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 #include <asm/plpar_wrappers.h>
  58
  59 #ifndef CONFIG_SMP
  60 struct task_struct *last_task_used_math = NULL;
  61 struct task_struct *last_task_used_altivec = NULL;
  62 #endif
  63
  64 /*
  65  * Make sure the floating-point register state in the
  66  * the thread_struct is up to date for task tsk.
  67  */
  68 void flush_fp_to_thread(struct task_struct *tsk)
  69 {
  70         if (tsk->thread.regs) {
  71                 /*
  72                  * We need to disable preemption here because if we didn't,
  73                  * another process could get scheduled after the regs->msr
  74                  * test but before we have finished saving the FP registers
  75                  * to the thread_struct.  That process could take over the
  76                  * FPU, and then when we get scheduled again we would store
  77                  * bogus values for the remaining FP registers.
  78                  */
  79                 preempt_disable();
  80                 if (tsk->thread.regs->msr & MSR_FP) {
  81 #ifdef CONFIG_SMP
  82                         /*
  83                          * This should only ever be called for current or
  84                          * for a stopped child process.  Since we save away
  85                          * the FP register state on context switch on SMP,
  86                          * there is something wrong if a stopped child appears
  87                          * to still have its FP state in the CPU registers.
  88                          */
  89                         BUG_ON(tsk != current);
  90 #endif
  91                         giveup_fpu(current);
  92                 }
  93                 preempt_enable();
  94         }
  95 }
  96
  97 void enable_kernel_fp(void)
  98 {
  99         WARN_ON(preemptible());
 100
 101 #ifdef CONFIG_SMP
 102         if (current->thread.regs && (current->thread.regs->msr & MSR_FP))
 103                 giveup_fpu(current);
 104         else
 105                 giveup_fpu(NULL);       /* just enables FP for kernel */
 106 #else
 107         giveup_fpu(last_task_used_math);
 108 #endif /* CONFIG_SMP */
 109 }
 110 EXPORT_SYMBOL(enable_kernel_fp);
 111
 112 int dump_task_fpu(struct task_struct *tsk, elf_fpregset_t *fpregs)
 113 {
 114         if (!tsk->thread.regs)
 115                 return 0;
 116         flush_fp_to_thread(current);
 117
 118         memcpy(fpregs, &tsk->thread.fpr[0], sizeof(*fpregs));
 119
 120         return 1;
 121 }
 122
 123 #ifdef CONFIG_ALTIVEC
 124
 125 void enable_kernel_altivec(void)
 126 {
 127         WARN_ON(preemptible());
 128
 129 #ifdef CONFIG_SMP
 130         if (current->thread.regs && (current->thread.regs->msr & MSR_VEC))
 131                 giveup_altivec(current);
 132         else
 133                 giveup_altivec(NULL);   /* just enables FP for kernel */
 134 #else
 135         giveup_altivec(last_task_used_altivec);
 136 #endif /* CONFIG_SMP */
 137 }
 138 EXPORT_SYMBOL(enable_kernel_altivec);
 139
 140 /*
 141  * Make sure the VMX/Altivec register state in the
 142  * the thread_struct is up to date for task tsk.
 143  */
 144 void flush_altivec_to_thread(struct task_struct *tsk)
 145 {
 146         if (tsk->thread.regs) {
 147                 preempt_disable();
 148                 if (tsk->thread.regs->msr & MSR_VEC) {
 149 #ifdef CONFIG_SMP
 150                         BUG_ON(tsk != current);
 151 #endif
 152                         giveup_altivec(current);
 153                 }
 154                 preempt_enable();
 155         }
 156 }
 157
 158 int dump_task_altivec(struct pt_regs *regs, elf_vrregset_t *vrregs)
 159 {
 160         flush_altivec_to_thread(current);
 161         memcpy(vrregs, &current->thread.vr[0], sizeof(*vrregs));
 162         return 1;
 163 }
 164
 165 #endif /* CONFIG_ALTIVEC */
 166
 167 static void set_dabr_spr(unsigned long val)
 168 {
 169         mtspr(SPRN_DABR, val);
 170 }
 171
 172 int set_dabr(unsigned long dabr)
 173 {
 174         int ret = 0;
 175
 176         if (firmware_has_feature(FW_FEATURE_XDABR)) {
 177                 /* We want to catch accesses from kernel and userspace */
 178                 unsigned long flags = H_DABRX_KERNEL|H_DABRX_USER;
 179                 ret = plpar_set_xdabr(dabr, flags);
 180         } else if (firmware_has_feature(FW_FEATURE_DABR)) {
 181                 ret = plpar_set_dabr(dabr);
 182         } else {
 183                 set_dabr_spr(dabr);
 184         }
 185
 186         return ret;
 187 }
 188
 189 DEFINE_PER_CPU(struct cpu_usage, cpu_usage_array);
 190 static DEFINE_PER_CPU(unsigned long, current_dabr);
 191
 192 struct task_struct *__switch_to(struct task_struct *prev,
 193                                 struct task_struct *new)
 194 {
 195         struct thread_struct *new_thread, *old_thread;
 196         unsigned long flags;
 197         struct task_struct *last;
 198
 199 #ifdef CONFIG_SMP
 200         /* avoid complexity of lazy save/restore of fpu
 201          * by just saving it every time we switch out if
 202          * this task used the fpu during the last quantum.
