SAFE public projects git trees. - safe/jmp/linux-2.6/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@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 static 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 atomic_t                        kgdb_setting_breakpoint;
 118
 119 struct task_struct              *kgdb_usethread;
 120 struct task_struct              *kgdb_contthread;
 121
 122 int                             kgdb_single_step;
 123 static pid_t                    kgdb_sstep_pid;
 124
 125 /* to keep track of the CPU which is doing the single stepping*/
 126 atomic_t                        kgdb_cpu_doing_single_step = ATOMIC_INIT(-1);
 127
 128 /*
 129  * If you are debugging a problem where roundup (the collection of
 130  * all other CPUs) is a problem [this should be extremely rare],
 131  * then use the nokgdbroundup option to avoid roundup. In that case
 132  * the other CPUs might interfere with your debugging context, so
 133  * use this with care:
 134  */
 135 static int kgdb_do_roundup = 1;
 136
 137 static int __init opt_nokgdbroundup(char *str)
 138 {
 139         kgdb_do_roundup = 0;
 140
 141         return 0;
 142 }
 143
 144 early_param("nokgdbroundup", opt_nokgdbroundup);
 145
 146 /*
 147  * Finally, some KGDB code :-)
 148  */
 149
 150 /*
 151  * Weak aliases for breakpoint management,
 152  * can be overriden by architectures when needed:
 153  */
 154 int __weak kgdb_arch_set_breakpoint(unsigned long addr, char *saved_instr)
 155 {
 156         int err;
 157
 158         err = probe_kernel_read(saved_instr, (char *)addr, BREAK_INSTR_SIZE);
 159         if (err)
 160                 return err;
 161
 162         return probe_kernel_write((char *)addr, arch_kgdb_ops.gdb_bpt_instr,
 163                                   BREAK_INSTR_SIZE);
 164 }
 165
 166 int __weak kgdb_arch_remove_breakpoint(unsigned long addr, char *bundle)
 167 {
 168         return probe_kernel_write((char *)addr,
 169                                   (char *)bundle, BREAK_INSTR_SIZE);
 170 }
 171
 172 int __weak kgdb_validate_break_address(unsigned long addr)
 173 {
 174         char tmp_variable[BREAK_INSTR_SIZE];
 175         int err;
 176         /* Validate setting the breakpoint and then removing it.  In the
 177          * remove fails, the kernel needs to emit a bad message because we
 178          * are deep trouble not being able to put things back the way we
 179          * found them.
 180          */
 181         err = kgdb_arch_set_breakpoint(addr, tmp_variable);
 182         if (err)
 183                 return err;
 184         err = kgdb_arch_remove_breakpoint(addr, tmp_variable);
 185         if (err)
 186                 printk(KERN_ERR "KGDB: Critical breakpoint error, kernel "
 187                    "memory destroyed at: %lx", addr);
 188         return err;
 189 }
 190
 191 unsigned long __weak kgdb_arch_pc(int exception, struct pt_regs *regs)
 192 {
 193         return instruction_pointer(regs);
 194 }
 195
 196 int __weak kgdb_arch_init(void)
 197 {
 198         return 0;
 199 }
 200
 201 int __weak kgdb_skipexception(int exception, struct pt_regs *regs)
 202 {
 203         return 0;
 204 }
 205
 206 /**
 207  *      kgdb_disable_hw_debug - Disable hardware debugging while we in kgdb.
 208  *      @regs: Current &struct pt_regs.
 209  *
 210  *      This function will be called if the particular architecture must
 211  *      disable hardware debugging while it is processing gdb packets or
 212  *      handling exception.
