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(¤t->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(¤t->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(¤t->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(mm, 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 } 549