1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * S390 version 4 * Copyright IBM Corp. 1999 5 * Author(s): Hartmut Penner (hp@de.ibm.com) 6 * Ulrich Weigand (uweigand@de.ibm.com) 7 * 8 * Derived from "arch/i386/mm/fault.c" 9 * Copyright (C) 1995 Linus Torvalds 10 */ 11 12 #include <linux/kernel_stat.h> 13 #include <linux/mmu_context.h> 14 #include <linux/perf_event.h> 15 #include <linux/signal.h> 16 #include <linux/sched.h> 17 #include <linux/sched/debug.h> 18 #include <linux/jump_label.h> 19 #include <linux/kernel.h> 20 #include <linux/errno.h> 21 #include <linux/string.h> 22 #include <linux/types.h> 23 #include <linux/ptrace.h> 24 #include <linux/mman.h> 25 #include <linux/mm.h> 26 #include <linux/compat.h> 27 #include <linux/smp.h> 28 #include <linux/kdebug.h> 29 #include <linux/init.h> 30 #include <linux/console.h> 31 #include <linux/extable.h> 32 #include <linux/hardirq.h> 33 #include <linux/kprobes.h> 34 #include <linux/uaccess.h> 35 #include <linux/hugetlb.h> 36 #include <linux/kfence.h> 37 #include <asm/asm-extable.h> 38 #include <asm/asm-offsets.h> 39 #include <asm/ptrace.h> 40 #include <asm/fault.h> 41 #include <asm/diag.h> 42 #include <asm/gmap.h> 43 #include <asm/irq.h> 44 #include <asm/facility.h> 45 #include <asm/uv.h> 46 #include "../kernel/entry.h" 47 48 enum fault_type { 49 KERNEL_FAULT, 50 USER_FAULT, 51 GMAP_FAULT, 52 }; 53 54 static DEFINE_STATIC_KEY_FALSE(have_store_indication); 55 56 static int __init fault_init(void) 57 { 58 if (test_facility(75)) 59 static_branch_enable(&have_store_indication); 60 return 0; 61 } 62 early_initcall(fault_init); 63 64 /* 65 * Find out which address space caused the exception. 66 */ 67 static enum fault_type get_fault_type(struct pt_regs *regs) 68 { 69 union teid teid = { .val = regs->int_parm_long }; 70 71 if (likely(teid.as == PSW_BITS_AS_PRIMARY)) { 72 if (user_mode(regs)) 73 return USER_FAULT; 74 if (!IS_ENABLED(CONFIG_PGSTE)) 75 return KERNEL_FAULT; 76 if (test_pt_regs_flag(regs, PIF_GUEST_FAULT)) 77 return GMAP_FAULT; 78 return KERNEL_FAULT; 79 } 80 if (teid.as == PSW_BITS_AS_SECONDARY) 81 return USER_FAULT; 82 /* Access register mode, not used in the kernel */ 83 if (teid.as == PSW_BITS_AS_ACCREG) 84 return USER_FAULT; 85 /* Home space -> access via kernel ASCE */ 86 return KERNEL_FAULT; 87 } 88 89 static unsigned long get_fault_address(struct pt_regs *regs) 90 { 91 union teid teid = { .val = regs->int_parm_long }; 92 93 return teid.addr * PAGE_SIZE; 94 } 95 96 static __always_inline bool fault_is_write(struct pt_regs *regs) 97 { 98 union teid teid = { .val = regs->int_parm_long }; 99 100 if (static_branch_likely(&have_store_indication)) 101 return teid.fsi == TEID_FSI_STORE; 102 return false; 103 } 104 105 static void dump_pagetable(unsigned long asce, unsigned long address) 106 { 107 unsigned long entry, *table = __va(asce & _ASCE_ORIGIN); 108 109 pr_alert("AS:%016lx ", asce); 110 switch (asce & _ASCE_TYPE_MASK) { 111 case _ASCE_TYPE_REGION1: 112 table += (address & _REGION1_INDEX) >> _REGION1_SHIFT; 113 if (get_kernel_nofault(entry, table)) 114 goto bad; 115 pr_cont("R1:%016lx ", entry); 116 if (entry & _REGION_ENTRY_INVALID) 117 goto out; 118 table = __va(entry & _REGION_ENTRY_ORIGIN); 119 fallthrough; 120 case _ASCE_TYPE_REGION2: 121 table += (address & _REGION2_INDEX) >> _REGION2_SHIFT; 122 if (get_kernel_nofault(entry, table)) 123 goto bad; 124 pr_cont("R2:%016lx ", entry); 125 if (entry & _REGION_ENTRY_INVALID) 126 goto out; 127 table = __va(entry & _REGION_ENTRY_ORIGIN); 128 fallthrough; 129 case _ASCE_TYPE_REGION3: 130 table += (address & _REGION3_INDEX) >> _REGION3_SHIFT; 131 if (get_kernel_nofault(entry, table)) 132 goto bad; 133 pr_cont("R3:%016lx ", entry); 134 if (entry & (_REGION_ENTRY_INVALID | _REGION3_ENTRY_LARGE)) 135 goto out; 136 table = __va(entry & _REGION_ENTRY_ORIGIN); 137 fallthrough; 138 case _ASCE_TYPE_SEGMENT: 139 table += (address & _SEGMENT_INDEX) >> _SEGMENT_SHIFT; 140 if (get_kernel_nofault(entry, table)) 141 goto bad; 142 pr_cont("S:%016lx ", entry); 143 if (entry & (_SEGMENT_ENTRY_INVALID | _SEGMENT_ENTRY_LARGE)) 144 goto out; 145 table = __va(entry & _SEGMENT_ENTRY_ORIGIN); 146 } 147 table += (address & _PAGE_INDEX) >> _PAGE_SHIFT; 148 if (get_kernel_nofault(entry, table)) 149 goto bad; 150 pr_cont("P:%016lx ", entry); 151 out: 152 pr_cont("\n"); 153 return; 154 bad: 155 pr_cont("BAD\n"); 156 } 157 158 static void dump_fault_info(struct pt_regs *regs) 159 { 160 union teid teid = { .val = regs->int_parm_long }; 161 unsigned long asce; 162 163 pr_alert("Failing address: %016lx TEID: %016lx\n", 164 get_fault_address(regs), teid.val); 165 pr_alert("Fault in "); 166 switch (teid.as) { 167 case PSW_BITS_AS_HOME: 168 pr_cont("home space "); 169 break; 170 case PSW_BITS_AS_SECONDARY: 171 pr_cont("secondary space "); 172 break; 173 case PSW_BITS_AS_ACCREG: 174 pr_cont("access register "); 175 break; 176 case PSW_BITS_AS_PRIMARY: 177 pr_cont("primary space "); 178 break; 179 } 180 pr_cont("mode while using "); 181 switch (get_fault_type(regs)) { 182 case USER_FAULT: 183 asce = S390_lowcore.user_asce.val; 184 pr_cont("user "); 185 break; 186 case GMAP_FAULT: 187 asce = ((struct gmap *)S390_lowcore.gmap)->asce; 188 pr_cont("gmap "); 189 break; 190 case KERNEL_FAULT: 191 asce = S390_lowcore.kernel_asce.val; 192 pr_cont("kernel "); 193 break; 194 default: 195 unreachable(); 196 } 197 pr_cont("ASCE.\n"); 198 dump_pagetable(asce, get_fault_address(regs)); 199 } 200 201 int show_unhandled_signals = 1; 202 203 void report_user_fault(struct pt_regs *regs, long signr, int is_mm_fault) 204 { 205 static DEFINE_RATELIMIT_STATE(rs, DEFAULT_RATELIMIT_INTERVAL, DEFAULT_RATELIMIT_BURST); 206 207 if ((task_pid_nr(current) > 1) && !show_unhandled_signals) 208 return; 209 if (!unhandled_signal(current, signr)) 210 return; 211 if (!__ratelimit(&rs)) 212 return; 213 pr_alert("User process fault: interruption code %04x ilc:%d ", 214 regs->int_code & 0xffff, regs->int_code >> 17); 215 print_vma_addr(KERN_CONT "in ", regs->psw.addr); 216 pr_cont("\n"); 217 if (is_mm_fault) 218 dump_fault_info(regs); 219 show_regs(regs); 220 } 221 222 static void do_sigsegv(struct pt_regs *regs, int si_code) 223 { 224 report_user_fault(regs, SIGSEGV, 1); 225 force_sig_fault(SIGSEGV, si_code, (void __user *)get_fault_address(regs)); 226 } 227 228 static void handle_fault_error_nolock(struct pt_regs *regs, int si_code) 229 { 230 enum fault_type fault_type; 231 unsigned long address; 232 bool is_write; 233 234 if (user_mode(regs)) { 235 if (WARN_ON_ONCE(!si_code)) 236 si_code = SEGV_MAPERR; 237 return do_sigsegv(regs, si_code); 238 } 239 if (fixup_exception(regs)) 240 return; 241 fault_type = get_fault_type(regs); 242 if (fault_type == KERNEL_FAULT) { 243 address = get_fault_address(regs); 244 is_write = fault_is_write(regs); 245 if (kfence_handle_page_fault(address, is_write, regs)) 246 return; 247 } 248 if (fault_type == KERNEL_FAULT) 249 pr_alert("Unable to handle kernel pointer dereference in virtual