 213  */
 214 void __weak kgdb_disable_hw_debug(struct pt_regs *regs)
 215 {
 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         unsigned long addr;
 241         int error;
 242         int ret = 0;
 243         int i;
 244
 245         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
 246                 if (kgdb_break[i].state != BP_SET)
 247                         continue;
 248
 249                 addr = kgdb_break[i].bpt_addr;
 250                 error = kgdb_arch_set_breakpoint(addr,
 251                                 kgdb_break[i].saved_instr);
 252                 if (error) {
 253                         ret = error;
 254                         printk(KERN_INFO "KGDB: BP install failed: %lx", addr);
 255                         continue;
 256                 }
 257
 258                 kgdb_flush_swbreak_addr(addr);
 259                 kgdb_break[i].state = BP_ACTIVE;
 260         }
 261         return ret;
 262 }
 263
 264 int dbg_set_sw_break(unsigned long addr)
 265 {
 266         int err = kgdb_validate_break_address(addr);
 267         int breakno = -1;
 268         int i;
 269
 270         if (err)
 271                 return err;
 272
 273         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
 274                 if ((kgdb_break[i].state == BP_SET) &&
 275                                         (kgdb_break[i].bpt_addr == addr))
 276                         return -EEXIST;
 277         }
 278         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
 279                 if (kgdb_break[i].state == BP_REMOVED &&
 280                                         kgdb_break[i].bpt_addr == addr) {
 281                         breakno = i;
 282                         break;
 283                 }
 284         }
 285
 286         if (breakno == -1) {
 287                 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
 288                         if (kgdb_break[i].state == BP_UNDEFINED) {
 289                                 breakno = i;
 290                                 break;
 291                         }
 292                 }
 293         }
 294
 295         if (breakno == -1)
 296                 return -E2BIG;
 297
 298         kgdb_break[breakno].state = BP_SET;
 299         kgdb_break[breakno].type = BP_BREAKPOINT;
 300         kgdb_break[breakno].bpt_addr = addr;
 301
 302         return 0;
 303 }
 304
 305 int dbg_deactivate_sw_breakpoints(void)
 306 {
 307         unsigned long addr;
 308         int error;
 309         int ret = 0;
 310         int i;
 311
 312         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
 313                 if (kgdb_break[i].state != BP_ACTIVE)
 314                         continue;
 315                 addr = kgdb_break[i].bpt_addr;
 316                 error = kgdb_arch_remove_breakpoint(addr,
 317                                         kgdb_break[i].saved_instr);
 318                 if (error) {
 319                         printk(KERN_INFO "KGDB: BP remove failed: %lx\n", addr);
 320                         ret = error;
 321                 }
 322
 323                 kgdb_flush_swbreak_addr(addr);
 324                 kgdb_break[i].state = BP_SET;
 325         }
 326         return ret;
 327 }
 328
 329 int dbg_remove_sw_break(unsigned long addr)
 330 {
 331         int i;
 332
 333         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
 334                 if ((kgdb_break[i].state == BP_SET) &&
 335                                 (kgdb_break[i].bpt_addr == addr)) {
 336                         kgdb_break[i].state = BP_REMOVED;
 337                         return 0;
 338                 }
 339         }
 340         return -ENOENT;
 341 }
 342
 343 int kgdb_isremovedbreak(unsigned long addr)
 344 {
 345         int i;
 346
 347         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
 348                 if ((kgdb_break[i].state == BP_REMOVED) &&
 349                                         (kgdb_break[i].bpt_addr == addr))
 350                         return 1;
 351         }
 352         return 0;
 353 }
 354
 355 int dbg_remove_all_break(void)
 356 {
 357         unsigned long addr;
 358         int error;
 359         int i;
 360
 361         /* Clear memory breakpoints. */
 362         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
 363                 if (kgdb_break[i].state != BP_ACTIVE)
 364                         goto setundefined;
 365                 addr = kgdb_break[i].bpt_addr;
 366                 error = kgdb_arch_remove_breakpoint(addr,
 367                                 kgdb_break[i].saved_instr);
 368                 if (error)
 369                         printk(KERN_ERR "KGDB: breakpoint remove failed: %lx\n",
 370                            addr);
 371 setundefined:
 372                 kgdb_break[i].state = BP_UNDEFINED;
 373         }
 374
 375         /* Clear hardware breakpoints. */
 376         if (arch_kgdb_ops.remove_all_hw_break)
 377                 arch_kgdb_ops.remove_all_hw_break();
 378
 379         return 0;
 380 }
 381
 382 /*
 383  * Return true if there is a valid kgdb I/O module.  Also if no
 384  * debugger is attached a message can be printed to the console about
 385  * waiting for the debugger to attach.
