git.oblomov.eu Git - linux-2.6/blob - arch/ppc64/kernel/process.c

   1 /*
   2  *  linux/arch/ppc64/kernel/process.c
   3  *
   4  *  Derived from "arch/i386/kernel/process.c"
   5  *    Copyright (C) 1995  Linus Torvalds
   6  *
   7  *  Updated and modified by Cort Dougan (cort@cs.nmt.edu) and
   8  *  Paul Mackerras (paulus@cs.anu.edu.au)
   9  *
  10  *  PowerPC version
  11  *    Copyright (C) 1995-1996 Gary Thomas (gdt@linuxppc.org)
  12  *
  13  *  This program is free software; you can redistribute it and/or
  14  *  modify it under the terms of the GNU General Public License
  15  *  as published by the Free Software Foundation; either version
  16  *  2 of the License, or (at your option) any later version.
  17  */
  18
  19 #include <linux/config.h>
  20 #include <linux/module.h>
  21 #include <linux/errno.h>
  22 #include <linux/sched.h>
  23 #include <linux/kernel.h>
  24 #include <linux/mm.h>
  25 #include <linux/smp.h>
  26 #include <linux/smp_lock.h>
  27 #include <linux/stddef.h>
  28 #include <linux/unistd.h>
  29 #include <linux/slab.h>
  30 #include <linux/user.h>
  31 #include <linux/elf.h>
  32 #include <linux/init.h>
  33 #include <linux/init_task.h>
  34 #include <linux/prctl.h>
  35 #include <linux/ptrace.h>
  36 #include <linux/kallsyms.h>
  37 #include <linux/interrupt.h>
  38 #include <linux/utsname.h>
  39
  40 #include <asm/pgtable.h>
  41 #include <asm/uaccess.h>
  42 #include <asm/system.h>
  43 #include <asm/io.h>
  44 #include <asm/processor.h>
  45 #include <asm/mmu.h>
  46 #include <asm/mmu_context.h>
  47 #include <asm/prom.h>
  48 #include <asm/ppcdebug.h>
  49 #include <asm/machdep.h>
  50 #include <asm/iSeries/HvCallHpt.h>
  51 #include <asm/cputable.h>
  52 #include <asm/sections.h>
  53 #include <asm/tlbflush.h>
  54 #include <asm/time.h>
  55
  56 #ifndef CONFIG_SMP
  57 struct task_struct *last_task_used_math = NULL;
  58 struct task_struct *last_task_used_altivec = NULL;
  59 #endif
  60
  61 struct mm_struct ioremap_mm = {
  62         .pgd            = ioremap_dir,
  63         .mm_users       = ATOMIC_INIT(2),
  64         .mm_count       = ATOMIC_INIT(1),
  65         .cpu_vm_mask    = CPU_MASK_ALL,
  66         .page_table_lock = SPIN_LOCK_UNLOCKED,
  67 };
  68
  69 /*
  70  * Make sure the floating-point register state in the
  71  * the thread_struct is up to date for task tsk.
  72  */
  73 void flush_fp_to_thread(struct task_struct *tsk)
  74 {
  75         if (tsk->thread.regs) {
  76                 /*
  77                  * We need to disable preemption here because if we didn't,
  78                  * another process could get scheduled after the regs->msr
  79                  * test but before we have finished saving the FP registers
  80                  * to the thread_struct.  That process could take over the
  81                  * FPU, and then when we get scheduled again we would store
  82                  * bogus values for the remaining FP registers.
  83                  */
  84                 preempt_disable();
  85                 if (tsk->thread.regs->msr & MSR_FP) {
  86 #ifdef CONFIG_SMP
  87                         /*
  88                          * This should only ever be called for current or
  89                          * for a stopped child process.  Since we save away
  90                          * the FP register state on context switch on SMP,
  91                          * there is something wrong if a stopped child appears
  92                          * to still have its FP state in the CPU registers.
