arch/x86/kernel/kgdb.c

   1 /*
   2  * This program is free software; you can redistribute it and/or modify it
   3  * under the terms of the GNU General Public License as published by the
   4  * Free Software Foundation; either version 2, or (at your option) any
   5  * later version.
   6  *
   7  * This program is distributed in the hope that it will be useful, but
   8  * WITHOUT ANY WARRANTY; without even the implied warranty of
   9  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  10  * General Public License for more details.
  11  *
  12  */
  13
  14 /*
  15  * Copyright (C) 2004 Amit S. Kale <amitkale@linsyssoft.com>
  16  * Copyright (C) 2000-2001 VERITAS Software Corporation.
  17  * Copyright (C) 2002 Andi Kleen, SuSE Labs
  18  * Copyright (C) 2004 LinSysSoft Technologies Pvt. Ltd.
  19  * Copyright (C) 2007 MontaVista Software, Inc.
  20  * Copyright (C) 2007-2008 Jason Wessel, Wind River Systems, Inc.
  21  */
  22 /****************************************************************************
  23  *  Contributor:     Lake Stevens Instrument Division$
  24  *  Written by:      Glenn Engel $
  25  *  Updated by:      Amit Kale<akale@veritas.com>
  26  *  Updated by:      Tom Rini <trini@kernel.crashing.org>
  27  *  Updated by:      Jason Wessel <jason.wessel@windriver.com>
  28  *  Modified for 386 by Jim Kingdon, Cygnus Support.
  29  *  Origianl kgdb, compatibility with 2.1.xx kernel by
  30  *  David Grothe <dave@gcom.com>
  31  *  Integrated into 2.2.5 kernel by Tigran Aivazian <tigran@sco.com>
  32  *  X86_64 changes from Andi Kleen's patch merged by Jim Houston
  33  */
  34 #include <linux/spinlock.h>
  35 #include <linux/kdebug.h>
  36 #include <linux/string.h>
  37 #include <linux/kernel.h>
  38 #include <linux/ptrace.h>
  39 #include <linux/sched.h>
  40 #include <linux/delay.h>
  41 #include <linux/kgdb.h>
  42 #include <linux/init.h>
  43 #include <linux/smp.h>
  44 #include <linux/nmi.h>
  45 #include <linux/hw_breakpoint.h>
  46
  47 #include <asm/debugreg.h>
  48 #include <asm/apicdef.h>
  49 #include <asm/system.h>
  50
  51 #include <asm/apic.h>
  52
  53 /*
  54  * Put the error code here just in case the user cares:
  55  */
  56 static int gdb_x86errcode;
  57
  58 /*
  59  * Likewise, the vector number here (since GDB only gets the signal
  60  * number through the usual means, and that's not very specific):
  61  */
  62 static int gdb_x86vector = -1;
  63
  64 /**
  65  *      pt_regs_to_gdb_regs - Convert ptrace regs to GDB regs
  66  *      @gdb_regs: A pointer to hold the registers in the order GDB wants.
  67  *      @regs: The &struct pt_regs of the current process.
  68  *
  69  *      Convert the pt_regs in @regs into the format for registers that
  70  *      GDB expects, stored in @gdb_regs.
