1 /* 2 * Copyright (C) 1991, 1992 Linus Torvalds 3 * Copyright (C) 2000, 2001, 2002 Andi Kleen, SuSE Labs 4 * 5 * Pentium III FXSR, SSE support 6 * Gareth Hughes <gareth@valinux.com>, May 2000 7 */ 8 9 /* 10 * Handle hardware traps and faults. 11 */ 12 13 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt 14 15 #include <linux/context_tracking.h> 16 #include <linux/interrupt.h> 17 #include <linux/kallsyms.h> 18 #include <linux/spinlock.h> 19 #include <linux/kprobes.h> 20 #include <linux/uaccess.h> 21 #include <linux/kdebug.h> 22 #include <linux/kgdb.h> 23 #include <linux/kernel.h> 24 #include <linux/module.h> 25 #include <linux/ptrace.h> 26 #include <linux/uprobes.h> 27 #include <linux/string.h> 28 #include <linux/delay.h> 29 #include <linux/errno.h> 30 #include <linux/kexec.h> 31 #include <linux/sched.h> 32 #include <linux/timer.h> 33 #include <linux/init.h> 34 #include <linux/bug.h> 35 #include <linux/nmi.h> 36 #include <linux/mm.h> 37 #include <linux/smp.h> 38 #include <linux/io.h> 39 40 #ifdef CONFIG_EISA 41 #include <linux/ioport.h> 42 #include <linux/eisa.h> 43 #endif 44 45 #if defined(CONFIG_EDAC) 46 #include <linux/edac.h> 47 #endif 48 49 #include <asm/kmemcheck.h> 50 #include <asm/stacktrace.h> 51 #include <asm/processor.h> 52 #include <asm/debugreg.h> 53 #include <linux/atomic.h> 54 #include <asm/text-patching.h> 55 #include <asm/ftrace.h> 56 #include <asm/traps.h> 57 #include <asm/desc.h> 58 #include <asm/fpu/internal.h> 59 #include <asm/mce.h> 60 #include <asm/fixmap.h> 61 #include <asm/mach_traps.h> 62 #include <asm/alternative.h> 63 #include <asm/fpu/xstate.h> 64 #include <asm/trace/mpx.h> 65 #include <asm/mpx.h> 66 #include <asm/vm86.h> 67 68 #ifdef CONFIG_X86_64 69 #include <asm/x86_init.h> 70 #include <asm/pgalloc.h> 71 #include <asm/proto.h> 72 73 /* No need to be aligned, but done to keep all IDTs defined the same way. */ 74 gate_desc debug_idt_table[NR_VECTORS] __page_aligned_bss; 75 #else 76 #include <asm/processor-flags.h> 77 #include <asm/setup.h> 78 #include <asm/proto.h> 79 #endif 80 81 /* Must be page-aligned because the real IDT is used in a fixmap. */ 82 gate_desc idt_table[NR_VECTORS] __page_aligned_bss; 83 84 DECLARE_BITMAP(used_vectors, NR_VECTORS); 85 EXPORT_SYMBOL_GPL(used_vectors); 86 87 static inline void cond_local_irq_enable(struct pt_regs *regs) 88 { 89 if (regs->flags & X86_EFLAGS_IF) 90 local_irq_enable(); 91 } 92 93 static inline void cond_local_irq_disable(struct pt_regs *regs) 94 { 95 if (regs->flags & X86_EFLAGS_IF) 96 local_irq_disable(); 97 } 98 99 /* 100 * In IST context, we explicitly disable preemption. This serves two 101 * purposes: it makes it much less likely that we would accidentally 102 * schedule in IST context and it will force a warning if we somehow 103 * manage to schedule by accident. 104 */ 105 void ist_enter(struct pt_regs *regs) 106 { 107 if (user_mode(regs)) { 108 RCU_LOCKDEP_WARN(!rcu_is_watching(), "entry code didn't wake RCU"); 109 } else { 110 /* 111 * We might have interrupted pretty much anything. In 112 * fact, if we're a machine check, we can even interrupt 113 * NMI processing. We don't want in_nmi() to return true, 114 * but we need to notify RCU. 115 */ 116 rcu_nmi_enter(); 117 } 118 119 preempt_disable(); 120 121 /* This code is a bit fragile. Test it. */ 122 RCU_LOCKDEP_WARN(!rcu_is_watching(), "ist_enter didn't work"); 123 } 124 125 void ist_exit(struct pt_regs *regs) 126 { 127 preempt_enable_no_resched(); 128 129 if (!user_mode(regs)) 130 rcu_nmi_exit(); 131 } 132 133 /** 134 * ist_begin_non_atomic() - begin a non-atomic section in an IST exception 135 * @regs: regs passed to the IST exception handler 136 * 137 * IST exception handlers normally cannot schedule. As a special 138 * exception, if the exception interrupted userspace code (i.e. 139 * user_mode(regs) would return true) and the exception was not 140 * a double fault, it can be safe to schedule. ist_begin_non_atomic() 141 * begins a non-atomic section within an ist_enter()/ist_exit() region. 