  93                          */
  94                         BUG_ON(tsk != current);
  95 #endif
  96                         giveup_fpu(current);
  97                 }
  98                 preempt_enable();
  99         }
 100 }
 101
 102 void enable_kernel_fp(void)
 103 {
 104         WARN_ON(preemptible());
 105
 106 #ifdef CONFIG_SMP
 107         if (current->thread.regs && (current->thread.regs->msr & MSR_FP))
 108                 giveup_fpu(current);
 109         else
 110                 giveup_fpu(NULL);       /* just enables FP for kernel */
 111 #else
 112         giveup_fpu(last_task_used_math);
 113 #endif /* CONFIG_SMP */
 114 }
 115 EXPORT_SYMBOL(enable_kernel_fp);
 116
 117 int dump_task_fpu(struct task_struct *tsk, elf_fpregset_t *fpregs)
 118 {
 119         if (!tsk->thread.regs)
 120                 return 0;
 121         flush_fp_to_thread(current);
 122
 123         memcpy(fpregs, &tsk->thread.fpr[0], sizeof(*fpregs));
 124
 125         return 1;
 126 }
 127
 128 #ifdef CONFIG_ALTIVEC
 129
 130 void enable_kernel_altivec(void)
 131 {
 132         WARN_ON(preemptible());
 133
 134 #ifdef CONFIG_SMP
 135         if (current->thread.regs && (current->thread.regs->msr & MSR_VEC))
 136                 giveup_altivec(current);
 137         else
 138                 giveup_altivec(NULL);   /* just enables FP for kernel */
 139 #else
 140         giveup_altivec(last_task_used_altivec);
 141 #endif /* CONFIG_SMP */
 142 }
 143 EXPORT_SYMBOL(enable_kernel_altivec);
 144
 145 /*
 146  * Make sure the VMX/Altivec register state in the
 147  * the thread_struct is up to date for task tsk.
 148  */
 149 void flush_altivec_to_thread(struct task_struct *tsk)
 150 {
 151         if (tsk->thread.regs) {
 152                 preempt_disable();
 153                 if (tsk->thread.regs->msr & MSR_VEC) {
 154 #ifdef CONFIG_SMP
 155                         BUG_ON(tsk != current);
 156 #endif
 157                         giveup_altivec(current);
 158                 }
 159                 preempt_enable();
 160         }
 161 }
 162
 163 int dump_task_altivec(struct pt_regs *regs, elf_vrregset_t *vrregs)
 164 {
 165         flush_altivec_to_thread(current);
 166         memcpy(vrregs, &current->thread.vr[0], sizeof(*vrregs));
 167         return 1;
 168 }
 169
 170 #endif /* CONFIG_ALTIVEC */
 171
 172 DEFINE_PER_CPU(struct cpu_usage, cpu_usage_array);
 173
 174 struct task_struct *__switch_to(struct task_struct *prev,
 175                                 struct task_struct *new)
 176 {
 177         struct thread_struct *new_thread, *old_thread;
 178         unsigned long flags;
 179         struct task_struct *last;
 180
 181 #ifdef CONFIG_SMP
 182         /* avoid complexity of lazy save/restore of fpu
 183          * by just saving it every time we switch out if
 184          * this task used the fpu during the last quantum.
 185          *
 186          * If it tries to use the fpu again, it'll trap and
 187          * reload its fp regs.  So we don't have to do a restore
 188          * every switch, just a save.