  71  */
  72 void pt_regs_to_gdb_regs(unsigned long *gdb_regs, struct pt_regs *regs)
  73 {
  74 #ifndef CONFIG_X86_32
  75         u32 *gdb_regs32 = (u32 *)gdb_regs;
  76 #endif
  77         gdb_regs[GDB_AX]        = regs->ax;
  78         gdb_regs[GDB_BX]        = regs->bx;
  79         gdb_regs[GDB_CX]        = regs->cx;
  80         gdb_regs[GDB_DX]        = regs->dx;
  81         gdb_regs[GDB_SI]        = regs->si;
  82         gdb_regs[GDB_DI]        = regs->di;
  83         gdb_regs[GDB_BP]        = regs->bp;
  84         gdb_regs[GDB_PC]        = regs->ip;
  85 #ifdef CONFIG_X86_32
  86         gdb_regs[GDB_PS]        = regs->flags;
  87         gdb_regs[GDB_DS]        = regs->ds;
  88         gdb_regs[GDB_ES]        = regs->es;
  89         gdb_regs[GDB_CS]        = regs->cs;
  90         gdb_regs[GDB_FS]        = 0xFFFF;
  91         gdb_regs[GDB_GS]        = 0xFFFF;
  92         if (user_mode_vm(regs)) {
  93                 gdb_regs[GDB_SS] = regs->ss;
  94                 gdb_regs[GDB_SP] = regs->sp;
  95         } else {
  96                 gdb_regs[GDB_SS] = __KERNEL_DS;
  97                 gdb_regs[GDB_SP] = kernel_stack_pointer(regs);
  98         }
  99 #else
 100         gdb_regs[GDB_R8]        = regs->r8;
 101         gdb_regs[GDB_R9]        = regs->r9;
 102         gdb_regs[GDB_R10]       = regs->r10;
 103         gdb_regs[GDB_R11]       = regs->r11;
 104         gdb_regs[GDB_R12]       = regs->r12;
 105         gdb_regs[GDB_R13]       = regs->r13;
 106         gdb_regs[GDB_R14]       = regs->r14;
 107         gdb_regs[GDB_R15]       = regs->r15;
 108         gdb_regs32[GDB_PS]      = regs->flags;
 109         gdb_regs32[GDB_CS]      = regs->cs;
 110         gdb_regs32[GDB_SS]      = regs->ss;
 111         gdb_regs[GDB_SP]        = kernel_stack_pointer(regs);
 112 #endif
 113 }
 114
 115 /**
 116  *      sleeping_thread_to_gdb_regs - Convert ptrace regs to GDB regs
 117  *      @gdb_regs: A pointer to hold the registers in the order GDB wants.
 118  *      @p: The &struct task_struct of the desired process.
 119  *
 120  *      Convert the register values of the sleeping process in @p to
 121  *      the format that GDB expects.
 122  *      This function is called when kgdb does not have access to the
 123  *      &struct pt_regs and therefore it should fill the gdb registers
 124  *      @gdb_regs with what has been saved in &struct thread_struct
 125  *      thread field during switch_to.
 126  */
 127 void sleeping_thread_to_gdb_regs(unsigned long *gdb_regs, struct task_struct *p)
 128 {
 129 #ifndef CONFIG_X86_32
 130         u32 *gdb_regs32 = (u32 *)gdb_regs;
 131 #endif
 132         gdb_regs[GDB_AX]        = 0;
 133         gdb_regs[GDB_BX]        = 0;
 134         gdb_regs[GDB_CX]        = 0;
 135         gdb_regs[GDB_DX]        = 0;
 136         gdb_regs[GDB_SI]        = 0;
 137         gdb_regs[GDB_DI]        = 0;
 138         gdb_regs[GDB_BP]        = *(unsigned long *)p->thread.sp;
 139 #ifdef CONFIG_X86_32
 140         gdb_regs[GDB_DS]        = __KERNEL_DS;
 141         gdb_regs[GDB_ES]        = __KERNEL_DS;
 142         gdb_regs[GDB_PS]        = 0;
 143         gdb_regs[GDB_CS]        = __KERNEL_CS;
 144         gdb_regs[GDB_PC]        = p->thread.ip;
 145         gdb_regs[GDB_SS]        = __KERNEL_DS;
 146         gdb_regs[GDB_FS]        = 0xFFFF;
 147         gdb_regs[GDB_GS]        = 0xFFFF;
 148 #else
 149         gdb_regs32[GDB_PS]      = *(unsigned long *)(p->thread.sp + 8);
 150         gdb_regs32[GDB_CS]      = __KERNEL_CS;
 151         gdb_regs32[GDB_SS]      = __KERNEL_DS;
 152         gdb_regs[GDB_PC]        = 0;
 153         gdb_regs[GDB_R8]        = 0;
 154         gdb_regs[GDB_R9]        = 0;
 155         gdb_regs[GDB_R10]       = 0;
 156         gdb_regs[GDB_R11]       = 0;
 157         gdb_regs[GDB_R12]       = 0;
 158         gdb_regs[GDB_R13]       = 0;
 159         gdb_regs[GDB_R14]       = 0;
 160         gdb_regs[GDB_R15]       = 0;
 161 #endif
 162         gdb_regs[GDB_SP]        = p->thread.sp;
 163 }
 164
 165 /**
 166  *      gdb_regs_to_pt_regs - Convert GDB regs to ptrace regs.
