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 37 #include <asm/firmware.h> 38 #include <asm/page.h> 39 #include <asm/pgtable.h> 40 #include <asm/mmu.h> 41 #include <asm/mmu_context.h> 42 #include <asm/uaccess.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 (in_atomic() || mm == NULL) { 276 if (!user_mode(regs)) { 277 rc = SIGSEGV; 278 goto bail; 279 } 280 /* in_atomic() in user mode is really bad, 281 as is current->mm == NULL. */ 282 printk(KERN_EMERG "Page fault in user mode with " 283 "in_atomic() = %d mm = %p\n", in_atomic(), mm); 284 printk(KERN_EMERG "NIP = %lx MSR = %lx\n", 285 regs->nip, regs->msr); 286 die("Weird page fault", regs, SIGSEGV); 287 } 288 289 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address); 290 291 /* 292 * We want to do this outside mmap_sem, because reading code around nip 293 * can result in fault, which will cause a deadlock when called with 294 * mmap_sem held 295 */ 296 if (user_mode(regs)) 297 store_update_sp = store_updates_sp(regs); 298 299 if (user_mode(regs)) 300 flags |= FAULT_FLAG_USER; 301 302 /* When running in the kernel we expect faults to occur only to 303 * addresses in user space. All other faults represent errors in the 304 * kernel and should generate an OOPS. Unfortunately, in the case of an 305 * erroneous fault occurring in a code path which already holds mmap_sem 306 * we will deadlock attempting to validate the fault against the 307 * address space. Luckily the kernel only validly references user 308 * space from well defined areas of code, which are listed in the 309 * exceptions table. 310 * 311 * As the vast majority of faults will be valid we will only perform 312 * the source reference check when there is a possibility of a deadlock. 313 * Attempt to lock the address space, if we cannot we then validate the 314 * source. If this is invalid we can skip the address space check, 315 * thus avoiding the deadlock. 316 */ 317 if (!down_read_trylock(&mm->mmap_sem)) { 318 if (!user_mode(regs) && !search_exception_tables(regs->nip)) 319 goto bad_area_nosemaphore; 320 321 retry: 322 down_read(&mm->mmap_sem); 323 } else { 324 /* 325 * The above down_read_trylock() might have succeeded in 326 * which case we'll have missed the might_sleep() from 327 * down_read(): 328 */ 329 might_sleep(); 330 } 331 332 vma = find_vma(mm, address); 333 if (!vma) 334 goto bad_area; 335 if (vma->vm_start <= address) 336 goto good_area; 337 if (!(vma->vm_flags & VM_GROWSDOWN)) 338 goto bad_area; 339 340 /* 341 * N.B. The POWER/Open ABI allows programs to access up to 342 * 288 bytes below the stack pointer. 343 * The kernel signal delivery code writes up to about 1.5kB 344 * below the stack pointer (r1) before decrementing it. 345 * The exec code can write slightly over 640kB to the stack 346 * before setting the user r1. Thus we allow the stack to 347 * expand to 1MB without further checks. 348 */ 349 if (address + 0x100000 < vma->vm_end) { 350 /* get user regs even if this fault is in kernel mode */ 351 struct pt_regs *uregs = current->thread.regs; 352 if (uregs == NULL) 353 goto bad_area; 354 355 /* 356 * A user-mode access to an address a long way below 357 * the stack pointer is only valid if the instruction 358 * is one which would update the stack pointer to the 359 * address accessed if the instruction completed, 360 * i.e. either stwu rs,n(r1) or stwux rs,r1,rb 361 * (or the byte, halfword, float or double forms). 362 * 363 * If we don't check this then any write to the area 364 * between the last mapped region and the stack will 365 * expand the stack rather than segfaulting. 366 */ 367 if (address + 2048 < uregs->gpr[1] && !store_update_sp) 368 goto bad_area; 369 } 370 if (expand_stack(vma, address)) 371 goto bad_area; 372 373 good_area: 374 code = SEGV_ACCERR; 375 #if defined(CONFIG_6xx) 376 if (error_code & 0x95700000) 377 /* an error such as lwarx to I/O controller space, 378 address matching DABR, eciwx, etc. */ 379 goto bad_area; 380 #endif /* CONFIG_6xx */ 381 #if defined(CONFIG_8xx) 382 /* The MPC8xx seems to always set 0x80000000, which is 383 * "undefined". Of those that can be set, this is the only 384 * one which seems bad. 385 */ 386 if (error_code & 0x10000000) 387 /* Guarded storage error. */ 388 goto bad_area; 389 #endif /* CONFIG_8xx */ 390 391 if (is_exec) { 392 #ifdef CONFIG_PPC_STD_MMU 393 /* Protection fault on exec go straight to failure on 394 * Hash based MMUs as they either don't support per-page 395 * execute permission, or if they do, it's handled already 396 * at the hash level. This test would probably have to 397 * be removed if we change the way this works to make hash 398 * processors use the same I/D cache coherency mechanism 399 * as embedded. 