142 * Callers are responsible for enabling interrupts themselves inside 143 * the non-atomic section, and callers must call ist_end_non_atomic() 144 * before ist_exit(). 145 */ 146 void ist_begin_non_atomic(struct pt_regs *regs) 147 { 148 BUG_ON(!user_mode(regs)); 149 150 /* 151 * Sanity check: we need to be on the normal thread stack. This 152 * will catch asm bugs and any attempt to use ist_preempt_enable 153 * from double_fault. 154 */ 155 BUG_ON((unsigned long)(current_top_of_stack() - 156 current_stack_pointer()) >= THREAD_SIZE); 157 158 preempt_enable_no_resched(); 159 } 160 161 /** 162 * ist_end_non_atomic() - begin a non-atomic section in an IST exception 163 * 164 * Ends a non-atomic section started with ist_begin_non_atomic(). 165 */ 166 void ist_end_non_atomic(void) 167 { 168 preempt_disable(); 169 } 170 171 static nokprobe_inline int 172 do_trap_no_signal(struct task_struct *tsk, int trapnr, char *str, 173 struct pt_regs *regs, long error_code) 174 { 175 if (v8086_mode(regs)) { 176 /* 177 * Traps 0, 1, 3, 4, and 5 should be forwarded to vm86. 178 * On nmi (interrupt 2), do_trap should not be called. 179 */ 180 if (trapnr < X86_TRAP_UD) { 181 if (!handle_vm86_trap((struct kernel_vm86_regs *) regs, 182 error_code, trapnr)) 183 return 0; 184 } 185 return -1; 186 } 187 188 if (!user_mode(regs)) { 189 if (!fixup_exception(regs, trapnr)) { 190 tsk->thread.error_code = error_code; 191 tsk->thread.trap_nr = trapnr; 192 die(str, regs, error_code); 193 } 194 return 0; 195 } 196 197 return -1; 198 } 199 200 static siginfo_t *fill_trap_info(struct pt_regs *regs, int signr, int trapnr, 201 siginfo_t *info) 202 { 203 unsigned long siaddr; 204 int sicode; 205 206 switch (trapnr) { 207 default: 208 return SEND_SIG_PRIV; 209 210 case X86_TRAP_DE: 211 sicode = FPE_INTDIV; 212 siaddr = uprobe_get_trap_addr(regs); 213 break; 214 case X86_TRAP_UD: 215 sicode = ILL_ILLOPN; 216 siaddr = uprobe_get_trap_addr(regs); 217 break; 218 case X86_TRAP_AC: 219 sicode = BUS_ADRALN; 220 siaddr = 0; 221 break; 222 } 223 224 info->si_signo = signr; 225 info->si_errno = 0; 226 info->si_code = sicode; 227 info->si_addr = (void __user *)siaddr; 228 return info; 229 } 230 231 static void 232 do_trap(int trapnr, int signr, char *str, struct pt_regs *regs, 233 long error_code, siginfo_t *info) 234 { 235 struct task_struct *tsk = current; 236 237 238 if (!do_trap_no_signal(tsk, trapnr, str, regs, error_code)) 239 return; 240 /* 241 * We want error_code and trap_nr set for userspace faults and 242 * kernelspace faults which result in die(), but not 243 * kernelspace faults which are fixed up. die() gives the 244 * process no chance to handle the signal and notice the 245 * kernel fault information, so that won't result in polluting 246 * the information about previously queued, but not yet 247 * delivered, faults. See also do_general_protection below. 