 167  *      @gdb_regs: A pointer to hold the registers we've received from GDB.
 168  *      @regs: A pointer to a &struct pt_regs to hold these values in.
 169  *
 170  *      Convert the GDB regs in @gdb_regs into the pt_regs, and store them
 171  *      in @regs.
 172  */
 173 void gdb_regs_to_pt_regs(unsigned long *gdb_regs, struct pt_regs *regs)
 174 {
 175 #ifndef CONFIG_X86_32
 176         u32 *gdb_regs32 = (u32 *)gdb_regs;
 177 #endif
 178         regs->ax                = gdb_regs[GDB_AX];
 179         regs->bx                = gdb_regs[GDB_BX];
 180         regs->cx                = gdb_regs[GDB_CX];
 181         regs->dx                = gdb_regs[GDB_DX];
 182         regs->si                = gdb_regs[GDB_SI];
 183         regs->di                = gdb_regs[GDB_DI];
 184         regs->bp                = gdb_regs[GDB_BP];
 185         regs->ip                = gdb_regs[GDB_PC];
 186 #ifdef CONFIG_X86_32
 187         regs->flags             = gdb_regs[GDB_PS];
 188         regs->ds                = gdb_regs[GDB_DS];
 189         regs->es                = gdb_regs[GDB_ES];
 190         regs->cs                = gdb_regs[GDB_CS];
 191 #else
 192         regs->r8                = gdb_regs[GDB_R8];
 193         regs->r9                = gdb_regs[GDB_R9];
 194         regs->r10               = gdb_regs[GDB_R10];
 195         regs->r11               = gdb_regs[GDB_R11];
 196         regs->r12               = gdb_regs[GDB_R12];
 197         regs->r13               = gdb_regs[GDB_R13];
 198         regs->r14               = gdb_regs[GDB_R14];
 199         regs->r15               = gdb_regs[GDB_R15];
 200         regs->flags             = gdb_regs32[GDB_PS];
 201         regs->cs                = gdb_regs32[GDB_CS];
 202         regs->ss                = gdb_regs32[GDB_SS];
 203 #endif
 204 }
 205
 206 static struct hw_breakpoint {
 207         unsigned                enabled;
 208         unsigned long           addr;
 209         int                     len;
 210         int                     type;
 211         struct perf_event       **pev;
 212 } breakinfo[4];
 213
 214 static void kgdb_correct_hw_break(void)
 215 {
 216         int breakno;
 217
 218         for (breakno = 0; breakno < 4; breakno++) {
 219                 struct perf_event *bp;
 220                 struct arch_hw_breakpoint *info;
 221                 int val;
 222                 int cpu = raw_smp_processor_id();
 223                 if (!breakinfo[breakno].enabled)
 224                         continue;
 225                 bp = *per_cpu_ptr(breakinfo[breakno].pev, cpu);
 226                 info = counter_arch_bp(bp);
 227                 if (bp->attr.disabled != 1)
 228                         continue;
 229                 bp->attr.bp_addr = breakinfo[breakno].addr;
 230                 bp->attr.bp_len = breakinfo[breakno].len;
 231                 bp->attr.bp_type = breakinfo[breakno].type;
 232                 info->address = breakinfo[breakno].addr;
 233                 info->len = breakinfo[breakno].len;
 234                 info->type = breakinfo[breakno].type;
 235                 val = arch_install_hw_breakpoint(bp);
 236                 if (!val)
 237                         bp->attr.disabled = 0;
 238         }
 239         hw_breakpoint_restore();
 240 }
 241
 242 static int hw_break_reserve_slot(int breakno)
 243 {
 244         int cpu;
 245         int cnt = 0;
 246         struct perf_event **pevent;
 247
 248         for_each_online_cpu(cpu) {
 249                 cnt++;
 250                 pevent = per_cpu_ptr(breakinfo[breakno].pev, cpu);
 251                 if (dbg_reserve_bp_slot(*pevent))
 252                         goto fail;
 253         }
 254
 255         return 0;
 256
 257 fail:
 258         for_each_online_cpu(cpu) {
 259                 cnt--;
 260                 if (!cnt)
 261                         break;
 262                 pevent = per_cpu_ptr(breakinfo[breakno].pev, cpu);
 263                 dbg_release_bp_slot(*pevent);
 264         }
 265         return -1;
 266 }
 267
 268 static int hw_break_release_slot(int breakno)
 269 {
 270         struct perf_event **pevent;
 271         int cpu;
 272
 273         for_each_online_cpu(cpu) {
 274                 pevent = per_cpu_ptr(breakinfo[breakno].pev, cpu);
 275                 if (dbg_release_bp_slot(*pevent))
 276                         /*
 277                          * The debugger is responisble for handing the retry on
 278                          * remove failure.
