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 #ifdef CONFIG_PPC_ISERIES
 382                 set_ti_thread_flag(p->thread_info, TIF_RUN_LIGHT);
 383 #endif
 384         } else {
 385                 childregs->gpr[1] = usp;
 386                 p->thread.regs = childregs;
 387                 if (clone_flags & CLONE_SETTLS) {
 388                         if (test_thread_flag(TIF_32BIT))
 389                                 childregs->gpr[2] = childregs->gpr[6];
 390                         else
 391                                 childregs->gpr[13] = childregs->gpr[6];
 392                 }
 393         }
 394         childregs->gpr[3] = 0;  /* Result from fork() */
 395         sp -= STACK_FRAME_OVERHEAD;
 396
 397         /*
 398          * The way this works is that at some point in the future
 399          * some task will call _switch to switch to the new task.
 400          * That will pop off the stack frame created below and start
 401          * the new task running at ret_from_fork.  The new task will
 402          * do some house keeping and then return from the fork or clone
 403          * system call, using the stack frame created above.
 404          */
 405         sp -= sizeof(struct pt_regs);
 406         kregs = (struct pt_regs *) sp;
 407         sp -= STACK_FRAME_OVERHEAD;
 408         p->thread.ksp = sp;
 409         if (cpu_has_feature(CPU_FTR_SLB)) {
 410                 unsigned long sp_vsid = get_kernel_vsid(sp);
 411
 412                 sp_vsid <<= SLB_VSID_SHIFT;
 413                 sp_vsid |= SLB_VSID_KERNEL;
 414                 if (cpu_has_feature(CPU_FTR_16M_PAGE))
 415                         sp_vsid |= SLB_VSID_L;
 416
 417                 p->thread.ksp_vsid = sp_vsid;
 418         }
 419
 420         /*
 421          * The PPC64 ABI makes use of a TOC to contain function
 422          * pointers.  The function (ret_from_except) is actually a pointer
 423          * to the TOC entry.  The first entry is a pointer to the actual
 424          * function.
 425          */
 426         kregs->nip = *((unsigned long *)ret_from_fork);
 427
 428         return 0;
 429 }
 430
 431 /*
 432  * Set up a thread for executing a new program
 433  */
 434 void start_thread(struct pt_regs *regs, unsigned long fdptr, unsigned long sp)
 435 {
 436         unsigned long entry, toc, load_addr = regs->gpr[2];
 437
 438         /* fdptr is a relocated pointer to the function descriptor for
 439          * the elf _start routine.  The first entry in the function
 440          * descriptor is the entry address of _start and the second
 441          * entry is the TOC value we need to use.
 442          */
 443         set_fs(USER_DS);
 444         __get_user(entry, (unsigned long __user *)fdptr);
 445         __get_user(toc, (unsigned long __user *)fdptr+1);
 446
 447         /* Check whether the e_entry function descriptor entries
 448          * need to be relocated before we can use them.
 449          */
 450         if (load_addr != 0) {
 451                 entry += load_addr;
 452                 toc   += load_addr;
 453         }
 454
 455         /*
 456          * If we exec out of a kernel thread then thread.regs will not be
 457          * set. Do it now.