 203          *
 204          * If it tries to use the fpu again, it'll trap and
 205          * reload its fp regs.  So we don't have to do a restore
 206          * every switch, just a save.
 207          *  -- Cort
 208          */
 209         if (prev->thread.regs && (prev->thread.regs->msr & MSR_FP))
 210                 giveup_fpu(prev);
 211 #ifdef CONFIG_ALTIVEC
 212         if (prev->thread.regs && (prev->thread.regs->msr & MSR_VEC))
 213                 giveup_altivec(prev);
 214 #endif /* CONFIG_ALTIVEC */
 215 #endif /* CONFIG_SMP */
 216
 217 #if defined(CONFIG_ALTIVEC) && !defined(CONFIG_SMP)
 218         /* Avoid the trap.  On smp this this never happens since
 219          * we don't set last_task_used_altivec -- Cort
 220          */
 221         if (new->thread.regs && last_task_used_altivec == new)
 222                 new->thread.regs->msr |= MSR_VEC;
 223 #endif /* CONFIG_ALTIVEC */
 224
 225         if (unlikely(__get_cpu_var(current_dabr) != new->thread.dabr)) {
 226                 set_dabr(new->thread.dabr);
 227                 __get_cpu_var(current_dabr) = new->thread.dabr;
 228         }
 229
 230         flush_tlb_pending();
 231
 232         new_thread = &new->thread;
 233         old_thread = &current->thread;
 234
 235         /* Collect purr utilization data per process and per processor
 236          * wise purr is nothing but processor time base
 237          */
 238         if (firmware_has_feature(FW_FEATURE_SPLPAR)) {
 239                 struct cpu_usage *cu = &__get_cpu_var(cpu_usage_array);
 240                 long unsigned start_tb, current_tb;
 241                 start_tb = old_thread->start_tb;
 242                 cu->current_tb = current_tb = mfspr(SPRN_PURR);
 243                 old_thread->accum_tb += (current_tb - start_tb);
 244                 new_thread->start_tb = current_tb;
 245         }
 246
 247         local_irq_save(flags);
 248         last = _switch(old_thread, new_thread);
 249
 250         local_irq_restore(flags);
 251
 252         return last;
 253 }
 254
 255 static int instructions_to_print = 16;
 256
 257 static void show_instructions(struct pt_regs *regs)
 258 {
 259         int i;
 260         unsigned long pc = regs->nip - (instructions_to_print * 3 / 4 *
 261                         sizeof(int));
 262
 263         printk("Instruction dump:");
 264
 265         for (i = 0; i < instructions_to_print; i++) {
 266                 int instr;
 267
 268                 if (!(i % 8))
 269                         printk("\n");
 270
 271                 if (((REGION_ID(pc) != KERNEL_REGION_ID) &&
 272                      (REGION_ID(pc) != VMALLOC_REGION_ID)) ||
 273                      __get_user(instr, (unsigned int *)pc)) {
 274                         printk("XXXXXXXX ");
 275                 } else {
 276                         if (regs->nip == pc)
 277                                 printk("<%08x> ", instr);
 278                         else
 279                                 printk("%08x ", instr);
 280                 }
 281
 282                 pc += sizeof(int);
 283         }
 284
 285         printk("\n");
 286 }
 287
 288 void show_regs(struct pt_regs * regs)
 289 {
 290         int i;
 291         unsigned long trap;
 292
 293         printk("NIP: %016lX XER: %08X LR: %016lX CTR: %016lX\n",
