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 #include <linux/pid_namespace.h>
  31 #include <linux/clocksource.h>
  32 #include <linux/interrupt.h>
  33 #include <linux/spinlock.h>
  34 #include <linux/console.h>
  35 #include <linux/threads.h>
  36 #include <linux/uaccess.h>
  37 #include <linux/kernel.h>
  38 #include <linux/module.h>
  39 #include <linux/ptrace.h>
  40 #include <linux/string.h>
  41 #include <linux/delay.h>
  42 #include <linux/sched.h>
  43 #include <linux/sysrq.h>
  44 #include <linux/reboot.h>
  45 #include <linux/init.h>
  46 #include <linux/kgdb.h>
  47 #include <linux/kdb.h>
  48 #include <linux/pid.h>
  49 #include <linux/smp.h>
  50 #include <linux/mm.h>
  51 #include <linux/rcupdate.h>
  52
  53 #include <asm/cacheflush.h>
  54 #include <asm/byteorder.h>
  55 #include <linux/atomic.h>
  56
  57 #include "debug_core.h"
  58
  59 static int kgdb_break_asap;
  60
  61 struct debuggerinfo_struct kgdb_info[NR_CPUS];
  62
  63 /**
  64  * kgdb_connected - Is a host GDB connected to us?
  65  */
  66 int                             kgdb_connected;
  67 EXPORT_SYMBOL_GPL(kgdb_connected);
  68
  69 /* All the KGDB handlers are installed */
  70 int                     kgdb_io_module_registered;
  71
  72 /* Guard for recursive entry */
  73 static int                      exception_level;
  74
  75 struct kgdb_io          *dbg_io_ops;
  76 static DEFINE_SPINLOCK(kgdb_registration_lock);
  77
  78 /* Action for the reboot notifiter, a global allow kdb to change it */
  79 static int kgdbreboot;
  80 /* kgdb console driver is loaded */
  81 static int kgdb_con_registered;
  82 /* determine if kgdb console output should be used */
  83 static int kgdb_use_con;
  84 /* Flag for alternate operations for early debugging */
  85 bool dbg_is_early = true;
  86 /* Next cpu to become the master debug core */
  87 int dbg_switch_cpu;
  88
  89 /* Use kdb or gdbserver mode */
  90 int dbg_kdb_mode = 1;
  91
  92 static int __init opt_kgdb_con(char *str)
  93 {
  94         kgdb_use_con = 1;
  95         return 0;
  96 }
  97
  98 early_param("kgdbcon", opt_kgdb_con);
  99
 100 module_param(kgdb_use_con, int, 0644);
 101 module_param(kgdbreboot, int, 0644);
 102
 103 /*
 104  * Holds information about breakpoints in a kernel. These breakpoints are
 105  * added and removed by gdb.
 106  */
 107 static struct kgdb_bkpt         kgdb_break[KGDB_MAX_BREAKPOINTS] = {
 108         [0 ... KGDB_MAX_BREAKPOINTS-1] = { .state = BP_UNDEFINED }
 109 };
 110
 111 /*
 112  * The CPU# of the active CPU, or -1 if none:
 113  */
 114 atomic_t                        kgdb_active = ATOMIC_INIT(-1);
 115 EXPORT_SYMBOL_GPL(kgdb_active);
 116 static DEFINE_RAW_SPINLOCK(dbg_master_lock);
 117 static DEFINE_RAW_SPINLOCK(dbg_slave_lock);
 118
 119 /*
 120  * We use NR_CPUs not PERCPU, in case kgdb is used to debug early
 121  * bootup code (which might not have percpu set up yet):
 122  */
 123 static atomic_t                 masters_in_kgdb;
 124 static atomic_t                 slaves_in_kgdb;
 125 static atomic_t                 kgdb_break_tasklet_var;
 126 atomic_t                        kgdb_setting_breakpoint;
 127
 128 struct task_struct              *kgdb_usethread;
 129 struct task_struct              *kgdb_contthread;
 130
 131 int                             kgdb_single_step;
 132 static pid_t                    kgdb_sstep_pid;
 133
 134 /* to keep track of the CPU which is doing the single stepping*/
 135 atomic_t                        kgdb_cpu_doing_single_step = ATOMIC_INIT(-1);
 136
 137 /*
 138  * If you are debugging a problem where roundup (the collection of
 139  * all other CPUs) is a problem [this should be extremely rare],
 140  * then use the nokgdbroundup option to avoid roundup. In that case
 141  * the other CPUs might interfere with your debugging context, so
 142  * use this with care:
 143  */
 144 static int kgdb_do_roundup = 1;
 145
 146 static int __init opt_nokgdbroundup(char *str)
 147 {
 148         kgdb_do_roundup = 0;
 149
 150         return 0;
 151 }
 152
 153 early_param("nokgdbroundup", opt_nokgdbroundup);
 154
 155 /*
 156  * Finally, some KGDB code :-)
 157  */
 158
 159 /*
 160  * Weak aliases for breakpoint management,
 161  * can be overriden by architectures when needed:
 162  */
 163 int __weak kgdb_arch_set_breakpoint(unsigned long addr, char *saved_instr)
 164 {
 165         int err;
 166
 167         err = probe_kernel_read(saved_instr, (char *)addr, BREAK_INSTR_SIZE);
