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 void __weak
 207 kgdb_post_primary_code(struct pt_regs *regs, int e_vector, int err_code)
 208 {
 209         return;
 210 }
 211
 212 /**
 213  *      kgdb_disable_hw_debug - Disable hardware debugging while we in kgdb.
 214  *      @regs: Current &struct pt_regs.
 215  *
 216  *      This function will be called if the particular architecture must
 217  *      disable hardware debugging while it is processing gdb packets or
 218  *      handling exception.
 219  */
 220 void __weak kgdb_disable_hw_debug(struct pt_regs *regs)
 221 {
 222 }
 223
 224 /*
 225  * Some architectures need cache flushes when we set/clear a
 226  * breakpoint:
 227  */
 228 static void kgdb_flush_swbreak_addr(unsigned long addr)
 229 {
 230         if (!CACHE_FLUSH_IS_SAFE)
 231                 return;
 232
 233         if (current->mm && current->mm->mmap_cache) {
 234                 flush_cache_range(current->mm->mmap_cache,
 235                                   addr, addr + BREAK_INSTR_SIZE);
 236         }
 237         /* Force flush instruction cache if it was outside the mm */
 238         flush_icache_range(addr, addr + BREAK_INSTR_SIZE);
 239 }
 240
 241 /*
 242  * SW breakpoint management:
 243  */
 244 int dbg_activate_sw_breakpoints(void)
 245 {
 246         unsigned long addr;
 247         int error;
 248         int ret = 0;
 249         int i;
 250
 251         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
 252                 if (kgdb_break[i].state != BP_SET)
 253                         continue;
 254
 255                 addr = kgdb_break[i].bpt_addr;
 256                 error = kgdb_arch_set_breakpoint(addr,
 257                                 kgdb_break[i].saved_instr);
 258                 if (error) {
 259                         ret = error;
 260                         printk(KERN_INFO "KGDB: BP install failed: %lx", addr);
 261                         continue;
 262                 }
 263
 264                 kgdb_flush_swbreak_addr(addr);
 265                 kgdb_break[i].state = BP_ACTIVE;
 266         }
 267         return ret;
 268 }
 269
 270 int dbg_set_sw_break(unsigned long addr)
 271 {
 272         int err = kgdb_validate_break_address(addr);
 273         int breakno = -1;
 274         int i;
 275
 276         if (err)
 277                 return err;
 278
 279         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
 280                 if ((kgdb_break[i].state == BP_SET) &&
 281                                         (kgdb_break[i].bpt_addr == addr))
 282                         return -EEXIST;
 283         }
 284         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
 285                 if (kgdb_break[i].state == BP_REMOVED &&
 286                                         kgdb_break[i].bpt_addr == addr) {
 287                         breakno = i;
 288                         break;
 289                 }
 290         }
 291
 292         if (breakno == -1) {
 293                 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
 294                         if (kgdb_break[i].state == BP_UNDEFINED) {
 295                                 breakno = i;
 296                                 break;
 297                         }
 298                 }
 299         }
 300
 301         if (breakno == -1)
 302                 return -E2BIG;
 303
 304         kgdb_break[breakno].state = BP_SET;
 305         kgdb_break[breakno].type = BP_BREAKPOINT;
 306         kgdb_break[breakno].bpt_addr = addr;
 307
 308         return 0;
 309 }
 310
 311 int dbg_deactivate_sw_breakpoints(void)
 312 {
 313         unsigned long addr;
 314         int error;
 315         int ret = 0;
 316         int i;
 317
 318         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
 319                 if (kgdb_break[i].state != BP_ACTIVE)
 320                         continue;
 321                 addr = kgdb_break[i].bpt_addr;
