kernel/debug/debug_core.c

   1 /*
   2  * Kernel Debug Core
   3  *
   4  * Maintainer: Jason Wessel <jason.wessel@windriver.com>
   5  *
   6  * Copyright (C) 2000-2001 VERITAS Software Corporation.
   7  * Copyright (C) 2002-2004 Timesys Corporation
   8  * Copyright (C) 2003-2004 Amit S. Kale <amitkale@linsyssoft.com>
   9  * Copyright (C) 2004 Pavel Machek <pavel@ucw.cz>
  10  * Copyright (C) 2004-2006 Tom Rini <trini@kernel.crashing.org>
  11  * Copyright (C) 2004-2006 LinSysSoft Technologies Pvt. Ltd.
  12  * Copyright (C) 2005-2009 Wind River Systems, Inc.
  13  * Copyright (C) 2007 MontaVista Software, Inc.
  14  * Copyright (C) 2008 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
  15  *
  16  * Contributors at various stages not listed above:
  17  *  Jason Wessel ( jason.wessel@windriver.com )
  18  *  George Anzinger <george@mvista.com>
  19  *  Anurekh Saxena (anurekh.saxena@timesys.com)
  20  *  Lake Stevens Instrument Division (Glenn Engel)
  21  *  Jim Kingdon, Cygnus Support.
  22  *
  23  * Original KGDB stub: David Grothe <dave@gcom.com>,
  24  * Tigran Aivazian <tigran@sco.com>
  25  *
  26  * This file is licensed under the terms of the GNU General Public License
  27  * version 2. This program is licensed "as is" without any warranty of any
  28  * kind, whether express or implied.
  29  */
  30
  31 #define pr_fmt(fmt) "KGDB: " fmt
  32
  33 #include <linux/pid_namespace.h>
  34 #include <linux/clocksource.h>
  35 #include <linux/serial_core.h>
  36 #include <linux/interrupt.h>
  37 #include <linux/spinlock.h>
  38 #include <linux/console.h>
  39 #include <linux/threads.h>
  40 #include <linux/uaccess.h>
  41 #include <linux/kernel.h>
  42 #include <linux/module.h>
  43 #include <linux/ptrace.h>
  44 #include <linux/string.h>
  45 #include <linux/delay.h>
  46 #include <linux/sched.h>
  47 #include <linux/sysrq.h>
  48 #include <linux/reboot.h>
  49 #include <linux/init.h>
  50 #include <linux/kgdb.h>
  51 #include <linux/kdb.h>
  52 #include <linux/nmi.h>
  53 #include <linux/pid.h>
  54 #include <linux/smp.h>
  55 #include <linux/mm.h>
  56 #include <linux/vmacache.h>
  57 #include <linux/rcupdate.h>
  58 #include <linux/irq.h>
  59
  60 #include <asm/cacheflush.h>
  61 #include <asm/byteorder.h>
  62 #include <linux/atomic.h>
  63
  64 #include "debug_core.h"
  65
  66 static int kgdb_break_asap;
  67
  68 struct debuggerinfo_struct kgdb_info[NR_CPUS];
  69
  70 /**
  71  * kgdb_connected - Is a host GDB connected to us?
  72  */
  73 int                             kgdb_connected;
  74 EXPORT_SYMBOL_GPL(kgdb_connected);
  75
  76 /* All the KGDB handlers are installed */
  77 int                     kgdb_io_module_registered;
  78
  79 /* Guard for recursive entry */
  80 static int                      exception_level;
  81
  82 struct kgdb_io          *dbg_io_ops;
  83 static DEFINE_SPINLOCK(kgdb_registration_lock);
  84
  85 /* Action for the reboot notifiter, a global allow kdb to change it */
  86 static int kgdbreboot;
  87 /* kgdb console driver is loaded */
  88 static int kgdb_con_registered;
  89 /* determine if kgdb console output should be used */
  90 static int kgdb_use_con;
  91 /* Flag for alternate operations for early debugging */
  92 bool dbg_is_early = true;
  93 /* Next cpu to become the master debug core */
  94 int dbg_switch_cpu;
  95
  96 /* Use kdb or gdbserver mode */
  97 int dbg_kdb_mode = 1;
  98
  99 static int __init opt_kgdb_con(char *str)
 100 {
 101         kgdb_use_con = 1;
 102         return 0;
 103 }
 104
 105 early_param("kgdbcon", opt_kgdb_con);
 106
 107 module_param(kgdb_use_con, int, 0644);
 108 module_param(kgdbreboot, int, 0644);
 109
 110 /*
 111  * Holds information about breakpoints in a kernel. These breakpoints are
 112  * added and removed by gdb.