 279                          */
 280                         return -1;
 281         }
 282         return 0;
 283 }
 284
 285 static int
 286 kgdb_remove_hw_break(unsigned long addr, int len, enum kgdb_bptype bptype)
 287 {
 288         int i;
 289
 290         for (i = 0; i < 4; i++)
 291                 if (breakinfo[i].addr == addr && breakinfo[i].enabled)
 292                         break;
 293         if (i == 4)
 294                 return -1;
 295
 296         if (hw_break_release_slot(i)) {
 297                 printk(KERN_ERR "Cannot remove hw breakpoint at %lx\n", addr);
 298                 return -1;
 299         }
 300         breakinfo[i].enabled = 0;
 301
 302         return 0;
 303 }
 304
 305 static void kgdb_remove_all_hw_break(void)
 306 {
 307         int i;
 308         int cpu = raw_smp_processor_id();
 309         struct perf_event *bp;
 310
 311         for (i = 0; i < 4; i++) {
 312                 if (!breakinfo[i].enabled)
 313                         continue;
 314                 bp = *per_cpu_ptr(breakinfo[i].pev, cpu);
 315                 if (bp->attr.disabled == 1)
 316                         continue;
 317                 arch_uninstall_hw_breakpoint(bp);
 318                 bp->attr.disabled = 1;
 319         }
 320 }
 321
 322 static int
 323 kgdb_set_hw_break(unsigned long addr, int len, enum kgdb_bptype bptype)
 324 {
 325         int i;
 326
 327         for (i = 0; i < 4; i++)
 328                 if (!breakinfo[i].enabled)
 329                         break;
 330         if (i == 4)
 331                 return -1;
 332
 333         switch (bptype) {
 334         case BP_HARDWARE_BREAKPOINT:
 335                 len = 1;
 336                 breakinfo[i].type = X86_BREAKPOINT_EXECUTE;
 337                 break;
 338         case BP_WRITE_WATCHPOINT:
 339                 breakinfo[i].type = X86_BREAKPOINT_WRITE;
 340                 break;
 341         case BP_ACCESS_WATCHPOINT:
 342                 breakinfo[i].type = X86_BREAKPOINT_RW;
 343                 break;
 344         default:
 345                 return -1;
 346         }
 347         switch (len) {
 348         case 1:
 349                 breakinfo[i].len = X86_BREAKPOINT_LEN_1;
 350                 break;
 351         case 2:
 352                 breakinfo[i].len = X86_BREAKPOINT_LEN_2;
 353                 break;
 354         case 4:
 355                 breakinfo[i].len = X86_BREAKPOINT_LEN_4;
 356                 break;
 357 #ifdef CONFIG_X86_64
 358         case 8:
 359                 breakinfo[i].len = X86_BREAKPOINT_LEN_8;
 360                 break;
 361 #endif
 362         default:
 363                 return -1;
 364         }
 365         breakinfo[i].addr = addr;
 366         if (hw_break_reserve_slot(i)) {
 367                 breakinfo[i].addr = 0;
 368                 return -1;
 369         }
 370         breakinfo[i].enabled = 1;
 371
 372         return 0;
 373 }
 374
 375 /**
 376  *      kgdb_disable_hw_debug - Disable hardware debugging while we in kgdb.
 377  *      @regs: Current &struct pt_regs.
 378  *
 379  *      This function will be called if the particular architecture must
 380  *      disable hardware debugging while it is processing gdb packets or
 381  *      handling exception.
