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/cpufeature.h> 15 #include <linux/perf_event.h> 16 #include <linux/signal.h> 17 #include <linux/sched.h> 18 #include <linux/sched/debug.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/smp.h> 27 #include <linux/kdebug.h> 28 #include <linux/init.h> 29 #include <linux/console.h> 30 #include <linux/extable.h> 31 #include <linux/hardirq.h> 32 #include <linux/kprobes.h> 33 #include <linux/uaccess.h> 34 #include <linux/hugetlb.h> 35 #include <linux/kfence.h> 36 #include <linux/pagewalk.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/irq.h> 43 #include <asm/facility.h> 44 #include <asm/uv.h> 45 #include "../kernel/entry.h" 46 47 /* 48 * Find out which address space caused the exception. 49 */ 50 static bool is_kernel_fault(struct pt_regs *regs) 51 { 52 union teid teid = { .val = regs->int_parm_long }; 53 54 if (user_mode(regs)) 55 return false; 56 if (teid.as == PSW_BITS_AS_SECONDARY) 57 return false; 58 return true; 59 } 60 61 static unsigned long get_fault_address(struct pt_regs *regs) 62 { 63 union teid teid = { .val = regs->int_parm_long }; 64 65 return teid.addr * PAGE_SIZE; 66 } 67 68 static __always_inline bool fault_is_write(struct pt_regs *regs) 69 { 70 union teid teid = { .val = regs->int_parm_long }; 71 72 if (test_facility(75)) 73 return teid.fsi == TEID_FSI_STORE; 74 return false; 75 } 76 77 static void dump_pagetable(unsigned long asce, unsigned long address) 78 { 79 unsigned long entry, *table = __va(asce & _ASCE_ORIGIN); 80 81 pr_alert("AS:%016lx ", asce); 82 switch (asce & _ASCE_TYPE_MASK) { 83 case _ASCE_TYPE_REGION1: 84 table += (address & _REGION1_INDEX) >> _REGION1_SHIFT; 85 if (get_kernel_nofault(entry, table)) 86 goto bad; 87 pr_cont("R1:%016lx ", entry); 88 if (entry & _REGION_ENTRY_INVALID) 89 goto out; 90 table = __va(entry & _REGION_ENTRY_ORIGIN); 91 fallthrough; 92 case _ASCE_TYPE_REGION2: 93 table += (address & _REGION2_INDEX) >> _REGION2_SHIFT; 94 if (get_kernel_nofault(entry, table)) 95 goto bad; 96 pr_cont("R2:%016lx ", entry); 97 if (entry & _REGION_ENTRY_INVALID) 98 goto out; 99 table = __va(entry & _REGION_ENTRY_ORIGIN); 100 fallthrough; 101 case _ASCE_TYPE_REGION3: 102 table += (address & _REGION3_INDEX) >> _REGION3_SHIFT; 103 if (get_kernel_nofault(entry, table)) 104 goto bad; 105 pr_cont("R3:%016lx ", entry); 106 if (entry & (_REGION_ENTRY_INVALID | _REGION3_ENTRY_LARGE)) 107 goto out; 108 table = __va(entry & _REGION_ENTRY_ORIGIN); 109 fallthrough; 110 case _ASCE_TYPE_SEGMENT: 111 table += (address & _SEGMENT_INDEX) >> _SEGMENT_SHIFT; 112 if (get_kernel_nofault(entry, table)) 113 goto bad; 114 pr_cont("S:%016lx ", entry); 115 if (entry & (_SEGMENT_ENTRY_INVALID | _SEGMENT_ENTRY_LARGE)) 116 goto out; 117 table = __va(entry & _SEGMENT_ENTRY_ORIGIN); 118 } 119 table += (address & _PAGE_INDEX) >> PAGE_SHIFT; 120 if (get_kernel_nofault(entry, table)) 121 goto bad; 122 pr_cont("P:%016lx ", entry); 123 out: 124 pr_cont("\n"); 125 return; 126 bad: 127 pr_cont("BAD\n"); 128 } 129 130 static void dump_fault_info(struct pt_regs *regs) 131 { 132 union teid teid = { .val = regs->int_parm_long }; 133 unsigned long asce; 134 135 pr_alert("Failing address: %016lx TEID: %016lx", 136 get_fault_address(regs), teid.val); 137 if (test_facility(131)) 138 pr_cont(" ESOP-2"); 