arch/ppc/kernel/process.c

   1 /*
   2  *  arch/ppc/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
  20 #include <linux/config.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/ptrace.h>
  30 #include <linux/slab.h>
  31 #include <linux/user.h>
  32 #include <linux/elf.h>
  33 #include <linux/init.h>
  34 #include <linux/prctl.h>
  35 #include <linux/init_task.h>
  36 #include <linux/module.h>
  37 #include <linux/kallsyms.h>
  38
  39 #include <asm/pgtable.h>
  40 #include <asm/uaccess.h>
  41 #include <asm/system.h>
  42 #include <asm/io.h>
  43 #include <asm/processor.h>
  44 #include <asm/mmu.h>
  45 #include <asm/prom.h>
  46 #include <asm/hardirq.h>
  47
  48 extern unsigned long _get_SP(void);
  49
  50 struct task_struct *last_task_used_math = NULL;
  51 struct task_struct *last_task_used_altivec = NULL;
  52
  53 static struct fs_struct init_fs = INIT_FS;
  54 static struct files_struct init_files = INIT_FILES;
  55 static struct signal_struct init_signals = INIT_SIGNALS(init_signals);
  56 static struct sighand_struct init_sighand = INIT_SIGHAND(init_sighand);
  57 struct mm_struct init_mm = INIT_MM(init_mm);
  58 EXPORT_SYMBOL(init_mm);
  59
  60 /* this is 8kB-aligned so we can get to the thread_info struct
  61    at the base of it from the stack pointer with 1 integer instruction. */
  62 union thread_union init_thread_union
  63         __attribute__((__section__(".data.init_task"))) =
  64 { INIT_THREAD_INFO(init_task) };
  65
  66 /* initial task structure */
  67 struct task_struct init_task = INIT_TASK(init_task);
  68 EXPORT_SYMBOL(init_task);
  69
  70 /* only used to get secondary processor up */
  71 struct task_struct *current_set[NR_CPUS] = {&init_task, };
  72
  73 #undef SHOW_TASK_SWITCHES
  74 #undef CHECK_STACK
  75
  76 #if defined(CHECK_STACK)
  77 unsigned long
  78 kernel_stack_top(struct task_struct *tsk)
  79 {
  80         return ((unsigned long)tsk) + sizeof(union task_union);
  81 }
  82
  83 unsigned long
  84 task_top(struct task_struct *tsk)
  85 {
  86         return ((unsigned long)tsk) + sizeof(struct thread_info);
  87 }
  88
  89 /* check to make sure the kernel stack is healthy */
  90 int check_stack(struct task_struct *tsk)
  91 {
  92         unsigned long stack_top = kernel_stack_top(tsk);
  93         unsigned long tsk_top = task_top(tsk);
  94         int ret = 0;
  95
  96 #if 0
  97         /* check thread magic */
  98         if ( tsk->thread.magic != THREAD_MAGIC )
  99         {
 100                 ret |= 1;
 101                 printk("thread.magic bad: %08x\n", tsk->thread.magic);
 102         }
 103 #endif
 104
 105         if ( !tsk )
 106                 printk("check_stack(): tsk bad tsk %p\n",tsk);
 107
 108         /* check if stored ksp is bad */
 109         if ( (tsk->thread.ksp > stack_top) || (tsk->thread.ksp < tsk_top) )
 110         {
 111                 printk("stack out of bounds: %s/%d\n"
 112                        " tsk_top %08lx ksp %08lx stack_top %08lx\n",
 113                        tsk->comm,tsk->pid,
 114                        tsk_top, tsk->thread.ksp, stack_top);
 115                 ret |= 2;
 116         }
 117
 118         /* check if stack ptr RIGHT NOW is bad */
 119         if ( (tsk == current) && ((_get_SP() > stack_top ) || (_get_SP() < tsk_top)) )
 120         {
 121                 printk("current stack ptr out of bounds: %s/%d\n"
 122                        " tsk_top %08lx sp %08lx stack_top %08lx\n",
 123                        current->comm,current->pid,
 124                        tsk_top, _get_SP(), stack_top);
 125                 ret |= 4;
 126         }
 127
 128 #if 0
 129         /* check amount of free stack */
 130         for ( i = (unsigned long *)task_top(tsk) ; i < kernel_stack_top(tsk) ; i++ )
 131         {
 132                 if ( !i )
 133                         printk("check_stack(): i = %p\n", i);
 134                 if ( *i != 0 )
 135                 {
 136                         /* only notify if it's less than 900 bytes */
 137                         if ( (i - (unsigned long *)task_top(tsk))  < 900 )
 138                                 printk("%d bytes free on stack\n",
 139                                        i - task_top(tsk));
 140                         break;
 141                 }
 142         }
 143 #endif
 144
 145         if (ret)
 146         {
 147                 panic("bad kernel stack");
 148         }
 149         return(ret);
 150 }
 151 #endif /* defined(CHECK_STACK) */
 152
 153 #ifdef CONFIG_ALTIVEC
 154 int
 155 dump_altivec(struct pt_regs *regs, elf_vrregset_t *vrregs)
 156 {