 189          *  -- Cort
 190          */
 191         if (prev->thread.regs && (prev->thread.regs->msr & MSR_FP))
 192                 giveup_fpu(prev);
 193 #ifdef CONFIG_ALTIVEC
 194         if (prev->thread.regs && (prev->thread.regs->msr & MSR_VEC))
 195                 giveup_altivec(prev);
 196 #endif /* CONFIG_ALTIVEC */
 197 #endif /* CONFIG_SMP */
 198
 199 #if defined(CONFIG_ALTIVEC) && !defined(CONFIG_SMP)
 200         /* Avoid the trap.  On smp this this never happens since
 201          * we don't set last_task_used_altivec -- Cort
 202          */
 203         if (new->thread.regs && last_task_used_altivec == new)
 204                 new->thread.regs->msr |= MSR_VEC;
 205 #endif /* CONFIG_ALTIVEC */
 206
 207         flush_tlb_pending();
 208
 209         new_thread = &new->thread;
 210         old_thread = &current->thread;
 211
 212 /* Collect purr utilization data per process and per processor wise */
 213 /* purr is nothing but processor time base                          */
 214
 215 #if defined(CONFIG_PPC_PSERIES)
 216         if (cur_cpu_spec->firmware_features & FW_FEATURE_SPLPAR) {
 217                 struct cpu_usage *cu = &__get_cpu_var(cpu_usage_array);
 218                 long unsigned start_tb, current_tb;
 219                 start_tb = old_thread->start_tb;
 220                 cu->current_tb = current_tb = mfspr(SPRN_PURR);
 221                 old_thread->accum_tb += (current_tb - start_tb);
 222                 new_thread->start_tb = current_tb;
 223         }
 224 #endif
 225
 226
 227         local_irq_save(flags);
 228         last = _switch(old_thread, new_thread);
 229
 230         local_irq_restore(flags);
 231
 232         return last;
 233 }
 234
 235 static int instructions_to_print = 16;
 236
 237 static void show_instructions(struct pt_regs *regs)
 238 {
 239         int i;
 240         unsigned long pc = regs->nip - (instructions_to_print * 3 / 4 *
 241                         sizeof(int));
 242
 243         printk("Instruction dump:");
 244
 245         for (i = 0; i < instructions_to_print; i++) {
 246                 int instr;
 247
 248                 if (!(i % 8))
 249                         printk("\n");
 250
 251                 if (((REGION_ID(pc) != KERNEL_REGION_ID) &&
 252                      (REGION_ID(pc) != VMALLOC_REGION_ID)) ||
 253                      __get_user(instr, (unsigned int *)pc)) {
 254                         printk("XXXXXXXX ");
 255                 } else {
 256                         if (regs->nip == pc)
 257                                 printk("<%08x> ", instr);
 258                         else
 259                                 printk("%08x ", instr);
 260                 }
 261
 262                 pc += sizeof(int);
 263         }
 264
 265         printk("\n");
 266 }
 267
 268 void show_regs(struct pt_regs * regs)
 269 {
 270         int i;
 271         unsigned long trap;
 272
 273         printk("NIP: %016lX XER: %08X LR: %016lX CTR: %016lX\n",
 274                regs->nip, (unsigned int)regs->xer, regs->link, regs->ctr);
 275         printk("REGS: %p TRAP: %04lx   %s  (%s)\n",
 276                regs, regs->trap, print_tainted(), system_utsname.release);
 277         printk("MSR: %016lx EE: %01x PR: %01x FP: %01x ME: %01x "
 278                "IR/DR: %01x%01x CR: %08X\n",
 279                regs->msr, regs->msr&MSR_EE ? 1 : 0, regs->msr&MSR_PR ? 1 : 0,
 280                regs->msr & MSR_FP ? 1 : 0,regs->msr&MSR_ME ? 1 : 0,
 281                regs->msr&MSR_IR ? 1 : 0,
 282                regs->msr&MSR_DR ? 1 : 0,
 283                (unsigned int)regs->ccr);
 284         trap = TRAP(regs);
 285         printk("DAR: %016lx DSISR: %016lx\n", regs->dar, regs->dsisr);
 286         printk("TASK: %p[%d] '%s' THREAD: %p",
 287                current, current->pid, current->comm, current->thread_info);