 322                 error = kgdb_arch_remove_breakpoint(addr,
 323                                         kgdb_break[i].saved_instr);
 324                 if (error) {
 325                         printk(KERN_INFO "KGDB: BP remove failed: %lx\n", addr);
 326                         ret = error;
 327                 }
 328
 329                 kgdb_flush_swbreak_addr(addr);
 330                 kgdb_break[i].state = BP_SET;
 331         }
 332         return ret;
 333 }
 334
 335 int dbg_remove_sw_break(unsigned long addr)
 336 {
 337         int i;
 338
 339         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
 340                 if ((kgdb_break[i].state == BP_SET) &&
 341                                 (kgdb_break[i].bpt_addr == addr)) {
 342                         kgdb_break[i].state = BP_REMOVED;
 343                         return 0;
 344                 }
 345         }
 346         return -ENOENT;
 347 }
 348
 349 int kgdb_isremovedbreak(unsigned long addr)
 350 {
 351         int i;
 352
 353         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
 354                 if ((kgdb_break[i].state == BP_REMOVED) &&
 355                                         (kgdb_break[i].bpt_addr == addr))
 356                         return 1;
 357         }
 358         return 0;
 359 }
 360
 361 int dbg_remove_all_break(void)
 362 {
 363         unsigned long addr;
 364         int error;
 365         int i;
 366
 367         /* Clear memory breakpoints. */
 368         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
 369                 if (kgdb_break[i].state != BP_ACTIVE)
 370                         goto setundefined;
 371                 addr = kgdb_break[i].bpt_addr;
 372                 error = kgdb_arch_remove_breakpoint(addr,
 373                                 kgdb_break[i].saved_instr);
 374                 if (error)
 375                         printk(KERN_ERR "KGDB: breakpoint remove failed: %lx\n",
 376                            addr);
 377 setundefined:
 378                 kgdb_break[i].state = BP_UNDEFINED;
 379         }
 380
 381         /* Clear hardware breakpoints. */
 382         if (arch_kgdb_ops.remove_all_hw_break)
 383                 arch_kgdb_ops.remove_all_hw_break();
 384
 385         return 0;
 386 }
 387
 388 /*
 389  * Return true if there is a valid kgdb I/O module.  Also if no
 390  * debugger is attached a message can be printed to the console about
 391  * waiting for the debugger to attach.
 392  *
 393  * The print_wait argument is only to be true when called from inside
 394  * the core kgdb_handle_exception, because it will wait for the
 395  * debugger to attach.
 396  */
 397 static int kgdb_io_ready(int print_wait)
 398 {
 399         if (!dbg_io_ops)
 400                 return 0;
 401         if (kgdb_connected)
 402                 return 1;
 403         if (atomic_read(&kgdb_setting_breakpoint))
 404                 return 1;
 405         if (print_wait) {
 406 #ifdef CONFIG_KGDB_KDB
 407                 if (!dbg_kdb_mode)
 408                         printk(KERN_CRIT "KGDB: waiting... or $3#33 for KDB\n");
 409 #else
 410                 printk(KERN_CRIT "KGDB: Waiting for remote debugger\n");
 411 #endif
 412         }
 413         return 1;
 414 }
 415
 416 static int kgdb_reenter_check(struct kgdb_state *ks)
 417 {
 418         unsigned long addr;
 419
 420         if (atomic_read(&kgdb_active) != raw_smp_processor_id())
 421                 return 0;
 422
 423         /* Panic on recursive debugger calls: */
 424         exception_level++;
 425         addr = kgdb_arch_pc(ks->ex_vector, ks->linux_regs);
 426         dbg_deactivate_sw_breakpoints();
 427
 428         /*
 429          * If the break point removed ok at the place exception
 430          * occurred, try to recover and print a warning to the end
 431          * user because the user planted a breakpoint in a place that
 432          * KGDB needs in order to function.