kernel address space\n"); 250 else 251 pr_alert("Unable to handle kernel paging request in virtual user address space\n"); 252 dump_fault_info(regs); 253 die(regs, "Oops"); 254 } 255 256 static void handle_fault_error(struct pt_regs *regs, int si_code) 257 { 258 struct mm_struct *mm = current->mm; 259 260 mmap_read_unlock(mm); 261 handle_fault_error_nolock(regs, si_code); 262 } 263 264 static void do_sigbus(struct pt_regs *regs) 265 { 266 force_sig_fault(SIGBUS, BUS_ADRERR, (void __user *)get_fault_address(regs)); 267 } 268 269 /* 270 * This routine handles page faults. It determines the address, 271 * and the problem, and then passes it off to one of the appropriate 272 * routines. 273 * 274 * interruption code (int_code): 275 * 04 Protection -> Write-Protection (suppression) 276 * 10 Segment translation -> Not present (nullification) 277 * 11 Page translation -> Not present (nullification) 278 * 3b Region third trans. -> Not present (nullification) 279 */ 280 static void do_exception(struct pt_regs *regs, int access) 281 { 282 struct vm_area_struct *vma; 283 struct task_struct *tsk; 284 unsigned long address; 285 struct mm_struct *mm; 286 enum fault_type type; 287 unsigned int flags; 288 struct gmap *gmap; 289 vm_fault_t fault; 290 bool is_write; 291 292 tsk = current; 293 /* 294 * The instruction that caused the program check has 295 * been nullified. Don't signal single step via SIGTRAP. 296 */ 297 clear_thread_flag(TIF_PER_TRAP); 298 if (kprobe_page_fault(regs, 14)) 299 return; 300 mm = tsk->mm; 301 address = get_fault_address(regs); 302 is_write = fault_is_write(regs); 303 type = get_fault_type(regs); 304 switch (type) { 305 case KERNEL_FAULT: 306 return handle_fault_error_nolock(regs, 0); 307 case USER_FAULT: 308 case GMAP_FAULT: 309 if (faulthandler_disabled() || !mm) 310 return handle_fault_error_nolock(regs, 0); 311 break; 312 } 313 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address); 314 flags = FAULT_FLAG_DEFAULT; 315 if (user_mode(regs)) 316 flags |= FAULT_FLAG_USER; 317 if (is_write) 318 access = VM_WRITE; 319 if (access == VM_WRITE) 320 flags |= FAULT_FLAG_WRITE; 321 if (!(flags & FAULT_FLAG_USER)) 322 goto lock_mmap; 323 vma = lock_vma_under_rcu(mm, address); 324 if (!vma) 325 goto lock_mmap; 326 if (!(vma->vm_flags & access)) { 327 vma_end_read(vma); 328 goto lock_mmap; 329 } 330 fault = handle_mm_fault(vma, address, flags | FAULT_FLAG_VMA_LOCK, regs); 331 if (!(fault & (VM_FAULT_RETRY | VM_FAULT_COMPLETED))) 332 vma_end_read(vma); 333 if (!(fault & VM_FAULT_RETRY)) { 334 count_vm_vma_lock_event(VMA_LOCK_SUCCESS); 335 if (unlikely(fault & VM_FAULT_ERROR)) 336 goto error; 337 return; 338 } 339 count_vm_vma_lock_event(VMA_LOCK_RETRY); 340 if (fault & VM_FAULT_MAJOR) 341 flags |= FAULT_FLAG_TRIED; 342 343 /* Quick path to respond to signals */ 344 if (fault_signal_pending(fault, regs)) { 345 if (!user_mode(regs)) 346 handle_fault_error_nolock(regs, 0); 347 return; 348 } 349 lock_mmap: 350 mmap_read_lock(mm); 351 gmap = NULL; 352 if (IS_ENABLED(CONFIG_PGSTE) && type == GMAP_FAULT) { 353 gmap = (struct gmap *)S390_lowcore.gmap; 354 current->thread.gmap_addr = address; 355 current->thread.gmap_write_flag = !!(flags & FAULT_FLAG_WRITE); 356 current->thread.gmap_int_code = regs->int_code & 0xffff; 357 address = __gmap_translate(gmap, address); 358 if (address == -EFAULT) 359 return handle_fault_error(regs, SEGV_MAPERR); 360 if (gmap->pfault_enabled) 361 flags |= FAULT_FLAG_RETRY_NOWAIT; 362 } 363 retry: 364 vma = find_vma(mm, address); 365 if (!vma) 366 return handle_fault_error(regs, SEGV_MAPERR); 367 if (unlikely(vma->vm_start > address)) { 368 if (!