 386  *
 387  * The print_wait argument is only to be true when called from inside
 388  * the core kgdb_handle_exception, because it will wait for the
 389  * debugger to attach.
 390  */
 391 static int kgdb_io_ready(int print_wait)
 392 {
 393         if (!dbg_io_ops)
 394                 return 0;
 395         if (kgdb_connected)
 396                 return 1;
 397         if (atomic_read(&kgdb_setting_breakpoint))
 398                 return 1;
 399         if (print_wait) {
 400 #ifdef CONFIG_KGDB_KDB
 401                 if (!dbg_kdb_mode)
 402                         printk(KERN_CRIT "KGDB: waiting... or $3#33 for KDB\n");
 403 #else
 404                 printk(KERN_CRIT "KGDB: Waiting for remote debugger\n");
 405 #endif
 406         }
 407         return 1;
 408 }
 409
 410 static int kgdb_reenter_check(struct kgdb_state *ks)
 411 {
 412         unsigned long addr;
 413
 414         if (atomic_read(&kgdb_active) != raw_smp_processor_id())
 415                 return 0;
 416
 417         /* Panic on recursive debugger calls: */
 418         exception_level++;
 419         addr = kgdb_arch_pc(ks->ex_vector, ks->linux_regs);
 420         dbg_deactivate_sw_breakpoints();
 421
 422         /*
 423          * If the break point removed ok at the place exception
 424          * occurred, try to recover and print a warning to the end
 425          * user because the user planted a breakpoint in a place that
 426          * KGDB needs in order to function.
 427          */
 428         if (dbg_remove_sw_break(addr) == 0) {
 429                 exception_level = 0;
 430                 kgdb_skipexception(ks->ex_vector, ks->linux_regs);
 431                 dbg_activate_sw_breakpoints();
 432                 printk(KERN_CRIT "KGDB: re-enter error: breakpoint removed %lx\n",
 433                         addr);
 434                 WARN_ON_ONCE(1);
 435
 436                 return 1;
 437         }
 438         dbg_remove_all_break();
 439         kgdb_skipexception(ks->ex_vector, ks->linux_regs);
 440
 441         if (exception_level > 1) {
 442                 dump_stack();
 443                 panic("Recursive entry to debugger");
 444         }
 445
 446         printk(KERN_CRIT "KGDB: re-enter exception: ALL breakpoints killed\n");
 447         dump_stack();
 448         panic("Recursive entry to debugger");
 449
 450         return 1;
 451 }
 452
 453 static void dbg_cpu_switch(int cpu, int next_cpu)
 454 {
 455         /* Mark the cpu we are switching away from as a slave when it
 456          * holds the kgdb_active token.  This must be done so that the
 457          * that all the cpus wait in for the debug core will not enter
 458          * again as the master. */
 459         if (cpu == atomic_read(&kgdb_active)) {
 460                 kgdb_info[cpu].exception_state |= DCPU_IS_SLAVE;
 461                 kgdb_info[cpu].exception_state &= ~DCPU_WANT_MASTER;
 462         }
 463         kgdb_info[next_cpu].exception_state |= DCPU_NEXT_MASTER;
 464 }
 465
 466 static int kgdb_cpu_enter(struct kgdb_state *ks, struct pt_regs *regs)
 467 {
 468         unsigned long flags;
 469         int sstep_tries = 100;
 470         int error;
 471         int i, cpu;
 472         int trace_on = 0;
 473 acquirelock:
 474         /*
 475          * Interrupts will be restored by the 'trap return' code, except when
 476          * single stepping.
