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