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