 477          */
 478         local_irq_save(flags);
 479
 480         cpu = ks->cpu;
 481         kgdb_info[cpu].debuggerinfo = regs;
 482         kgdb_info[cpu].task = current;
 483         kgdb_info[cpu].ret_state = 0;
 484         kgdb_info[cpu].irq_depth = hardirq_count() >> HARDIRQ_SHIFT;
 485         /*
 486          * Make sure the above info reaches the primary CPU before
 487          * our cpu_in_kgdb[] flag setting does:
 488          */
 489         atomic_inc(&cpu_in_kgdb[cpu]);
 490
 491         /*
 492          * CPU will loop if it is a slave or request to become a kgdb
 493          * master cpu and acquire the kgdb_active lock:
 494          */
 495         while (1) {
 496 cpu_loop:
 497                 if (kgdb_info[cpu].exception_state & DCPU_NEXT_MASTER) {
 498                         kgdb_info[cpu].exception_state &= ~DCPU_NEXT_MASTER;
 499                         goto cpu_master_loop;
 500                 } else if (kgdb_info[cpu].exception_state & DCPU_WANT_MASTER) {
 501                         if (atomic_cmpxchg(&kgdb_active, -1, cpu) == cpu)
 502                                 break;
 503                 } else if (kgdb_info[cpu].exception_state & DCPU_IS_SLAVE) {
 504                         if (!atomic_read(&passive_cpu_wait[cpu]))
 505                                 goto return_normal;
 506                 } else {
 507 return_normal:
 508                         /* Return to normal operation by executing any
 509                          * hw breakpoint fixup.
 510                          */
 511                         if (arch_kgdb_ops.correct_hw_break)
 512                                 arch_kgdb_ops.correct_hw_break();
 513                         if (trace_on)
 514                                 tracing_on();
 515                         atomic_dec(&cpu_in_kgdb[cpu]);
 516                         touch_softlockup_watchdog_sync();
 517                         clocksource_touch_watchdog();
 518                         local_irq_restore(flags);
 519                         return 0;
 520                 }
 521                 cpu_relax();
 522         }
 523
 524         /*
 525          * For single stepping, try to only enter on the processor
 526          * that was single stepping.  To gaurd against a deadlock, the
 527          * kernel will only try for the value of sstep_tries before
 528          * giving up and continuing on.
 529          */
 530         if (atomic_read(&kgdb_cpu_doing_single_step) != -1 &&
 531             (kgdb_info[cpu].task &&
 532              kgdb_info[cpu].task->pid != kgdb_sstep_pid) && --sstep_tries) {
 533                 atomic_set(&kgdb_active, -1);
 534                 touch_softlockup_watchdog_sync();
 535                 clocksource_touch_watchdog();
 536                 local_irq_restore(flags);
 537
 538                 goto acquirelock;
 539         }
 540
 541         if (!kgdb_io_ready(1)) {
 542                 kgdb_info[cpu].ret_state = 1;
 543                 goto kgdb_restore; /* No I/O connection, resume the system */
 544         }
 545
 546         /*
 547          * Don't enter if we have hit a removed breakpoint.
 548          */
 549         if (kgdb_skipexception(ks->ex_vector, ks->linux_regs))
 550                 goto kgdb_restore;
 551
 552         /* Call the I/O driver's pre_exception routine */
 553         if (dbg_io_ops->pre_exception)
 554                 dbg_io_ops->pre_exception();
 555
 556         kgdb_disable_hw_debug(ks->linux_regs);
 557
 558         /*
 559          * Get the passive CPU lock which will hold all the non-primary
 560          * CPU in a spin state while the debugger is active
 561          */
 562         if (!kgdb_single_step) {
 563                 for (i = 0; i < NR_CPUS; i++)
 564                         atomic_inc(&passive_cpu_wait[i]);
 565         }
 566
 567 #ifdef CONFIG_SMP
 568         /* Signal the other CPUs to enter kgdb_wait() */
 569         if ((!kgdb_single_step) && kgdb_do_roundup)
 570                 kgdb_roundup_cpus(flags);
 571 #endif
 572
 573         /*
 574          * Wait for the other CPUs to be notified and be waiting for us:
 575          */
 576         for_each_online_cpu(i) {
 577                 while (kgdb_do_roundup && !atomic_read(&cpu_in_kgdb[i]))
 578                         cpu_relax();
 579         }
 580
 581         /*
 582          * At this point the primary processor is completely
 583          * in the debugger and all secondary CPUs are quiescent
 584          */
 585         dbg_deactivate_sw_breakpoints();
 586         kgdb_single_step = 0;
 587         kgdb_contthread = current;
 588         exception_level = 0;
 589         trace_on = tracing_is_on();
 590         if (trace_on)
 591                 tracing_off();
 592
 593         while (1) {
 594 cpu_master_loop:
 595                 if (dbg_kdb_mode) {
 596                         kgdb_connected = 1;
 597                         error = kdb_stub(ks);
 598                 } else {
 599                         error = gdb_serial_stub(ks);
 600                 }
 601
 602                 if (error == DBG_PASS_EVENT) {
 603                         dbg_kdb_mode = !dbg_kdb_mode;
 604                         kgdb_connected = 0;
 605                 } else if (error == DBG_SWITCH_CPU_EVENT) {
 606                         dbg_cpu_switch(cpu, dbg_switch_cpu);
 607                         goto cpu_loop;
 608                 } else {
 609                         kgdb_info[cpu].ret_state = error;
 610                         break;
 611                 }
 612         }
 613
 614         /* Call the I/O driver's post_exception routine */
 615         if (dbg_io_ops->post_exception)
 616                 dbg_io_ops->post_exception();
 617
 618         atomic_dec(&cpu_in_kgdb[ks->cpu]);
 619
 620         if (!kgdb_single_step) {
 621                 for (i = NR_CPUS-1; i >= 0; i--)
 622                         atomic_dec(&passive_cpu_wait[i]);
 623                 /*
 624                  * Wait till all the CPUs have quit from the debugger,
 625                  * but allow a CPU that hit an exception and is
 626                  * waiting to become the master to remain in the debug
 627                  * core.
 628                  */
 629                 for_each_online_cpu(i) {
 630                         while (kgdb_do_roundup &&
 631                                atomic_read(&cpu_in_kgdb[i]) &&
 632                                !(kgdb_info[i].exception_state &
 633                                  DCPU_WANT_MASTER))
 634                                 cpu_relax();
 635                 }
 636         }
 637
 638 kgdb_restore:
 639         if (atomic_read(&kgdb_cpu_doing_single_step) != -1) {
 640                 int sstep_cpu = atomic_read(&kgdb_cpu_doing_single_step);
 641                 if (kgdb_info[sstep_cpu].task)
 642                         kgdb_sstep_pid = kgdb_info[sstep_cpu].task->pid;
 643                 else
 644                         kgdb_sstep_pid = 0;
 645         }
 646         if (trace_on)
 647                 tracing_on();
 648         /* Free kgdb_active */
 649         atomic_set(&kgdb_active, -1);
 650         touch_softlockup_watchdog_sync();
 651         clocksource_touch_watchdog();
 652         local_irq_restore(flags);
 653
 654         return kgdb_info[cpu].ret_state;
 655 }
 656
 657 /*
 658  * kgdb_handle_exception() - main entry point from a kernel exception
 659  *
 660  * Locking hierarchy:
 661  *      interface locks, if any (begin_session)
 662  *      kgdb lock (kgdb_active)
 663  */
 664 int
 665 kgdb_handle_exception(int evector, int signo, int ecode, struct pt_regs *regs)
 666 {
 667         struct kgdb_state kgdb_var;
 668         struct kgdb_state *ks = &kgdb_var;
 669         int ret;
 670
 671         ks->cpu                 = raw_smp_processor_id();
 672         ks->ex_vector           = evector;
 673         ks->signo               = signo;
 674         ks->err_code            = ecode;
 675         ks->kgdb_usethreadid    = 0;
 676         ks->linux_regs          = regs;
 677
 678         if (kgdb_reenter_check(ks))
 679                 return 0; /* Ouch, double exception ! */
 680         kgdb_info[ks->cpu].exception_state |= DCPU_WANT_MASTER;