 168         if (err)
 169                 return err;
 170
 171         return probe_kernel_write((char *)addr, arch_kgdb_ops.gdb_bpt_instr,
 172                                   BREAK_INSTR_SIZE);
 173 }
 174
 175 int __weak kgdb_arch_remove_breakpoint(unsigned long addr, char *bundle)
 176 {
 177         return probe_kernel_write((char *)addr,
 178                                   (char *)bundle, BREAK_INSTR_SIZE);
 179 }
 180
 181 int __weak kgdb_validate_break_address(unsigned long addr)
 182 {
 183         char tmp_variable[BREAK_INSTR_SIZE];
 184         int err;
 185         /* Validate setting the breakpoint and then removing it.  In the
 186          * remove fails, the kernel needs to emit a bad message because we
 187          * are deep trouble not being able to put things back the way we
 188          * found them.
 189          */
 190         err = kgdb_arch_set_breakpoint(addr, tmp_variable);
 191         if (err)
 192                 return err;
 193         err = kgdb_arch_remove_breakpoint(addr, tmp_variable);
 194         if (err)
 195                 printk(KERN_ERR "KGDB: Critical breakpoint error, kernel "
 196                    "memory destroyed at: %lx", addr);
 197         return err;
 198 }
 199
 200 unsigned long __weak kgdb_arch_pc(int exception, struct pt_regs *regs)
 201 {
 202         return instruction_pointer(regs);
 203 }
 204
 205 int __weak kgdb_arch_init(void)
 206 {
 207         return 0;
 208 }
 209
 210 int __weak kgdb_skipexception(int exception, struct pt_regs *regs)
 211 {
 212         return 0;
 213 }
 214
 215 /*
 216  * Some architectures need cache flushes when we set/clear a
 217  * breakpoint:
 218  */
 219 static void kgdb_flush_swbreak_addr(unsigned long addr)
 220 {
 221         if (!CACHE_FLUSH_IS_SAFE)
 222                 return;
 223
 224         if (current->mm && current->mm->mmap_cache) {
 225                 flush_cache_range(current->mm->mmap_cache,
 226                                   addr, addr + BREAK_INSTR_SIZE);
 227         }
 228         /* Force flush instruction cache if it was outside the mm */
 229         flush_icache_range(addr, addr + BREAK_INSTR_SIZE);
 230 }
 231
 232 /*
 233  * SW breakpoint management:
 234  */
 235 int dbg_activate_sw_breakpoints(void)
 236 {
 237         unsigned long addr;
 238         int error;
 239         int ret = 0;
 240         int i;
 241
 242         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
 243                 if (kgdb_break[i].state != BP_SET)
 244                         continue;
 245
 246                 addr = kgdb_break[i].bpt_addr;
 247                 error = kgdb_arch_set_breakpoint(addr,
 248                                 kgdb_break[i].saved_instr);
 249                 if (error) {
 250                         ret = error;
 251                         printk(KERN_INFO "KGDB: BP install failed: %lx", addr);
 252                         continue;
 253                 }
 254
 255                 kgdb_flush_swbreak_addr(addr);
 256                 kgdb_break[i].state = BP_ACTIVE;
 257         }
 258         return ret;
 259 }
 260
 261 int dbg_set_sw_break(unsigned long addr)
 262 {
 263         int err = kgdb_validate_break_address(addr);
 264         int breakno = -1;
 265         int i;
 266
 267         if (err)
 268                 return err;
 269
 270         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
 271                 if ((kgdb_break[i].state == BP_SET) &&
 272                                         (kgdb_break[i].bpt_addr == addr))
 273                         return -EEXIST;
 274         }
 275         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
 276                 if (kgdb_break[i].state == BP_REMOVED &&
 277                                         kgdb_break[i].bpt_addr == addr) {
 278                         breakno = i;
 279                         break;
 280                 }
 281         }
 282
 283         if (breakno == -1) {
 284                 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
 285                         if (kgdb_break[i].state == BP_UNDEFINED) {
 286                                 breakno = i;
 287                                 break;
 288                         }
 289                 }
 290         }
 291
 292         if (breakno == -1)
 293                 return -E2BIG;
 294
 295         kgdb_break[breakno].state = BP_SET;
 296         kgdb_break[breakno].type = BP_BREAKPOINT;