139 else if (machine_has_esop()) 140 pr_cont(" ESOP-1"); 141 else 142 pr_cont(" SOP"); 143 if (test_facility(75)) 144 pr_cont(" FSI"); 145 pr_cont("\n"); 146 pr_alert("Fault in "); 147 switch (teid.as) { 148 case PSW_BITS_AS_HOME: 149 pr_cont("home space "); 150 break; 151 case PSW_BITS_AS_SECONDARY: 152 pr_cont("secondary space "); 153 break; 154 case PSW_BITS_AS_ACCREG: 155 pr_cont("access register "); 156 break; 157 case PSW_BITS_AS_PRIMARY: 158 pr_cont("primary space "); 159 break; 160 } 161 pr_cont("mode while using "); 162 if (is_kernel_fault(regs)) { 163 asce = get_lowcore()->kernel_asce.val; 164 pr_cont("kernel "); 165 } else { 166 asce = get_lowcore()->user_asce.val; 167 pr_cont("user "); 168 } 169 pr_cont("ASCE.\n"); 170 dump_pagetable(asce, get_fault_address(regs)); 171 } 172 173 int show_unhandled_signals = 1; 174 175 static const struct ctl_table s390_fault_sysctl_table[] = { 176 { 177 .procname = "userprocess_debug", 178 .data = &show_unhandled_signals, 179 .maxlen = sizeof(int), 180 .mode = 0644, 181 .proc_handler = proc_dointvec, 182 }, 183 }; 184 185 static int __init init_s390_fault_sysctls(void) 186 { 187 register_sysctl_init("kernel", s390_fault_sysctl_table); 188 return 0; 189 } 190 arch_initcall(init_s390_fault_sysctls); 191 192 void report_user_fault(struct pt_regs *regs, long signr, int is_mm_fault) 193 { 194 static DEFINE_RATELIMIT_STATE(rs, DEFAULT_RATELIMIT_INTERVAL, DEFAULT_RATELIMIT_BURST); 195 196 if ((task_pid_nr(current) > 1) && !show_unhandled_signals) 197 return; 198 if (!unhandled_signal(current, signr)) 199 return; 200 if (!__ratelimit(&rs)) 201 return; 202 pr_alert("User process fault: interruption code %04x ilc:%d ", 203 regs->int_code & 0xffff, regs->int_code >> 17); 204 print_vma_addr(KERN_CONT "in ", regs->psw.addr); 205 pr_cont("\n"); 206 if (is_mm_fault) 207 dump_fault_info(regs); 208 show_regs(regs); 209 } 210 211 static void do_sigsegv(struct pt_regs *regs, int si_code) 212 { 213 report_user_fault(regs, SIGSEGV, 1); 214 force_sig_fault(SIGSEGV, si_code, (void __user *)get_fault_address(regs)); 215 } 216 217 static void handle_fault_error_nolock(struct pt_regs *regs, int si_code) 218 { 219 unsigned long address; 220 bool is_write; 221 222 if (user_mode(regs)) { 223 if (WARN_ON_ONCE(!si_code)) 224 si_code = SEGV_MAPERR; 225 return do_sigsegv(regs, si_code); 226 } 227 if (fixup_exception(regs)) 228 return; 229 if (is_kernel_fault(regs)) { 230 address = get_fault_address(regs); 231 is_write = fault_is_write(regs); 232 if (kfence_handle_page_fault(address, is_write, regs)) 233 return; 234 pr_alert("Unable to handle kernel pointer dereference in virtual kernel address space\n"); 235 } else { 236 pr_alert("Unable to handle kernel paging request in virtual user address space\n"); 237 } 238 dump_fault_info(regs); 239 die(regs, "Oops"); 240 } 241 242 static void handle_fault_error(struct pt_regs *regs, int si_code) 243 { 244 struct mm_struct *mm = current->mm; 245 246 mmap_read_unlock(mm); 247 handle_fault_error_nolock(regs, si_code); 248 } 249 250 static void do_sigbus(struct pt_regs *regs) 251 { 252 force_sig_fault(SIGBUS, BUS_ADRERR, (void __user *)get_fault_address(regs)); 253 } 254 255 /* 256 * This routine handles page faults. It determines the address, 257 * and the problem, and then passes it off to one of the appropriate 258 * routines. 