400 */ 401 if (error_code & DSISR_PROTFAULT) 402 goto bad_area; 403 #endif /* CONFIG_PPC_STD_MMU */ 404 405 /* 406 * Allow execution from readable areas if the MMU does not 407 * provide separate controls over reading and executing. 408 * 409 * Note: That code used to not be enabled for 4xx/BookE. 410 * It is now as I/D cache coherency for these is done at 411 * set_pte_at() time and I see no reason why the test 412 * below wouldn't be valid on those processors. This -may- 413 * break programs compiled with a really old ABI though. 414 */ 415 if (!(vma->vm_flags & VM_EXEC) && 416 (cpu_has_feature(CPU_FTR_NOEXECUTE) || 417 !(vma->vm_flags & (VM_READ | VM_WRITE)))) 418 goto bad_area; 419 /* a write */ 420 } else if (is_write) { 421 if (!(vma->vm_flags & VM_WRITE)) 422 goto bad_area; 423 flags |= FAULT_FLAG_WRITE; 424 /* a read */ 425 } else { 426 /* protection fault */ 427 if (error_code & 0x08000000) 428 goto bad_area; 429 if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE))) 430 goto bad_area; 431 } 432 433 /* 434 * If for any reason at all we couldn't handle the fault, 435 * make sure we exit gracefully rather than endlessly redo 436 * the fault. 437 */ 438 fault = handle_mm_fault(mm, vma, address, flags); 439 if (unlikely(fault & (VM_FAULT_RETRY|VM_FAULT_ERROR))) { 440 if (fault & VM_FAULT_SIGSEGV) 441 goto bad_area; 442 rc = mm_fault_error(regs, address, fault); 443 if (rc >= MM_FAULT_RETURN) 444 goto bail; 445 else 446 rc = 0; 447 } 448 449 /* 450 * Major/minor page fault accounting is only done on the 451 * initial attempt. If we go through a retry, it is extremely 452 * likely that the page will be found in page cache at that point. 453 */ 454 if (flags & FAULT_FLAG_ALLOW_RETRY) { 455 if (fault & VM_FAULT_MAJOR) { 456 current->maj_flt++; 457 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, 458 regs, address); 459 #ifdef CONFIG_PPC_SMLPAR 460 if (firmware_has_feature(FW_FEATURE_CMO)) { 461 u32 page_ins; 462 463 preempt_disable(); 464 page_ins = be32_to_cpu(get_lppaca()->page_ins); 465 page_ins += 1 << PAGE_FACTOR; 466 get_lppaca()->page_ins = cpu_to_be32(page_ins); 467 preempt_enable(); 468 } 469 #endif /* CONFIG_PPC_SMLPAR */ 470 } else { 471 current->min_flt++; 472 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, 473 regs, address); 474 } 475 if (fault & VM_FAULT_RETRY) { 476 /* Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk 477 * of starvation. */ 478 flags &= ~FAULT_FLAG_ALLOW_RETRY; 479 flags |= FAULT_FLAG_TRIED; 480 goto retry; 481 } 482 } 483 484 up_read(&mm->mmap_sem); 485 goto bail; 486 487 bad_area: 488 up_read(&mm->mmap_sem); 489 490 bad_area_nosemaphore: 491 /* User mode accesses cause a SIGSEGV */ 492 if (user_mode(regs)) { 493 _exception(SIGSEGV, regs, code, address); 494 goto bail; 495 } 496 497 if (is_exec && (error_code & DSISR_PROTFAULT)) 498 printk_ratelimited(KERN_CRIT "kernel tried to execute NX-protected" 499 " page (%lx) - exploit attempt? (uid: %d)\n", 500 address, from_kuid(&init_user_ns, current_uid())); 501 502 rc = SIGSEGV; 503 504 bail: 505 exception_exit(prev_state); 506 return rc; 507 508 } 509 510 /* 511 * bad_page_fault is called when we have a bad access from the kernel. 512 * It is called from the DSI and ISI handlers in head.S and from some 513 * of the procedures in traps.c. 514 */ 515 void bad_page_fault(struct pt_regs *regs, unsigned long address, int sig) 516 { 517 const struct exception_table_entry *entry; 518 519 /* Are we prepared to handle this fault? */ 520 if ((entry = search_exception_tables(regs->nip)) != NULL) { 521 regs->nip = entry->fixup; 522 return; 523 } 524 525 /* kernel has accessed a bad area */ 526 527 switch (regs->trap) { 528 case 0x300: 529 case 0x380: 530 printk(KERN_ALERT "Unable to handle kernel paging request for " 531 "data at address 0x%08lx\n", regs->dar); 532 break; 533 case 0x400: 534 case 0x480: 535 printk(KERN_ALERT "Unable to handle kernel paging request for " 536 "instruction fetch\n"); 537 break; 538 default: 539 printk(KERN_ALERT "Unable to handle kernel paging request for " 540 "unknown fault\n"); 541 break; 542 } 543 printk(KERN_ALERT "Faulting instruction address: 0x%08lx\n", 544 regs->nip); 545 546 if (task_stack_end_corrupted(current)) 547 printk(KERN_ALERT "Thread overran stack, or stack corrupted\n"); 548 549 die("Kernel access of bad area", regs, sig); 550 } 551