 288
 289 #ifdef CONFIG_SMP
 290         printk(" CPU: %d", smp_processor_id());
 291 #endif /* CONFIG_SMP */
 292
 293         for (i = 0; i < 32; i++) {
 294                 if ((i % 4) == 0) {
 295                         printk("\n" KERN_INFO "GPR%02d: ", i);
 296                 }
 297
 298                 printk("%016lX ", regs->gpr[i]);
 299                 if (i == 13 && !FULL_REGS(regs))
 300                         break;
 301         }
 302         printk("\n");
 303         /*
 304          * Lookup NIP late so we have the best change of getting the
 305          * above info out without failing
 306          */
 307         printk("NIP [%016lx] ", regs->nip);
 308         print_symbol("%s\n", regs->nip);
 309         printk("LR [%016lx] ", regs->link);
 310         print_symbol("%s\n", regs->link);
 311         show_stack(current, (unsigned long *)regs->gpr[1]);
 312         if (!user_mode(regs))
 313                 show_instructions(regs);
 314 }
 315
 316 void exit_thread(void)
 317 {
 318 #ifndef CONFIG_SMP
 319         if (last_task_used_math == current)
 320                 last_task_used_math = NULL;
 321 #ifdef CONFIG_ALTIVEC
 322         if (last_task_used_altivec == current)
 323                 last_task_used_altivec = NULL;
 324 #endif /* CONFIG_ALTIVEC */
 325 #endif /* CONFIG_SMP */
 326 }
 327
 328 void flush_thread(void)
 329 {
 330         struct thread_info *t = current_thread_info();
 331
 332         if (t->flags & _TIF_ABI_PENDING)
 333                 t->flags ^= (_TIF_ABI_PENDING | _TIF_32BIT);
 334
 335 #ifndef CONFIG_SMP
 336         if (last_task_used_math == current)
 337                 last_task_used_math = NULL;
 338 #ifdef CONFIG_ALTIVEC
 339         if (last_task_used_altivec == current)
 340                 last_task_used_altivec = NULL;
 341 #endif /* CONFIG_ALTIVEC */
 342 #endif /* CONFIG_SMP */
 343 }
 344
 345 void
 346 release_thread(struct task_struct *t)
 347 {
 348 }
 349
 350
 351 /*
 352  * This gets called before we allocate a new thread and copy
 353  * the current task into it.
 354  */
 355 void prepare_to_copy(struct task_struct *tsk)
 356 {
 357         flush_fp_to_thread(current);
 358         flush_altivec_to_thread(current);
 359 }
 360
 361 /*
 362  * Copy a thread..
 363  */
 364 int
 365 copy_thread(int nr, unsigned long clone_flags, unsigned long usp,
 366             unsigned long unused, struct task_struct *p, struct pt_regs *regs)
 367 {
 368         struct pt_regs *childregs, *kregs;
 369         extern void ret_from_fork(void);
 370         unsigned long sp = (unsigned long)p->thread_info + THREAD_SIZE;
 371
 372         /* Copy registers */
 373         sp -= sizeof(struct pt_regs);
 374         childregs = (struct pt_regs *) sp;
 375         *childregs = *regs;
 376         if ((childregs->msr & MSR_PR) == 0) {
 377                 /* for kernel thread, set stackptr in new task */
 378                 childregs->gpr[1] = sp + sizeof(struct pt_regs);
 379                 p->thread.regs = NULL;  /* no user register state */
 380                 clear_ti_thread_flag(p->thread_info, TIF_32BIT);
 381         } else {
 382                 childregs->gpr[1] = usp;
 383                 p->thread.regs = childregs;
 384                 if (clone_flags & CLONE_SETTLS) {
 385                         if (test_thread_flag(TIF_32BIT))
 386                                 childregs->gpr[2] = childregs->gpr[6];
 387                         else
 388                                 childregs->gpr[13] = childregs->gpr[6];
 389                 }
 390         }
 391         childregs->gpr[3] = 0;  /* Result from fork() */
 392         sp -= STACK_FRAME_OVERHEAD;
 393
 394         /*
 395          * The way this works is that at some point in the future
 396          * some task will call _switch to switch to the new task.