259 * 260 * interruption code (int_code): 261 * 04 Protection -> Write-Protection (suppression) 262 * 10 Segment translation -> Not present (nullification) 263 * 11 Page translation -> Not present (nullification) 264 * 3b Region third trans. -> Not present (nullification) 265 */ 266 static void do_exception(struct pt_regs *regs, int access) 267 { 268 struct vm_area_struct *vma; 269 unsigned long address; 270 struct mm_struct *mm; 271 unsigned int flags; 272 vm_fault_t fault; 273 bool is_write; 274 275 /* 276 * The instruction that caused the program check has 277 * been nullified. Don't signal single step via SIGTRAP. 278 */ 279 clear_thread_flag(TIF_PER_TRAP); 280 if (kprobe_page_fault(regs, 14)) 281 return; 282 mm = current->mm; 283 address = get_fault_address(regs); 284 is_write = fault_is_write(regs); 285 if (is_kernel_fault(regs) || faulthandler_disabled() || !mm) 286 return handle_fault_error_nolock(regs, 0); 287 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address); 288 flags = FAULT_FLAG_DEFAULT; 289 if (user_mode(regs)) 290 flags |= FAULT_FLAG_USER; 291 if (is_write) 292 access = VM_WRITE; 293 if (access == VM_WRITE) 294 flags |= FAULT_FLAG_WRITE; 295 if (!(flags & FAULT_FLAG_USER)) 296 goto lock_mmap; 297 vma = lock_vma_under_rcu(mm, address); 298 if (!vma) 299 goto lock_mmap; 300 if (!(vma->vm_flags & access)) { 301 vma_end_read(vma); 302 count_vm_vma_lock_event(VMA_LOCK_SUCCESS); 303 return handle_fault_error_nolock(regs, SEGV_ACCERR); 304 } 305 fault = handle_mm_fault(vma, address, flags | FAULT_FLAG_VMA_LOCK, regs); 306 if (!(fault & (VM_FAULT_RETRY | VM_FAULT_COMPLETED))) 307 vma_end_read(vma); 308 if (!(fault & VM_FAULT_RETRY)) { 309 count_vm_vma_lock_event(VMA_LOCK_SUCCESS); 310 goto done; 311 } 312 count_vm_vma_lock_event(VMA_LOCK_RETRY); 313 if (fault & VM_FAULT_MAJOR) 314 flags |= FAULT_FLAG_TRIED; 315 /* Quick path to respond to signals */ 316 if (fault_signal_pending(fault, regs)) { 317 if (!user_mode(regs)) 318 handle_fault_error_nolock(regs, 0); 319 return; 320 } 321 lock_mmap: 322 retry: 323 vma = lock_mm_and_find_vma(mm, address, regs); 324 if (!vma) 325 return handle_fault_error_nolock(regs, SEGV_MAPERR); 326 if (unlikely(!(vma->vm_flags & access))) 327 return handle_fault_error(regs, SEGV_ACCERR); 328 fault = handle_mm_fault(vma, address, flags, regs); 329 if (fault_signal_pending(fault, regs)) { 330 if (!user_mode(regs)) 331 handle_fault_error_nolock(regs, 0); 332 return; 333 } 334 /* The fault is fully completed (including releasing mmap lock) */ 335 if (fault & VM_FAULT_COMPLETED) 336 return; 337 if (fault & VM_FAULT_RETRY) { 338 flags |= FAULT_FLAG_TRIED; 339 goto retry; 340 } 341 mmap_read_unlock(mm); 342 done: 343 if (!(fault & VM_FAULT_ERROR)) 344 return; 345 if (fault & VM_FAULT_OOM) { 346 if (!user_mode(regs)) 347 handle_fault_error_nolock(regs, 0); 348 else 349 pagefault_out_of_memory(); 350 } else if (fault & VM_FAULT_SIGSEGV) { 351 if (!user_mode(regs)) 352 handle_fault_error_nolock(regs, 0); 353 else 354 do_sigsegv(regs, SEGV_MAPERR); 355 } else if (fault & (VM_FAULT_SIGBUS | VM_FAULT_HWPOISON | 356 VM_FAULT_HWPOISON_LARGE)) { 357 if (!user_mode(regs)) 358 handle_fault_error_nolock(regs, 0); 359 else 360 do_sigbus(regs); 361 } else { 362 pr_emerg("Unexpected fault flags: %08x\n", fault); 363 BUG(); 364 } 365 } 366 367 void do_protection_exception(struct pt_regs *regs) 368 { 369 union teid teid = { .val = regs->int_parm_long }; 370 371 /* 372 * Protection exceptions are suppressing, decrement psw address. 