 433          */
 434         if (dbg_remove_sw_break(addr) == 0) {
 435                 exception_level = 0;
 436                 kgdb_skipexception(ks->ex_vector, ks->linux_regs);
 437                 dbg_activate_sw_breakpoints();
 438                 printk(KERN_CRIT "KGDB: re-enter error: breakpoint removed %lx\n",
 439                         addr);
 440                 WARN_ON_ONCE(1);
 441
 442                 return 1;
 443         }
 444         dbg_remove_all_break();
 445         kgdb_skipexception(ks->ex_vector, ks->linux_regs);
 446
 447         if (exception_level > 1) {
 448                 dump_stack();
 449                 panic("Recursive entry to debugger");
 450         }
 451
 452         printk(KERN_CRIT "KGDB: re-enter exception: ALL breakpoints killed\n");
 453         dump_stack();
 454         panic("Recursive entry to debugger");
 455
 456         return 1;
 457 }
 458
 459 static void dbg_cpu_switch(int cpu, int next_cpu)
 460 {
 461         /* Mark the cpu we are switching away from as a slave when it
 462          * holds the kgdb_active token.  This must be done so that the
 463          * that all the cpus wait in for the debug core will not enter
 464          * again as the master. */
 465         if (cpu == atomic_read(&kgdb_active)) {
 466                 kgdb_info[cpu].exception_state |= DCPU_IS_SLAVE;
 467                 kgdb_info[cpu].exception_state &= ~DCPU_WANT_MASTER;
 468         }
 469         kgdb_info[next_cpu].exception_state |= DCPU_NEXT_MASTER;
 470 }
 471
 472 static int kgdb_cpu_enter(struct kgdb_state *ks, struct pt_regs *regs)
 473 {
 474         unsigned long flags;
 475         int sstep_tries = 100;
 476         int error;
 477         int i, cpu;
 478         int trace_on = 0;
 479 acquirelock:
 480         /*
 481          * Interrupts will be restored by the 'trap return' code, except when
 482          * single stepping.
 483          */
 484         local_irq_save(flags);
 485
 486         cpu = ks->cpu;
 487         kgdb_info[cpu].debuggerinfo = regs;
 488         kgdb_info[cpu].task = current;
 489         kgdb_info[cpu].ret_state = 0;
 490         kgdb_info[cpu].irq_depth = hardirq_count() >> HARDIRQ_SHIFT;
 491         /*
 492          * Make sure the above info reaches the primary CPU before
 493          * our cpu_in_kgdb[] flag setting does:
 494          */
 495         atomic_inc(&cpu_in_kgdb[cpu]);
 496
 497         /*
 498          * CPU will loop if it is a slave or request to become a kgdb
 499          * master cpu and acquire the kgdb_active lock:
 500          */
 501         while (1) {
 502 cpu_loop:
 503                 if (kgdb_info[cpu].exception_state & DCPU_NEXT_MASTER) {
 504                         kgdb_info[cpu].exception_state &= ~DCPU_NEXT_MASTER;
 505                         goto cpu_master_loop;
 506                 } else if (kgdb_info[cpu].exception_state & DCPU_WANT_MASTER) {
 507                         if (atomic_cmpxchg(&kgdb_active, -1, cpu) == cpu)
 508                                 break;
 509                 } else if (kgdb_info[cpu].exception_state & DCPU_IS_SLAVE) {
 510                         if (!atomic_read(&passive_cpu_wait[cpu]))
 511                                 goto return_normal;
 512                 } else {
 513 return_normal:
 514                         /* Return to normal operation by executing any
 515                          * hw breakpoint fixup.
 516                          */
 517                         if (arch_kgdb_ops.correct_hw_break)
 518                                 arch_kgdb_ops.correct_hw_break();
 519                         if (trace_on)
 520                                 tracing_on();
 521                         atomic_dec(&cpu_in_kgdb[cpu]);
 522                         touch_softlockup_watchdog_sync();
 523                         clocksource_touch_watchdog();
 524                         local_irq_restore(flags);
 525                         return 0;
 526                 }
 527                 cpu_relax();
 528         }
 529
 530         /*
 531          * For single stepping, try to only enter on the processor
 532          * that was single stepping.  To gaurd against a deadlock, the
 533          * kernel will only try for the value of sstep_tries before
 534          * giving up and continuing on.