248 */ 249 tsk->thread.error_code = error_code; 250 tsk->thread.trap_nr = trapnr; 251 252 if (show_unhandled_signals && unhandled_signal(tsk, signr) && 253 printk_ratelimit()) { 254 pr_info("%s[%d] trap %s ip:%lx sp:%lx error:%lx", 255 tsk->comm, tsk->pid, str, 256 regs->ip, regs->sp, error_code); 257 print_vma_addr(" in ", regs->ip); 258 pr_cont("\n"); 259 } 260 261 force_sig_info(signr, info ?: SEND_SIG_PRIV, tsk); 262 } 263 NOKPROBE_SYMBOL(do_trap); 264 265 static void do_error_trap(struct pt_regs *regs, long error_code, char *str, 266 unsigned long trapnr, int signr) 267 { 268 siginfo_t info; 269 270 RCU_LOCKDEP_WARN(!rcu_is_watching(), "entry code didn't wake RCU"); 271 272 if (notify_die(DIE_TRAP, str, regs, error_code, trapnr, signr) != 273 NOTIFY_STOP) { 274 cond_local_irq_enable(regs); 275 do_trap(trapnr, signr, str, regs, error_code, 276 fill_trap_info(regs, signr, trapnr, &info)); 277 } 278 } 279 280 #define DO_ERROR(trapnr, signr, str, name) \ 281 dotraplinkage void do_##name(struct pt_regs *regs, long error_code) \ 282 { \ 283 do_error_trap(regs, error_code, str, trapnr, signr); \ 284 } 285 286 DO_ERROR(X86_TRAP_DE, SIGFPE, "divide error", divide_error) 287 DO_ERROR(X86_TRAP_OF, SIGSEGV, "overflow", overflow) 288 DO_ERROR(X86_TRAP_UD, SIGILL, "invalid opcode", invalid_op) 289 DO_ERROR(X86_TRAP_OLD_MF, SIGFPE, "coprocessor segment overrun",coprocessor_segment_overrun) 290 DO_ERROR(X86_TRAP_TS, SIGSEGV, "invalid TSS", invalid_TSS) 291 DO_ERROR(X86_TRAP_NP, SIGBUS, "segment not present", segment_not_present) 292 DO_ERROR(X86_TRAP_SS, SIGBUS, "stack segment", stack_segment) 293 DO_ERROR(X86_TRAP_AC, SIGBUS, "alignment check", alignment_check) 294 295 #ifdef CONFIG_X86_64 296 /* Runs on IST stack */ 297 dotraplinkage void do_double_fault(struct pt_regs *regs, long error_code) 298 { 299 static const char str[] = "double fault"; 300 struct task_struct *tsk = current; 301 302 #ifdef CONFIG_X86_ESPFIX64 303 extern unsigned char native_irq_return_iret[]; 304 305 /* 306 * If IRET takes a non-IST fault on the espfix64 stack, then we 307 * end up promoting it to a doublefault. In that case, modify 308 * the stack to make it look like we just entered the #GP 309 * handler from user space, similar to bad_iret. 310 * 311 * No need for ist_enter here because we don't use RCU. 312 */ 313 if (((long)regs->sp >> PGDIR_SHIFT) == ESPFIX_PGD_ENTRY && 314 regs->cs == __KERNEL_CS && 315 regs->ip == (unsigned long)native_irq_return_iret) 316 { 317 struct pt_regs *normal_regs = task_pt_regs(current); 318 319 /* Fake a #GP(0) from userspace. */ 320 memmove(&normal_regs->ip, (void *)regs->sp, 5*8); 321 normal_regs->orig_ax = 0; /* Missing (lost) #GP error code */ 322 regs->ip = (unsigned long)general_protection; 323 regs->sp = (unsigned long)&normal_regs->orig_ax; 324 325 return; 326 } 327 #endif 328 329 ist_enter(regs); 330 notify_die(DIE_TRAP, str, regs, error_code, X86_TRAP_DF, SIGSEGV); 331 332 tsk->thread.error_code = error_code; 333 tsk->thread.trap_nr = X86_TRAP_DF; 334 335 #ifdef CONFIG_DOUBLEFAULT 336 df_debug(regs, error_code); 337 #endif 338 /* 339 * This is always a kernel trap and never fixable (and thus must 340 * never return). 341 */ 342 for (;;) 343 die(str, regs, error_code); 344 } 345 #endif 346 347 dotraplinkage void do_bounds(struct pt_regs *regs, long error_code) 348 { 349 const struct mpx_bndcsr *bndcsr; 350 siginfo_t *info; 351 352 RCU_LOCKDEP_WARN(!rcu_is_watching(), "entry code didn't wake RCU"); 353 if (notify_die(DIE_TRAP, "bounds", regs, error_code, 354 X86_TRAP_BR, SIGSEGV) == NOTIFY_STOP) 355 return; 356 cond_local_irq_enable(regs); 357 358 if (!user_mode(regs)) 359 die("bounds", regs, error_code); 360 361 if (!cpu_feature_enabled(X86_FEATURE_MPX)) { 362 /* The exception is not from Intel MPX */ 363 goto exit_trap; 364 } 365 366 /* 367 * We need to look at BNDSTATUS to resolve this exception. 368 * A NULL here might mean that it is in its 'init state', 369 * which is all zeros which indicates MPX was not 370 * responsible for the exception. 