 113  */
 114 static struct kgdb_bkpt         kgdb_break[KGDB_MAX_BREAKPOINTS] = {
 115         [0 ... KGDB_MAX_BREAKPOINTS-1] = { .state = BP_UNDEFINED }
 116 };
 117
 118 /*
 119  * The CPU# of the active CPU, or -1 if none:
 120  */
 121 atomic_t                        kgdb_active = ATOMIC_INIT(-1);
 122 EXPORT_SYMBOL_GPL(kgdb_active);
 123 static DEFINE_RAW_SPINLOCK(dbg_master_lock);
 124 static DEFINE_RAW_SPINLOCK(dbg_slave_lock);
 125
 126 /*
 127  * We use NR_CPUs not PERCPU, in case kgdb is used to debug early
 128  * bootup code (which might not have percpu set up yet):
 129  */
 130 static atomic_t                 masters_in_kgdb;
 131 static atomic_t                 slaves_in_kgdb;
 132 static atomic_t                 kgdb_break_tasklet_var;
 133 atomic_t                        kgdb_setting_breakpoint;
 134
 135 struct task_struct              *kgdb_usethread;
 136 struct task_struct              *kgdb_contthread;
 137
 138 int                             kgdb_single_step;
 139 static pid_t                    kgdb_sstep_pid;
 140
 141 /* to keep track of the CPU which is doing the single stepping*/
 142 atomic_t                        kgdb_cpu_doing_single_step = ATOMIC_INIT(-1);
 143
 144 /*
 145  * If you are debugging a problem where roundup (the collection of
 146  * all other CPUs) is a problem [this should be extremely rare],
 147  * then use the nokgdbroundup option to avoid roundup. In that case
 148  * the other CPUs might interfere with your debugging context, so
 149  * use this with care:
 150  */
 151 static int kgdb_do_roundup = 1;
 152
 153 static int __init opt_nokgdbroundup(char *str)
 154 {
 155         kgdb_do_roundup = 0;
 156
 157         return 0;
 158 }
 159
 160 early_param("nokgdbroundup", opt_nokgdbroundup);
 161
 162 /*
 163  * Finally, some KGDB code :-)
 164  */
 165
 166 /*
 167  * Weak aliases for breakpoint management,
 168  * can be overriden by architectures when needed:
 169  */
 170 int __weak kgdb_arch_set_breakpoint(struct kgdb_bkpt *bpt)
 171 {
 172         int err;
 173
 174         err = probe_kernel_read(bpt->saved_instr, (char *)bpt->bpt_addr,
 175                                 BREAK_INSTR_SIZE);
 176         if (err)
 177                 return err;
 178         err = probe_kernel_write((char *)bpt->bpt_addr,
 179                                  arch_kgdb_ops.gdb_bpt_instr, BREAK_INSTR_SIZE);
 180         return err;
 181 }
 182
 183 int __weak kgdb_arch_remove_breakpoint(struct kgdb_bkpt *bpt)
 184 {
 185         return probe_kernel_write((char *)bpt->bpt_addr,
 186                                   (char *)bpt->saved_instr, BREAK_INSTR_SIZE);
 187 }
 188
 189 int __weak kgdb_validate_break_address(unsigned long addr)
 190 {
 191         struct kgdb_bkpt tmp;
 192         int err;
 193         /* Validate setting the breakpoint and then removing it.  If the
 194          * remove fails, the kernel needs to emit a bad message because we
 195          * are deep trouble not being able to put things back the way we
 196          * found them.
 197          */
 198         tmp.bpt_addr = addr;
 199         err = kgdb_arch_set_breakpoint(&tmp);
 200         if (err)
 201                 return err;
 202         err = kgdb_arch_remove_breakpoint(&tmp);
 203         if (err)
 204                 pr_err("Critical breakpoint error, kernel memory destroyed at: %lx\n",
 205                        addr);
 206         return err;
 207 }
 208
 209 unsigned long __weak kgdb_arch_pc(int exception, struct pt_regs *regs)
 210 {
 211         return instruction_pointer(regs);
 212 }
 213
 214 int __weak kgdb_arch_init(void)
 215 {
 216         return 0;
 217 }
 218
 219 int __weak kgdb_skipexception(int exception, struct pt_regs *regs)
 220 {
 221         return 0;
 222 }
 223
 224 #ifdef CONFIG_SMP
 225
 226 /*
 227  * Default (weak) implementation for kgdb_roundup_cpus
 228  */
 229
 230 static DEFINE_PER_CPU(call_single_data_t, kgdb_roundup_csd);
 231
 232 void __weak kgdb_call_nmi_hook(void *ignored)
 233 {
 234         /*
 235          * NOTE: get_irq_regs() is supposed to get the registers from
 236          * before the IPI interrupt happened and so is supposed to
 237          * show where the processor was.  In some situations it's
 238          * possible we might be called without an IPI, so it might be
 239          * safer to figure out how to make kgdb_breakpoint() work
 240          * properly here.
 241          */
 242         kgdb_nmicallback(raw_smp_processor_id(), get_irq_regs());
 243 }
 244
 245 void __weak kgdb_roundup_cpus(void)
 246 {
 247         call_single_data_t *csd;
 248         int this_cpu = raw_smp_processor_id();
 249         int cpu;
 250         int ret;
 251
 252         for_each_online_cpu(cpu) {
 253                 /* No need to roundup ourselves */
 254                 if (cpu == this_cpu)
 255                         continue;
 256
 257                 csd = &per_cpu(kgdb_roundup_csd, cpu);
 258
 259                 /*
 260                  * If it didn't round up last time, don't try again
 261                  * since smp_call_function_single_async() will block.
 262                  *
 263                  * If rounding_up is false then we know that the
 264                  * previous call must have at least started and that
 265                  * means smp_call_function_single_async() won't block.