 397          * That will pop off the stack frame created below and start
 398          * the new task running at ret_from_fork.  The new task will
 399          * do some house keeping and then return from the fork or clone
 400          * system call, using the stack frame created above.
 401          */
 402         sp -= sizeof(struct pt_regs);
 403         kregs = (struct pt_regs *) sp;
 404         sp -= STACK_FRAME_OVERHEAD;
 405         p->thread.ksp = sp;
 406         if (cpu_has_feature(CPU_FTR_SLB)) {
 407                 unsigned long sp_vsid = get_kernel_vsid(sp);
 408
 409                 sp_vsid <<= SLB_VSID_SHIFT;
 410                 sp_vsid |= SLB_VSID_KERNEL;
 411                 if (cpu_has_feature(CPU_FTR_16M_PAGE))
 412                         sp_vsid |= SLB_VSID_L;
 413
 414                 p->thread.ksp_vsid = sp_vsid;
 415         }
 416
 417         /*
 418          * The PPC64 ABI makes use of a TOC to contain function
 419          * pointers.  The function (ret_from_except) is actually a pointer
 420          * to the TOC entry.  The first entry is a pointer to the actual
 421          * function.
 422          */
 423         kregs->nip = *((unsigned long *)ret_from_fork);
 424
 425         return 0;
 426 }
 427
 428 /*
 429  * Set up a thread for executing a new program
 430  */
 431 void start_thread(struct pt_regs *regs, unsigned long fdptr, unsigned long sp)
 432 {
 433         unsigned long entry, toc, load_addr = regs->gpr[2];
 434
 435         /* fdptr is a relocated pointer to the function descriptor for
 436          * the elf _start routine.  The first entry in the function
 437          * descriptor is the entry address of _start and the second
 438          * entry is the TOC value we need to use.
 439          */
 440         set_fs(USER_DS);
 441         __get_user(entry, (unsigned long __user *)fdptr);
 442         __get_user(toc, (unsigned long __user *)fdptr+1);
 443
 444         /* Check whether the e_entry function descriptor entries
 445          * need to be relocated before we can use them.
 446          */
 447         if (load_addr != 0) {
 448                 entry += load_addr;
 449                 toc   += load_addr;
 450         }
 451
 452         /*
 453          * If we exec out of a kernel thread then thread.regs will not be
 454          * set. Do it now.
 455          */
 456         if (!current->thread.regs) {
 457                 unsigned long childregs = (unsigned long)current->thread_info +
 458                                                 THREAD_SIZE;
 459                 childregs -= sizeof(struct pt_regs);
 460                 current->thread.regs = (struct pt_regs *)childregs;
 461         }
 462
 463         regs->nip = entry;
 464         regs->gpr[1] = sp;
 465         regs->gpr[2] = toc;
 466         regs->msr = MSR_USER64;
 467 #ifndef CONFIG_SMP
 468         if (last_task_used_math == current)
 469                 last_task_used_math = 0;
 470 #endif /* CONFIG_SMP */
 471         memset(current->thread.fpr, 0, sizeof(current->thread.fpr));
 472         current->thread.fpscr = 0;
 473 #ifdef CONFIG_ALTIVEC
 474 #ifndef CONFIG_SMP
 475         if (last_task_used_altivec == current)
 476                 last_task_used_altivec = 0;
 477 #endif /* CONFIG_SMP */
 478         memset(current->thread.vr, 0, sizeof(current->thread.vr));
 479         current->thread.vscr.u[0] = 0;
 480         current->thread.vscr.u[1] = 0;
 481         current->thread.vscr.u[2] = 0;
 482         current->thread.vscr.u[3] = 0x00010000; /* Java mode disabled */
 483         current->thread.vrsave = 0;
 484         current->thread.used_vr = 0;
