Pileus Git - ~andy/linux/blob - 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(struct kgdb_bkpt *bpt)
 164 {
 165         int err;
 166
 167         err = probe_kernel_read(bpt->saved_instr, (char *)bpt->bpt_addr,
 168                                 BREAK_INSTR_SIZE);
 169         if (err)
 170                 return err;
 171         err = probe_kernel_write((char *)bpt->bpt_addr,
 172                                  arch_kgdb_ops.gdb_bpt_instr, BREAK_INSTR_SIZE);
 173         return err;
 174 }
 175
 176 int __weak kgdb_arch_remove_breakpoint(struct kgdb_bkpt *bpt)
 177 {
 178         return probe_kernel_write((char *)bpt->bpt_addr,
 179                                   (char *)bpt->saved_instr, BREAK_INSTR_SIZE);
 180 }
 181
 182 int __weak kgdb_validate_break_address(unsigned long addr)
 183 {
 184         struct kgdb_bkpt tmp;
 185         int err;
 186         /* Validate setting the breakpoint and then removing it.  If the
 187          * remove fails, the kernel needs to emit a bad message because we
 188          * are deep trouble not being able to put things back the way we
 189          * found them.
 190          */
 191         tmp.bpt_addr = addr;
 192         err = kgdb_arch_set_breakpoint(&tmp);
 193         if (err)
 194                 return err;
 195         err = kgdb_arch_remove_breakpoint(&tmp);
 196         if (err)
 197                 printk(KERN_ERR "KGDB: Critical breakpoint error, kernel "
 198                    "memory destroyed at: %lx", addr);
 199         return err;
 200 }
 201
 202 unsigned long __weak kgdb_arch_pc(int exception, struct pt_regs *regs)
 203 {
 204         return instruction_pointer(regs);
 205 }
 206
 207 int __weak kgdb_arch_init(void)
 208 {
 209         return 0;
 210 }
 211
 212 int __weak kgdb_skipexception(int exception, struct pt_regs *regs)
 213 {
 214         return 0;
 215 }
 216
 217 /*
 218  * Some architectures need cache flushes when we set/clear a
 219  * breakpoint:
 220  */
 221 static void kgdb_flush_swbreak_addr(unsigned long addr)
 222 {
 223         if (!CACHE_FLUSH_IS_SAFE)
 224                 return;
 225
 226         if (current->mm && current->mm->mmap_cache) {
 227                 flush_cache_range(current->mm->mmap_cache,
 228                                   addr, addr + BREAK_INSTR_SIZE);
 229         }
 230         /* Force flush instruction cache if it was outside the mm */
 231         flush_icache_range(addr, addr + BREAK_INSTR_SIZE);
 232 }
 233
 234 /*
 235  * SW breakpoint management:
 236  */
 237 int dbg_activate_sw_breakpoints(void)
 238 {
 239         int error;
 240         int ret = 0;
 241         int i;
 242
 243         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
 244                 if (kgdb_break[i].state != BP_SET)
 245                         continue;
 246
 247                 error = kgdb_arch_set_breakpoint(&kgdb_break[i]);
 248                 if (error) {
 249                         ret = error;
 250                         printk(KERN_INFO "KGDB: BP install failed: %lx",
 251                                kgdb_break[i].bpt_addr);
 252                         continue;
 253                 }
 254
 255                 kgdb_flush_swbreak_addr(kgdb_break[i].bpt_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         int error;
 305         int ret = 0;
 306         int i;
 307
 308         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
 309                 if (kgdb_break[i].state != BP_ACTIVE)
 310                         continue;
 311                 error = kgdb_arch_remove_breakpoint(&kgdb_break[i]);
 312                 if (error) {
 313                         printk(KERN_INFO "KGDB: BP remove failed: %lx\n",
 314                                kgdb_break[i].bpt_addr);
 315                         ret = error;
 316                 }
 317
 318                 kgdb_flush_swbreak_addr(kgdb_break[i].bpt_addr);
 319                 kgdb_break[i].state = BP_SET;
 320         }
 321         return ret;
 322 }
 323
 324 int dbg_remove_sw_break(unsigned long addr)
 325 {
 326         int i;
 327
 328         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
 329                 if ((kgdb_break[i].state == BP_SET) &&
 330                                 (kgdb_break[i].bpt_addr == addr)) {
 331                         kgdb_break[i].state = BP_REMOVED;
 332                         return 0;
 333                 }
 334         }
 335         return -ENOENT;
 336 }
 337
 338 int kgdb_isremovedbreak(unsigned long addr)
 339 {
 340         int i;
 341
 342         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
 343                 if ((kgdb_break[i].state == BP_REMOVED) &&
 344                                         (kgdb_break[i].bpt_addr == addr))
 345                         return 1;
 346         }
 347         return 0;
 348 }
 349
 350 int dbg_remove_all_break(void)
 351 {
 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                 error = kgdb_arch_remove_breakpoint(&kgdb_break[i]);
 360                 if (error)
 361                         printk(KERN_ERR "KGDB: breakpoint remove failed: %lx\n",
 362                                kgdb_break[i].bpt_addr);
 363 setundefined:
 364                 kgdb_break[i].state = BP_UNDEFINED;
 365         }
 366
 367         /* Clear hardware breakpoints. */
 368         if (arch_kgdb_ops.remove_all_hw_break)
 369                 arch_kgdb_ops.remove_all_hw_break();
 370
 371         return 0;
 372 }
 373
 374 /*
 375  * Return true if there is a valid kgdb I/O module.  Also if no
 376  * debugger is attached a message can be printed to the console about
 377  * waiting for the debugger to attach.