 681         ret = kgdb_cpu_enter(ks, regs);
 682         kgdb_info[ks->cpu].exception_state &= ~(DCPU_WANT_MASTER |
 683                                                 DCPU_IS_SLAVE);
 684         return ret;
 685 }
 686
 687 int kgdb_nmicallback(int cpu, void *regs)
 688 {
 689 #ifdef CONFIG_SMP
 690         struct kgdb_state kgdb_var;
 691         struct kgdb_state *ks = &kgdb_var;
 692
 693         memset(ks, 0, sizeof(struct kgdb_state));
 694         ks->cpu                 = cpu;
 695         ks->linux_regs          = regs;
 696
 697         if (!atomic_read(&cpu_in_kgdb[cpu]) &&
 698             atomic_read(&kgdb_active) != -1 &&
 699             atomic_read(&kgdb_active) != cpu) {
 700                 kgdb_info[cpu].exception_state |= DCPU_IS_SLAVE;
 701                 kgdb_cpu_enter(ks, regs);
 702                 kgdb_info[cpu].exception_state &= ~DCPU_IS_SLAVE;
 703                 return 0;
 704         }
 705 #endif
 706         return 1;
 707 }
 708
 709 static void kgdb_console_write(struct console *co, const char *s,
 710    unsigned count)
 711 {
 712         unsigned long flags;
 713
 714         /* If we're debugging, or KGDB has not connected, don't try
 715          * and print. */
 716         if (!kgdb_connected || atomic_read(&kgdb_active) != -1 || dbg_kdb_mode)
 717                 return;
 718
 719         local_irq_save(flags);
 720         gdbstub_msg_write(s, count);
 721         local_irq_restore(flags);
 722 }
 723
 724 static struct console kgdbcons = {
 725         .name           = "kgdb",
 726         .write          = kgdb_console_write,
 727         .flags          = CON_PRINTBUFFER | CON_ENABLED,
 728         .index          = -1,
 729 };
 730
 731 #ifdef CONFIG_MAGIC_SYSRQ
 732 static void sysrq_handle_dbg(int key, struct tty_struct *tty)
 733 {
 734         if (!dbg_io_ops) {
 735                 printk(KERN_CRIT "ERROR: No KGDB I/O module available\n");
 736                 return;
 737         }
 738         if (!kgdb_connected) {
 739 #ifdef CONFIG_KGDB_KDB
 740                 if (!dbg_kdb_mode)
 741                         printk(KERN_CRIT "KGDB or $3#33 for KDB\n");
 742 #else
 743                 printk(KERN_CRIT "Entering KGDB\n");
 744 #endif
 745         }
 746
 747         kgdb_breakpoint();
 748 }
 749
 750 static struct sysrq_key_op sysrq_dbg_op = {
 751         .handler        = sysrq_handle_dbg,
 752         .help_msg       = "debug(G)",
 753         .action_msg     = "DEBUG",
 754 };
 755 #endif
 756
 757 static void kgdb_register_callbacks(void)
 758 {
 759         if (!kgdb_io_module_registered) {
 760                 kgdb_io_module_registered = 1;
 761                 kgdb_arch_init();
 762 #ifdef CONFIG_MAGIC_SYSRQ
 763                 register_sysrq_key('g', &sysrq_dbg_op);
 764 #endif
 765                 if (kgdb_use_con && !kgdb_con_registered) {
 766                         register_console(&kgdbcons);
 767                         kgdb_con_registered = 1;
 768                 }
 769         }
 770 }
 771
 772 static void kgdb_unregister_callbacks(void)
 773 {
 774         /*
 775          * When this routine is called KGDB should unregister from the
 776          * panic handler and clean up, making sure it is not handling any
 777          * break exceptions at the time.
 778          */
 779         if (kgdb_io_module_registered) {
 780                 kgdb_io_module_registered = 0;
 781                 kgdb_arch_exit();
 782 #ifdef CONFIG_MAGIC_SYSRQ
 783                 unregister_sysrq_key('g', &sysrq_dbg_op);
 784 #endif
 785                 if (kgdb_con_registered) {
 786                         unregister_console(&kgdbcons);
 787                         kgdb_con_registered = 0;
 788                 }
 789         }
 790 }
 791
 792 static void kgdb_initial_breakpoint(void)
 793 {
 794         kgdb_break_asap = 0;
 795
 796         printk(KERN_CRIT "kgdb: Waiting for connection from remote gdb...\n");
 797         kgdb_breakpoint();
 798 }
 799
 800 /**
 801  *      kgdb_register_io_module - register KGDB IO module
 802  *      @new_dbg_io_ops: the io ops vector
 803  *
 804  *      Register it with the KGDB core.
