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
  45 #include <asm/apicdef.h>
  46 #include <asm/system.h>
  47
  48 #ifdef CONFIG_X86_32
  49 # include <mach_ipi.h>
  50 #else
  51 # include <asm/mach_apic.h>
  52 #endif
  53
  54 /*
  55  * Put the error code here just in case the user cares:
  56  */
  57 static int gdb_x86errcode;
  58
  59 /*
  60  * Likewise, the vector number here (since GDB only gets the signal
  61  * number through the usual means, and that's not very specific):
  62  */
  63 static int gdb_x86vector = -1;
  64
  65 /**
  66  *      pt_regs_to_gdb_regs - Convert ptrace regs to GDB regs
  67  *      @gdb_regs: A pointer to hold the registers in the order GDB wants.
  68  *      @regs: The &struct pt_regs of the current process.
  69  *
  70  *      Convert the pt_regs in @regs into the format for registers that
  71  *      GDB expects, stored in @gdb_regs.
  72  */
  73 void pt_regs_to_gdb_regs(unsigned long *gdb_regs, struct pt_regs *regs)
  74 {
  75         gdb_regs[GDB_AX]        = regs->ax;
  76         gdb_regs[GDB_BX]        = regs->bx;
  77         gdb_regs[GDB_CX]        = regs->cx;
  78         gdb_regs[GDB_DX]        = regs->dx;
  79         gdb_regs[GDB_SI]        = regs->si;
  80         gdb_regs[GDB_DI]        = regs->di;
  81         gdb_regs[GDB_BP]        = regs->bp;
  82         gdb_regs[GDB_PS]        = regs->flags;
  83         gdb_regs[GDB_PC]        = regs->ip;
  84 #ifdef CONFIG_X86_32
  85         gdb_regs[GDB_DS]        = regs->ds;
  86         gdb_regs[GDB_ES]        = regs->es;
  87         gdb_regs[GDB_CS]        = regs->cs;
  88         gdb_regs[GDB_SS]        = __KERNEL_DS;
  89         gdb_regs[GDB_FS]        = 0xFFFF;
  90         gdb_regs[GDB_GS]        = 0xFFFF;
  91 #else
  92         gdb_regs[GDB_R8]        = regs->r8;
  93         gdb_regs[GDB_R9]        = regs->r9;
  94         gdb_regs[GDB_R10]       = regs->r10;
  95         gdb_regs[GDB_R11]       = regs->r11;
  96         gdb_regs[GDB_R12]       = regs->r12;
  97         gdb_regs[GDB_R13]       = regs->r13;
  98         gdb_regs[GDB_R14]       = regs->r14;
  99         gdb_regs[GDB_R15]       = regs->r15;
 100 #endif
 101         gdb_regs[GDB_SP]        = regs->sp;
 102 }
 103
 104 /**
 105  *      sleeping_thread_to_gdb_regs - Convert ptrace regs to GDB regs
 106  *      @gdb_regs: A pointer to hold the registers in the order GDB wants.
 107  *      @p: The &struct task_struct of the desired process.
 108  *
 109  *      Convert the register values of the sleeping process in @p to
 110  *      the format that GDB expects.
 111  *      This function is called when kgdb does not have access to the
 112  *      &struct pt_regs and therefore it should fill the gdb registers
 113  *      @gdb_regs with what has been saved in &struct thread_struct
 114  *      thread field during switch_to.
