx */
 382 #if defined(CONFIG_8xx)
 383         /* The MPC8xx seems to always set 0x80000000, which is
 384          * "undefined".  Of those that can be set, this is the only
 385          * one which seems bad.
 386          */
 387         if (error_code & 0x10000000)
 388                 /* Guarded storage error. */
 389                 goto bad_area;
 390 #endif /* CONFIG_8xx */
 391
 392         if (is_exec) {
 393                 /*
 394                  * Allow execution from readable areas if the MMU does not
 395                  * provide separate controls over reading and executing.
 396                  *
 397                  * Note: That code used to not be enabled for 4xx/BookE.
 398                  * It is now as I/D cache coherency for these is done at
 399                  * set_pte_at() time and I see no reason why the test
 400                  * below wouldn't be valid on those processors. This -may-
 401                  * break programs compiled with a really old ABI though.
 402                  */
 403                 if (!(vma->vm_flags & VM_EXEC) &&
 404                     (cpu_has_feature(CPU_FTR_NOEXECUTE) ||
 405                      !(vma->vm_flags & (VM_READ | VM_WRITE))))
 406                         goto bad_area;
 407 #ifdef CONFIG_PPC_STD_MMU
 408                 /*
 409                  * protfault should only happen due to us
 410                  * mapping a region readonly temporarily. PROT_NONE
 411                  * is also covered by the VMA check above.
 412                  */
 413                 WARN_ON_ONCE(error_code & DSISR_PROTFAULT);
 414 #endif /* CONFIG_PPC_STD_MMU */
 415         /* a write */
 416         } else if (is_write) {
 417                 if (!(vma->vm_flags & VM_WRITE))
 418                         goto bad_area;
 419                 flags |= FAULT_FLAG_WRITE;
 420         /* a read */
 421         } else {
 422                 if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)))
 423                         goto bad_area;
 424                 WARN_ON_ONCE(error_code & DSISR_PROTFAULT);
 425         }
 426
 427         /*
 428          * If for any reason at all we couldn't handle the fault,
 429          * make sure we exit gracefully rather than endlessly redo
 430          * the fault.
 431          */
 432         fault = handle_mm_fault(vma, address, flags);
 433         if (unlikely(fault & (VM_FAULT_RETRY|VM_FAULT_ERROR))) {
 434                 if (fault & VM_FAULT_SIGSEGV)
 435                         goto bad_area;
 436                 rc = mm_fault_error(regs, address, fault);
 437                 if (rc >= MM_FAULT_RETURN)
 438                         goto bail;
 439                 else
 440                         rc = 0;
 441         }
 442
 443         /*
 444          * Major/minor page fault accounting is only done on the
 445          * initial attempt. If we go through a retry, it is extremely
 446          * likely that the page will be found in page cache at that point.
 447          */
 448         if (flags & FAULT_FLAG_ALLOW_RETRY) {
 449                 if (fault & VM_FAULT_MAJOR) {
 450                         current->maj_flt++;
 451                         perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1,
 452                                       regs, address);
 453 #ifdef CONFIG_PPC_SMLPAR
 454                         if (firmware_has_feature(FW_FEATURE_CMO)) {
 455                                 u32 page_ins;
 456
 457                                 preempt_disable();
 458                                 page_ins = be32_to_cpu(get_lppaca()->page_ins);
 459                                 page_ins += 1 << PAGE_FACTOR;
 460                                 get_lppaca()->page_ins = cpu_to_be32(page_ins);
 461                                 preempt_enable();
 462                         }
 463 #endif /* CONFIG_PPC_SMLPAR */
 464                 } else {
 465                         current->min_flt++;
 466                         perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1,
 467                                       regs, address);
 468                 }
 469                 if (fault & VM_FAULT_RETRY) {
 470                         /* Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk
 471                          * of starvation. */
 472                         flags &= ~FAULT_FLAG_ALLOW_RETRY;
 473                         flags |= FAULT_FLAG_TRIED;
 474                         goto retry;
 475                 }
 476         }
 477
 478         up_read(&mm->mmap_sem);
 479         goto bail;
 480
 481 bad_area:
 482         up_read(&mm->mmap_sem);
 483
 484 bad_area_nosemaphore:
 485         /* User mode accesses cause a SIGSEGV */
 486         if (user_mode(regs)) {
 487                 _exception(SIGSEGV, regs, code, address);
 488                 goto bail;
 489         }
 490
 491         if (is_exec && (error_code & DSISR_PROTFAULT))
 492                 printk_ratelimited(KERN_CRIT "kernel tried to execute NX-protected"
 493                                    " page (%lx) - exploit attempt? (uid: %d)\n",
 494                                    address, from_kuid(&init_user_ns, current_uid()));
 495
 496         rc = SIGSEGV;
 497
 498 bail:
 499         exception_exit(prev_state);
 500         return rc;
 501
 502 }
 503
 504 /*
 505  * bad_page_fault is called when we have a bad access from the kernel.
 506  * It is called from the DSI and ISI handlers in head.S and from some
 507  * of the procedures in traps.c.
 508  */
 509 void bad_page_fault(struct pt_regs *regs, unsigned long address, int sig)
 510 {
 511         const struct exception_table_entry *entry;
 512
 513         /* Are we prepared to handle this fault?  */
 514         if ((entry = search_exception_tables(regs->nip)) != NULL) {
 515                 regs->nip = entry->fixup;
 516                 return;
 517         }
 518
 519         /* kernel has accessed a bad area */
 520
 521         switch (regs->trap) {
 522         case 0x300:
 523         case 0x380:
 524                 printk(KERN_ALERT "Unable to handle kernel paging request for "
 525                         "data at address 0x%08lx\n", regs->dar);
 526                 break;
 527         case 0x400:
 528         case 0x480:
 529                 printk(KERN_ALERT "Unable to handle kernel paging request for "
 530                         "instruction fetch\n");
 531                 break;
 532         case 0x600:
 533                 printk(KERN_ALERT "Unable to handle kernel paging request for "
 534                         "unaligned access at address 0x%08lx\n", regs->dar);
 535                 break;
 536         default:
 537                 printk(KERN_ALERT "Unable to handle kernel paging request for "
 538                         "unknown fault\n");
 539                 break;
 540         }
 541         printk(KERN_ALERT "Faulting instruction address: 0x%08lx\n",
 542                 regs->nip);
 543
 544         if (task_stack_end_corrupted(current))
 545                 printk(KERN_ALERT "Thread overran stack, or stack corrupted\n");
 546
 547         die("Kernel access of bad area", regs, sig);
 548 }