 297         kgdb_break[breakno].bpt_addr = addr;
 298
 299         return 0;
 300 }
 301
 302 int dbg_deactivate_sw_breakpoints(void)
 303 {
 304         unsigned long addr;
 305         int error;
 306         int ret = 0;
 307         int i;
 308
 309         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
 310                 if (kgdb_break[i].state != BP_ACTIVE)
 311                         continue;
 312                 addr = kgdb_break[i].bpt_addr;
 313                 error = kgdb_arch_remove_breakpoint(addr,
 314                                         kgdb_break[i].saved_instr);
 315                 if (error) {
 316                         printk(KERN_INFO "KGDB: BP remove failed: %lx\n", addr);
 317                         ret = error;
 318                 }
 319
 320                 kgdb_flush_swbreak_addr(addr);
 321                 kgdb_break[i].state = BP_SET;
 322         }
 323         return ret;
 324 }
 325
 326 int dbg_remove_sw_break(unsigned long addr)
 327 {
 328         int i;
 329
 330         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
 331                 if ((kgdb_break[i].state == BP_SET) &&
 332                                 (kgdb_break[i].bpt_addr == addr)) {
 333                         kgdb_break[i].state = BP_REMOVED;
 334                         return 0;
 335                 }
 336         }
 337         return -ENOENT;
 338 }
 339
 340 int kgdb_isremovedbreak(unsigned long addr)
 341 {
 342         int i;
 343
 344         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
 345                 if ((kgdb_break[i].state == BP_REMOVED) &&
 346                                         (kgdb_break[i].bpt_addr == addr))
 347                         return 1;
 348         }
 349         return 0;
 350 }
 351
 352 int dbg_remove_all_break(void)
 353 {
 354         unsigned long addr;
 355         int error;
 356         int i;
 357
 358         /* Clear memory breakpoints. */
 359         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
 360                 if (kgdb_break[i].state != BP_ACTIVE)
 361                         goto setundefined;
 362                 addr = kgdb_break[i].bpt_addr;
 363                 error = kgdb_arch_remove_breakpoint(addr,
 364                                 kgdb_break[i].saved_instr);
 365                 if (error)
 366                         printk(KERN_ERR "KGDB: breakpoint remove failed: %lx\n",
 367                            addr);
 368 setundefined:
 369                 kgdb_break[i].state = BP_UNDEFINED;
 370         }
 371
 372         /* Clear hardware breakpoints. */
 373         if (arch_kgdb_ops.remove_all_hw_break)
 374                 arch_kgdb_ops.remove_all_hw_break();
 375
 376         return 0;
 377 }
 378
 379 /*
 380  * Return true if there is a valid kgdb I/O module.  Also if no
 381  * debugger is attached a message can be printed to the console about
 382  * waiting for the debugger to attach.
 383  *
 384  * The print_wait argument is only to be true when called from inside
 385  * the core kgdb_handle_exception, because it will wait for the
 386  * debugger to attach.
 387  */
 388 static int kgdb_io_ready(int print_wait)
 389 {
 390         if (!dbg_io_ops)
 391                 return 0;
 392         if (kgdb_connected)
 393                 return 1;
 394         if (atomic_read(&kgdb_setting_breakpoint))
 395                 return 1;
 396         if (print_wait) {
 397 #ifdef CONFIG_KGDB_KDB
 398                 if (!dbg_kdb_mode)
 399                         printk(KERN_CRIT "KGDB: waiting... or $3#33 for KDB\n");
 400 #else
 401                 printk(KERN_CRIT "KGDB: Waiting for remote debugger\n");
 402 #endif
 403         }
 404         return 1;
 405 }
 406
 407 static int kgdb_reenter_check(struct kgdb_state *ks)
 408 {
 409         unsigned long addr;
 410
 411         if (atomic_read(&kgdb_active) != raw_smp_processor_id())
 412                 return 0;
 413
 414         /* Panic on recursive debugger calls: */
 415         exception_level++;
 416         addr = kgdb_arch_pc(ks->ex_vector, ks->linux_regs);
 417         dbg_deactivate_sw_breakpoints();
 418
 419         /*
 420          * If the break point removed ok at the place exception
 421          * occurred, try to recover and print a warning to the end
 422          * user because the user planted a breakpoint in a place that
 423          * KGDB needs in order to function.