 382  */
 383 void kgdb_disable_hw_debug(struct pt_regs *regs)
 384 {
 385         int i;
 386         int cpu = raw_smp_processor_id();
 387         struct perf_event *bp;
 388
 389         /* Disable hardware debugging while we are in kgdb: */
 390         set_debugreg(0UL, 7);
 391         for (i = 0; i < 4; i++) {
 392                 if (!breakinfo[i].enabled)
 393                         continue;
 394                 bp = *per_cpu_ptr(breakinfo[i].pev, cpu);
 395                 if (bp->attr.disabled == 1)
 396                         continue;
 397                 arch_uninstall_hw_breakpoint(bp);
 398                 bp->attr.disabled = 1;
 399         }
 400 }
 401
 402 /**
 403  *      kgdb_post_primary_code - Save error vector/code numbers.
 404  *      @regs: Original pt_regs.
 405  *      @e_vector: Original error vector.
 406  *      @err_code: Original error code.
 407  *
 408  *      This is needed on architectures which support SMP and KGDB.
 409  *      This function is called after all the slave cpus have been put
 410  *      to a know spin state and the primary CPU has control over KGDB.
 411  */
 412 void kgdb_post_primary_code(struct pt_regs *regs, int e_vector, int err_code)
 413 {
 414         /* primary processor is completely in the debugger */
 415         gdb_x86vector = e_vector;
 416         gdb_x86errcode = err_code;
 417 }
 418
 419 #ifdef CONFIG_SMP
 420 /**
 421  *      kgdb_roundup_cpus - Get other CPUs into a holding pattern
 422  *      @flags: Current IRQ state
 423  *
 424  *      On SMP systems, we need to get the attention of the other CPUs
 425  *      and get them be in a known state.  This should do what is needed
 426  *      to get the other CPUs to call kgdb_wait(). Note that on some arches,
 427  *      the NMI approach is not used for rounding up all the CPUs. For example,
 428  *      in case of MIPS, smp_call_function() is used to roundup CPUs. In
 429  *      this case, we have to make sure that interrupts are enabled before
 430  *      calling smp_call_function(). The argument to this function is
 431  *      the flags that will be used when restoring the interrupts. There is
 432  *      local_irq_save() call before kgdb_roundup_cpus().
 433  *
 434  *      On non-SMP systems, this is not called.
 435  */
 436 void kgdb_roundup_cpus(unsigned long flags)
 437 {
 438         apic->send_IPI_allbutself(APIC_DM_NMI);
 439 }
 440 #endif
 441
 442 /**
 443  *      kgdb_arch_handle_exception - Handle architecture specific GDB packets.
 444  *      @vector: The error vector of the exception that happened.
 445  *      @signo: The signal number of the exception that happened.
 446  *      @err_code: The error code of the exception that happened.
 447  *      @remcom_in_buffer: The buffer of the packet we have read.
 448  *      @remcom_out_buffer: The buffer of %BUFMAX bytes to write a packet into.
 449  *      @regs: The &struct pt_regs of the current process.
 450  *
 451  *      This function MUST handle the 'c' and 's' command packets,
 452  *      as well packets to set / remove a hardware breakpoint, if used.
 453  *      If there are additional packets which the hardware needs to handle,
 454  *      they are handled here.  The code should return -1 if it wants to
 455  *      process more packets, and a %0 or %1 if it wants to exit from the
 456  *      kgdb callback.