 266                  */
 267                 if (kgdb_info[cpu].rounding_up)
 268                         continue;
 269                 kgdb_info[cpu].rounding_up = true;
 270
 271                 csd->func = kgdb_call_nmi_hook;
 272                 ret = smp_call_function_single_async(cpu, csd);
 273                 if (ret)
 274                         kgdb_info[cpu].rounding_up = false;
 275         }
 276 }
 277
 278 #endif
 279
 280 /*
 281  * Some architectures need cache flushes when we set/clear a
 282  * breakpoint:
 283  */
 284 static void kgdb_flush_swbreak_addr(unsigned long addr)
 285 {
 286         if (!CACHE_FLUSH_IS_SAFE)
 287                 return;
 288
 289         if (current->mm) {
 290                 int i;
 291
 292                 for (i = 0; i < VMACACHE_SIZE; i++) {
 293                         if (!current->vmacache.vmas[i])
 294                                 continue;
 295                         flush_cache_range(current->vmacache.vmas[i],
 296                                           addr, addr + BREAK_INSTR_SIZE);
 297                 }
 298         }
 299
 300         /* Force flush instruction cache if it was outside the mm */
 301         flush_icache_range(addr, addr + BREAK_INSTR_SIZE);
 302 }
 303
 304 /*
 305  * SW breakpoint management:
 306  */
 307 int dbg_activate_sw_breakpoints(void)
 308 {
 309         int error;
 310         int ret = 0;
 311         int i;
 312
 313         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
 314                 if (kgdb_break[i].state != BP_SET)
 315                         continue;
 316
 317                 error = kgdb_arch_set_breakpoint(&kgdb_break[i]);
 318                 if (error) {
 319                         ret = error;
 320                         pr_info("BP install failed: %lx\n",
 321                                 kgdb_break[i].bpt_addr);
 322                         continue;
 323                 }
 324
 325                 kgdb_flush_swbreak_addr(kgdb_break[i].bpt_addr);
 326                 kgdb_break[i].state = BP_ACTIVE;
 327         }
 328         return ret;
 329 }
 330
 331 int dbg_set_sw_break(unsigned long addr)
 332 {
 333         int err = kgdb_validate_break_address(addr);
 334         int breakno = -1;
 335         int i;
 336
 337         if (err)
 338                 return err;
 339
 340         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
 341                 if ((kgdb_break[i].state == BP_SET) &&
 342                                         (kgdb_break[i].bpt_addr == addr))
 343                         return -EEXIST;
 344         }
 345         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
 346                 if (kgdb_break[i].state == BP_REMOVED &&
 347                                         kgdb_break[i].bpt_addr == addr) {
 348                         breakno = i;
 349                         break;
 350                 }
 351         }
 352
 353         if (breakno == -1) {
 354                 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
 355                         if (kgdb_break[i].state == BP_UNDEFINED) {
 356                                 breakno = i;
 357                                 break;
 358                         }
 359                 }
 360         }
 361
 362         if (breakno == -1)
 363                 return -E2BIG;
 364
 365         kgdb_break[breakno].state = BP_SET;
 366         kgdb_break[breakno].type = BP_BREAKPOINT;
 367         kgdb_break[breakno].bpt_addr = addr;
 368
 369         return 0;
 370 }
 371
 372 int dbg_deactivate_sw_breakpoints(void)
 373 {
 374         int error;
 375         int ret = 0;
 376         int i;
 377
 378         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
 379                 if (kgdb_break[i].state != BP_ACTIVE)
 380                         continue;
 381                 error = kgdb_arch_remove_breakpoint(&kgdb_break[i]);
 382                 if (error) {
 383                         pr_info("BP remove failed: %lx\n",
 384                                 kgdb_break[i].bpt_addr);
 385                         ret = error;
 386                 }
 387
 388                 kgdb_flush_swbreak_addr(kgdb_break[i].bpt_addr);
 389                 kgdb_break[i].state = BP_SET;
 390         }
 391         return ret;
 392 }
 393
 394 int dbg_remove_sw_break(unsigned long addr)
 395 {
 396         int i;
 397
 398         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
 399                 if ((kgdb_break[i].state == BP_SET) &&
 400                                 (kgdb_break[i].bpt_addr == addr)) {
 401                         kgdb_break[i].state = BP_REMOVED;
 402                         return 0;
 403                 }
 404         }
 405         return -ENOENT;
 406 }
 407
 408 int kgdb_isremovedbreak(unsigned long addr)
 409 {
 410         int i;
 411
 412         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
 413                 if ((kgdb_break[i].state == BP_REMOVED) &&
 414                                         (kgdb_break[i].bpt_addr == addr))
 415                         return 1;
 416         }
 417         return 0;
 418 }
 419
 420 int dbg_remove_all_break(void)
 421 {
 422         int error;
 423         int i;
 424
 425         /* Clear memory breakpoints. */
 426         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
 427                 if (kgdb_break[i].state != BP_ACTIVE)
 428                         goto setundefined;
 429                 error = kgdb_arch_remove_breakpoint(&kgdb_break[i]);
 430                 if (error)
 431                         pr_err("breakpoint remove failed: %lx\n",
 432                                kgdb_break[i].bpt_addr);
 433 setundefined:
 434                 kgdb_break[i].state = BP_UNDEFINED;
 435         }
 436
 437         /* Clear hardware breakpoints. */
 438         if (arch_kgdb_ops.remove_all_hw_break)
 439                 arch_kgdb_ops.remove_all_hw_break();
 440
 441         return 0;
 442 }
 443
 444 #ifdef CONFIG_KGDB_KDB
 445 void kdb_dump_stack_on_cpu(int cpu)
 446 {
 447         if (cpu == raw_smp_processor_id() || !IS_ENABLED(CONFIG_SMP)) {
 448                 dump_stack();
 449                 return;
 450         }
 451
 452         if (!(kgdb_info[cpu].exception_state & DCPU_IS_SLAVE)) {
 453                 kdb_printf("ERROR: Task on cpu %d didn't stop in the debugger\n",
 454                            cpu);
 455                 return;
 456         }
 457
 458         /*
 459          * In general, architectures don't support dumping the stack of a
 460          * "running" process that's not the current one.  From the point of
 461          * view of the Linux, kernel processes that are looping in the kgdb
 462          * slave loop are still "running".  There's also no API (that actually
 463          * works across all architectures) that can do a stack crawl based
 464          * on registers passed as a parameter.