 115  */
 116 void sleeping_thread_to_gdb_regs(unsigned long *gdb_regs, struct task_struct *p)
 117 {
 118         gdb_regs[GDB_AX]        = 0;
 119         gdb_regs[GDB_BX]        = 0;
 120         gdb_regs[GDB_CX]        = 0;
 121         gdb_regs[GDB_DX]        = 0;
 122         gdb_regs[GDB_SI]        = 0;
 123         gdb_regs[GDB_DI]        = 0;
 124         gdb_regs[GDB_BP]        = *(unsigned long *)p->thread.sp;
 125 #ifdef CONFIG_X86_32
 126         gdb_regs[GDB_DS]        = __KERNEL_DS;
 127         gdb_regs[GDB_ES]        = __KERNEL_DS;
 128         gdb_regs[GDB_PS]        = 0;
 129         gdb_regs[GDB_CS]        = __KERNEL_CS;
 130         gdb_regs[GDB_PC]        = p->thread.ip;
 131         gdb_regs[GDB_SS]        = __KERNEL_DS;
 132         gdb_regs[GDB_FS]        = 0xFFFF;
 133         gdb_regs[GDB_GS]        = 0xFFFF;
 134 #else
 135         gdb_regs[GDB_PS]        = *(unsigned long *)(p->thread.sp + 8);
 136         gdb_regs[GDB_PC]        = 0;
 137         gdb_regs[GDB_R8]        = 0;
 138         gdb_regs[GDB_R9]        = 0;
 139         gdb_regs[GDB_R10]       = 0;
 140         gdb_regs[GDB_R11]       = 0;
 141         gdb_regs[GDB_R12]       = 0;
 142         gdb_regs[GDB_R13]       = 0;
 143         gdb_regs[GDB_R14]       = 0;
 144         gdb_regs[GDB_R15]       = 0;
 145 #endif
 146         gdb_regs[GDB_SP]        = p->thread.sp;
 147 }
 148
 149 /**
 150  *      gdb_regs_to_pt_regs - Convert GDB regs to ptrace regs.
 151  *      @gdb_regs: A pointer to hold the registers we've received from GDB.
 152  *      @regs: A pointer to a &struct pt_regs to hold these values in.
 153  *
 154  *      Convert the GDB regs in @gdb_regs into the pt_regs, and store them
 155  *      in @regs.
 156  */
 157 void gdb_regs_to_pt_regs(unsigned long *gdb_regs, struct pt_regs *regs)
 158 {
 159         regs->ax                = gdb_regs[GDB_AX];
 160         regs->bx                = gdb_regs[GDB_BX];
 161         regs->cx                = gdb_regs[GDB_CX];
 162         regs->dx                = gdb_regs[GDB_DX];
 163         regs->si                = gdb_regs[GDB_SI];
 164         regs->di                = gdb_regs[GDB_DI];
 165         regs->bp                = gdb_regs[GDB_BP];
 166         regs->flags             = gdb_regs[GDB_PS];
 167         regs->ip                = gdb_regs[GDB_PC];
 168 #ifdef CONFIG_X86_32
 169         regs->ds                = gdb_regs[GDB_DS];
 170         regs->es                = gdb_regs[GDB_ES];
 171         regs->cs                = gdb_regs[GDB_CS];
 172 #else
 173         regs->r8                = gdb_regs[GDB_R8];
 174         regs->r9                = gdb_regs[GDB_R9];
 175         regs->r10               = gdb_regs[GDB_R10];
 176         regs->r11               = gdb_regs[GDB_R11];
 177         regs->r12               = gdb_regs[GDB_R12];
 178         regs->r13               = gdb_regs[GDB_R13];
 179         regs->r14               = gdb_regs[GDB_R14];
 180         regs->r15               = gdb_regs[GDB_R15];
 181 #endif
 182 }
 183
 184 /**
 185  *      kgdb_post_primary_code - Save error vector/code numbers.
 186  *      @regs: Original pt_regs.
 187  *      @e_vector: Original error vector.
 188  *      @err_code: Original error code.
 189  *
 190  *      This is needed on architectures which support SMP and KGDB.
 191  *      This function is called after all the slave cpus have been put
 192  *      to a know spin state and the primary CPU has control over KGDB.