 458          */
 459         if (!current->thread.regs) {
 460                 unsigned long childregs = (unsigned long)current->thread_info +
 461                                                 THREAD_SIZE;
 462                 childregs -= sizeof(struct pt_regs);
 463                 current->thread.regs = (struct pt_regs *)childregs;
 464         }
 465
 466         regs->nip = entry;
 467         regs->gpr[1] = sp;
 468         regs->gpr[2] = toc;
 469         regs->msr = MSR_USER64;
 470 #ifndef CONFIG_SMP
 471         if (last_task_used_math == current)
 472                 last_task_used_math = 0;
 473 #endif /* CONFIG_SMP */
 474         memset(current->thread.fpr, 0, sizeof(current->thread.fpr));
 475         current->thread.fpscr = 0;
 476 #ifdef CONFIG_ALTIVEC
 477 #ifndef CONFIG_SMP
 478         if (last_task_used_altivec == current)
 479                 last_task_used_altivec = 0;
 480 #endif /* CONFIG_SMP */
 481         memset(current->thread.vr, 0, sizeof(current->thread.vr));
 482         current->thread.vscr.u[0] = 0;
 483         current->thread.vscr.u[1] = 0;
 484         current->thread.vscr.u[2] = 0;
 485         current->thread.vscr.u[3] = 0x00010000; /* Java mode disabled */
 486         current->thread.vrsave = 0;
 487         current->thread.used_vr = 0;
 488 #endif /* CONFIG_ALTIVEC */
 489 }
 490 EXPORT_SYMBOL(start_thread);
 491
 492 int set_fpexc_mode(struct task_struct *tsk, unsigned int val)
 493 {
 494         struct pt_regs *regs = tsk->thread.regs;
 495
 496         if (val > PR_FP_EXC_PRECISE)
 497                 return -EINVAL;
 498         tsk->thread.fpexc_mode = __pack_fe01(val);
 499         if (regs != NULL && (regs->msr & MSR_FP) != 0)
 500                 regs->msr = (regs->msr & ~(MSR_FE0|MSR_FE1))
 501                         | tsk->thread.fpexc_mode;
 502         return 0;
 503 }
 504
 505 int get_fpexc_mode(struct task_struct *tsk, unsigned long adr)
 506 {
 507         unsigned int val;
 508
 509         val = __unpack_fe01(tsk->thread.fpexc_mode);
 510         return put_user(val, (unsigned int __user *) adr);
 511 }
 512
 513 int sys_clone(unsigned long clone_flags, unsigned long p2, unsigned long p3,
 514               unsigned long p4, unsigned long p5, unsigned long p6,
 515               struct pt_regs *regs)
 516 {
 517         unsigned long parent_tidptr = 0;
 518         unsigned long child_tidptr = 0;
 519
 520         if (p2 == 0)
 521                 p2 = regs->gpr[1];      /* stack pointer for child */
 522
 523         if (clone_flags & (CLONE_PARENT_SETTID | CLONE_CHILD_SETTID |
 524                            CLONE_CHILD_CLEARTID)) {
 525                 parent_tidptr = p3;
 526                 child_tidptr = p5;
 527                 if (test_thread_flag(TIF_32BIT)) {
 528                         parent_tidptr &= 0xffffffff;
 529                         child_tidptr &= 0xffffffff;
 530                 }
 531         }
 532
 533         return do_fork(clone_flags, p2, regs, 0,
 534                     (int __user *)parent_tidptr, (int __user *)child_tidptr);
 535 }
 536
 537 int sys_fork(unsigned long p1, unsigned long p2, unsigned long p3,
 538              unsigned long p4, unsigned long p5, unsigned long p6,
 539              struct pt_regs *regs)
 540 {
 541         return do_fork(SIGCHLD, regs->gpr[1], regs, 0, NULL, NULL);
 542 }
 543
 544 int sys_vfork(unsigned long p1, unsigned long p2, unsigned long p3,
 545               unsigned long p4, unsigned long p5, unsigned long p6,
 546               struct pt_regs *regs)
 547 {
 548         return do_fork(CLONE_VFORK | CLONE_VM | SIGCHLD, regs->gpr[1], regs, 0,
 549                     NULL, NULL);
 550 }
 551
 552 int sys_execve(unsigned long a0, unsigned long a1, unsigned long a2,
 553                unsigned long a3, unsigned long a4, unsigned long a5,
 554                struct pt_regs *regs)
 555 {
 556         int error;
 557         char * filename;
 558
 559         filename = getname((char __user *) a0);
 560         error = PTR_ERR(filename);
 561         if (IS_ERR(filename))
 562                 goto out;
 563         flush_fp_to_thread(current);
 564         flush_altivec_to_thread(current);
 565         error = do_execve(filename, (char __user * __user *) a1,