 465          *
 466          * Solve this conundrum by asking slave CPUs to do the backtrace
 467          * themselves.
 468          */
 469         kgdb_info[cpu].exception_state |= DCPU_WANT_BT;
 470         while (kgdb_info[cpu].exception_state & DCPU_WANT_BT)
 471                 cpu_relax();
 472 }
 473 #endif
 474
 475 /*
 476  * Return true if there is a valid kgdb I/O module.  Also if no
 477  * debugger is attached a message can be printed to the console about
 478  * waiting for the debugger to attach.
 479  *
 480  * The print_wait argument is only to be true when called from inside
 481  * the core kgdb_handle_exception, because it will wait for the
 482  * debugger to attach.
 483  */
 484 static int kgdb_io_ready(int print_wait)
 485 {
 486         if (!dbg_io_ops)
 487                 return 0;
 488         if (kgdb_connected)
 489                 return 1;
 490         if (atomic_read(&kgdb_setting_breakpoint))
 491                 return 1;
 492         if (print_wait) {
 493 #ifdef CONFIG_KGDB_KDB
 494                 if (!dbg_kdb_mode)
 495                         pr_crit("waiting... or $3#33 for KDB\n");
 496 #else
 497                 pr_crit("Waiting for remote debugger\n");
 498 #endif
 499         }
 500         return 1;
 501 }
 502
 503 static int kgdb_reenter_check(struct kgdb_state *ks)
 504 {
 505         unsigned long addr;
 506
 507         if (atomic_read(&kgdb_active) != raw_smp_processor_id())
 508                 return 0;
 509
 510         /* Panic on recursive debugger calls: */
 511         exception_level++;
 512         addr = kgdb_arch_pc(ks->ex_vector, ks->linux_regs);
 513         dbg_deactivate_sw_breakpoints();
 514
 515         /*
 516          * If the break point removed ok at the place exception
 517          * occurred, try to recover and print a warning to the end
 518          * user because the user planted a breakpoint in a place that
 519          * KGDB needs in order to function.
 520          */
 521         if (dbg_remove_sw_break(addr) == 0) {
 522                 exception_level = 0;
 523                 kgdb_skipexception(ks->ex_vector, ks->linux_regs);
 524                 dbg_activate_sw_breakpoints();
 525                 pr_crit("re-enter error: breakpoint removed %lx\n", addr);
 526                 WARN_ON_ONCE(1);
 527
 528                 return 1;
 529         }
 530         dbg_remove_all_break();
 531         kgdb_skipexception(ks->ex_vector, ks->linux_regs);
 532
 533         if (exception_level > 1) {
 534                 dump_stack();
 535                 panic("Recursive entry to debugger");
 536         }
 537
 538         pr_crit("re-enter exception: ALL breakpoints killed\n");
 539 #ifdef CONFIG_KGDB_KDB
 540         /* Allow kdb to debug itself one level */
 541         return 0;
 542 #endif
 543         dump_stack();
 544         panic("Recursive entry to debugger");
 545
 546         return 1;
 547 }
 548
 549 static void dbg_touch_watchdogs(void)
 550 {
 551         touch_softlockup_watchdog_sync();
 552         clocksource_touch_watchdog();
 553         rcu_cpu_stall_reset();
 554 }
 555
 556 static int kgdb_cpu_enter(struct kgdb_state *ks, struct pt_regs *regs,
 557                 int exception_state)
 558 {
 559         unsigned long flags;
 560         int sstep_tries = 100;
 561         int error;
 562         int cpu;
 563         int trace_on = 0;
 564         int online_cpus = num_online_cpus();
 565         u64 time_left;
 566
 567         kgdb_info[ks->cpu].enter_kgdb++;
 568         kgdb_info[ks->cpu].exception_state |= exception_state;
 569
 570         if (exception_state == DCPU_WANT_MASTER)
 571                 atomic_inc(&masters_in_kgdb);
 572         else
 573                 atomic_inc(&slaves_in_kgdb);
 574
 575         if (arch_kgdb_ops.disable_hw_break)
 576                 arch_kgdb_ops.disable_hw_break(regs);
 577
 578 acquirelock:
 579         /*
 580          * Interrupts will be restored by the 'trap return' code, except when
 581          * single stepping.
