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