 378  *
 379  * The print_wait argument is only to be true when called from inside
 380  * the core kgdb_handle_exception, because it will wait for the
 381  * debugger to attach.
 382  */
 383 static int kgdb_io_ready(int print_wait)
 384 {
 385         if (!dbg_io_ops)
 386                 return 0;
 387         if (kgdb_connected)
 388                 return 1;
 389         if (atomic_read(&kgdb_setting_breakpoint))
 390                 return 1;
 391         if (print_wait) {
 392 #ifdef CONFIG_KGDB_KDB
 393                 if (!dbg_kdb_mode)
 394                         printk(KERN_CRIT "KGDB: waiting... or $3#33 for KDB\n");
 395 #else
 396                 printk(KERN_CRIT "KGDB: Waiting for remote debugger\n");
 397 #endif
 398         }
 399         return 1;
 400 }
 401
 402 static int kgdb_reenter_check(struct kgdb_state *ks)
 403 {
 404         unsigned long addr;
 405
 406         if (atomic_read(&kgdb_active) != raw_smp_processor_id())
 407                 return 0;
 408
 409         /* Panic on recursive debugger calls: */
 410         exception_level++;
 411         addr = kgdb_arch_pc(ks->ex_vector, ks->linux_regs);
 412         dbg_deactivate_sw_breakpoints();
 413
 414         /*
 415          * If the break point removed ok at the place exception
 416          * occurred, try to recover and print a warning to the end
 417          * user because the user planted a breakpoint in a place that
 418          * KGDB needs in order to function.
 419          */
 420         if (dbg_remove_sw_break(addr) == 0) {
 421                 exception_level = 0;
 422                 kgdb_skipexception(ks->ex_vector, ks->linux_regs);
 423                 dbg_activate_sw_breakpoints();
 424                 printk(KERN_CRIT "KGDB: re-enter error: breakpoint removed %lx\n",
 425                         addr);
 426                 WARN_ON_ONCE(1);
 427
 428                 return 1;
 429         }
 430         dbg_remove_all_break();
 431         kgdb_skipexception(ks->ex_vector, ks->linux_regs);
 432
 433         if (exception_level > 1) {
 434                 dump_stack();
 435                 panic("Recursive entry to debugger");
 436         }
 437
 438         printk(KERN_CRIT "KGDB: re-enter exception: ALL breakpoints killed\n");
 439 #ifdef CONFIG_KGDB_KDB
 440         /* Allow kdb to debug itself one level */
 441         return 0;
 442 #endif
 443         dump_stack();
 444         panic("Recursive entry to debugger");
 445
 446         return 1;
 447 }
 448
 449 static void dbg_touch_watchdogs(void)
 450 {
 451         touch_softlockup_watchdog_sync();
 452         clocksource_touch_watchdog();
 453         rcu_cpu_stall_reset();
 454 }
 455
 456 static int kgdb_cpu_enter(struct kgdb_state *ks, struct pt_regs *regs,
 457                 int exception_state)
 458 {
 459         unsigned long flags;
 460         int sstep_tries = 100;
 461         int error;
 462         int cpu;
 463         int trace_on = 0;
 464         int online_cpus = num_online_cpus();
 465
 466         kgdb_info[ks->cpu].enter_kgdb++;
 467         kgdb_info[ks->cpu].exception_state |= exception_state;
 468
 469         if (exception_state == DCPU_WANT_MASTER)
 470                 atomic_inc(&masters_in_kgdb);
 471         else
 472                 atomic_inc(&slaves_in_kgdb);
 473
 474         if (arch_kgdb_ops.disable_hw_break)
 475                 arch_kgdb_ops.disable_hw_break(regs);
 476
 477 acquirelock:
 478         /*
 479          * Interrupts will be restored by the 'trap return' code, except when
 480          * single stepping.