 805  */
 806 int kgdb_register_io_module(struct kgdb_io *new_dbg_io_ops)
 807 {
 808         int err;
 809
 810         spin_lock(&kgdb_registration_lock);
 811
 812         if (dbg_io_ops) {
 813                 spin_unlock(&kgdb_registration_lock);
 814
 815                 printk(KERN_ERR "kgdb: Another I/O driver is already "
 816                                 "registered with KGDB.\n");
 817                 return -EBUSY;
 818         }
 819
 820         if (new_dbg_io_ops->init) {
 821                 err = new_dbg_io_ops->init();
 822                 if (err) {
 823                         spin_unlock(&kgdb_registration_lock);
 824                         return err;
 825                 }
 826         }
 827
 828         dbg_io_ops = new_dbg_io_ops;
 829
 830         spin_unlock(&kgdb_registration_lock);
 831
 832         printk(KERN_INFO "kgdb: Registered I/O driver %s.\n",
 833                new_dbg_io_ops->name);
 834
 835         /* Arm KGDB now. */
 836         kgdb_register_callbacks();
 837
 838         if (kgdb_break_asap)
 839                 kgdb_initial_breakpoint();
 840
 841         return 0;
 842 }
 843 EXPORT_SYMBOL_GPL(kgdb_register_io_module);
 844
 845 /**
 846  *      kkgdb_unregister_io_module - unregister KGDB IO module
 847  *      @old_dbg_io_ops: the io ops vector
 848  *
 849  *      Unregister it with the KGDB core.
 850  */
 851 void kgdb_unregister_io_module(struct kgdb_io *old_dbg_io_ops)
 852 {
 853         BUG_ON(kgdb_connected);
 854
 855         /*
 856          * KGDB is no longer able to communicate out, so
 857          * unregister our callbacks and reset state.
 858          */
 859         kgdb_unregister_callbacks();
 860
 861         spin_lock(&kgdb_registration_lock);
 862
 863         WARN_ON_ONCE(dbg_io_ops != old_dbg_io_ops);
 864         dbg_io_ops = NULL;
 865
 866         spin_unlock(&kgdb_registration_lock);
 867
 868         printk(KERN_INFO
 869                 "kgdb: Unregistered I/O driver %s, debugger disabled.\n",
 870                 old_dbg_io_ops->name);
 871 }
 872 EXPORT_SYMBOL_GPL(kgdb_unregister_io_module);
 873
 874 int dbg_io_get_char(void)
 875 {
 876         int ret = dbg_io_ops->read_char();
 877         if (ret == NO_POLL_CHAR)
 878                 return -1;
 879         if (!dbg_kdb_mode)
 880                 return ret;
 881         if (ret == 127)
 882                 return 8;
 883         return ret;
 884 }
 885
 886 /**
 887  * kgdb_breakpoint - generate breakpoint exception
 888  *
 889  * This function will generate a breakpoint exception.  It is used at the
 890  * beginning of a program to sync up with a debugger and can be used
 891  * otherwise as a quick means to stop program execution and "break" into
 892  * the debugger.
 893  */
 894 void kgdb_breakpoint(void)
 895 {
 896         atomic_inc(&kgdb_setting_breakpoint);
 897         wmb(); /* Sync point before breakpoint */
 898         arch_kgdb_breakpoint();
 899         wmb(); /* Sync point after breakpoint */
 900         atomic_dec(&kgdb_setting_breakpoint);
 901 }
 902 EXPORT_SYMBOL_GPL(kgdb_breakpoint);
 903
 904 static int __init opt_kgdb_wait(char *str)
 905 {
 906         kgdb_break_asap = 1;
 907
 908         kdb_init(KDB_INIT_EARLY);
 909         if (kgdb_io_module_registered)
 910                 kgdb_initial_breakpoint();
 911
 912         return 0;
 913 }
 914
 915 early_param("kgdbwait", opt_kgdb_wait);