 424          */
 425         if (dbg_remove_sw_break(addr) == 0) {
 426                 exception_level = 0;
 427                 kgdb_skipexception(ks->ex_vector, ks->linux_regs);
 428                 dbg_activate_sw_breakpoints();
 429                 printk(KERN_CRIT "KGDB: re-enter error: breakpoint removed %lx\n",
 430                         addr);
 431                 WARN_ON_ONCE(1);
 432
 433                 return 1;
 434         }
 435         dbg_remove_all_break();
 436         kgdb_skipexception(ks->ex_vector, ks->linux_regs);
 437
 438         if (exception_level > 1) {
 439                 dump_stack();
 440                 panic("Recursive entry to debugger");
 441         }
 442
 443         printk(KERN_CRIT "KGDB: re-enter exception: ALL breakpoints killed\n");
 444 #ifdef CONFIG_KGDB_KDB
 445         /* Allow kdb to debug itself one level */
 446         return 0;
 447 #endif
 448         dump_stack();
 449         panic("Recursive entry to debugger");
 450
 451         return 1;
 452 }
 453
 454 static void dbg_touch_watchdogs(void)
 455 {
 456         touch_softlockup_watchdog_sync();
 457         clocksource_touch_watchdog();
 458         rcu_cpu_stall_reset();
 459 }
 460
 461 static int kgdb_cpu_enter(struct kgdb_state *ks, struct pt_regs *regs,
 462                 int exception_state)
 463 {
 464         unsigned long flags;
 465         int sstep_tries = 100;
 466         int error;
 467         int cpu;
 468         int trace_on = 0;
 469         int online_cpus = num_online_cpus();
 470
 471         kgdb_info[ks->cpu].enter_kgdb++;
 472         kgdb_info[ks->cpu].exception_state |= exception_state;
 473
 474         if (exception_state == DCPU_WANT_MASTER)
 475                 atomic_inc(&masters_in_kgdb);
 476         else
 477                 atomic_inc(&slaves_in_kgdb);
 478
 479         if (arch_kgdb_ops.disable_hw_break)
 480                 arch_kgdb_ops.disable_hw_break(regs);
 481
 482 acquirelock:
 483         /*
 484          * Interrupts will be restored by the 'trap return' code, except when
 485          * single stepping.
 486          */
 487         local_irq_save(flags);
 488
 489         cpu = ks->cpu;
 490         kgdb_info[cpu].debuggerinfo = regs;
 491         kgdb_info[cpu].task = current;
 492         kgdb_info[cpu].ret_state = 0;
 493         kgdb_info[cpu].irq_depth = hardirq_count() >> HARDIRQ_SHIFT;
 494
 495         /* Make sure the above info reaches the primary CPU */
 496         smp_mb();
 497
 498         if (exception_level == 1) {
 499                 if (raw_spin_trylock(&dbg_master_lock))
 500                         atomic_xchg(&kgdb_active, cpu);
 501                 goto cpu_master_loop;
 502         }
 503
 504         /*
 505          * CPU will loop if it is a slave or request to become a kgdb
 506          * master cpu and acquire the kgdb_active lock:
 507          */
 508         while (1) {
 509 cpu_loop:
 510                 if (kgdb_info[cpu].exception_state & DCPU_NEXT_MASTER) {
 511                         kgdb_info[cpu].exception_state &= ~DCPU_NEXT_MASTER;
 512                         goto cpu_master_loop;
 513                 } else if (kgdb_info[cpu].exception_state & DCPU_WANT_MASTER) {
 514                         if (raw_spin_trylock(&dbg_master_lock)) {
 515                                 atomic_xchg(&kgdb_active, cpu);
 516                                 break;
 517                         }
 518                 } else if (kgdb_info[cpu].exception_state & DCPU_IS_SLAVE) {
 519                         if (!raw_spin_is_locked(&dbg_slave_lock))
 520                                 goto return_normal;
 521                 } else {
 522 return_normal:
 523                         /* Return to normal operation by executing any
 524                          * hw breakpoint fixup.