 535          */
 536         if (atomic_read(&kgdb_cpu_doing_single_step) != -1 &&
 537             (kgdb_info[cpu].task &&
 538              kgdb_info[cpu].task->pid != kgdb_sstep_pid) && --sstep_tries) {
 539                 atomic_set(&kgdb_active, -1);
 540                 touch_softlockup_watchdog_sync();
 541                 clocksource_touch_watchdog();
 542                 local_irq_restore(flags);
 543
 544                 goto acquirelock;
 545         }
 546
 547         if (!kgdb_io_ready(1)) {
 548                 kgdb_info[cpu].ret_state = 1;
 549                 goto kgdb_restore; /* No I/O connection, resume the system */
 550         }
 551
 552         /*
 553          * Don't enter if we have hit a removed breakpoint.
 554          */
 555         if (kgdb_skipexception(ks->ex_vector, ks->linux_regs))
 556                 goto kgdb_restore;
 557
 558         /* Call the I/O driver's pre_exception routine */
 559         if (dbg_io_ops->pre_exception)
 560                 dbg_io_ops->pre_exception();
 561
 562         kgdb_disable_hw_debug(ks->linux_regs);
 563
 564         /*
 565          * Get the passive CPU lock which will hold all the non-primary
 566          * CPU in a spin state while the debugger is active
 567          */
 568         if (!kgdb_single_step) {
 569                 for (i = 0; i < NR_CPUS; i++)
 570                         atomic_inc(&passive_cpu_wait[i]);
 571         }
 572
 573 #ifdef CONFIG_SMP
 574         /* Signal the other CPUs to enter kgdb_wait() */
 575         if ((!kgdb_single_step) && kgdb_do_roundup)
 576                 kgdb_roundup_cpus(flags);
 577 #endif
 578
 579         /*
 580          * Wait for the other CPUs to be notified and be waiting for us:
 581          */
 582         for_each_online_cpu(i) {
 583                 while (kgdb_do_roundup && !atomic_read(&cpu_in_kgdb[i]))
 584                         cpu_relax();
 585         }
 586
 587         /*
 588          * At this point the primary processor is completely
 589          * in the debugger and all secondary CPUs are quiescent
 590          */
 591         kgdb_post_primary_code(ks->linux_regs, ks->ex_vector, ks->err_code);
 592         dbg_deactivate_sw_breakpoints();
 593         kgdb_single_step = 0;
 594         kgdb_contthread = current;
 595         exception_level = 0;
 596         trace_on = tracing_is_on();
 597         if (trace_on)
 598                 tracing_off();
 599
 600         while (1) {
 601 cpu_master_loop:
 602                 if (dbg_kdb_mode) {
 603                         kgdb_connected = 1;
 604                         error = kdb_stub(ks);
 605                 } else {
 606                         error = gdb_serial_stub(ks);
 607                 }
 608
 609                 if (error == DBG_PASS_EVENT) {
 610                         dbg_kdb_mode = !dbg_kdb_mode;
 611                         kgdb_connected = 0;
 612                 } else if (error == DBG_SWITCH_CPU_EVENT) {
 613                         dbg_cpu_switch(cpu, dbg_switch_cpu);
 614                         goto cpu_loop;
 615                 } else {
 616                         kgdb_info[cpu].ret_state = error;
 617                         break;
 618                 }
 619         }
 620
 621         /* Call the I/O driver's post_exception routine */
 622         if (dbg_io_ops->post_exception)
 623                 dbg_io_ops->post_exception();
 624
 625         atomic_dec(&cpu_in_kgdb[ks->cpu]);
 626
 627         if (!kgdb_single_step) {
 628                 for (i = NR_CPUS-1; i >= 0; i--)
 629                         atomic_dec(&passive_cpu_wait[i]);
 630                 /*
 631                  * Wait till all the CPUs have quit from the debugger,
 632                  * but allow a CPU that hit an exception and is
 633                  * waiting to become the master to remain in the debug
 634                  * core.