 566                                     (char __user * __user *) a2, regs);
 567
 568         if (error == 0) {
 569                 task_lock(current);
 570                 current->ptrace &= ~PT_DTRACE;
 571                 task_unlock(current);
 572         }
 573         putname(filename);
 574
 575 out:
 576         return error;
 577 }
 578
 579 static int kstack_depth_to_print = 64;
 580
 581 static int validate_sp(unsigned long sp, struct task_struct *p,
 582                        unsigned long nbytes)
 583 {
 584         unsigned long stack_page = (unsigned long)p->thread_info;
 585
 586         if (sp >= stack_page + sizeof(struct thread_struct)
 587             && sp <= stack_page + THREAD_SIZE - nbytes)
 588                 return 1;
 589
 590 #ifdef CONFIG_IRQSTACKS
 591         stack_page = (unsigned long) hardirq_ctx[task_cpu(p)];
 592         if (sp >= stack_page + sizeof(struct thread_struct)
 593             && sp <= stack_page + THREAD_SIZE - nbytes)
 594                 return 1;
 595
 596         stack_page = (unsigned long) softirq_ctx[task_cpu(p)];
 597         if (sp >= stack_page + sizeof(struct thread_struct)
 598             && sp <= stack_page + THREAD_SIZE - nbytes)
 599                 return 1;
 600 #endif
 601
 602         return 0;
 603 }
 604
 605 unsigned long get_wchan(struct task_struct *p)
 606 {
 607         unsigned long ip, sp;
 608         int count = 0;
 609
 610         if (!p || p == current || p->state == TASK_RUNNING)
 611                 return 0;
 612
 613         sp = p->thread.ksp;
 614         if (!validate_sp(sp, p, 112))
 615                 return 0;
 616
 617         do {
 618                 sp = *(unsigned long *)sp;
 619                 if (!validate_sp(sp, p, 112))
 620                         return 0;
 621                 if (count > 0) {
 622                         ip = *(unsigned long *)(sp + 16);
 623                         if (!in_sched_functions(ip))
 624                                 return ip;
 625                 }
 626         } while (count++ < 16);
 627         return 0;
 628 }
 629 EXPORT_SYMBOL(get_wchan);
 630
 631 void show_stack(struct task_struct *p, unsigned long *_sp)
 632 {
 633         unsigned long ip, newsp, lr;
 634         int count = 0;
 635         unsigned long sp = (unsigned long)_sp;
 636         int firstframe = 1;
 637
 638         if (sp == 0) {
 639                 if (p) {
 640                         sp = p->thread.ksp;
 641                 } else {
 642                         sp = __get_SP();
 643                         p = current;
 644                 }
 645         }
 646
 647         lr = 0;
 648         printk("Call Trace:\n");
 649         do {
 650                 if (!validate_sp(sp, p, 112))
 651                         return;
 652
 653                 _sp = (unsigned long *) sp;
 654                 newsp = _sp[0];
 655                 ip = _sp[2];
 656                 if (!firstframe || ip != lr) {
 657                         printk("[%016lx] [%016lx] ", sp, ip);
 658                         print_symbol("%s", ip);
 659                         if (firstframe)
 660                                 printk(" (unreliable)");
 661                         printk("\n");
 662                 }
 663                 firstframe = 0;
 664
 665                 /*
 666                  * See if this is an exception frame.
 667                  * We look for the "regshere" marker in the current frame.
 668                  */
 669                 if (validate_sp(sp, p, sizeof(struct pt_regs) + 400)
 670                     && _sp[12] == 0x7265677368657265ul) {
 671                         struct pt_regs *regs = (struct pt_regs *)
 672                                 (sp + STACK_FRAME_OVERHEAD);
 673                         printk("--- Exception: %lx", regs->trap);
 674                         print_symbol(" at %s\n", regs->nip);
 675                         lr = regs->link;
 676                         print_symbol("    LR = %s\n", lr);
 677                         firstframe = 1;
 678                 }
 679
 680                 sp = newsp;
 681         } while (count++ < kstack_depth_to_print);
 682 }
 683
 684 void dump_stack(void)
 685 {
 686         show_stack(current, (unsigned long *)__get_SP());
 687 }
 688 EXPORT_SYMBOL(dump_stack);