 525                          */
 526                         if (arch_kgdb_ops.correct_hw_break)
 527                                 arch_kgdb_ops.correct_hw_break();
 528                         if (trace_on)
 529                                 tracing_on();
 530                         kgdb_info[cpu].exception_state &=
 531                                 ~(DCPU_WANT_MASTER | DCPU_IS_SLAVE);
 532                         kgdb_info[cpu].enter_kgdb--;
 533                         smp_mb__before_atomic_dec();
 534                         atomic_dec(&slaves_in_kgdb);
 535                         dbg_touch_watchdogs();
 536                         local_irq_restore(flags);
 537                         return 0;
 538                 }
 539                 cpu_relax();
 540         }
 541
 542         /*
 543          * For single stepping, try to only enter on the processor
 544          * that was single stepping.  To guard against a deadlock, the
 545          * kernel will only try for the value of sstep_tries before
 546          * giving up and continuing on.
 547          */
 548         if (atomic_read(&kgdb_cpu_doing_single_step) != -1 &&
 549             (kgdb_info[cpu].task &&
 550              kgdb_info[cpu].task->pid != kgdb_sstep_pid) && --sstep_tries) {
 551                 atomic_set(&kgdb_active, -1);
 552                 raw_spin_unlock(&dbg_master_lock);
 553                 dbg_touch_watchdogs();
 554                 local_irq_restore(flags);
 555
 556                 goto acquirelock;
 557         }
 558
 559         if (!kgdb_io_ready(1)) {
 560                 kgdb_info[cpu].ret_state = 1;
 561                 goto kgdb_restore; /* No I/O connection, resume the system */
 562         }
 563
 564         /*
 565          * Don't enter if we have hit a removed breakpoint.
 566          */
 567         if (kgdb_skipexception(ks->ex_vector, ks->linux_regs))
 568                 goto kgdb_restore;
 569
 570         /* Call the I/O driver's pre_exception routine */
 571         if (dbg_io_ops->pre_exception)
 572                 dbg_io_ops->pre_exception();
 573
 574         /*
 575          * Get the passive CPU lock which will hold all the non-primary
 576          * CPU in a spin state while the debugger is active
 577          */
 578         if (!kgdb_single_step)
 579                 raw_spin_lock(&dbg_slave_lock);
 580
 581 #ifdef CONFIG_SMP
 582         /* Signal the other CPUs to enter kgdb_wait() */
 583         if ((!kgdb_single_step) && kgdb_do_roundup)
 584                 kgdb_roundup_cpus(flags);
 585 #endif
 586
 587         /*
 588          * Wait for the other CPUs to be notified and be waiting for us:
 589          */
 590         while (kgdb_do_roundup && (atomic_read(&masters_in_kgdb) +
 591                                 atomic_read(&slaves_in_kgdb)) != online_cpus)
 592                 cpu_relax();
 593
 594         /*
 595          * At this point the primary processor is completely
 596          * in the debugger and all secondary CPUs are quiescent
 597          */
 598         dbg_deactivate_sw_breakpoints();
 599         kgdb_single_step = 0;
 600         kgdb_contthread = current;
 601         exception_level = 0;
 602         trace_on = tracing_is_on();
 603         if (trace_on)
 604                 tracing_off();
 605
 606         while (1) {
 607 cpu_master_loop:
 608                 if (dbg_kdb_mode) {
 609                         kgdb_connected = 1;
 610                         error = kdb_stub(ks);
 611                         if (error == -1)
 612                                 continue;
 613                         kgdb_connected = 0;
 614                 } else {
 615                         error = gdb_serial_stub(ks);
 616                 }
 617
 618                 if (error == DBG_PASS_EVENT) {
 619                         dbg_kdb_mode = !dbg_kdb_mode;
 620                 } else if (error == DBG_SWITCH_CPU_EVENT) {
 621                         kgdb_info[dbg_switch_cpu].exception_state |=
 622                                 DCPU_NEXT_MASTER;
 623                         goto cpu_loop;
 624                 } else {
 625                         kgdb_info[cpu].ret_state = error;
 626                         break;
 627                 }
 628         }
 629
 630         /* Call the I/O driver's post_exception routine */
 631         if (dbg_io_ops->post_exception)
 632                 dbg_io_ops->post_exception();
 633
 634         if (!kgdb_single_step) {
 635                 raw_spin_unlock(&dbg_slave_lock);