 481          */
 482         local_irq_save(flags);
 483
 484         cpu = ks->cpu;
 485         kgdb_info[cpu].debuggerinfo = regs;
 486         kgdb_info[cpu].task = current;
 487         kgdb_info[cpu].ret_state = 0;
 488         kgdb_info[cpu].irq_depth = hardirq_count() >> HARDIRQ_SHIFT;
 489
 490         /* Make sure the above info reaches the primary CPU */
 491         smp_mb();
 492
 493         if (exception_level == 1) {
 494                 if (raw_spin_trylock(&dbg_master_lock))
 495                         atomic_xchg(&kgdb_active, cpu);
 496                 goto cpu_master_loop;
 497         }
 498
 499         /*
 500          * CPU will loop if it is a slave or request to become a kgdb
 501          * master cpu and acquire the kgdb_active lock:
 502          */
 503         while (1) {
 504 cpu_loop:
 505                 if (kgdb_info[cpu].exception_state & DCPU_NEXT_MASTER) {
 506                         kgdb_info[cpu].exception_state &= ~DCPU_NEXT_MASTER;
 507                         goto cpu_master_loop;
 508                 } else if (kgdb_info[cpu].exception_state & DCPU_WANT_MASTER) {
 509                         if (raw_spin_trylock(&dbg_master_lock)) {
 510                                 atomic_xchg(&kgdb_active, cpu);
 511                                 break;
 512                         }
 513                 } else if (kgdb_info[cpu].exception_state & DCPU_IS_SLAVE) {
 514                         if (!raw_spin_is_locked(&dbg_slave_lock))
 515                                 goto return_normal;
 516                 } else {
 517 return_normal:
 518                         /* Return to normal operation by executing any
 519                          * hw breakpoint fixup.
 520                          */
 521                         if (arch_kgdb_ops.correct_hw_break)
 522                                 arch_kgdb_ops.correct_hw_break();
 523                         if (trace_on)
 524                                 tracing_on();
 525                         kgdb_info[cpu].exception_state &=
 526                                 ~(DCPU_WANT_MASTER | DCPU_IS_SLAVE);
 527                         kgdb_info[cpu].enter_kgdb--;
 528                         smp_mb__before_atomic_dec();
 529                         atomic_dec(&slaves_in_kgdb);
 530                         dbg_touch_watchdogs();
 531                         local_irq_restore(flags);
 532                         return 0;
 533                 }
 534                 cpu_relax();
 535         }
 536
 537         /*
 538          * For single stepping, try to only enter on the processor
 539          * that was single stepping.  To guard against a deadlock, the
 540          * kernel will only try for the value of sstep_tries before
 541          * giving up and continuing on.
 542          */
 543         if (atomic_read(&kgdb_cpu_doing_single_step) != -1 &&
 544             (kgdb_info[cpu].task &&
 545              kgdb_info[cpu].task->pid != kgdb_sstep_pid) && --sstep_tries) {
 546                 atomic_set(&kgdb_active, -1);
 547                 raw_spin_unlock(&dbg_master_lock);
 548                 dbg_touch_watchdogs();
 549                 local_irq_restore(flags);
 550
 551                 goto acquirelock;
 552         }
 553
 554         if (!kgdb_io_ready(1)) {
 555                 kgdb_info[cpu].ret_state = 1;
 556                 goto kgdb_restore; /* No I/O connection, resume the system */
 557         }
 558
 559         /*
 560          * Don't enter if we have hit a removed breakpoint.
