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