 636                 /* Wait till all the CPUs have quit from the debugger. */
 637                 while (kgdb_do_roundup && atomic_read(&slaves_in_kgdb))
 638                         cpu_relax();
 639         }
 640
 641 kgdb_restore:
 642         if (atomic_read(&kgdb_cpu_doing_single_step) != -1) {
 643                 int sstep_cpu = atomic_read(&kgdb_cpu_doing_single_step);
 644                 if (kgdb_info[sstep_cpu].task)
 645                         kgdb_sstep_pid = kgdb_info[sstep_cpu].task->pid;
 646                 else
 647                         kgdb_sstep_pid = 0;
 648         }
 649         if (arch_kgdb_ops.correct_hw_break)
 650                 arch_kgdb_ops.correct_hw_break();
 651         if (trace_on)
 652                 tracing_on();
 653
 654         kgdb_info[cpu].exception_state &=
 655                 ~(DCPU_WANT_MASTER | DCPU_IS_SLAVE);
 656         kgdb_info[cpu].enter_kgdb--;
 657         smp_mb__before_atomic_dec();
 658         atomic_dec(&masters_in_kgdb);
 659         /* Free kgdb_active */
 660         atomic_set(&kgdb_active, -1);
 661         raw_spin_unlock(&dbg_master_lock);
 662         dbg_touch_watchdogs();
 663         local_irq_restore(flags);
 664
 665         return kgdb_info[cpu].ret_state;
 666 }
 667
 668 /*
 669  * kgdb_handle_exception() - main entry point from a kernel exception
 670  *
 671  * Locking hierarchy:
 672  *      interface locks, if any (begin_session)
 673  *      kgdb lock (kgdb_active)
 674  */
 675 int
 676 kgdb_handle_exception(int evector, int signo, int ecode, struct pt_regs *regs)
 677 {
 678         struct kgdb_state kgdb_var;
 679         struct kgdb_state *ks = &kgdb_var;
 680
 681         ks->cpu                 = raw_smp_processor_id();
 682         ks->ex_vector           = evector;
 683         ks->signo               = signo;
 684         ks->err_code            = ecode;
 685         ks->kgdb_usethreadid    = 0;
 686         ks->linux_regs          = regs;
 687
 688         if (kgdb_reenter_check(ks))
 689                 return 0; /* Ouch, double exception ! */
 690         if (kgdb_info[ks->cpu].enter_kgdb != 0)
 691                 return 0;
 692
 693         return kgdb_cpu_enter(ks, regs, DCPU_WANT_MASTER);
 694 }
 695
 696 int kgdb_nmicallback(int cpu, void *regs)
 697 {
 698 #ifdef CONFIG_SMP
 699         struct kgdb_state kgdb_var;
 700         struct kgdb_state *ks = &kgdb_var;
 701
 702         memset(ks, 0, sizeof(struct kgdb_state));
 703         ks->cpu                 = cpu;
 704         ks->linux_regs          = regs;
 705
 706         if (kgdb_info[ks->cpu].enter_kgdb == 0 &&
 707                         raw_spin_is_locked(&dbg_master_lock)) {
 708                 kgdb_cpu_enter(ks, regs, DCPU_IS_SLAVE);
 709                 return 0;
 710         }
 711 #endif
 712         return 1;
 713 }
 714
 715 static void kgdb_console_write(struct console *co, const char *s,
 716    unsigned count)
 717 {
 718         unsigned long flags;
 719
 720         /* If we're debugging, or KGDB has not connected, don't try
 721          * and print. */
 722         if (!kgdb_connected || atomic_read(&kgdb_active) != -1 || dbg_kdb_mode)
 723                 return;
 724
 725         local_irq_save(flags);
 726         gdbstub_msg_write(s, count);
 727         local_irq_restore(flags);
 728 }
 729
 730 static struct console kgdbcons = {
 731         .name           = "kgdb",
 732         .write          = kgdb_console_write,
 733         .flags          = CON_PRINTBUFFER | CON_ENABLED,
 734         .index          = -1,
 735 };
 736
 737 #ifdef CONFIG_MAGIC_SYSRQ
 738 static void sysrq_handle_dbg(int key)
 739 {
 740         if (!dbg_io_ops) {
 741                 printk(KERN_CRIT "ERROR: No KGDB I/O module available\n");
 742                 return;
 743         }
 744         if (!kgdb_connected) {
 745 #ifdef CONFIG_KGDB_KDB
 746                 if (!dbg_kdb_mode)
 747                         printk(KERN_CRIT "KGDB or $3#33 for KDB\n");
 748 #else
 749                 printk(KERN_CRIT "Entering KGDB\n");
 750 #endif
 751         }
 752
 753         kgdb_breakpoint();
 754 }
 755
 756 static struct sysrq_key_op sysrq_dbg_op = {
 757         .handler        = sysrq_handle_dbg,
 758         .help_msg       = "debug(G)",
 759         .action_msg     = "DEBUG",
 760 };
 761 #endif
 762
 763 static int kgdb_panic_event(struct notifier_block *self,
 764                             unsigned long val,
 765                             void *data)
 766 {
 767         if (dbg_kdb_mode)
 768                 kdb_printf("PANIC: %s\n", (char *)data);