 457  */
 458 int kgdb_arch_handle_exception(int e_vector, int signo, int err_code,
 459                                char *remcomInBuffer, char *remcomOutBuffer,
 460                                struct pt_regs *linux_regs)
 461 {
 462         unsigned long addr;
 463         char *ptr;
 464         int newPC;
 465
 466         switch (remcomInBuffer[0]) {
 467         case 'c':
 468         case 's':
 469                 /* try to read optional parameter, pc unchanged if no parm */
 470                 ptr = &remcomInBuffer[1];
 471                 if (kgdb_hex2long(&ptr, &addr))
 472                         linux_regs->ip = addr;
 473         case 'D':
 474         case 'k':
 475                 newPC = linux_regs->ip;
 476
 477                 /* clear the trace bit */
 478                 linux_regs->flags &= ~X86_EFLAGS_TF;
 479                 atomic_set(&kgdb_cpu_doing_single_step, -1);
 480
 481                 /* set the trace bit if we're stepping */
 482                 if (remcomInBuffer[0] == 's') {
 483                         linux_regs->flags |= X86_EFLAGS_TF;
 484                         atomic_set(&kgdb_cpu_doing_single_step,
 485                                    raw_smp_processor_id());
 486                 }
 487
 488                 kgdb_correct_hw_break();
 489
 490                 return 0;
 491         }
 492
 493         /* this means that we do not want to exit from the handler: */
 494         return -1;
 495 }
 496
 497 static inline int
 498 single_step_cont(struct pt_regs *regs, struct die_args *args)
 499 {
 500         /*
 501          * Single step exception from kernel space to user space so
 502          * eat the exception and continue the process:
 503          */
 504         printk(KERN_ERR "KGDB: trap/step from kernel to user space, "
 505                         "resuming...\n");
 506         kgdb_arch_handle_exception(args->trapnr, args->signr,
 507                                    args->err, "c", "", regs);
 508         /*
 509          * Reset the BS bit in dr6 (pointed by args->err) to
 510          * denote completion of processing
 511          */
 512         (*(unsigned long *)ERR_PTR(args->err)) &= ~DR_STEP;
 513
 514         return NOTIFY_STOP;
 515 }
 516
 517 static int was_in_debug_nmi[NR_CPUS];
 518
 519 static int __kgdb_notify(struct die_args *args, unsigned long cmd)
 520 {
 521         struct pt_regs *regs = args->regs;
 522
 523         switch (cmd) {
 524         case DIE_NMI:
 525                 if (atomic_read(&kgdb_active) != -1) {
 526                         /* KGDB CPU roundup */
 527                         kgdb_nmicallback(raw_smp_processor_id(), regs);
 528                         was_in_debug_nmi[raw_smp_processor_id()] = 1;
 529                         touch_nmi_watchdog();
 530                         return NOTIFY_STOP;
 531                 }
 532                 return NOTIFY_DONE;
 533
 534         case DIE_NMI_IPI:
 535                 /* Just ignore, we will handle the roundup on DIE_NMI. */
 536                 return NOTIFY_DONE;
 537
 538         case DIE_NMIUNKNOWN:
 539                 if (was_in_debug_nmi[raw_smp_processor_id()]) {
 540                         was_in_debug_nmi[raw_smp_processor_id()] = 0;
 541                         return NOTIFY_STOP;
 542                 }
 543                 return NOTIFY_DONE;
 544
 545         case DIE_NMIWATCHDOG:
 546                 if (atomic_read(&kgdb_active) != -1) {
 547                         /* KGDB CPU roundup: */
 548                         kgdb_nmicallback(raw_smp_processor_id(), regs);
 549                         return NOTIFY_STOP;
 550                 }
 551                 /* Enter debugger: */
 552                 break;
 553
 554         case DIE_DEBUG:
 555                 if (atomic_read(&kgdb_cpu_doing_single_step) != -1) {
 556                         if (user_mode(regs))
 557                                 return single_step_cont(regs, args);
 558                         break;
 559                 } else if (test_thread_flag(TIF_SINGLESTEP))
 560                         /* This means a user thread is single stepping
 561                          * a system call which should be ignored
 562                          */
 563                         return NOTIFY_DONE;
 564                 /* fall through */
 565         default:
 566                 if (user_mode(regs))
 567                         return NOTIFY_DONE;
 568         }
 569
 570         if (kgdb_handle_exception(args->trapnr, args->signr, args->err, regs))
 571                 return NOTIFY_DONE;
 572
 573         /* Must touch watchdog before return to normal operation */
 574         touch_nmi_watchdog();
 575         return NOTIFY_STOP;
 576 }
 577
 578 static int
 579 kgdb_notify(struct notifier_block *self, unsigned long cmd, void *ptr)
 580 {
 581         unsigned long flags;
 582         int ret;
 583
 584         local_irq_save(flags);
 585         ret = __kgdb_notify(ptr, cmd);
 586         local_irq_restore(flags);
 587
 588         return ret;
 589 }
 590
 591 static struct notifier_block kgdb_notifier = {
 592         .notifier_call  = kgdb_notify,
 593
 594         /*
 595          * Lowest-prio notifier priority, we want to be notified last:
 596          */
 597         .priority       = -INT_MAX,
 598 };
 599
 600 /**
 601  *      kgdb_arch_init - Perform any architecture specific initalization.