 635                  */
 636                 for_each_online_cpu(i) {
 637                         while (kgdb_do_roundup &&
 638                                atomic_read(&cpu_in_kgdb[i]) &&
 639                                !(kgdb_info[i].exception_state &
 640                                  DCPU_WANT_MASTER))
 641                                 cpu_relax();
 642                 }
 643         }
 644
 645 kgdb_restore:
 646         if (atomic_read(&kgdb_cpu_doing_single_step) != -1) {
 647                 int sstep_cpu = atomic_read(&kgdb_cpu_doing_single_step);
 648                 if (kgdb_info[sstep_cpu].task)
 649                         kgdb_sstep_pid = kgdb_info[sstep_cpu].task->pid;
 650                 else
 651                         kgdb_sstep_pid = 0;
 652         }
 653         if (trace_on)
 654                 tracing_on();
 655         /* Free kgdb_active */
 656         atomic_set(&kgdb_active, -1);
 657         touch_softlockup_watchdog_sync();
 658         clocksource_touch_watchdog();
 659         local_irq_restore(flags);
 660
 661         return kgdb_info[cpu].ret_state;
 662 }
 663
 664 /*
 665  * kgdb_handle_exception() - main entry point from a kernel exception
 666  *
 667  * Locking hierarchy:
 668  *      interface locks, if any (begin_session)
 669  *      kgdb lock (kgdb_active)
 670  */
 671 int
 672 kgdb_handle_exception(int evector, int signo, int ecode, struct pt_regs *regs)
 673 {
 674         struct kgdb_state kgdb_var;
 675         struct kgdb_state *ks = &kgdb_var;
 676         int ret;
 677
 678         ks->cpu                 = raw_smp_processor_id();
 679         ks->ex_vector           = evector;
 680         ks->signo               = signo;
 681         ks->ex_vector           = evector;
 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 void kgdb_register_callbacks(void)
 766 {
 767         if (!kgdb_io_module_registered) {
 768                 kgdb_io_module_registered = 1;
 769                 kgdb_arch_init();
 770 #ifdef CONFIG_MAGIC_SYSRQ
 771                 register_sysrq_key('g', &sysrq_dbg_op);
 772 #endif
 773                 if (kgdb_use_con && !kgdb_con_registered) {
 774                         register_console(&kgdbcons);
 775                         kgdb_con_registered = 1;
 776                 }
 777         }
 778 }
 779
 780 static void kgdb_unregister_callbacks(void)
 781 {
 782         /*
 783          * When this routine is called KGDB should unregister from the
 784          * panic handler and clean up, making sure it is not handling any
 785          * break exceptions at the time.
 786          */
 787         if (kgdb_io_module_registered) {
 788                 kgdb_io_module_registered = 0;
 789                 kgdb_arch_exit();
 790 #ifdef CONFIG_MAGIC_SYSRQ
 791                 unregister_sysrq_key('g', &sysrq_dbg_op);
 792 #endif
 793                 if (kgdb_con_registered) {
 794                         unregister_console(&kgdbcons);
 795                         kgdb_con_registered = 0;
 796                 }
 797         }
 798 }
 799
 800 static void kgdb_initial_breakpoint(void)
 801 {
 802         kgdb_break_asap = 0;
 803
 804         printk(KERN_CRIT "kgdb: Waiting for connection from remote gdb...\n");
 805         kgdb_breakpoint();
 806 }
 807
 808 /**
 809  *      kgdb_register_io_module - register KGDB IO module
 810  *      @new_dbg_io_ops: the io ops vector
 811  *
 812  *      Register it with the KGDB core.