 193  */
 194 void kgdb_post_primary_code(struct pt_regs *regs, int e_vector, int err_code)
 195 {
 196         /* primary processor is completely in the debugger */
 197         gdb_x86vector = e_vector;
 198         gdb_x86errcode = err_code;
 199 }
 200
 201 #ifdef CONFIG_SMP
 202 /**
 203  *      kgdb_roundup_cpus - Get other CPUs into a holding pattern
 204  *      @flags: Current IRQ state
 205  *
 206  *      On SMP systems, we need to get the attention of the other CPUs
 207  *      and get them be in a known state.  This should do what is needed
 208  *      to get the other CPUs to call kgdb_wait(). Note that on some arches,
 209  *      the NMI approach is not used for rounding up all the CPUs. For example,
 210  *      in case of MIPS, smp_call_function() is used to roundup CPUs. In
 211  *      this case, we have to make sure that interrupts are enabled before
 212  *      calling smp_call_function(). The argument to this function is
 213  *      the flags that will be used when restoring the interrupts. There is
 214  *      local_irq_save() call before kgdb_roundup_cpus().
 215  *
 216  *      On non-SMP systems, this is not called.
 217  */
 218 void kgdb_roundup_cpus(unsigned long flags)
 219 {
 220         send_IPI_allbutself(APIC_DM_NMI);
 221 }
 222 #endif
 223
 224 /**
 225  *      kgdb_arch_handle_exception - Handle architecture specific GDB packets.
 226  *      @vector: The error vector of the exception that happened.
 227  *      @signo: The signal number of the exception that happened.
 228  *      @err_code: The error code of the exception that happened.
 229  *      @remcom_in_buffer: The buffer of the packet we have read.
 230  *      @remcom_out_buffer: The buffer of %BUFMAX bytes to write a packet into.
 231  *      @regs: The &struct pt_regs of the current process.
 232  *
 233  *      This function MUST handle the 'c' and 's' command packets,
 234  *      as well packets to set / remove a hardware breakpoint, if used.
 235  *      If there are additional packets which the hardware needs to handle,
 236  *      they are handled here.  The code should return -1 if it wants to
 237  *      process more packets, and a %0 or %1 if it wants to exit from the
 238  *      kgdb callback.
 239  */
 240 int kgdb_arch_handle_exception(int e_vector, int signo, int err_code,
 241                                char *remcomInBuffer, char *remcomOutBuffer,
 242                                struct pt_regs *linux_regs)
 243 {
 244         unsigned long addr;
 245         char *ptr;
 246         int newPC;
 247
 248         switch (remcomInBuffer[0]) {
 249         case 'c':
 250         case 's':
 251                 /* try to read optional parameter, pc unchanged if no parm */
 252                 ptr = &remcomInBuffer[1];
 253                 if (kgdb_hex2long(&ptr, &addr))
 254                         linux_regs->ip = addr;
 255                 newPC = linux_regs->ip;
 256
 257                 /* clear the trace bit */
 258                 linux_regs->flags &= ~TF_MASK;
 259                 atomic_set(&kgdb_cpu_doing_single_step, -1);
 260
 261                 /* set the trace bit if we're stepping */
 262                 if (remcomInBuffer[0] == 's') {
 263                         linux_regs->flags |= TF_MASK;
 264                         kgdb_single_step = 1;
 265                         if (kgdb_contthread) {
 266                                 atomic_set(&kgdb_cpu_doing_single_step,
 267                                            raw_smp_processor_id());
 268                         }
 269                 }
 270
 271                 return 0;
 272         }
 273
 274         /* this means that we do not want to exit from the handler: */
 275         return -1;
 276 }
 277
 278 static inline int
 279 single_step_cont(struct pt_regs *regs, struct die_args *args)
 280 {
 281         /*
 282          * Single step exception from kernel space to user space so
 283          * eat the exception and continue the process:
 284          */
 285         printk(KERN_ERR "KGDB: trap/step from kernel to user space, "
 286                         "resuming...\n");
 287         kgdb_arch_handle_exception(args->trapnr, args->signr,
 288                                    args->err, "c", "", regs);
 289
 290         return NOTIFY_STOP;