371 */ 372 bndcsr = get_xsave_field_ptr(XFEATURE_MASK_BNDCSR); 373 if (!bndcsr) 374 goto exit_trap; 375 376 trace_bounds_exception_mpx(bndcsr); 377 /* 378 * The error code field of the BNDSTATUS register communicates status 379 * information of a bound range exception #BR or operation involving 380 * bound directory. 381 */ 382 switch (bndcsr->bndstatus & MPX_BNDSTA_ERROR_CODE) { 383 case 2: /* Bound directory has invalid entry. */ 384 if (mpx_handle_bd_fault()) 385 goto exit_trap; 386 break; /* Success, it was handled */ 387 case 1: /* Bound violation. */ 388 info = mpx_generate_siginfo(regs); 389 if (IS_ERR(info)) { 390 /* 391 * We failed to decode the MPX instruction. Act as if 392 * the exception was not caused by MPX. 393 */ 394 goto exit_trap; 395 } 396 /* 397 * Success, we decoded the instruction and retrieved 398 * an 'info' containing the address being accessed 399 * which caused the exception. This information 400 * allows and application to possibly handle the 401 * #BR exception itself. 402 */ 403 do_trap(X86_TRAP_BR, SIGSEGV, "bounds", regs, error_code, info); 404 kfree(info); 405 break; 406 case 0: /* No exception caused by Intel MPX operations. */ 407 goto exit_trap; 408 default: 409 die("bounds", regs, error_code); 410 } 411 412 return; 413 414 exit_trap: 415 /* 416 * This path out is for all the cases where we could not 417 * handle the exception in some way (like allocating a 418 * table or telling userspace about it. We will also end 419 * up here if the kernel has MPX turned off at compile 420 * time.. 421 */ 422 do_trap(X86_TRAP_BR, SIGSEGV, "bounds", regs, error_code, NULL); 423 } 424 425 dotraplinkage void 426 do_general_protection(struct pt_regs *regs, long error_code) 427 { 428 struct task_struct *tsk; 429 430 RCU_LOCKDEP_WARN(!rcu_is_watching(), "entry code didn't wake RCU"); 431 cond_local_irq_enable(regs); 432 433 if (v8086_mode(regs)) { 434 local_irq_enable(); 435 handle_vm86_fault((struct kernel_vm86_regs *) regs, error_code); 436 return; 437 } 438 439 tsk = current; 440 if (!user_mode(regs)) { 441 if (fixup_exception(regs, X86_TRAP_GP)) 442 return; 443 444 tsk->thread.error_code = error_code; 445 tsk->thread.trap_nr = X86_TRAP_GP; 446 if (notify_die(DIE_GPF, "general protection fault", regs, error_code, 447 X86_TRAP_GP, SIGSEGV) != NOTIFY_STOP) 448 die("general protection fault", regs, error_code); 449 return; 450 } 451 452 tsk->thread.error_code = error_code; 453 tsk->thread.trap_nr = X86_TRAP_GP; 454 455 if (show_unhandled_signals && unhandled_signal(tsk, SIGSEGV) && 456 printk_ratelimit()) { 457 pr_info("%s[%d] general protection ip:%lx sp:%lx error:%lx", 458 tsk->comm, task_pid_nr(tsk), 459 regs->ip, regs->sp, error_code); 460 print_vma_addr(" in ", regs->ip); 461 pr_cont("\n"); 462 } 463 464 force_sig_info(SIGSEGV, SEND_SIG_PRIV, tsk); 465 } 466 NOKPROBE_SYMBOL(do_general_protection); 467 468 /* May run on IST stack. */ 469 dotraplinkage void notrace do_int3(struct pt_regs *regs, long error_code) 470 { 471 #ifdef CONFIG_DYNAMIC_FTRACE 472 /* 473 * ftrace must be first, everything else may cause a recursive crash. 474 * See note by declaration of modifying_ftrace_code in ftrace.c 475 */ 476 if (unlikely(atomic_read(&modifying_ftrace_code)) && 477 ftrace_int3_handler(regs)) 478 return; 479 #endif 480 if (poke_int3_handler(regs)) 481 return; 482 483 ist_enter(regs); 484 RCU_LOCKDEP_WARN(!rcu_is_watching(), "entry code didn't wake RCU"); 485 #ifdef CONFIG_KGDB_LOW_LEVEL_TRAP 486 if (kgdb_ll_trap(DIE_INT3, "int3", regs, error_code, X86_TRAP_BP, 487 SIGTRAP) == NOTIFY_STOP) 488 goto exit; 489 #endif /* CONFIG_KGDB_LOW_LEVEL_TRAP */ 490 491 #ifdef CONFIG_KPROBES 492 if (kprobe_int3_handler(regs)) 493 goto exit; 494 #endif 495 496 if (notify_die(DIE_INT3, "int3", regs, error_code, X86_TRAP_BP, 497 SIGTRAP) == NOTIFY_STOP) 498 goto exit; 499 500 /* 501 * Let others (NMI) know that the debug stack is in use 502 * as we may switch to the interrupt stack. 