 294                regs->nip, (unsigned int)regs->xer, regs->link, regs->ctr);
 295         printk("REGS: %p TRAP: %04lx   %s  (%s)\n",
 296                regs, regs->trap, print_tainted(), system_utsname.release);
 297         printk("MSR: %016lx EE: %01x PR: %01x FP: %01x ME: %01x "
 298                "IR/DR: %01x%01x CR: %08X\n",
 299                regs->msr, regs->msr&MSR_EE ? 1 : 0, regs->msr&MSR_PR ? 1 : 0,
 300                regs->msr & MSR_FP ? 1 : 0,regs->msr&MSR_ME ? 1 : 0,
 301                regs->msr&MSR_IR ? 1 : 0,
 302                regs->msr&MSR_DR ? 1 : 0,
 303                (unsigned int)regs->ccr);
 304         trap = TRAP(regs);
 305         printk("DAR: %016lx DSISR: %016lx\n", regs->dar, regs->dsisr);
 306         printk("TASK: %p[%d] '%s' THREAD: %p",
 307                current, current->pid, current->comm, current->thread_info);
 308
 309 #ifdef CONFIG_SMP
 310         printk(" CPU: %d", smp_processor_id());
 311 #endif /* CONFIG_SMP */
 312
 313         for (i = 0; i < 32; i++) {
 314                 if ((i % 4) == 0) {
 315                         printk("\n" KERN_INFO "GPR%02d: ", i);
 316                 }
 317
 318                 printk("%016lX ", regs->gpr[i]);
 319                 if (i == 13 && !FULL_REGS(regs))
 320                         break;
 321         }
 322         printk("\n");
 323         /*
 324          * Lookup NIP late so we have the best change of getting the
 325          * above info out without failing
 326          */
 327         printk("NIP [%016lx] ", regs->nip);
 328         print_symbol("%s\n", regs->nip);
 329         printk("LR [%016lx] ", regs->link);
 330         print_symbol("%s\n", regs->link);
 331         show_stack(current, (unsigned long *)regs->gpr[1]);
 332         if (!user_mode(regs))
 333                 show_instructions(regs);
 334 }
 335
 336 void exit_thread(void)
 337 {
 338         kprobe_flush_task(current);
 339
 340 #ifndef CONFIG_SMP
 341         if (last_task_used_math == current)
 342                 last_task_used_math = NULL;
 343 #ifdef CONFIG_ALTIVEC
 344         if (last_task_used_altivec == current)
 345                 last_task_used_altivec = NULL;
 346 #endif /* CONFIG_ALTIVEC */
 347 #endif /* CONFIG_SMP */
 348 }
 349
 350 void flush_thread(void)
 351 {
 352         struct thread_info *t = current_thread_info();
 353
 354         kprobe_flush_task(current);
 355         if (t->flags & _TIF_ABI_PENDING)
 356                 t->flags ^= (_TIF_ABI_PENDING | _TIF_32BIT);
 357
 358 #ifndef CONFIG_SMP
 359         if (last_task_used_math == current)
 360                 last_task_used_math = NULL;
 361 #ifdef CONFIG_ALTIVEC
 362         if (last_task_used_altivec == current)
 363                 last_task_used_altivec = NULL;
 364 #endif /* CONFIG_ALTIVEC */
 365 #endif /* CONFIG_SMP */
 366
 367         if (current->thread.dabr) {
 368                 current->thread.dabr = 0;
 369                 set_dabr(0);
 370         }
 371 }
 372
 373 void
 374 release_thread(struct task_struct *t)
 375 {
 376 }
 377
 378
 379 /*
 380  * This gets called before we allocate a new thread and copy
 381  * the current task into it.
 382  */
 383 void prepare_to_copy(struct task_struct *tsk)
 384 {
 385         flush_fp_to_thread(current);
 386         flush_altivec_to_thread(current);
 387 }
 388
 389 /*
 390  * Copy a thread..