 291 }
 292
 293 static int __kgdb_notify(struct die_args *args, unsigned long cmd)
 294 {
 295         struct pt_regs *regs = args->regs;
 296
 297         switch (cmd) {
 298         case DIE_NMI:
 299                 if (atomic_read(&kgdb_active) != -1) {
 300                         /* KGDB CPU roundup */
 301                         kgdb_nmicallback(raw_smp_processor_id(), regs);
 302                         return NOTIFY_STOP;
 303                 }
 304                 return NOTIFY_DONE;
 305
 306         case DIE_NMI_IPI:
 307                 if (atomic_read(&kgdb_active) != -1) {
 308                         /* KGDB CPU roundup: */
 309                         if (kgdb_nmicallback(raw_smp_processor_id(), regs))
 310                                 return NOTIFY_DONE;
 311                         return NOTIFY_STOP;
 312                 }
 313                 return NOTIFY_DONE;
 314
 315         case DIE_NMIWATCHDOG:
 316                 if (atomic_read(&kgdb_active) != -1) {
 317                         /* KGDB CPU roundup: */
 318                         kgdb_nmicallback(raw_smp_processor_id(), regs);
 319                         return NOTIFY_STOP;
 320                 }
 321                 /* Enter debugger: */
 322                 break;
 323
 324         case DIE_DEBUG:
 325                 if (atomic_read(&kgdb_cpu_doing_single_step) ==
 326                         raw_smp_processor_id() &&
 327                         user_mode(regs))
 328                         return single_step_cont(regs, args);
 329                 /* fall through */
 330         default:
 331                 if (user_mode(regs))
 332                         return NOTIFY_DONE;
 333         }
 334
 335         if (kgdb_handle_exception(args->trapnr, args->signr, args->err, regs))
 336                 return NOTIFY_DONE;
 337
 338         return NOTIFY_STOP;
 339 }
 340
 341 static int
 342 kgdb_notify(struct notifier_block *self, unsigned long cmd, void *ptr)
 343 {
 344         unsigned long flags;
 345         int ret;
 346
 347         local_irq_save(flags);
 348         ret = __kgdb_notify(ptr, cmd);
 349         local_irq_restore(flags);
 350
 351         return ret;
 352 }
 353
 354 static struct notifier_block kgdb_notifier = {
 355         .notifier_call  = kgdb_notify,
 356
 357         /*
 358          * Lowest-prio notifier priority, we want to be notified last:
 359          */
 360         .priority       = -INT_MAX,
 361 };
 362
 363 /**
 364  *      kgdb_arch_init - Perform any architecture specific initalization.
 365  *
 366  *      This function will handle the initalization of any architecture
 367  *      specific callbacks.
 368  */
 369 int kgdb_arch_init(void)
 370 {
 371         return register_die_notifier(&kgdb_notifier);
 372 }
 373
 374 /**
 375  *      kgdb_arch_exit - Perform any architecture specific uninitalization.
 376  *
 377  *      This function will handle the uninitalization of any architecture
 378  *      specific callbacks, for dynamic registration and unregistration.
 379  */
 380 void kgdb_arch_exit(void)
 381 {
 382         unregister_die_notifier(&kgdb_notifier);
 383 }
 384
 385 /**
 386  *
 387  *      kgdb_skipexception - Bail out of KGDB when we've been triggered.
 388  *      @exception: Exception vector number
 389  *      @regs: Current &struct pt_regs.
 390  *
 391  *      On some architectures we need to skip a breakpoint exception when
 392  *      it occurs after a breakpoint has been removed.
 393  *
 394  * Skip an int3 exception when it occurs after a breakpoint has been
 395  * removed. Backtrack eip by 1 since the int3 would have caused it to
 396  * increment by 1.
 397  */
 398 int kgdb_skipexception(int exception, struct pt_regs *regs)
 399 {
 400         if (exception == 3 && kgdb_isremovedbreak(regs->ip - 1)) {
 401                 regs->ip -= 1;
 402                 return 1;
 403         }
 404         return 0;
 405 }
 406
 407 unsigned long kgdb_arch_pc(int exception, struct pt_regs *regs)
 408 {
 409         if (exception == 3)
 410                 return instruction_pointer(regs) - 1;
 411         return instruction_pointer(regs);
 412 }
 413
 414 struct kgdb_arch arch_kgdb_ops = {
 415         /* Breakpoint instruction: */
 416         .gdb_bpt_instr          = { 0xcc },
 417 };