503 */ 504 debug_stack_usage_inc(); 505 preempt_disable(); 506 cond_local_irq_enable(regs); 507 do_trap(X86_TRAP_BP, SIGTRAP, "int3", regs, error_code, NULL); 508 cond_local_irq_disable(regs); 509 preempt_enable_no_resched(); 510 debug_stack_usage_dec(); 511 exit: 512 ist_exit(regs); 513 } 514 NOKPROBE_SYMBOL(do_int3); 515 516 #ifdef CONFIG_X86_64 517 /* 518 * Help handler running on IST stack to switch off the IST stack if the 519 * interrupted code was in user mode. The actual stack switch is done in 520 * entry_64.S 521 */ 522 asmlinkage __visible notrace struct pt_regs *sync_regs(struct pt_regs *eregs) 523 { 524 struct pt_regs *regs = task_pt_regs(current); 525 *regs = *eregs; 526 return regs; 527 } 528 NOKPROBE_SYMBOL(sync_regs); 529 530 struct bad_iret_stack { 531 void *error_entry_ret; 532 struct pt_regs regs; 533 }; 534 535 asmlinkage __visible notrace 536 struct bad_iret_stack *fixup_bad_iret(struct bad_iret_stack *s) 537 { 538 /* 539 * This is called from entry_64.S early in handling a fault 540 * caused by a bad iret to user mode. To handle the fault 541 * correctly, we want move our stack frame to task_pt_regs 542 * and we want to pretend that the exception came from the 543 * iret target. 544 */ 545 struct bad_iret_stack *new_stack = 546 container_of(task_pt_regs(current), 547 struct bad_iret_stack, regs); 548 549 /* Copy the IRET target to the new stack. */ 550 memmove(&new_stack->regs.ip, (void *)s->regs.sp, 5*8); 551 552 /* Copy the remainder of the stack from the current stack. */ 553 memmove(new_stack, s, offsetof(struct bad_iret_stack, regs.ip)); 554 555 BUG_ON(!user_mode(&new_stack->regs)); 556 return new_stack; 557 } 558 NOKPROBE_SYMBOL(fixup_bad_iret); 559 #endif 560 561 static bool is_sysenter_singlestep(struct pt_regs *regs) 562 { 563 /* 564 * We don't try for precision here. If we're anywhere in the region of 565 * code that can be single-stepped in the SYSENTER entry path, then 566 * assume that this is a useless single-step trap due to SYSENTER 567 * being invoked with TF set. (We don't know in advance exactly 568 * which instructions will be hit because BTF could plausibly 569 * be set.) 570 */ 571 #ifdef CONFIG_X86_32 572 return (regs->ip - (unsigned long)__begin_SYSENTER_singlestep_region) < 573 (unsigned long)__end_SYSENTER_singlestep_region - 574 (unsigned long)__begin_SYSENTER_singlestep_region; 575 #elif defined(CONFIG_IA32_EMULATION) 576 return (regs->ip - (unsigned long)entry_SYSENTER_compat) < 577 (unsigned long)__end_entry_SYSENTER_compat - 578 (unsigned long)entry_SYSENTER_compat; 579 #else 580 return false; 581 #endif 582 } 583 584 /* 585 * Our handling of the processor debug registers is non-trivial. 586 * We do not clear them on entry and exit from the kernel. Therefore 587 * it is possible to get a watchpoint trap here from inside the kernel. 588 * However, the code in ./ptrace.c has ensured that the user can 589 * only set watchpoints on userspace addresses. Therefore the in-kernel 590 * watchpoint trap can only occur in code which is reading/writing 591 * from user space. Such code must not hold kernel locks (since it 592 * can equally take a page fault), therefore it is safe to call 593 * force_sig_info even though that claims and releases locks. 