 391  */
 392 int
 393 copy_thread(int nr, unsigned long clone_flags, unsigned long usp,
 394             unsigned long unused, struct task_struct *p, struct pt_regs *regs)
 395 {
 396         struct pt_regs *childregs, *kregs;
 397         extern void ret_from_fork(void);
 398         unsigned long sp = (unsigned long)p->thread_info + THREAD_SIZE;
 399
 400         /* Copy registers */
 401         sp -= sizeof(struct pt_regs);
 402         childregs = (struct pt_regs *) sp;
 403         *childregs = *regs;
 404         if ((childregs->msr & MSR_PR) == 0) {
 405                 /* for kernel thread, set stackptr in new task */
 406                 childregs->gpr[1] = sp + sizeof(struct pt_regs);
 407                 p->thread.regs = NULL;  /* no user register state */
 408                 clear_ti_thread_flag(p->thread_info, TIF_32BIT);
 409         } else {
 410                 childregs->gpr[1] = usp;
 411                 p->thread.regs = childregs;
 412                 if (clone_flags & CLONE_SETTLS) {
 413                         if (test_thread_flag(TIF_32BIT))
 414                                 childregs->gpr[2] = childregs->gpr[6];
 415                         else
 416                                 childregs->gpr[13] = childregs->gpr[6];
 417                 }
 418         }
 419         childregs->gpr[3] = 0;  /* Result from fork() */
 420         sp -= STACK_FRAME_OVERHEAD;
 421
 422         /*
 423          * The way this works is that at some point in the future
 424          * some task will call _switch to switch to the new task.
 425          * That will pop off the stack frame created below and start
 426          * the new task running at ret_from_fork.  The new task will
 427          * do some house keeping and then return from the fork or clone
 428          * system call, using the stack frame created above.
 429          */
 430         sp -= sizeof(struct pt_regs);
 431         kregs = (struct pt_regs *) sp;
 432         sp -= STACK_FRAME_OVERHEAD;
 433         p->thread.ksp = sp;
 434         if (cpu_has_feature(CPU_FTR_SLB)) {
 435                 unsigned long sp_vsid = get_kernel_vsid(sp);
 436
 437                 sp_vsid <<= SLB_VSID_SHIFT;
 438                 sp_vsid |= SLB_VSID_KERNEL;
 439                 if (cpu_has_feature(CPU_FTR_16M_PAGE))
 440                         sp_vsid |= SLB_VSID_L;
 441
 442                 p->thread.ksp_vsid = sp_vsid;
 443         }
 444
 445         /*
 446          * The PPC64 ABI makes use of a TOC to contain function
 447          * pointers.  The function (ret_from_except) is actually a pointer
 448          * to the TOC entry.  The first entry is a pointer to the actual
 449          * function.
 450          */
 451         kregs->nip = *((unsigned long *)ret_from_fork);
 452
 453         return 0;
 454 }
 455
 456 /*
 457  * Set up a thread for executing a new program
 458  */
 459 void start_thread(struct pt_regs *regs, unsigned long fdptr, unsigned long sp)
 460 {
 461         unsigned long entry, toc, load_addr = regs->gpr[2];
 462
 463         /* fdptr is a relocated pointer to the function descriptor for
 464          * the elf _start routine.  The first entry in the function
 465          * descriptor is the entry address of _start and the second
 466          * entry is the TOC value we need to use.
 467          */
 468         set_fs(USER_DS);
 469         __get_user(entry, (unsigned long __user *)fdptr);
 470         __get_user(toc, (unsigned long __user *)fdptr+1);
 471
 472         /* Check whether the e_entry function descriptor entries
 473          * need to be relocated before we can use them.
 474          */
 475         if (load_addr != 0) {
 476                 entry += load_addr;
 477                 toc   += load_addr;
 478         }
 479
 480         /*
 481          * If we exec out of a kernel thread then thread.regs will not be
 482          * set. Do it now.