 769         kgdb_breakpoint();
 770         return NOTIFY_DONE;
 771 }
 772
 773 static struct notifier_block kgdb_panic_event_nb = {
 774        .notifier_call   = kgdb_panic_event,
 775        .priority        = INT_MAX,
 776 };
 777
 778 void __weak kgdb_arch_late(void)
 779 {
 780 }
 781
 782 void __init dbg_late_init(void)
 783 {
 784         dbg_is_early = false;
 785         if (kgdb_io_module_registered)
 786                 kgdb_arch_late();
 787         kdb_init(KDB_INIT_FULL);
 788 }
 789
 790 static int
 791 dbg_notify_reboot(struct notifier_block *this, unsigned long code, void *x)
 792 {
 793         /*
 794          * Take the following action on reboot notify depending on value:
 795          *    1 == Enter debugger
 796          *    0 == [the default] detatch debug client
 797          *   -1 == Do nothing... and use this until the board resets
 798          */
 799         switch (kgdbreboot) {
 800         case 1:
 801                 kgdb_breakpoint();
 802         case -1:
 803                 goto done;
 804         }
 805         if (!dbg_kdb_mode)
 806                 gdbstub_exit(code);
 807 done:
 808         return NOTIFY_DONE;
 809 }
 810
 811 static struct notifier_block dbg_reboot_notifier = {
 812         .notifier_call          = dbg_notify_reboot,
 813         .next                   = NULL,
 814         .priority               = INT_MAX,
 815 };
 816
 817 static void kgdb_register_callbacks(void)
 818 {
 819         if (!kgdb_io_module_registered) {
 820                 kgdb_io_module_registered = 1;
 821                 kgdb_arch_init();
 822                 if (!dbg_is_early)
 823                         kgdb_arch_late();
 824                 register_reboot_notifier(&dbg_reboot_notifier);
 825                 atomic_notifier_chain_register(&panic_notifier_list,
 826                                                &kgdb_panic_event_nb);
 827 #ifdef CONFIG_MAGIC_SYSRQ
 828                 register_sysrq_key('g', &sysrq_dbg_op);
 829 #endif
 830                 if (kgdb_use_con && !kgdb_con_registered) {
 831                         register_console(&kgdbcons);
 832                         kgdb_con_registered = 1;
 833                 }
 834         }
 835 }
 836
 837 static void kgdb_unregister_callbacks(void)
 838 {
 839         /*
 840          * When this routine is called KGDB should unregister from the
 841          * panic handler and clean up, making sure it is not handling any
 842          * break exceptions at the time.
 843          */
 844         if (kgdb_io_module_registered) {
 845                 kgdb_io_module_registered = 0;
 846                 unregister_reboot_notifier(&dbg_reboot_notifier);
 847                 atomic_notifier_chain_unregister(&panic_notifier_list,
 848                                                &kgdb_panic_event_nb);
 849                 kgdb_arch_exit();
 850 #ifdef CONFIG_MAGIC_SYSRQ
 851                 unregister_sysrq_key('g', &sysrq_dbg_op);
 852 #endif
 853                 if (kgdb_con_registered) {
 854                         unregister_console(&kgdbcons);
 855                         kgdb_con_registered = 0;
 856                 }
 857         }
 858 }
 859
 860 /*
 861  * There are times a tasklet needs to be used vs a compiled in
 862  * break point so as to cause an exception outside a kgdb I/O module,
 863  * such as is the case with kgdboe, where calling a breakpoint in the
 864  * I/O driver itself would be fatal.
 865  */
 866 static void kgdb_tasklet_bpt(unsigned long ing)
 867 {
 868         kgdb_breakpoint();
 869         atomic_set(&kgdb_break_tasklet_var, 0);
 870 }
 871
 872 static DECLARE_TASKLET(kgdb_tasklet_breakpoint, kgdb_tasklet_bpt, 0);
 873
 874 void kgdb_schedule_breakpoint(void)
 875 {
 876         if (atomic_read(&kgdb_break_tasklet_var) ||
 877                 atomic_read(&kgdb_active) != -1 ||
 878                 atomic_read(&kgdb_setting_breakpoint))
 879                 return;
 880         atomic_inc(&kgdb_break_tasklet_var);
 881         tasklet_schedule(&kgdb_tasklet_breakpoint);
 882 }
 883 EXPORT_SYMBOL_GPL(kgdb_schedule_breakpoint);
 884
 885 static void kgdb_initial_breakpoint(void)
 886 {
 887         kgdb_break_asap = 0;
 888
 889         printk(KERN_CRIT "kgdb: Waiting for connection from remote gdb...\n");
 890         kgdb_breakpoint();
 891 }
 892
 893 /**
 894  *      kgdb_register_io_module - register KGDB IO module
 895  *      @new_dbg_io_ops: the io ops vector
 896  *
 897  *      Register it with the KGDB core.