594 * 595 * Code in ./signal.c ensures that the debug control register 596 * is restored before we deliver any signal, and therefore that 597 * user code runs with the correct debug control register even though 598 * we clear it here. 599 * 600 * Being careful here means that we don't have to be as careful in a 601 * lot of more complicated places (task switching can be a bit lazy 602 * about restoring all the debug state, and ptrace doesn't have to 603 * find every occurrence of the TF bit that could be saved away even 604 * by user code) 605 * 606 * May run on IST stack. 607 */ 608 dotraplinkage void do_debug(struct pt_regs *regs, long error_code) 609 { 610 struct task_struct *tsk = current; 611 int user_icebp = 0; 612 unsigned long dr6; 613 int si_code; 614 615 ist_enter(regs); 616 617 get_debugreg(dr6, 6); 618 /* 619 * The Intel SDM says: 620 * 621 * Certain debug exceptions may clear bits 0-3. The remaining 622 * contents of the DR6 register are never cleared by the 623 * processor. To avoid confusion in identifying debug 624 * exceptions, debug handlers should clear the register before 625 * returning to the interrupted task. 626 * 627 * Keep it simple: clear DR6 immediately. 628 */ 629 set_debugreg(0, 6); 630 631 /* Filter out all the reserved bits which are preset to 1 */ 632 dr6 &= ~DR6_RESERVED; 633 634 /* 635 * The SDM says "The processor clears the BTF flag when it 636 * generates a debug exception." Clear TIF_BLOCKSTEP to keep 637 * TIF_BLOCKSTEP in sync with the hardware BTF flag. 638 */ 639 clear_tsk_thread_flag(tsk, TIF_BLOCKSTEP); 640 641 if (unlikely(!user_mode(regs) && (dr6 & DR_STEP) && 642 is_sysenter_singlestep(regs))) { 643 dr6 &= ~DR_STEP; 644 if (!dr6) 645 goto exit; 646 /* 647 * else we might have gotten a single-step trap and hit a 648 * watchpoint at the same time, in which case we should fall 649 * through and handle the watchpoint. 650 */ 651 } 652 653 /* 654 * If dr6 has no reason to give us about the origin of this trap, 655 * then it's very likely the result of an icebp/int01 trap. 656 * User wants a sigtrap for that. 657 */ 658 if (!dr6 && user_mode(regs)) 659 user_icebp = 1; 660 661 /* Catch kmemcheck conditions! */ 662 if ((dr6 & DR_STEP) && kmemcheck_trap(regs)) 663 goto exit; 664 665 /* Store the virtualized DR6 value */ 666 tsk->thread.debugreg6 = dr6; 667 668 #ifdef CONFIG_KPROBES 669 if (kprobe_debug_handler(regs)) 670 goto exit; 671 #endif 672 673 if (notify_die(DIE_DEBUG, "debug", regs, (long)&dr6, error_code, 674 SIGTRAP) == NOTIFY_STOP) 675 goto exit; 676 677 /* 678 * Let others (NMI) know that the debug stack is in use 679 * as we may switch to the interrupt stack. 680 */ 681 debug_stack_usage_inc(); 682 683 /* It's safe to allow irq's after DR6 has been saved */ 684 preempt_disable(); 685 cond_local_irq_enable(regs); 686 687 if (v8086_mode(regs)) { 688 handle_vm86_trap((struct kernel_vm86_regs *) regs, error_code, 689 X86_TRAP_DB); 690 cond_local_irq_disable(regs); 691 preempt_enable_no_resched(); 692 debug_stack_usage_dec(); 693 goto exit; 694 } 695 696 if (WARN_ON_ONCE((dr6 & DR_STEP) && !user_mode(regs))) { 697 /* 698 * Historical junk that used to handle SYSENTER single-stepping. 