373 * The exception to this rule are aborted transactions, for these 374 * the PSW already points to the correct location. 375 */ 376 if (!(regs->int_code & 0x200)) { 377 regs->psw.addr = __rewind_psw(regs->psw, regs->int_code >> 16); 378 set_pt_regs_flag(regs, PIF_PSW_ADDR_ADJUSTED); 379 } 380 /* 381 * If bit 61 if the TEID is not set, the remainder of the 382 * TEID is unpredictable. Special handling is required. 383 */ 384 if (unlikely(!teid.b61)) { 385 if (user_mode(regs)) { 386 dump_fault_info(regs); 387 die(regs, "Unexpected TEID"); 388 } 389 /* Assume low-address protection in kernel mode. */ 390 return handle_fault_error_nolock(regs, 0); 391 } 392 if (unlikely(cpu_has_nx() && teid.b56)) { 393 regs->int_parm_long = (teid.addr * PAGE_SIZE) | (regs->psw.addr & PAGE_MASK); 394 return handle_fault_error_nolock(regs, SEGV_ACCERR); 395 } 396 do_exception(regs, VM_WRITE); 397 } 398 NOKPROBE_SYMBOL(do_protection_exception); 399 400 void do_dat_exception(struct pt_regs *regs) 401 { 402 do_exception(regs, VM_ACCESS_FLAGS); 403 } 404 NOKPROBE_SYMBOL(do_dat_exception); 405 406 #if IS_ENABLED(CONFIG_PGSTE) 407 408 void do_secure_storage_access(struct pt_regs *regs) 409 { 410 union teid teid = { .val = regs->int_parm_long }; 411 unsigned long addr = get_fault_address(regs); 412 struct vm_area_struct *vma; 413 struct folio_walk fw; 414 struct mm_struct *mm; 415 struct folio *folio; 416 int rc; 417 418 /* 419 * Bit 61 indicates if the address is valid, if it is not the 420 * kernel should be stopped or SIGSEGV should be sent to the 421 * process. Bit 61 is not reliable without the misc UV feature, 422 * therefore this needs to be checked too. 423 */ 424 if (uv_has_feature(BIT_UV_FEAT_MISC) && !teid.b61) { 425 /* 426 * When this happens, userspace did something that it 427 * was not supposed to do, e.g. branching into secure 428 * memory. Trigger a segmentation fault. 429 */ 430 if (user_mode(regs)) { 431 send_sig(SIGSEGV, current, 0); 432 return; 433 } 434 /* 435 * The kernel should never run into this case and 436 * there is no way out of this situation. 437 */ 438 panic("Unexpected PGM 0x3d with TEID bit 61=0"); 439 } 440 if (is_kernel_fault(regs)) { 441 folio = phys_to_folio(addr); 442 if (unlikely(!folio_try_get(folio))) 443 return; 444 rc = arch_make_folio_accessible(folio); 445 folio_put(folio); 446 if (rc) 447 BUG(); 448 } else { 449 if (faulthandler_disabled()) 450 return handle_fault_error_nolock(regs, 0); 451 mm = current->mm; 452 mmap_read_lock(mm); 453 vma = find_vma(mm, addr); 454 if (!vma) 455 return handle_fault_error(regs, SEGV_MAPERR); 456 folio = folio_walk_start(&fw, vma, addr, 0); 457 if (!folio) { 458 mmap_read_unlock(mm); 459 return; 460 } 461 /* arch_make_folio_accessible() needs a raised refcount. */ 462 folio_get(folio); 463 rc = arch_make_folio_accessible(folio); 464 folio_put(folio); 465 folio_walk_end(&fw, vma); 466 if (rc) 467 send_sig(SIGSEGV, current, 0); 468 mmap_read_unlock(mm); 469 } 470 } 471 NOKPROBE_SYMBOL(do_secure_storage_access); 472 473 #endif /* CONFIG_PGSTE */ 474