 813  */
 814 int kgdb_register_io_module(struct kgdb_io *new_dbg_io_ops)
 815 {
 816         int err;
 817
 818         spin_lock(&kgdb_registration_lock);
 819
 820         if (dbg_io_ops) {
 821                 spin_unlock(&kgdb_registration_lock);
 822
 823                 printk(KERN_ERR "kgdb: Another I/O driver is already "
 824                                 "registered with KGDB.\n");
 825                 return -EBUSY;
 826         }
 827
 828         if (new_dbg_io_ops->init) {
 829                 err = new_dbg_io_ops->init();
 830                 if (err) {
 831                         spin_unlock(&kgdb_registration_lock);
 832                         return err;
 833                 }
 834         }
 835
 836         dbg_io_ops = new_dbg_io_ops;
 837
 838         spin_unlock(&kgdb_registration_lock);
 839
 840         printk(KERN_INFO "kgdb: Registered I/O driver %s.\n",
 841                new_dbg_io_ops->name);
 842
 843         /* Arm KGDB now. */
 844         kgdb_register_callbacks();
 845
 846         if (kgdb_break_asap)
 847                 kgdb_initial_breakpoint();
 848
 849         return 0;
 850 }
 851 EXPORT_SYMBOL_GPL(kgdb_register_io_module);
 852
 853 /**
 854  *      kkgdb_unregister_io_module - unregister KGDB IO module
 855  *      @old_dbg_io_ops: the io ops vector
 856  *
 857  *      Unregister it with the KGDB core.
 858  */
 859 void kgdb_unregister_io_module(struct kgdb_io *old_dbg_io_ops)
 860 {
 861         BUG_ON(kgdb_connected);
 862
 863         /*
 864          * KGDB is no longer able to communicate out, so
 865          * unregister our callbacks and reset state.
 866          */
 867         kgdb_unregister_callbacks();
 868
 869         spin_lock(&kgdb_registration_lock);
 870
 871         WARN_ON_ONCE(dbg_io_ops != old_dbg_io_ops);
 872         dbg_io_ops = NULL;
 873
 874         spin_unlock(&kgdb_registration_lock);
 875
 876         printk(KERN_INFO
 877                 "kgdb: Unregistered I/O driver %s, debugger disabled.\n",
 878                 old_dbg_io_ops->name);
 879 }
 880 EXPORT_SYMBOL_GPL(kgdb_unregister_io_module);
 881
 882 int dbg_io_get_char(void)
 883 {
 884         int ret = dbg_io_ops->read_char();
 885         if (ret == NO_POLL_CHAR)
 886                 return -1;
 887         if (!dbg_kdb_mode)
 888                 return ret;
 889         if (ret == 127)
 890                 return 8;
 891         return ret;
 892 }
 893
 894 /**
 895  * kgdb_breakpoint - generate breakpoint exception
 896  *
 897  * This function will generate a breakpoint exception.  It is used at the
 898  * beginning of a program to sync up with a debugger and can be used
 899  * otherwise as a quick means to stop program execution and "break" into
 900  * the debugger.
 901  */
 902 void kgdb_breakpoint(void)
 903 {
 904         atomic_inc(&kgdb_setting_breakpoint);
 905         wmb(); /* Sync point before breakpoint */
 906         arch_kgdb_breakpoint();
 907         wmb(); /* Sync point after breakpoint */
 908         atomic_dec(&kgdb_setting_breakpoint);
 909 }
 910 EXPORT_SYMBOL_GPL(kgdb_breakpoint);
 911
 912 static int __init opt_kgdb_wait(char *str)
 913 {
 914         kgdb_break_asap = 1;
 915
 916         kdb_init(KDB_INIT_EARLY);
 917         if (kgdb_io_module_registered)
 918                 kgdb_initial_breakpoint();
 919
 920         return 0;
 921 }
 922
 923 early_param("kgdbwait", opt_kgdb_wait);