699 * This should be unreachable now. If we survive for a while 700 * without anyone hitting this warning, we'll turn this into 701 * an oops. 702 */ 703 tsk->thread.debugreg6 &= ~DR_STEP; 704 set_tsk_thread_flag(tsk, TIF_SINGLESTEP); 705 regs->flags &= ~X86_EFLAGS_TF; 706 } 707 si_code = get_si_code(tsk->thread.debugreg6); 708 if (tsk->thread.debugreg6 & (DR_STEP | DR_TRAP_BITS) || user_icebp) 709 send_sigtrap(tsk, regs, error_code, si_code); 710 cond_local_irq_disable(regs); 711 preempt_enable_no_resched(); 712 debug_stack_usage_dec(); 713 714 exit: 715 #if defined(CONFIG_X86_32) 716 /* 717 * This is the most likely code path that involves non-trivial use 718 * of the SYSENTER stack. Check that we haven't overrun it. 719 */ 720 WARN(this_cpu_read(cpu_tss.SYSENTER_stack_canary) != STACK_END_MAGIC, 721 "Overran or corrupted SYSENTER stack\n"); 722 #endif 723 ist_exit(regs); 724 } 725 NOKPROBE_SYMBOL(do_debug); 726 727 /* 728 * Note that we play around with the 'TS' bit in an attempt to get 729 * the correct behaviour even in the presence of the asynchronous 730 * IRQ13 behaviour 731 */ 732 static void math_error(struct pt_regs *regs, int error_code, int trapnr) 733 { 734 struct task_struct *task = current; 735 struct fpu *fpu = &task->thread.fpu; 736 siginfo_t info; 737 char *str = (trapnr == X86_TRAP_MF) ? "fpu exception" : 738 "simd exception"; 739 740 if (notify_die(DIE_TRAP, str, regs, error_code, trapnr, SIGFPE) == NOTIFY_STOP) 741 return; 742 cond_local_irq_enable(regs); 743 744 if (!user_mode(regs)) { 745 if (!fixup_exception(regs, trapnr)) { 746 task->thread.error_code = error_code; 747 task->thread.trap_nr = trapnr; 748 die(str, regs, error_code); 749 } 750 return; 751 } 752 753 /* 754 * Save the info for the exception handler and clear the error. 755 */ 756 fpu__save(fpu); 757 758 task->thread.trap_nr = trapnr; 759 task->thread.error_code = error_code; 760 info.si_signo = SIGFPE; 761 info.si_errno = 0; 762 info.si_addr = (void __user *)uprobe_get_trap_addr(regs); 763 764 info.si_code = fpu__exception_code(fpu, trapnr); 765 766 /* Retry when we get spurious exceptions: */ 767 if (!info.si_code) 768 return; 769 770 force_sig_info(SIGFPE, &info, task); 771 } 772 773 dotraplinkage void do_coprocessor_error(struct pt_regs *regs, long error_code) 774 { 775 RCU_LOCKDEP_WARN(!rcu_is_watching(), "entry code didn't wake RCU"); 776 math_error(regs, error_code, X86_TRAP_MF); 777 } 778 779 dotraplinkage void 780 do_simd_coprocessor_error(struct pt_regs *regs, long error_code) 781 { 782 RCU_LOCKDEP_WARN(!rcu_is_watching(), "entry code didn't wake RCU"); 783 math_error(regs, error_code, X86_TRAP_XF); 784 } 785 786 dotraplinkage void 787 do_spurious_interrupt_bug(struct pt_regs *regs, long error_code) 788 { 789 cond_local_irq_enable(regs); 790 } 791 792 dotraplinkage void 793 do_device_not_available(struct pt_regs *regs, long error_code) 794 { 795 RCU_LOCKDEP_WARN(!rcu_is_watching(), "entry code didn't wake RCU"); 796 797 #ifdef CONFIG_MATH_EMULATION 798 if (!boot_cpu_has(X86_FEATURE_FPU) && (read_cr0() & X86_CR0_EM)) { 799 struct math_emu_info info = { }; 800 801 cond_local_irq_enable(regs); 802 803 info.regs = regs; 804 math_emulate(&info); 805 return; 806 } 807 #endif 808 fpu__restore(¤t->thread.fpu); /* interrupts still off */ 809 #ifdef CONFIG_X86_32 810 cond_local_irq_enable(regs); 811 #endif 812 } 813 NOKPROBE_SYMBOL(do_device_not_available); 814 815 #ifdef CONFIG_X86_32 816 dotraplinkage void do_iret_error(struct pt_regs *regs, long error_code) 817 { 818 siginfo_t info; 819 820 RCU_LOCKDEP_WARN(!rcu_is_watching(), "entry code didn't wake RCU"); 821 local_irq_enable(); 822 823 info.si_signo = SIGILL; 824 info.si_errno = 0; 825 info.si_code = ILL_BADSTK; 826 info.si_addr = NULL; 827 if (notify_die(DIE_TRAP, "iret exception", regs, error_code, 828 X86_TRAP_IRET, SIGILL) != NOTIFY_STOP) { 829 do_trap(X86_TRAP_IRET, SIGILL, "iret exception", regs, error_code, 830 &info); 831 } 832 } 833 #endif 834 835 /* Set of traps needed for early debugging. */ 836 void __init early_trap_init(void) 837 { 838 /* 839 * Don't use IST to set DEBUG_STACK as it doesn't work until TSS 840 * is ready in cpu_init() <-- trap_init(). Before trap_init(), 841 * CPU runs at ring 0 so it is impossible to hit an invalid 842 * stack. Using the original stack works well enough at this 843 * early stage. DEBUG_STACK will be equipped after cpu_init() in 844 * trap_init(). 