 561          */
 562         if (kgdb_skipexception(ks->ex_vector, ks->linux_regs))
 563                 goto kgdb_restore;
 564
 565         /* Call the I/O driver's pre_exception routine */
 566         if (dbg_io_ops->pre_exception)
 567                 dbg_io_ops->pre_exception();
 568
 569         /*
 570          * Get the passive CPU lock which will hold all the non-primary
 571          * CPU in a spin state while the debugger is active
 572          */
 573         if (!kgdb_single_step)
 574                 raw_spin_lock(&dbg_slave_lock);
 575
 576 #ifdef CONFIG_SMP
 577         /* Signal the other CPUs to enter kgdb_wait() */
 578         if ((!kgdb_single_step) && kgdb_do_roundup)
 579                 kgdb_roundup_cpus(flags);
 580 #endif
 581
 582         /*
 583          * Wait for the other CPUs to be notified and be waiting for us:
 584          */
 585         while (kgdb_do_roundup && (atomic_read(&masters_in_kgdb) +
 586                                 atomic_read(&slaves_in_kgdb)) != online_cpus)
 587                 cpu_relax();
 588
 589         /*
 590          * At this point the primary processor is completely
 591          * in the debugger and all secondary CPUs are quiescent
 592          */
 593         dbg_deactivate_sw_breakpoints();
 594         kgdb_single_step = 0;
 595         kgdb_contthread = current;
 596         exception_level = 0;
 597         trace_on = tracing_is_on();
 598         if (trace_on)
 599                 tracing_off();
 600
 601         while (1) {
 602 cpu_master_loop:
 603                 if (dbg_kdb_mode) {
 604                         kgdb_connected = 1;
 605                         error = kdb_stub(ks);
 606                         if (error == -1)
 607                                 continue;
 608                         kgdb_connected = 0;
 609                 } else {
 610                         error = gdb_serial_stub(ks);
 611                 }
 612
 613                 if (error == DBG_PASS_EVENT) {
 614                         dbg_kdb_mode = !dbg_kdb_mode;
 615                 } else if (error == DBG_SWITCH_CPU_EVENT) {
 616                         kgdb_info[dbg_switch_cpu].exception_state |=
 617                                 DCPU_NEXT_MASTER;
 618                         goto cpu_loop;
 619                 } else {
 620                         kgdb_info[cpu].ret_state = error;
 621                         break;
 622                 }
 623         }
 624
 625         /* Call the I/O driver's post_exception routine */
 626         if (dbg_io_ops->post_exception)
 627                 dbg_io_ops->post_exception();
 628
 629         if (!kgdb_single_step) {
 630                 raw_spin_unlock(&dbg_slave_lock);
 631                 /* Wait till all the CPUs have quit from the debugger. */
 632                 while (kgdb_do_roundup && atomic_read(&slaves_in_kgdb))
 633                         cpu_relax();
 634         }
 635
 636 kgdb_restore:
 637         if (atomic_read(&kgdb_cpu_doing_single_step) != -1) {
 638                 int sstep_cpu = atomic_read(&kgdb_cpu_doing_single_step);
 639                 if (kgdb_info[sstep_cpu].task)
 640                         kgdb_sstep_pid = kgdb_info[sstep_cpu].task->pid;
 641                 else
 642                         kgdb_sstep_pid = 0;
 643         }
 644         if (arch_kgdb_ops.correct_hw_break)
 645                 arch_kgdb_ops.correct_hw_break();
 646         if (trace_on)
 647                 tracing_on();
 648
 649         kgdb_info[cpu].exception_state &=
 650                 ~(DCPU_WANT_MASTER | DCPU_IS_SLAVE);
 651         kgdb_info[cpu].enter_kgdb--;
 652         smp_mb__before_atomic_dec();
 653         atomic_dec(&masters_in_kgdb);
 654         /* Free kgdb_active */
 655         atomic_set(&kgdb_active, -1);
 656         raw_spin_unlock(&dbg_master_lock);
 657         dbg_touch_watchdogs();
 658         local_irq_restore(flags);
 659
 660         return kgdb_info[cpu].ret_state;
 661 }
 662
 663 /*
 664  * kgdb_handle_exception() - main entry point from a kernel exception
 665  *
 666  * Locking hierarchy:
 667  *      interface locks, if any (begin_session)
 668  *      kgdb lock (kgdb_active)
 669  */
 670 int
 671 kgdb_handle_exception(int evector, int signo, int ecode, struct pt_regs *regs)
 672 {
 673         struct kgdb_state kgdb_var;
 674         struct kgdb_state *ks = &kgdb_var;
 675         int ret = 0;
 676
 677         if (arch_kgdb_ops.enable_nmi)
 678                 arch_kgdb_ops.enable_nmi(0);
 679
 680         ks->cpu                 = raw_smp_processor_id();
 681         ks->ex_vector           = evector;
 682         ks->signo               = signo;
 683         ks->err_code            = ecode;
 684         ks->kgdb_usethreadid    = 0;
 685         ks->linux_regs          = regs;
 686
 687         if (kgdb_reenter_check(ks))
 688                 goto out; /* Ouch, double exception ! */
 689         if (kgdb_info[ks->cpu].enter_kgdb != 0)
 690                 goto out;
 691
 692         ret = kgdb_cpu_enter(ks, regs, DCPU_WANT_MASTER);
 693 out:
 694         if (arch_kgdb_ops.enable_nmi)
 695                 arch_kgdb_ops.enable_nmi(1);
 696         return ret;
 697 }
 698
 699 /*
 700  * GDB places a breakpoint at this function to know dynamically
 701  * loaded objects. It's not defined static so that only one instance with this
 702  * name exists in the kernel.