 157         if (regs->msr & MSR_VEC)
 158                 giveup_altivec(current);
 159         memcpy(vrregs, &current->thread.vr[0], sizeof(*vrregs));
 160         return 1;
 161 }
 162
 163 void
 164 enable_kernel_altivec(void)
 165 {
 166         WARN_ON(preemptible());
 167
 168 #ifdef CONFIG_SMP
 169         if (current->thread.regs && (current->thread.regs->msr & MSR_VEC))
 170                 giveup_altivec(current);
 171         else
 172                 giveup_altivec(NULL);   /* just enable AltiVec for kernel - force */
 173 #else
 174         giveup_altivec(last_task_used_altivec);
 175 #endif /* __SMP __ */
 176 }
 177 EXPORT_SYMBOL(enable_kernel_altivec);
 178 #endif /* CONFIG_ALTIVEC */
 179
 180 void
 181 enable_kernel_fp(void)
 182 {
 183         WARN_ON(preemptible());
 184
 185 #ifdef CONFIG_SMP
 186         if (current->thread.regs && (current->thread.regs->msr & MSR_FP))
 187                 giveup_fpu(current);
 188         else
 189                 giveup_fpu(NULL);       /* just enables FP for kernel */
 190 #else
 191         giveup_fpu(last_task_used_math);
 192 #endif /* CONFIG_SMP */
 193 }
 194 EXPORT_SYMBOL(enable_kernel_fp);
 195
 196 int
 197 dump_task_fpu(struct task_struct *tsk, elf_fpregset_t *fpregs)
 198 {
 199         preempt_disable();
 200         if (tsk->thread.regs && (tsk->thread.regs->msr & MSR_FP))
 201                 giveup_fpu(tsk);
 202         preempt_enable();
 203         memcpy(fpregs, &tsk->thread.fpr[0], sizeof(*fpregs));
 204         return 1;
 205 }
 206
 207 struct task_struct *__switch_to(struct task_struct *prev,
 208         struct task_struct *new)
 209 {
 210         struct thread_struct *new_thread, *old_thread;
 211         unsigned long s;
 212         struct task_struct *last;
 213
 214         local_irq_save(s);
 215 #ifdef CHECK_STACK
 216         check_stack(prev);
 217         check_stack(new);
 218 #endif
 219
 220 #ifdef CONFIG_SMP
 221         /* avoid complexity of lazy save/restore of fpu
 222          * by just saving it every time we switch out if
 223          * this task used the fpu during the last quantum.
 224          *
 225          * If it tries to use the fpu again, it'll trap and
 226          * reload its fp regs.  So we don't have to do a restore
 227          * every switch, just a save.
 228          *  -- Cort
 229          */
 230         if (prev->thread.regs && (prev->thread.regs->msr & MSR_FP))
 231                 giveup_fpu(prev);
 232 #ifdef CONFIG_ALTIVEC
 233         /*
 234          * If the previous thread used altivec in the last quantum
 235          * (thus changing altivec regs) then save them.
 236          * We used to check the VRSAVE register but not all apps
 237          * set it, so we don't rely on it now (and in fact we need
 238          * to save & restore VSCR even if VRSAVE == 0).  -- paulus
 239          *
 240          * On SMP we always save/restore altivec regs just to avoid the
 241          * complexity of changing processors.
 242          *  -- Cort
 243          */
 244         if ((prev->thread.regs && (prev->thread.regs->msr & MSR_VEC)))
 245                 giveup_altivec(prev);
 246 #endif /* CONFIG_ALTIVEC */
 247 #endif /* CONFIG_SMP */
 248
 249         /* Avoid the trap.  On smp this this never happens since
 250          * we don't set last_task_used_altivec -- Cort
 251          */
 252         if (new->thread.regs && last_task_used_altivec == new)
 253                 new->thread.regs->msr |= MSR_VEC;
 254         new_thread = &new->thread;
 255         old_thread = &current->thread;
 256         last = _switch(old_thread, new_thread);
 257         local_irq_restore(s);
 258         return last;
 259 }
 260
 261 void show_regs(struct pt_regs * regs)
 262 {
 263         int i, trap;
 264
 265         printk("NIP: %08lX LR: %08lX SP: %08lX REGS: %p TRAP: %04lx    %s\n",
 266                regs->nip, regs->link, regs->gpr[1], regs, regs->trap,
 267                print_tainted());
 268         printk("MSR: %08lx EE: %01x PR: %01x FP: %01x ME: %01x IR/DR: %01x%01x\n",
 269                regs->msr, regs->msr&MSR_EE ? 1 : 0, regs->msr&MSR_PR ? 1 : 0,
 270                regs->msr & MSR_FP ? 1 : 0,regs->msr&MSR_ME ? 1 : 0,
 271                regs->msr&MSR_IR ? 1 : 0,
 272                regs->msr&MSR_DR ? 1 : 0);
 273         trap = TRAP(regs);
 274         if (trap == 0x300 || trap == 0x600)
 275                 printk("DAR: %08lX, DSISR: %08lX\n", regs->dar, regs->dsisr);
 276         printk("TASK = %p[%d] '%s' THREAD: %p",
 277                current, current->pid, current->comm, current->thread_info);