 483          */
 484         if (!current->thread.regs) {
 485                 unsigned long childregs = (unsigned long)current->thread_info +
 486                                                 THREAD_SIZE;
 487                 childregs -= sizeof(struct pt_regs);
 488                 current->thread.regs = (struct pt_regs *)childregs;
 489         }
 490
 491         regs->nip = entry;
 492         regs->gpr[1] = sp;
 493         regs->gpr[2] = toc;
 494         regs->msr = MSR_USER64;
 495 #ifndef CONFIG_SMP
 496         if (last_task_used_math == current)
 497                 last_task_used_math = 0;
 498 #endif /* CONFIG_SMP */
 499         memset(current->thread.fpr, 0, sizeof(current->thread.fpr));
 500         current->thread.fpscr = 0;
 501 #ifdef CONFIG_ALTIVEC
 502 #ifndef CONFIG_SMP
 503         if (last_task_used_altivec == current)
 504                 last_task_used_altivec = 0;
 505 #endif /* CONFIG_SMP */
 506         memset(current->thread.vr, 0, sizeof(current->thread.vr));
 507         current->thread.vscr.u[0] = 0;
 508         current->thread.vscr.u[1] = 0;
 509         current->thread.vscr.u[2] = 0;
 510         current->thread.vscr.u[3] = 0x00010000; /* Java mode disabled */
 511         current->thread.vrsave = 0;
 512         current->thread.used_vr = 0;
 513 #endif /* CONFIG_ALTIVEC */
 514 }
 515 EXPORT_SYMBOL(start_thread);
 516
 517 int set_fpexc_mode(struct task_struct *tsk, unsigned int val)
 518 {
 519         struct pt_regs *regs = tsk->thread.regs;
 520
 521         if (val > PR_FP_EXC_PRECISE)
 522                 return -EINVAL;
 523         tsk->thread.fpexc_mode = __pack_fe01(val);
 524         if (regs != NULL && (regs->msr & MSR_FP) != 0)
 525                 regs->msr = (regs->msr & ~(MSR_FE0|MSR_FE1))
 526                         | tsk->thread.fpexc_mode;
 527         return 0;
 528 }
 529
 530 int get_fpexc_mode(struct task_struct *tsk, unsigned long adr)
 531 {
 532         unsigned int val;
 533
 534         val = __unpack_fe01(tsk->thread.fpexc_mode);
 535         return put_user(val, (unsigned int __user *) adr);
 536 }
 537
 538 int sys_clone(unsigned long clone_flags, unsigned long p2, unsigned long p3,
 539               unsigned long p4, unsigned long p5, unsigned long p6,
 540               struct pt_regs *regs)
 541 {
 542         unsigned long parent_tidptr = 0;
 543         unsigned long child_tidptr = 0;
 544
 545         if (p2 == 0)
 546                 p2 = regs->gpr[1];      /* stack pointer for child */
 547
 548         if (clone_flags & (CLONE_PARENT_SETTID | CLONE_CHILD_SETTID |
 549                            CLONE_CHILD_CLEARTID)) {
 550                 parent_tidptr = p3;
 551                 child_tidptr = p5;
 552                 if (test_thread_flag(TIF_32BIT)) {
 553                         parent_tidptr &= 0xffffffff;
 554                         child_tidptr &= 0xffffffff;
 555                 }
 556         }
 557
 558         return do_fork(clone_flags, p2, regs, 0,
 559                     (int __user *)parent_tidptr, (int __user *)child_tidptr);
 560 }
 561
 562 int sys_fork(unsigned long p1, unsigned long p2, unsigned long p3,
 563              unsigned long p4, unsigned long p5, unsigned long p6,
 564              struct pt_regs *regs)
 565 {
 566         return do_fork(SIGCHLD, regs->gpr[1], regs, 0, NULL, NULL);
 567 }
 568
 569 int sys_vfork(unsigned long p1, unsigned long p2, unsigned long p3,
 570               unsigned long p4, unsigned long p5, unsigned long p6,
 571               struct pt_regs *regs)
 572 {
 573         return do_fork(CLONE_VFORK | CLONE_VM | SIGCHLD, regs->gpr[1], regs, 0,
 574                     NULL, NULL);
 575 }
 576
 577 int sys_execve(unsigned long a0, unsigned long a1, unsigned long a2,
 578                unsigned long a3, unsigned long a4, unsigned long a5,
 579                struct pt_regs *regs)
 580 {
 581         int error;
 582         char * filename;
 583
 584         filename = getname((char __user *) a0);
 585         error = PTR_ERR(filename);
 586         if (IS_ERR(filename))
 587                 goto out;
 588         flush_fp_to_thread(current);
 589         flush_altivec_to_thread(current);
 590         error = do_execve(filename, (char __user * __user *) a1,