 582          */
 583         local_irq_save(flags);
 584
 585         cpu = ks->cpu;
 586         kgdb_info[cpu].debuggerinfo = regs;
 587         kgdb_info[cpu].task = current;
 588         kgdb_info[cpu].ret_state = 0;
 589         kgdb_info[cpu].irq_depth = hardirq_count() >> HARDIRQ_SHIFT;
 590
 591         /* Make sure the above info reaches the primary CPU */
 592         smp_mb();
 593
 594         if (exception_level == 1) {
 595                 if (raw_spin_trylock(&dbg_master_lock))
 596                         atomic_xchg(&kgdb_active, cpu);
 597                 goto cpu_master_loop;
 598         }
 599
 600         /*
 601          * CPU will loop if it is a slave or request to become a kgdb
 602          * master cpu and acquire the kgdb_active lock:
 603          */
 604         while (1) {
 605 cpu_loop:
 606                 if (kgdb_info[cpu].exception_state & DCPU_NEXT_MASTER) {
 607                         kgdb_info[cpu].exception_state &= ~DCPU_NEXT_MASTER;
 608                         goto cpu_master_loop;
 609                 } else if (kgdb_info[cpu].exception_state & DCPU_WANT_MASTER) {
 610                         if (raw_spin_trylock(&dbg_master_lock)) {
 611                                 atomic_xchg(&kgdb_active, cpu);
 612                                 break;
 613                         }
 614                 } else if (kgdb_info[cpu].exception_state & DCPU_WANT_BT) {
 615                         dump_stack();
 616                         kgdb_info[cpu].exception_state &= ~DCPU_WANT_BT;
 617                 } else if (kgdb_info[cpu].exception_state & DCPU_IS_SLAVE) {
 618                         if (!raw_spin_is_locked(&dbg_slave_lock))
 619                                 goto return_normal;
 620                 } else {
 621 return_normal:
 622                         /* Return to normal operation by executing any
 623                          * hw breakpoint fixup.
 624                          */
 625                         if (arch_kgdb_ops.correct_hw_break)
 626                                 arch_kgdb_ops.correct_hw_break();
 627                         if (trace_on)
 628                                 tracing_on();
 629                         kgdb_info[cpu].debuggerinfo = NULL;
 630                         kgdb_info[cpu].task = NULL;
 631                         kgdb_info[cpu].exception_state &=
 632                                 ~(DCPU_WANT_MASTER | DCPU_IS_SLAVE);
 633                         kgdb_info[cpu].enter_kgdb--;
 634                         smp_mb__before_atomic();
 635                         atomic_dec(&slaves_in_kgdb);
 636                         dbg_touch_watchdogs();
 637                         local_irq_restore(flags);
 638                         return 0;
 639                 }
 640                 cpu_relax();
 641         }
 642
 643         /*
 644          * For single stepping, try to only enter on the processor
 645          * that was single stepping.  To guard against a deadlock, the
 646          * kernel will only try for the value of sstep_tries before
 647          * giving up and continuing on.
 648          */
 649         if (atomic_read(&kgdb_cpu_doing_single_step) != -1 &&
 650             (kgdb_info[cpu].task &&
 651              kgdb_info[cpu].task->pid != kgdb_sstep_pid) && --sstep_tries) {
 652                 atomic_set(&kgdb_active, -1);
 653                 raw_spin_unlock(&dbg_master_lock);
 654                 dbg_touch_watchdogs();
 655                 local_irq_restore(flags);
 656
 657                 goto acquirelock;
 658         }
 659
 660         if (!kgdb_io_ready(1)) {
 661                 kgdb_info[cpu].ret_state = 1;
 662                 goto kgdb_restore; /* No I/O connection, resume the system */
 663         }
 664
 665         /*
 666          * Don't enter if we have hit a removed breakpoint.
 667          */
 668         if (kgdb_skipexception(ks->ex_vector, ks->linux_regs))
 669                 goto kgdb_restore;
 670
 671         /* Call the I/O driver's pre_exception routine */
 672         if (dbg_io_ops->pre_exception)
 673                 dbg_io_ops->pre_exception();
 674
 675         /*
 676          * Get the passive CPU lock which will hold all the non-primary
 677          * CPU in a spin state while the debugger is active
 678          */
 679         if (!kgdb_single_step)
 680                 raw_spin_lock(&dbg_slave_lock);
 681
 682 #ifdef CONFIG_SMP
 683         /* If send_ready set, slaves are already waiting */
 684         if (ks->send_ready)
 685                 atomic_set(ks->send_ready, 1);
 686
 687         /* Signal the other CPUs to enter kgdb_wait() */
 688         else if ((!kgdb_single_step) && kgdb_do_roundup)
 689                 kgdb_roundup_cpus();
 690 #endif
 691
 692         /*
 693          * Wait for the other CPUs to be notified and be waiting for us:
 694          */
 695         time_left = MSEC_PER_SEC;
 696         while (kgdb_do_roundup && --time_left &&