845 * 846 * We don't need to set trace_idt_table like set_intr_gate(), 847 * since we don't have trace_debug and it will be reset to 848 * 'debug' in trap_init() by set_intr_gate_ist(). 849 */ 850 set_intr_gate_notrace(X86_TRAP_DB, debug); 851 /* int3 can be called from all */ 852 set_system_intr_gate(X86_TRAP_BP, &int3); 853 #ifdef CONFIG_X86_32 854 set_intr_gate(X86_TRAP_PF, page_fault); 855 #endif 856 load_idt(&idt_descr); 857 } 858 859 void __init early_trap_pf_init(void) 860 { 861 #ifdef CONFIG_X86_64 862 set_intr_gate(X86_TRAP_PF, page_fault); 863 #endif 864 } 865 866 void __init trap_init(void) 867 { 868 int i; 869 870 #ifdef CONFIG_EISA 871 void __iomem *p = early_ioremap(0x0FFFD9, 4); 872 873 if (readl(p) == 'E' + ('I'<<8) + ('S'<<16) + ('A'<<24)) 874 EISA_bus = 1; 875 early_iounmap(p, 4); 876 #endif 877 878 set_intr_gate(X86_TRAP_DE, divide_error); 879 set_intr_gate_ist(X86_TRAP_NMI, &nmi, NMI_STACK); 880 /* int4 can be called from all */ 881 set_system_intr_gate(X86_TRAP_OF, &overflow); 882 set_intr_gate(X86_TRAP_BR, bounds); 883 set_intr_gate(X86_TRAP_UD, invalid_op); 884 set_intr_gate(X86_TRAP_NM, device_not_available); 885 #ifdef CONFIG_X86_32 886 set_task_gate(X86_TRAP_DF, GDT_ENTRY_DOUBLEFAULT_TSS); 887 #else 888 set_intr_gate_ist(X86_TRAP_DF, &double_fault, DOUBLEFAULT_STACK); 889 #endif 890 set_intr_gate(X86_TRAP_OLD_MF, coprocessor_segment_overrun); 891 set_intr_gate(X86_TRAP_TS, invalid_TSS); 892 set_intr_gate(X86_TRAP_NP, segment_not_present); 893 set_intr_gate(X86_TRAP_SS, stack_segment); 894 set_intr_gate(X86_TRAP_GP, general_protection); 895 set_intr_gate(X86_TRAP_SPURIOUS, spurious_interrupt_bug); 896 set_intr_gate(X86_TRAP_MF, coprocessor_error); 897 set_intr_gate(X86_TRAP_AC, alignment_check); 898 #ifdef CONFIG_X86_MCE 899 set_intr_gate_ist(X86_TRAP_MC, &machine_check, MCE_STACK); 900 #endif 901 set_intr_gate(X86_TRAP_XF, simd_coprocessor_error); 902 903 /* Reserve all the builtin and the syscall vector: */ 904 for (i = 0; i < FIRST_EXTERNAL_VECTOR; i++) 905 set_bit(i, used_vectors); 906 907 #ifdef CONFIG_IA32_EMULATION 908 set_system_intr_gate(IA32_SYSCALL_VECTOR, entry_INT80_compat); 909 set_bit(IA32_SYSCALL_VECTOR, used_vectors); 910 #endif 911 912 #ifdef CONFIG_X86_32 913 set_system_intr_gate(IA32_SYSCALL_VECTOR, entry_INT80_32); 914 set_bit(IA32_SYSCALL_VECTOR, used_vectors); 915 #endif 916 917 /* 918 * Set the IDT descriptor to a fixed read-only location, so that the 919 * "sidt" instruction will not leak the location of the kernel, and 920 * to defend the IDT against arbitrary memory write vulnerabilities. 921 * It will be reloaded in cpu_init() */ 922 __set_fixmap(FIX_RO_IDT, __pa_symbol(idt_table), PAGE_KERNEL_RO); 923 idt_descr.address = fix_to_virt(FIX_RO_IDT); 924 925 /* 926 * Should be a barrier for any external CPU state: 927 */ 928 cpu_init(); 929 930 /* 931 * X86_TRAP_DB and X86_TRAP_BP have been set 932 * in early_trap_init(). However, ITS works only after 933 * cpu_init() loads TSS. See comments in early_trap_init(). 934 */ 935 set_intr_gate_ist(X86_TRAP_DB, &debug, DEBUG_STACK); 936 /* int3 can be called from all */ 937 set_system_intr_gate_ist(X86_TRAP_BP, &int3, DEBUG_STACK); 938 939 x86_init.irqs.trap_init(); 940 941 #ifdef CONFIG_X86_64 942 memcpy(&debug_idt_table, &idt_table, IDT_ENTRIES * 16); 943 set_nmi_gate(X86_TRAP_DB, &debug); 944 set_nmi_gate(X86_TRAP_BP, &int3); 945 #endif 946 } 947