(vma->vm_flags & VM_GROWSDOWN)) 369 return handle_fault_error(regs, SEGV_MAPERR); 370 vma = expand_stack(mm, address); 371 if (!vma) 372 return handle_fault_error_nolock(regs, SEGV_MAPERR); 373 } 374 if (unlikely(!(vma->vm_flags & access))) 375 return handle_fault_error(regs, SEGV_ACCERR); 376 fault = handle_mm_fault(vma, address, flags, regs); 377 if (fault_signal_pending(fault, regs)) { 378 if (flags & FAULT_FLAG_RETRY_NOWAIT) 379 mmap_read_unlock(mm); 380 if (!user_mode(regs)) 381 handle_fault_error_nolock(regs, 0); 382 return; 383 } 384 /* The fault is fully completed (including releasing mmap lock) */ 385 if (fault & VM_FAULT_COMPLETED) { 386 if (gmap) { 387 mmap_read_lock(mm); 388 goto gmap; 389 } 390 return; 391 } 392 if (unlikely(fault & VM_FAULT_ERROR)) { 393 mmap_read_unlock(mm); 394 goto error; 395 } 396 if (fault & VM_FAULT_RETRY) { 397 if (IS_ENABLED(CONFIG_PGSTE) && gmap && (flags & FAULT_FLAG_RETRY_NOWAIT)) { 398 /* 399 * FAULT_FLAG_RETRY_NOWAIT has been set, 400 * mmap_lock has not been released 401 */ 402 current->thread.gmap_pfault = 1; 403 return handle_fault_error(regs, 0); 404 } 405 flags &= ~FAULT_FLAG_RETRY_NOWAIT; 406 flags |= FAULT_FLAG_TRIED; 407 mmap_read_lock(mm); 408 goto retry; 409 } 410 gmap: 411 if (IS_ENABLED(CONFIG_PGSTE) && gmap) { 412 address = __gmap_link(gmap, current->thread.gmap_addr, 413 address); 414 if (address == -EFAULT) 415 return handle_fault_error(regs, SEGV_MAPERR); 416 if (address == -ENOMEM) { 417 fault = VM_FAULT_OOM; 418 mmap_read_unlock(mm); 419 goto error; 420 } 421 } 422 mmap_read_unlock(mm); 423 return; 424 error: 425 if (fault & VM_FAULT_OOM) { 426 if (!user_mode(regs)) 427 handle_fault_error_nolock(regs, 0); 428 else 429 pagefault_out_of_memory(); 430 } else if (fault & VM_FAULT_SIGSEGV) { 431 if (!user_mode(regs)) 432 handle_fault_error_nolock(regs, 0); 433 else 434 do_sigsegv(regs, SEGV_MAPERR); 435 } else if (fault & VM_FAULT_SIGBUS) { 436 if (!user_mode(regs)) 437 handle_fault_error_nolock(regs, 0); 438 else 439 do_sigbus(regs); 440 } else { 441 BUG(); 442 } 443 } 444 445 void do_protection_exception(struct pt_regs *regs) 446 { 447 union teid teid = { .val = regs->int_parm_long }; 448 449 /* 450 * Protection exceptions are suppressing, decrement psw address. 451 * The exception to this rule are aborted transactions, for these 452 * the PSW already points to the correct location. 453 */ 454 if (!(regs->int_code & 0x200)) 455 regs->psw.addr = __rewind_psw(regs->psw, regs->int_code >> 16); 456 /* 457 * Check for low-address protection. This needs to be treated 458 * as a special case because the translation exception code 459 * field is not guaranteed to contain valid data in this case. 460 */ 461 if (unlikely(!teid.b61)) { 462 if (user_mode(regs)) { 463 /* Low-address protection in user mode: cannot happen */ 464 die(regs, "Low-address protection"); 465 } 466 /* 467 * Low-address protection in kernel mode means 468 * NULL pointer write access in kernel mode. 469 */ 470 return handle_fault_error_nolock(regs, 0); 471 } 472 if (unlikely(MACHINE_HAS_NX && teid.b56)) { 473 regs->int_parm_long = (teid.addr * PAGE_SIZE) | (regs->psw.addr & PAGE_MASK); 474 return handle_fault_error_nolock(regs, SEGV_ACCERR); 475 } 476 do_exception(regs, VM_WRITE); 477 } 478 NOKPROBE_SYMBOL(do_protection_exception); 479 480 void do_dat_exception(struct pt_regs *regs) 481 { 482 do_exception(regs, VM_ACCESS_FLAGS); 483 } 484 NOKPROBE_SYMBOL(do_dat_exception); 485 486 #if IS_ENABLED(CONFIG_PGSTE) 487 488 void do_secure_storage_access(struct pt_regs *regs) 489 { 490 union teid teid = { .val = regs->int_parm_long }; 491 unsigned long addr = get_fault_address(regs); 492 struct vm_area_struct *vma; 493 struct mm_struct *mm; 494 struct page *page; 495 struct gmap *gmap; 496 int rc; 497 498 /* 499 * Bit 61 indicates if the address is valid, if it is not the 500 * kernel should be stopped or SIGSEGV should be sent to the 501 * process. Bit 61 is not reliable without the misc UV feature, 502 * therefore this needs to be checked too. 503 */ 504 if (uv_has_feature(BIT_UV_FEAT_MISC) && !teid.b61) { 505 /* 506 * When this happens, userspace did something that it 507 * was not supposed to do, e.g. branching into secure 508 * memory. Trigger a segmentation fault. 509 */ 510 if (user_mode(regs)) { 511 send_sig(SIGSEGV, current, 0); 512 return; 513 } 514 /* 515 * The kernel should never run into this case and 516 * there is no way out of this situation. 517 */ 518 panic("Unexpected PGM 0x3d with TEID bit 61=0"); 519 } 520 switch (get_fault_type(regs)) { 521 case GMAP_FAULT: 522 mm = current->mm; 523 gmap = (struct gmap *)S390_lowcore.gmap; 524 mmap_read_lock(mm); 525 addr = __gmap_translate(gmap, addr); 526 mmap_read_unlock(mm); 527 if (IS_ERR_VALUE(addr)) 528 return handle_fault_error_nolock(regs, SEGV_MAPERR); 529 fallthrough; 530 case USER_FAULT: 531 mm = current->mm; 532 mmap_read_lock(mm); 533 vma = find_vma(mm, addr); 534 if (!vma) 535 return handle_fault_error(regs, SEGV_MAPERR); 536 page = follow_page(vma, addr, FOLL_WRITE | FOLL_GET); 537 if (IS_ERR_OR_NULL(page)) { 538 mmap_read_unlock(mm); 539 break; 540 } 541 if (arch_make_page_accessible(page)) 542 send_sig(SIGSEGV, current, 0); 543 put_page(page); 544 mmap_read_unlock(mm); 545 break; 546 case KERNEL_FAULT: 547 page = phys_to_page(addr); 548 if (unlikely(!try_get_page(page))) 549 break; 550 rc = arch_make_page_accessible(page); 551 put_page(page); 552 if (rc) 553 BUG(); 554 break; 555 default: 556 unreachable(); 557 } 558 } 559 NOKPROBE_SYMBOL(do_secure_storage_access); 560 561 void do_non_secure_storage_access(struct pt_regs *regs) 562 { 563 struct gmap *gmap = (struct gmap *)S390_lowcore.gmap; 564 unsigned long gaddr = get_fault_address(regs); 565 566 if (WARN_ON_ONCE(get_fault_type(regs) != GMAP_FAULT)) 567 return handle_fault_error_nolock(regs, SEGV_MAPERR); 568 if (gmap_convert_to_secure(gmap, gaddr) == -EINVAL) 569 send_sig(SIGSEGV, current, 0); 570 } 571 NOKPROBE_SYMBOL(do_non_secure_storage_access); 572 573 void do_secure_storage_violation(struct pt_regs *regs) 574 { 575 struct gmap *gmap = (struct gmap *)S390_lowcore.gmap; 576 unsigned long gaddr = get_fault_address(regs); 577 578 /* 579 * If the VM has been rebooted, its address space might still contain 580 * secure pages from the previous boot. 581 * Clear the page so it can be reused. 582 */ 583 if (!gmap_destroy_page(gmap, gaddr)) 584 return; 585 /* 586 * Either KVM messed up the secure guest mapping or the same 587 * page is mapped into multiple secure guests. 588 * 589 * This exception is only triggered when a guest 2 is running 590 * and can therefore never occur in kernel context. 591 */ 592 pr_warn_ratelimited("Secure storage violation in task: %s, pid %d\n", 593 current->comm, current->pid); 594 send_sig(SIGSEGV, current, 0); 595 } 596 597 #endif /* CONFIG_PGSTE */ 598