 703  */
 704
 705 static int module_event(struct notifier_block *self, unsigned long val,
 706         void *data)
 707 {
 708         return 0;
 709 }
 710
 711 static struct notifier_block dbg_module_load_nb = {
 712         .notifier_call  = module_event,
 713 };
 714
 715 int kgdb_nmicallback(int cpu, void *regs)
 716 {
 717 #ifdef CONFIG_SMP
 718         struct kgdb_state kgdb_var;
 719         struct kgdb_state *ks = &kgdb_var;
 720
 721         memset(ks, 0, sizeof(struct kgdb_state));
 722         ks->cpu                 = cpu;
 723         ks->linux_regs          = regs;
 724
 725         if (kgdb_info[ks->cpu].enter_kgdb == 0 &&
 726                         raw_spin_is_locked(&dbg_master_lock)) {
 727                 kgdb_cpu_enter(ks, regs, DCPU_IS_SLAVE);
 728                 return 0;
 729         }
 730 #endif
 731         return 1;
 732 }
 733
 734 static void kgdb_console_write(struct console *co, const char *s,
 735    unsigned count)
 736 {
 737         unsigned long flags;
 738
 739         /* If we're debugging, or KGDB has not connected, don't try
 740          * and print. */
 741         if (!kgdb_connected || atomic_read(&kgdb_active) != -1 || dbg_kdb_mode)
 742                 return;
 743
 744         local_irq_save(flags);
 745         gdbstub_msg_write(s, count);
 746         local_irq_restore(flags);
 747 }
 748
 749 static struct console kgdbcons = {
 750         .name           = "kgdb",
 751         .write          = kgdb_console_write,
 752         .flags          = CON_PRINTBUFFER | CON_ENABLED,
 753         .index          = -1,
 754 };
 755
 756 #ifdef CONFIG_MAGIC_SYSRQ
 757 static void sysrq_handle_dbg(int key)
 758 {
 759         if (!dbg_io_ops) {
 760                 printk(KERN_CRIT "ERROR: No KGDB I/O module available\n");
 761                 return;
 762         }
 763         if (!kgdb_connected) {
 764 #ifdef CONFIG_KGDB_KDB
 765                 if (!dbg_kdb_mode)
 766                         printk(KERN_CRIT "KGDB or $3#33 for KDB\n");
 767 #else
 768                 printk(KERN_CRIT "Entering KGDB\n");
 769 #endif
 770         }
 771
 772         kgdb_breakpoint();
 773 }
 774
 775 static struct sysrq_key_op sysrq_dbg_op = {
 776         .handler        = sysrq_handle_dbg,
 777         .help_msg       = "debug(G)",
 778         .action_msg     = "DEBUG",
 779 };
 780 #endif
 781
 782 static int kgdb_panic_event(struct notifier_block *self,
 783                             unsigned long val,
 784                             void *data)
 785 {
 786         if (dbg_kdb_mode)
 787                 kdb_printf("PANIC: %s\n", (char *)data);
 788         kgdb_breakpoint();
 789         return NOTIFY_DONE;
 790 }
 791
 792 static struct notifier_block kgdb_panic_event_nb = {
 793        .notifier_call   = kgdb_panic_event,
 794        .priority        = INT_MAX,
 795 };
 796
 797 void __weak kgdb_arch_late(void)
 798 {
 799 }
 800
 801 void __init dbg_late_init(void)
 802 {
 803         dbg_is_early = false;
 804         if (kgdb_io_module_registered)
 805                 kgdb_arch_late();
 806         kdb_init(KDB_INIT_FULL);
 807 }
 808
 809 static int
 810 dbg_notify_reboot(struct notifier_block *this, unsigned long code, void *x)
 811 {
 812         /*
 813          * Take the following action on reboot notify depending on value:
 814          *    1 == Enter debugger
 815          *    0 == [the default] detatch debug client
 816          *   -1 == Do nothing... and use this until the board resets
 817          */
 818         switch (kgdbreboot) {
 819         case 1:
 820                 kgdb_breakpoint();
 821         case -1:
 822                 goto done;
 823         }
 824         if (!dbg_kdb_mode)
 825                 gdbstub_exit(code);
 826 done:
 827         return NOTIFY_DONE;
 828 }
 829
 830 static struct notifier_block dbg_reboot_notifier = {
 831         .notifier_call          = dbg_notify_reboot,
 832         .next                   = NULL,
 833         .priority               = INT_MAX,
 834 };
 835
 836 static void kgdb_register_callbacks(void)
 837 {
 838         if (!kgdb_io_module_registered) {
 839                 kgdb_io_module_registered = 1;
 840                 kgdb_arch_init();
 841                 if (!dbg_is_early)
 842                         kgdb_arch_late();
 843                 register_module_notifier(&dbg_module_load_nb);
 844                 register_reboot_notifier(&dbg_reboot_notifier);
 845                 atomic_notifier_chain_register(&panic_notifier_list,
 846                                                &kgdb_panic_event_nb);
 847 #ifdef CONFIG_MAGIC_SYSRQ
 848                 register_sysrq_key('g', &sysrq_dbg_op);
 849 #endif
 850                 if (kgdb_use_con && !kgdb_con_registered) {
 851                         register_console(&kgdbcons);
 852                         kgdb_con_registered = 1;
 853                 }
 854         }
 855 }
 856
 857 static void kgdb_unregister_callbacks(void)
 858 {
 859         /*
 860          * When this routine is called KGDB should unregister from the
 861          * panic handler and clean up, making sure it is not handling any
 862          * break exceptions at the time.
 863          */
 864         if (kgdb_io_module_registered) {
 865                 kgdb_io_module_registered = 0;
 866                 unregister_reboot_notifier(&dbg_reboot_notifier);
 867                 unregister_module_notifier(&dbg_module_load_nb);
 868                 atomic_notifier_chain_unregister(&panic_notifier_list,
 869                                                &kgdb_panic_event_nb);
 870                 kgdb_arch_exit();
 871 #ifdef CONFIG_MAGIC_SYSRQ
 872                 unregister_sysrq_key('g', &sysrq_dbg_op);
 873 #endif
 874                 if (kgdb_con_registered) {
 875                         unregister_console(&kgdbcons);
 876                         kgdb_con_registered = 0;
 877                 }
 878         }
 879 }
 880
 881 /*
 882  * There are times a tasklet needs to be used vs a compiled in
 883  * break point so as to cause an exception outside a kgdb I/O module,
 884  * such as is the case with kgdboe, where calling a breakpoint in the
 885  * I/O driver itself would be fatal.
 886  */
 887 static void kgdb_tasklet_bpt(unsigned long ing)
 888 {
 889         kgdb_breakpoint();
 890         atomic_set(&kgdb_break_tasklet_var, 0);
 891 }
 892
 893 static DECLARE_TASKLET(kgdb_tasklet_breakpoint, kgdb_tasklet_bpt, 0);
 894
 895 void kgdb_schedule_breakpoint(void)
 896 {
 897         if (atomic_read(&kgdb_break_tasklet_var) ||
 898                 atomic_read(&kgdb_active) != -1 ||
 899                 atomic_read(&kgdb_setting_breakpoint))
 900                 return;
 901         atomic_inc(&kgdb_break_tasklet_var);
 902         tasklet_schedule(&kgdb_tasklet_breakpoint);
 903 }
 904 EXPORT_SYMBOL_GPL(kgdb_schedule_breakpoint);
 905
 906 static void kgdb_initial_breakpoint(void)
 907 {
 908         kgdb_break_asap = 0;
 909
 910         printk(KERN_CRIT "kgdb: Waiting for connection from remote gdb...\n");
 911         kgdb_breakpoint();
 912 }
 913
 914 /**
 915  *      kgdb_register_io_module - register KGDB IO module
 916  *      @new_dbg_io_ops: the io ops vector
 917  *
 918  *      Register it with the KGDB core.