 485 #endif /* CONFIG_ALTIVEC */
 486 }
 487 EXPORT_SYMBOL(start_thread);
 488
 489 int set_fpexc_mode(struct task_struct *tsk, unsigned int val)
 490 {
 491         struct pt_regs *regs = tsk->thread.regs;
 492
 493         if (val > PR_FP_EXC_PRECISE)
 494                 return -EINVAL;
 495         tsk->thread.fpexc_mode = __pack_fe01(val);
 496         if (regs != NULL && (regs->msr & MSR_FP) != 0)
 497                 regs->msr = (regs->msr & ~(MSR_FE0|MSR_FE1))
 498                         | tsk->thread.fpexc_mode;
 499         return 0;
 500 }
 501
 502 int get_fpexc_mode(struct task_struct *tsk, unsigned long adr)
 503 {
 504         unsigned int val;
 505
 506         val = __unpack_fe01(tsk->thread.fpexc_mode);
 507         return put_user(val, (unsigned int __user *) adr);
 508 }
 509
 510 int sys_clone(unsigned long clone_flags, unsigned long p2, unsigned long p3,
 511               unsigned long p4, unsigned long p5, unsigned long p6,
 512               struct pt_regs *regs)
 513 {
 514         unsigned long parent_tidptr = 0;
 515         unsigned long child_tidptr = 0;
 516
 517         if (p2 == 0)
 518                 p2 = regs->gpr[1];      /* stack pointer for child */
 519
 520         if (clone_flags & (CLONE_PARENT_SETTID | CLONE_CHILD_SETTID |
 521                            CLONE_CHILD_CLEARTID)) {
 522                 parent_tidptr = p3;
 523                 child_tidptr = p5;
 524                 if (test_thread_flag(TIF_32BIT)) {
 525                         parent_tidptr &= 0xffffffff;
 526                         child_tidptr &= 0xffffffff;
 527                 }
 528         }
 529
 530         return do_fork(clone_flags, p2, regs, 0,
 531                     (int __user *)parent_tidptr, (int __user *)child_tidptr);
 532 }
 533
 534 int sys_fork(unsigned long p1, unsigned long p2, unsigned long p3,
 535              unsigned long p4, unsigned long p5, unsigned long p6,
 536              struct pt_regs *regs)
 537 {
 538         return do_fork(SIGCHLD, regs->gpr[1], regs, 0, NULL, NULL);
 539 }
 540
 541 int sys_vfork(unsigned long p1, unsigned long p2, unsigned long p3,
 542               unsigned long p4, unsigned long p5, unsigned long p6,
 543               struct pt_regs *regs)
 544 {
 545         return do_fork(CLONE_VFORK | CLONE_VM | SIGCHLD, regs->gpr[1], regs, 0,
 546                     NULL, NULL);
 547 }
 548
 549 int sys_execve(unsigned long a0, unsigned long a1, unsigned long a2,
 550                unsigned long a3, unsigned long a4, unsigned long a5,
 551                struct pt_regs *regs)
 552 {
 553         int error;
 554         char * filename;
 555
 556         filename = getname((char __user *) a0);
 557         error = PTR_ERR(filename);
 558         if (IS_ERR(filename))
 559                 goto out;
 560         flush_fp_to_thread(current);
 561         flush_altivec_to_thread(current);
 562         error = do_execve(filename, (char __user * __user *) a1,
 563                                     (char __user * __user *) a2, regs);
 564
 565         if (error == 0) {
 566                 task_lock(current);
 567                 current->ptrace &= ~PT_DTRACE;
 568                 task_unlock(current);
 569         }
 570         putname(filename);
 571
 572 out:
 573         return error;
 574 }
 575
 576 static int kstack_depth_to_print = 64;
 577
 578 static int validate_sp(unsigned long sp, struct task_struct *p,
 579                        unsigned long nbytes)
 580 {
 581         unsigned long stack_page = (unsigned long)p->thread_info;
 582
 583         if (sp >= stack_page + sizeof(struct thread_struct)