 697                (atomic_read(&masters_in_kgdb) + atomic_read(&slaves_in_kgdb)) !=
 698                    online_cpus)
 699                 udelay(1000);
 700         if (!time_left)
 701                 pr_crit("Timed out waiting for secondary CPUs.\n");
 702
 703         /*
 704          * At this point the primary processor is completely
 705          * in the debugger and all secondary CPUs are quiescent
 706          */
 707         dbg_deactivate_sw_breakpoints();
 708         kgdb_single_step = 0;
 709         kgdb_contthread = current;
 710         exception_level = 0;
 711         trace_on = tracing_is_on();
 712         if (trace_on)
 713                 tracing_off();
 714
 715         while (1) {
 716 cpu_master_loop:
 717                 if (dbg_kdb_mode) {
 718                         kgdb_connected = 1;
 719                         error = kdb_stub(ks);
 720                         if (error == -1)
 721                                 continue;
 722                         kgdb_connected = 0;
 723                 } else {
 724                         error = gdb_serial_stub(ks);
 725                 }
 726
 727                 if (error == DBG_PASS_EVENT) {
 728                         dbg_kdb_mode = !dbg_kdb_mode;
 729                 } else if (error == DBG_SWITCH_CPU_EVENT) {
 730                         kgdb_info[dbg_switch_cpu].exception_state |=
 731                                 DCPU_NEXT_MASTER;
 732                         goto cpu_loop;
 733                 } else {
 734                         kgdb_info[cpu].ret_state = error;
 735                         break;
 736                 }
 737         }
 738
 739         /* Call the I/O driver's post_exception routine */
 740         if (dbg_io_ops->post_exception)
 741                 dbg_io_ops->post_exception();
 742
 743         if (!kgdb_single_step) {
 744                 raw_spin_unlock(&dbg_slave_lock);
 745                 /* Wait till all the CPUs have quit from the debugger. */
 746                 while (kgdb_do_roundup && atomic_read(&slaves_in_kgdb))
 747                         cpu_relax();
 748         }
 749
 750 kgdb_restore:
 751         if (atomic_read(&kgdb_cpu_doing_single_step) != -1) {
 752                 int sstep_cpu = atomic_read(&kgdb_cpu_doing_single_step);
 753                 if (kgdb_info[sstep_cpu].task)
 754                         kgdb_sstep_pid = kgdb_info[sstep_cpu].task->pid;
 755                 else
 756                         kgdb_sstep_pid = 0;
 757         }
 758         if (arch_kgdb_ops.correct_hw_break)
 759                 arch_kgdb_ops.correct_hw_break();
 760         if (trace_on)
 761                 tracing_on();
 762
 763         kgdb_info[cpu].debuggerinfo = NULL;
 764         kgdb_info[cpu].task = NULL;
 765         kgdb_info[cpu].exception_state &=
 766                 ~(DCPU_WANT_MASTER | DCPU_IS_SLAVE);
 767         kgdb_info[cpu].enter_kgdb--;
 768         smp_mb__before_atomic();
 769         atomic_dec(&masters_in_kgdb);
 770         /* Free kgdb_active */
 771         atomic_set(&kgdb_active, -1);
 772         raw_spin_unlock(&dbg_master_lock);
 773         dbg_touch_watchdogs();
 774         local_irq_restore(flags);
 775
 776         return kgdb_info[cpu].ret_state;
 777 }
 778
 779 /*
 780  * kgdb_handle_exception() - main entry point from a kernel exception
 781  *
 782  * Locking hierarchy:
 783  *      interface locks, if any (begin_session)
 784  *      kgdb lock (kgdb_active)
 785  */
 786 int
 787 kgdb_handle_exception(int evector, int signo, int ecode, struct pt_regs *regs)
 788 {
 789         struct kgdb_state kgdb_var;
 790         struct kgdb_state *ks = &kgdb_var;
 791         int ret = 0;
 792
 793         if (arch_kgdb_ops.enable_nmi)
 794                 arch_kgdb_ops.enable_nmi(0);
 795         /*
 796          * Avoid entering the debugger if we were triggered due to an oops
 797          * but panic_timeout indicates the system should automatically
 798          * reboot on panic. We don't want to get stuck waiting for input
 799          * on such systems, especially if its "just" an oops.
 800          */
 801         if (signo != SIGTRAP && panic_timeout)
 802                 return 1;
 803
 804         memset(ks, 0, sizeof(struct kgdb_state));
 805         ks->cpu                 = raw_smp_processor_id();
 806         ks->ex_vector           = evector;
 807         ks->signo               = signo;
 808         ks->err_code            = ecode;
 809         ks->linux_regs          = regs;
 810
 811         if (kgdb_reenter_check(ks))
 812                 goto out; /* Ouch, double exception ! */
 813         if (kgdb_info[ks->cpu].enter_kgdb != 0)
 814                 goto out;
 815
 816         ret = kgdb_cpu_enter(ks, regs, DCPU_WANT_MASTER);
 817 out:
 818         if (arch_kgdb_ops.enable_nmi)
 819                 arch_kgdb_ops.enable_nmi(1);
 820         return ret;
 821 }
 822
 823 /*
 824  * GDB places a breakpoint at this function to know dynamically loaded objects.