 591                                     (char __user * __user *) a2, regs);
 592
 593         if (error == 0) {
 594                 task_lock(current);
 595                 current->ptrace &= ~PT_DTRACE;
 596                 task_unlock(current);
 597         }
 598         putname(filename);
 599
 600 out:
 601         return error;
 602 }
 603
 604 static int kstack_depth_to_print = 64;
 605
 606 static int validate_sp(unsigned long sp, struct task_struct *p,
 607                        unsigned long nbytes)
 608 {
 609         unsigned long stack_page = (unsigned long)p->thread_info;
 610
 611         if (sp >= stack_page + sizeof(struct thread_struct)
 612             && sp <= stack_page + THREAD_SIZE - nbytes)
 613                 return 1;
 614
 615 #ifdef CONFIG_IRQSTACKS
 616         stack_page = (unsigned long) hardirq_ctx[task_cpu(p)];
 617         if (sp >= stack_page + sizeof(struct thread_struct)
 618             && sp <= stack_page + THREAD_SIZE - nbytes)
 619                 return 1;
 620
 621         stack_page = (unsigned long) softirq_ctx[task_cpu(p)];
 622         if (sp >= stack_page + sizeof(struct thread_struct)
 623             && sp <= stack_page + THREAD_SIZE - nbytes)
 624                 return 1;
 625 #endif
 626
 627         return 0;
 628 }
 629
 630 unsigned long get_wchan(struct task_struct *p)
 631 {
 632         unsigned long ip, sp;
 633         int count = 0;
 634
 635         if (!p || p == current || p->state == TASK_RUNNING)
 636                 return 0;
 637
 638         sp = p->thread.ksp;
 639         if (!validate_sp(sp, p, 112))
 640                 return 0;
 641
 642         do {
 643                 sp = *(unsigned long *)sp;
 644                 if (!validate_sp(sp, p, 112))
 645                         return 0;
 646                 if (count > 0) {
 647                         ip = *(unsigned long *)(sp + 16);
 648                         if (!in_sched_functions(ip))
 649                                 return ip;
 650                 }
 651         } while (count++ < 16);
 652         return 0;
 653 }
 654 EXPORT_SYMBOL(get_wchan);
 655
 656 void show_stack(struct task_struct *p, unsigned long *_sp)
 657 {
 658         unsigned long ip, newsp, lr;
 659         int count = 0;
 660         unsigned long sp = (unsigned long)_sp;
 661         int firstframe = 1;
 662
 663         if (sp == 0) {
 664                 if (p) {
 665                         sp = p->thread.ksp;
 666                 } else {
 667                         sp = __get_SP();
 668                         p = current;
 669                 }
 670         }
 671
 672         lr = 0;
 673         printk("Call Trace:\n");
 674         do {
 675                 if (!validate_sp(sp, p, 112))
 676                         return;
 677
 678                 _sp = (unsigned long *) sp;
 679                 newsp = _sp[0];
 680                 ip = _sp[2];
 681                 if (!firstframe || ip != lr) {
 682                         printk("[%016lx] [%016lx] ", sp, ip);
 683                         print_symbol("%s", ip);
 684                         if (firstframe)
 685                                 printk(" (unreliable)");
 686                         printk("\n");
 687                 }
 688                 firstframe = 0;
 689
 690                 /*
 691                  * See if this is an exception frame.
 692                  * We look for the "regshere" marker in the current frame.
 693                  */
 694                 if (validate_sp(sp, p, sizeof(struct pt_regs) + 400)
 695                     && _sp[12] == 0x7265677368657265ul) {
 696                         struct pt_regs *regs = (struct pt_regs *)
 697                                 (sp + STACK_FRAME_OVERHEAD);
 698                         printk("--- Exception: %lx", regs->trap);
 699                         print_symbol(" at %s\n", regs->nip);
 700                         lr = regs->link;
 701                         print_symbol("    LR = %s\n", lr);
 702                         firstframe = 1;
 703                 }
 704
 705                 sp = newsp;
 706         } while (count++ < kstack_depth_to_print);
 707 }
 708
 709 void dump_stack(void)
 710 {
 711         show_stack(current, (unsigned long *)__get_SP());
 712 }
 713 EXPORT_SYMBOL(dump_stack);