 898  */
 899 int kgdb_register_io_module(struct kgdb_io *new_dbg_io_ops)
 900 {
 901         int err;
 902
 903         spin_lock(&kgdb_registration_lock);
 904
 905         if (dbg_io_ops) {
 906                 spin_unlock(&kgdb_registration_lock);
 907
 908                 printk(KERN_ERR "kgdb: Another I/O driver is already "
 909                                 "registered with KGDB.\n");
 910                 return -EBUSY;
 911         }
 912
 913         if (new_dbg_io_ops->init) {
 914                 err = new_dbg_io_ops->init();
 915                 if (err) {
 916                         spin_unlock(&kgdb_registration_lock);
 917                         return err;
 918                 }
 919         }
 920
 921         dbg_io_ops = new_dbg_io_ops;
 922
 923         spin_unlock(&kgdb_registration_lock);
 924
 925         printk(KERN_INFO "kgdb: Registered I/O driver %s.\n",
 926                new_dbg_io_ops->name);
 927
 928         /* Arm KGDB now. */
 929         kgdb_register_callbacks();
 930
 931         if (kgdb_break_asap)
 932                 kgdb_initial_breakpoint();
 933
 934         return 0;
 935 }
 936 EXPORT_SYMBOL_GPL(kgdb_register_io_module);
 937
 938 /**
 939  *      kkgdb_unregister_io_module - unregister KGDB IO module
 940  *      @old_dbg_io_ops: the io ops vector
 941  *
 942  *      Unregister it with the KGDB core.
 943  */
 944 void kgdb_unregister_io_module(struct kgdb_io *old_dbg_io_ops)
 945 {
 946         BUG_ON(kgdb_connected);
 947
 948         /*
 949          * KGDB is no longer able to communicate out, so
 950          * unregister our callbacks and reset state.
 951          */
 952         kgdb_unregister_callbacks();
 953
 954         spin_lock(&kgdb_registration_lock);
 955
 956         WARN_ON_ONCE(dbg_io_ops != old_dbg_io_ops);
 957         dbg_io_ops = NULL;
 958
 959         spin_unlock(&kgdb_registration_lock);
 960
 961         printk(KERN_INFO
 962                 "kgdb: Unregistered I/O driver %s, debugger disabled.\n",
 963                 old_dbg_io_ops->name);
 964 }
 965 EXPORT_SYMBOL_GPL(kgdb_unregister_io_module);
 966
 967 int dbg_io_get_char(void)
 968 {
 969         int ret = dbg_io_ops->read_char();
 970         if (ret == NO_POLL_CHAR)
 971                 return -1;
 972         if (!dbg_kdb_mode)
 973                 return ret;
 974         if (ret == 127)
 975                 return 8;
 976         return ret;
 977 }
 978
 979 /**
 980  * kgdb_breakpoint - generate breakpoint exception
 981  *
 982  * This function will generate a breakpoint exception.  It is used at the
 983  * beginning of a program to sync up with a debugger and can be used
 984  * otherwise as a quick means to stop program execution and "break" into
 985  * the debugger.
 986  */
 987 void kgdb_breakpoint(void)
 988 {
 989         atomic_inc(&kgdb_setting_breakpoint);
 990         wmb(); /* Sync point before breakpoint */
 991         arch_kgdb_breakpoint();
 992         wmb(); /* Sync point after breakpoint */
 993         atomic_dec(&kgdb_setting_breakpoint);
 994 }
 995 EXPORT_SYMBOL_GPL(kgdb_breakpoint);
 996
 997 static int __init opt_kgdb_wait(char *str)
 998 {
 999         kgdb_break_asap = 1;
1000
1001         kdb_init(KDB_INIT_EARLY);
1002         if (kgdb_io_module_registered)
1003                 kgdb_initial_breakpoint();
1004
1005         return 0;
1006 }
1007
1008 early_param("kgdbwait", opt_kgdb_wait);