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