 584             && sp <= stack_page + THREAD_SIZE - nbytes)
 585                 return 1;
 586
 587 #ifdef CONFIG_IRQSTACKS
 588         stack_page = (unsigned long) hardirq_ctx[task_cpu(p)];
 589         if (sp >= stack_page + sizeof(struct thread_struct)
 590             && sp <= stack_page + THREAD_SIZE - nbytes)
 591                 return 1;
 592
 593         stack_page = (unsigned long) softirq_ctx[task_cpu(p)];
 594         if (sp >= stack_page + sizeof(struct thread_struct)
 595             && sp <= stack_page + THREAD_SIZE - nbytes)
 596                 return 1;
 597 #endif
 598
 599         return 0;
 600 }
 601
 602 unsigned long get_wchan(struct task_struct *p)
 603 {
 604         unsigned long ip, sp;
 605         int count = 0;
 606
 607         if (!p || p == current || p->state == TASK_RUNNING)
 608                 return 0;
 609
 610         sp = p->thread.ksp;
 611         if (!validate_sp(sp, p, 112))
 612                 return 0;
 613
 614         do {
 615                 sp = *(unsigned long *)sp;
 616                 if (!validate_sp(sp, p, 112))
 617                         return 0;
 618                 if (count > 0) {
 619                         ip = *(unsigned long *)(sp + 16);
 620                         if (!in_sched_functions(ip))
 621                                 return ip;
 622                 }
 623         } while (count++ < 16);
 624         return 0;
 625 }
 626 EXPORT_SYMBOL(get_wchan);
 627
 628 void show_stack(struct task_struct *p, unsigned long *_sp)
 629 {
 630         unsigned long ip, newsp, lr;
 631         int count = 0;
 632         unsigned long sp = (unsigned long)_sp;
 633         int firstframe = 1;
 634
 635         if (sp == 0) {
 636                 if (p) {
 637                         sp = p->thread.ksp;
 638                 } else {
 639                         sp = __get_SP();
 640                         p = current;
 641                 }
 642         }
 643
 644         lr = 0;
 645         printk("Call Trace:\n");
 646         do {
 647                 if (!validate_sp(sp, p, 112))
 648                         return;
 649
 650                 _sp = (unsigned long *) sp;
 651                 newsp = _sp[0];
 652                 ip = _sp[2];
 653                 if (!firstframe || ip != lr) {
 654                         printk("[%016lx] [%016lx] ", sp, ip);
 655                         print_symbol("%s", ip);
 656                         if (firstframe)
 657                                 printk(" (unreliable)");
 658                         printk("\n");
 659                 }
 660                 firstframe = 0;
 661
 662                 /*
 663                  * See if this is an exception frame.
 664                  * We look for the "regshere" marker in the current frame.
 665                  */
 666                 if (validate_sp(sp, p, sizeof(struct pt_regs) + 400)
 667                     && _sp[12] == 0x7265677368657265ul) {
 668                         struct pt_regs *regs = (struct pt_regs *)
 669                                 (sp + STACK_FRAME_OVERHEAD);
 670                         printk("--- Exception: %lx", regs->trap);
 671                         print_symbol(" at %s\n", regs->nip);
 672                         lr = regs->link;
 673                         print_symbol("    LR = %s\n", lr);
 674                         firstframe = 1;
 675                 }
 676
 677                 sp = newsp;
 678         } while (count++ < kstack_depth_to_print);
 679 }
 680
 681 void dump_stack(void)
 682 {
 683         show_stack(current, (unsigned long *)__get_SP());
 684 }
 685 EXPORT_SYMBOL(dump_stack);