 825  */
 826 static int module_event(struct notifier_block *self, unsigned long val,
 827         void *data)
 828 {
 829         return 0;
 830 }
 831
 832 static struct notifier_block dbg_module_load_nb = {
 833         .notifier_call  = module_event,
 834 };
 835
 836 int kgdb_nmicallback(int cpu, void *regs)
 837 {
 838 #ifdef CONFIG_SMP
 839         struct kgdb_state kgdb_var;
 840         struct kgdb_state *ks = &kgdb_var;
 841
 842         kgdb_info[cpu].rounding_up = false;
 843
 844         memset(ks, 0, sizeof(struct kgdb_state));
 845         ks->cpu                 = cpu;
 846         ks->linux_regs          = regs;
 847
 848         if (kgdb_info[ks->cpu].enter_kgdb == 0 &&
 849                         raw_spin_is_locked(&dbg_master_lock)) {
 850                 kgdb_cpu_enter(ks, regs, DCPU_IS_SLAVE);
 851                 return 0;
 852         }
 853 #endif
 854         return 1;
 855 }
 856
 857 int kgdb_nmicallin(int cpu, int trapnr, void *regs, int err_code,
 858                                                         atomic_t *send_ready)
 859 {
 860 #ifdef CONFIG_SMP
 861         if (!kgdb_io_ready(0) || !send_ready)
 862                 return 1;
 863
 864         if (kgdb_info[cpu].enter_kgdb == 0) {
 865                 struct kgdb_state kgdb_var;
 866                 struct kgdb_state *ks = &kgdb_var;
 867
 868                 memset(ks, 0, sizeof(struct kgdb_state));
 869                 ks->cpu                 = cpu;
 870                 ks->ex_vector           = trapnr;
 871                 ks->signo               = SIGTRAP;
 872                 ks->err_code            = err_code;
 873                 ks->linux_regs          = regs;
 874                 ks->send_ready          = send_ready;
 875                 kgdb_cpu_enter(ks, regs, DCPU_WANT_MASTER);
 876                 return 0;
 877         }
 878 #endif
 879         return 1;
 880 }
 881
 882 static void kgdb_console_write(struct console *co, const char *s,
 883    unsigned count)
 884 {
 885         unsigned long flags;
 886
 887         /* If we're debugging, or KGDB has not connected, don't try
 888          * and print. */
 889         if (!kgdb_connected || atomic_read(&kgdb_active) != -1 || dbg_kdb_mode)
 890                 return;
 891
 892         local_irq_save(flags);
 893         gdbstub_msg_write(s, count);
 894         local_irq_restore(flags);
 895 }
 896
 897 static struct console kgdbcons = {
 898         .name           = "kgdb",
 899         .write          = kgdb_console_write,
 900         .flags          = CON_PRINTBUFFER | CON_ENABLED,
 901         .index          = -1,
 902 };
 903
 904 #ifdef CONFIG_MAGIC_SYSRQ
 905 static void sysrq_handle_dbg(int key)
 906 {
 907         if (!dbg_io_ops) {
 908                 pr_crit("ERROR: No KGDB I/O module available\n");
 909                 return;
 910         }
 911         if (!kgdb_connected) {
 912 #ifdef CONFIG_KGDB_KDB
 913                 if (!dbg_kdb_mode)
 914                         pr_crit("KGDB or $3#33 for KDB\n");
 915 #else
 916                 pr_crit("Entering KGDB\n");
 917 #endif
 918         }
 919
 920         kgdb_breakpoint();
 921 }
 922
 923 static struct sysrq_key_op sysrq_dbg_op = {
 924         .handler        = sysrq_handle_dbg,
 925         .help_msg       = "debug(g)",
 926         .action_msg     = "DEBUG",
 927 };
 928 #endif
 929
 930 void kgdb_panic(const char *msg)
 931 {
 932         if (!kgdb_io_module_registered)
 933                 return;
 934
 935         /*
 936          * We don't want to get stuck waiting for input from user if
 937          * "panic_timeout" indicates the system should automatically
 938          * reboot on panic.
 939          */
 940         if (panic_timeout)
 941                 return;
 942
 943         if (dbg_kdb_mode)
 944                 kdb_printf("PANIC: %s\n", msg);
 945
 946         kgdb_breakpoint();
 947 }
 948
 949 void __weak kgdb_arch_late(void)
 950 {
 951 }
 952
 953 void __init dbg_late_init(void)
 954 {
 955         dbg_is_early = false;
 956         if (kgdb_io_module_registered)
 957                 kgdb_arch_late();
 958         kdb_init(KDB_INIT_FULL);
 959 }
 960
 961 static int
 962 dbg_notify_reboot(struct notifier_block *this, unsigned long code, void *x)
 963 {
 964         /*
 965          * Take the following action on reboot notify depending on value:
 966          *    1 == Enter debugger
 967          *    0 == [the default] detatch debug client
 968          *   -1 == Do nothing... and use this until the board resets
 969          */
 970         switch (kgdbreboot) {
 971         case 1:
 972                 kgdb_breakpoint();
 973         case -1:
 974                 goto done;
 975         }
 976         if (!dbg_kdb_mode)
 977                 gdbstub_exit(code);
 978 done:
 979         return NOTIFY_DONE;
 980 }
 981
 982 static struct notifier_block dbg_reboot_notifier = {
 983         .notifier_call          = dbg_notify_reboot,
 984         .next                   = NULL,
 985         .priority               = INT_MAX,
 986 };
 987
 988 static void kgdb_register_callbacks(void)
 989 {
 990         if (!kgdb_io_module_registered) {
 991                 kgdb_io_module_registered = 1;
 992                 kgdb_arch_init();
 993                 if (!dbg_is_early)
 994                         kgdb_arch_late();
 995                 register_module_notifier(&dbg_module_load_nb);
 996                 register_reboot_notifier(&dbg_reboot_notifier);
 997 #ifdef CONFIG_MAGIC_SYSRQ
 998                 register_sysrq_key('g', &sysrq_dbg_op);
 999 #endif
1000                 if (kgdb_use_con && !kgdb_con_registered) {
1001                         register_console(&kgdbcons);
1002                         kgdb_con_registered = 1;
1003                 }
1004         }
1005 }
1006
1007 static void kgdb_unregister_callbacks(void)
1008 {
1009         /*
1010          * When this routine is called KGDB should unregister from
1011          * handlers and clean up, making sure it is not handling any
1012          * break exceptions at the time.
1013          */
1014         if (kgdb_io_module_registered) {
1015                 kgdb_io_module_registered = 0;
1016                 unregister_reboot_notifier(&dbg_reboot_notifier);
1017                 unregister_module_notifier(&dbg_module_load_nb);
1018                 kgdb_arch_exit();
1019 #ifdef CONFIG_MAGIC_SYSRQ
1020                 unregister_sysrq_key('g', &sysrq_dbg_op);
1021 #endif
1022                 if (kgdb_con_registered) {
1023                         unregister_console(&kgdbcons);
1024                         kgdb_con_registered = 0;
1025                 }
1026         }
1027 }
1028
1029 /*
1030  * There are times a tasklet needs to be used vs a compiled in
1031  * break point so as to cause an exception outside a kgdb I/O module,
1032  * such as is the case with kgdboe, where calling a breakpoint in the
1033  * I/O driver itself would be fatal.