 919  */
 920 int kgdb_register_io_module(struct kgdb_io *new_dbg_io_ops)
 921 {
 922         int err;
 923
 924         spin_lock(&kgdb_registration_lock);
 925
 926         if (dbg_io_ops) {
 927                 spin_unlock(&kgdb_registration_lock);
 928
 929                 printk(KERN_ERR "kgdb: Another I/O driver is already "
 930                                 "registered with KGDB.\n");
 931                 return -EBUSY;
 932         }
 933
 934         if (new_dbg_io_ops->init) {
 935                 err = new_dbg_io_ops->init();
 936                 if (err) {
 937                         spin_unlock(&kgdb_registration_lock);
 938                         return err;
 939                 }
 940         }
 941
 942         dbg_io_ops = new_dbg_io_ops;
 943
 944         spin_unlock(&kgdb_registration_lock);
 945
 946         printk(KERN_INFO "kgdb: Registered I/O driver %s.\n",
 947                new_dbg_io_ops->name);
 948
 949         /* Arm KGDB now. */
 950         kgdb_register_callbacks();
 951
 952         if (kgdb_break_asap)
 953                 kgdb_initial_breakpoint();
 954
 955         return 0;
 956 }
 957 EXPORT_SYMBOL_GPL(kgdb_register_io_module);
 958
 959 /**
 960  *      kkgdb_unregister_io_module - unregister KGDB IO module
 961  *      @old_dbg_io_ops: the io ops vector
 962  *
 963  *      Unregister it with the KGDB core.
 964  */
 965 void kgdb_unregister_io_module(struct kgdb_io *old_dbg_io_ops)
 966 {
 967         BUG_ON(kgdb_connected);
 968
 969         /*
 970          * KGDB is no longer able to communicate out, so
 971          * unregister our callbacks and reset state.
 972          */
 973         kgdb_unregister_callbacks();
 974
 975         spin_lock(&kgdb_registration_lock);
 976
 977         WARN_ON_ONCE(dbg_io_ops != old_dbg_io_ops);
 978         dbg_io_ops = NULL;
 979
 980         spin_unlock(&kgdb_registration_lock);
 981
 982         printk(KERN_INFO
 983                 "kgdb: Unregistered I/O driver %s, debugger disabled.\n",
 984                 old_dbg_io_ops->name);
 985 }
 986 EXPORT_SYMBOL_GPL(kgdb_unregister_io_module);
 987
 988 int dbg_io_get_char(void)
 989 {
 990         int ret = dbg_io_ops->read_char();
 991         if (ret == NO_POLL_CHAR)
 992                 return -1;
 993         if (!dbg_kdb_mode)
 994                 return ret;
 995         if (ret == 127)
 996                 return 8;
 997         return ret;
 998 }
 999
1000 /**
1001  * kgdb_breakpoint - generate breakpoint exception
1002  *
1003  * This function will generate a breakpoint exception.  It is used at the
1004  * beginning of a program to sync up with a debugger and can be used
1005  * otherwise as a quick means to stop program execution and "break" into
1006  * the debugger.
1007  */
1008 void kgdb_breakpoint(void)
1009 {
1010         atomic_inc(&kgdb_setting_breakpoint);
1011         wmb(); /* Sync point before breakpoint */
1012         arch_kgdb_breakpoint();
1013         wmb(); /* Sync point after breakpoint */
1014         atomic_dec(&kgdb_setting_breakpoint);
1015 }
1016 EXPORT_SYMBOL_GPL(kgdb_breakpoint);
1017
1018 static int __init opt_kgdb_wait(char *str)
1019 {
1020         kgdb_break_asap = 1;
1021
1022         kdb_init(KDB_INIT_EARLY);
1023         if (kgdb_io_module_registered)
1024                 kgdb_initial_breakpoint();
1025
1026         return 0;
1027 }
1028
1029 early_param("kgdbwait", opt_kgdb_wait);