 602  *
 603  *      This function will handle the initalization of any architecture
 604  *      specific callbacks.
 605  */
 606 int kgdb_arch_init(void)
 607 {
 608         int i, cpu;
 609         int ret;
 610         struct perf_event_attr attr;
 611         struct perf_event **pevent;
 612
 613         ret = register_die_notifier(&kgdb_notifier);
 614         if (ret != 0)
 615                 return ret;
 616         /*
 617          * Pre-allocate the hw breakpoint structions in the non-atomic
 618          * portion of kgdb because this operation requires mutexs to
 619          * complete.
 620          */
 621         hw_breakpoint_init(&attr);
 622         attr.bp_addr = (unsigned long)kgdb_arch_init;
 623         attr.bp_len = HW_BREAKPOINT_LEN_1;
 624         attr.bp_type = HW_BREAKPOINT_W;
 625         attr.disabled = 1;
 626         for (i = 0; i < 4; i++) {
 627                 breakinfo[i].pev = register_wide_hw_breakpoint(&attr, NULL);
 628                 if (IS_ERR(breakinfo[i].pev)) {
 629                         printk(KERN_ERR "kgdb: Could not allocate hw breakpoints\n");
 630                         breakinfo[i].pev = NULL;
 631                         kgdb_arch_exit();
 632                         return -1;
 633                 }
 634                 for_each_online_cpu(cpu) {
 635                         pevent = per_cpu_ptr(breakinfo[i].pev, cpu);
 636                         pevent[0]->hw.sample_period = 1;
 637                         if (pevent[0]->destroy != NULL) {
 638                                 pevent[0]->destroy = NULL;
 639                                 release_bp_slot(*pevent);
 640                         }
 641                 }
 642         }
 643         return ret;
 644 }
 645
 646 /**
 647  *      kgdb_arch_exit - Perform any architecture specific uninitalization.
 648  *
 649  *      This function will handle the uninitalization of any architecture
 650  *      specific callbacks, for dynamic registration and unregistration.
 651  */
 652 void kgdb_arch_exit(void)
 653 {
 654         int i;
 655         for (i = 0; i < 4; i++) {
 656                 if (breakinfo[i].pev) {
 657                         unregister_wide_hw_breakpoint(breakinfo[i].pev);
 658                         breakinfo[i].pev = NULL;
 659                 }
 660         }
 661         unregister_die_notifier(&kgdb_notifier);
 662 }
 663
 664 /**
 665  *
 666  *      kgdb_skipexception - Bail out of KGDB when we've been triggered.
 667  *      @exception: Exception vector number
 668  *      @regs: Current &struct pt_regs.
 669  *
 670  *      On some architectures we need to skip a breakpoint exception when
 671  *      it occurs after a breakpoint has been removed.
 672  *
 673  * Skip an int3 exception when it occurs after a breakpoint has been
 674  * removed. Backtrack eip by 1 since the int3 would have caused it to
 675  * increment by 1.
 676  */
 677 int kgdb_skipexception(int exception, struct pt_regs *regs)
 678 {
 679         if (exception == 3 && kgdb_isremovedbreak(regs->ip - 1)) {
 680                 regs->ip -= 1;
 681                 return 1;
 682         }
 683         return 0;
 684 }
 685
 686 unsigned long kgdb_arch_pc(int exception, struct pt_regs *regs)
 687 {
 688         if (exception == 3)
 689                 return instruction_pointer(regs) - 1;
 690         return instruction_pointer(regs);
 691 }
 692
 693 struct kgdb_arch arch_kgdb_ops = {
 694         /* Breakpoint instruction: */
 695         .gdb_bpt_instr          = { 0xcc },
 696         .flags                  = KGDB_HW_BREAKPOINT,
 697         .set_hw_breakpoint      = kgdb_set_hw_break,
 698         .remove_hw_breakpoint   = kgdb_remove_hw_break,
 699         .remove_all_hw_break    = kgdb_remove_all_hw_break,
 700         .correct_hw_break       = kgdb_correct_hw_break,
 701 };