1034  */
1035 static void kgdb_tasklet_bpt(unsigned long ing)
1036 {
1037         kgdb_breakpoint();
1038         atomic_set(&kgdb_break_tasklet_var, 0);
1039 }
1040
1041 static DECLARE_TASKLET(kgdb_tasklet_breakpoint, kgdb_tasklet_bpt, 0);
1042
1043 void kgdb_schedule_breakpoint(void)
1044 {
1045         if (atomic_read(&kgdb_break_tasklet_var) ||
1046                 atomic_read(&kgdb_active) != -1 ||
1047                 atomic_read(&kgdb_setting_breakpoint))
1048                 return;
1049         atomic_inc(&kgdb_break_tasklet_var);
1050         tasklet_schedule(&kgdb_tasklet_breakpoint);
1051 }
1052 EXPORT_SYMBOL_GPL(kgdb_schedule_breakpoint);
1053
1054 static void kgdb_initial_breakpoint(void)
1055 {
1056         kgdb_break_asap = 0;
1057
1058         pr_crit("Waiting for connection from remote gdb...\n");
1059         kgdb_breakpoint();
1060 }
1061
1062 /**
1063  *      kgdb_register_io_module - register KGDB IO module
1064  *      @new_dbg_io_ops: the io ops vector
1065  *
1066  *      Register it with the KGDB core.
1067  */
1068 int kgdb_register_io_module(struct kgdb_io *new_dbg_io_ops)
1069 {
1070         int err;
1071
1072         spin_lock(&kgdb_registration_lock);
1073
1074         if (dbg_io_ops) {
1075                 spin_unlock(&kgdb_registration_lock);
1076
1077                 pr_err("Another I/O driver is already registered with KGDB\n");
1078                 return -EBUSY;
1079         }
1080
1081         if (new_dbg_io_ops->init) {
1082                 err = new_dbg_io_ops->init();
1083                 if (err) {
1084                         spin_unlock(&kgdb_registration_lock);
1085                         return err;
1086                 }
1087         }
1088
1089         dbg_io_ops = new_dbg_io_ops;
1090
1091         spin_unlock(&kgdb_registration_lock);
1092
1093         pr_info("Registered I/O driver %s\n", new_dbg_io_ops->name);
1094
1095         /* Arm KGDB now. */
1096         kgdb_register_callbacks();
1097
1098         if (kgdb_break_asap)
1099                 kgdb_initial_breakpoint();
1100
1101         return 0;
1102 }
1103 EXPORT_SYMBOL_GPL(kgdb_register_io_module);
1104
1105 /**
1106  *      kkgdb_unregister_io_module - unregister KGDB IO module
1107  *      @old_dbg_io_ops: the io ops vector
1108  *
1109  *      Unregister it with the KGDB core.
1110  */
1111 void kgdb_unregister_io_module(struct kgdb_io *old_dbg_io_ops)
1112 {
1113         BUG_ON(kgdb_connected);
1114
1115         /*
1116          * KGDB is no longer able to communicate out, so
1117          * unregister our callbacks and reset state.
1118          */
1119         kgdb_unregister_callbacks();
1120
1121         spin_lock(&kgdb_registration_lock);
1122
1123         WARN_ON_ONCE(dbg_io_ops != old_dbg_io_ops);
1124         dbg_io_ops = NULL;
1125
1126         spin_unlock(&kgdb_registration_lock);
1127
1128         pr_info("Unregistered I/O driver %s, debugger disabled\n",
1129                 old_dbg_io_ops->name);
1130 }
1131 EXPORT_SYMBOL_GPL(kgdb_unregister_io_module);
1132
1133 int dbg_io_get_char(void)
1134 {
1135         int ret = dbg_io_ops->read_char();
1136         if (ret == NO_POLL_CHAR)
1137                 return -1;
1138         if (!dbg_kdb_mode)
1139                 return ret;
1140         if (ret == 127)
1141                 return 8;
1142         return ret;
1143 }
1144
1145 /**
1146  * kgdb_breakpoint - generate breakpoint exception
1147  *
1148  * This function will generate a breakpoint exception.  It is used at the
1149  * beginning of a program to sync up with a debugger and can be used
1150  * otherwise as a quick means to stop program execution and "break" into
1151  * the debugger.
1152  */
1153 noinline void kgdb_breakpoint(void)
1154 {
1155         atomic_inc(&kgdb_setting_breakpoint);
1156         wmb(); /* Sync point before breakpoint */
1157         arch_kgdb_breakpoint();
1158         wmb(); /* Sync point after breakpoint */
1159         atomic_dec(&kgdb_setting_breakpoint);
1160 }
1161 EXPORT_SYMBOL_GPL(kgdb_breakpoint);
1162
1163 static int __init opt_kgdb_wait(char *str)
1164 {
1165         kgdb_break_asap = 1;
1166
1167         kdb_init(KDB_INIT_EARLY);
1168         if (kgdb_io_module_registered)
1169                 kgdb_initial_breakpoint();
1170
1171         return 0;
1172 }
1173
1174 early_param("kgdbwait", opt_kgdb_wait);