 278         printk("Last syscall: %ld ", current->thread.last_syscall);
 279
 280 #if defined(CONFIG_4xx) && defined(DCRN_PLB0_BEAR)
 281         printk("\nPLB0: bear= 0x%8.8x acr=   0x%8.8x besr=  0x%8.8x\n",
 282             mfdcr(DCRN_PLB0_BEAR), mfdcr(DCRN_PLB0_ACR),
 283             mfdcr(DCRN_PLB0_BESR));
 284 #endif
 285 #if defined(CONFIG_4xx) && defined(DCRN_POB0_BEAR)
 286         printk("PLB0 to OPB: bear= 0x%8.8x besr0= 0x%8.8x besr1= 0x%8.8x\n",
 287             mfdcr(DCRN_POB0_BEAR), mfdcr(DCRN_POB0_BESR0),
 288             mfdcr(DCRN_POB0_BESR1));
 289 #endif
 290
 291 #ifdef CONFIG_SMP
 292         printk(" CPU: %d", smp_processor_id());
 293 #endif /* CONFIG_SMP */
 294
 295         for (i = 0;  i < 32;  i++) {
 296                 long r;
 297                 if ((i % 8) == 0)
 298                         printk("\n" KERN_INFO "GPR%02d: ", i);
 299                 if (__get_user(r, &regs->gpr[i]))
 300                         break;
 301                 printk("%08lX ", r);
 302                 if (i == 12 && !FULL_REGS(regs))
 303                         break;
 304         }
 305         printk("\n");
 306 #ifdef CONFIG_KALLSYMS
 307         /*
 308          * Lookup NIP late so we have the best change of getting the
 309          * above info out without failing
 310          */
 311         printk("NIP [%08lx] ", regs->nip);
 312         print_symbol("%s\n", regs->nip);
 313         printk("LR [%08lx] ", regs->link);
 314         print_symbol("%s\n", regs->link);
 315 #endif
 316         show_stack(current, (unsigned long *) regs->gpr[1]);
 317 }
 318
 319 void exit_thread(void)
 320 {
 321         if (last_task_used_math == current)
 322                 last_task_used_math = NULL;
 323         if (last_task_used_altivec == current)
 324                 last_task_used_altivec = NULL;
 325 }
 326
 327 void flush_thread(void)
 328 {
 329         if (last_task_used_math == current)
 330                 last_task_used_math = NULL;
 331         if (last_task_used_altivec == current)
 332                 last_task_used_altivec = NULL;
 333 }
 334
 335 void
 336 release_thread(struct task_struct *t)
 337 {
 338 }
 339
 340 /*
 341  * This gets called before we allocate a new thread and copy
 342  * the current task into it.
 343  */
 344 void prepare_to_copy(struct task_struct *tsk)
 345 {
 346         struct pt_regs *regs = tsk->thread.regs;
 347
 348         if (regs == NULL)
 349                 return;
 350         preempt_disable();
 351         if (regs->msr & MSR_FP)
 352                 giveup_fpu(current);
 353 #ifdef CONFIG_ALTIVEC
 354         if (regs->msr & MSR_VEC)
 355                 giveup_altivec(current);
 356 #endif /* CONFIG_ALTIVEC */
 357         preempt_enable();
 358 }
 359
 360 /*
 361  * Copy a thread..
 362  */
 363 int
 364 copy_thread(int nr, unsigned long clone_flags, unsigned long usp,
 365             unsigned long unused,
 366             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         unsigned long childframe;
 372
 373         p->set_child_tid = p->clear_child_tid = NULL;
 374
 375         CHECK_FULL_REGS(regs);
 376         /* Copy registers */
 377         sp -= sizeof(struct pt_regs);
 378         childregs = (struct pt_regs *) sp;
 379         *childregs = *regs;
 380         if ((childregs->msr & MSR_PR) == 0) {
 381                 /* for kernel thread, set `current' and stackptr in new task */
 382                 childregs->gpr[1] = sp + sizeof(struct pt_regs);
 383                 childregs->gpr[2] = (unsigned long) p;
 384                 p->thread.regs = NULL;  /* no user register state */
 385         } else {
 386                 childregs->gpr[1] = usp;
 387                 p->thread.regs = childregs;
 388                 if (clone_flags & CLONE_SETTLS)
 389                         childregs->gpr[2] = childregs->gpr[6];
 390         }
 391         childregs->gpr[3] = 0;  /* Result from fork() */
 392         sp -= STACK_FRAME_OVERHEAD;
 393         childframe = sp;
 394
 395         /*
 396          * The way this works is that at some point in the future
 397          * some task will call _switch to switch to the new task.
 398          * That will pop off the stack frame created below and start
 399          * the new task running at ret_from_fork.  The new task will
 400          * do some house keeping and then return from the fork or clone
 401          * system call, using the stack frame created above.
 402          */
 403         sp -= sizeof(struct pt_regs);
 404         kregs = (struct pt_regs *) sp;
 405         sp -= STACK_FRAME_OVERHEAD;
 406         p->thread.ksp = sp;
 407         kregs->nip = (unsigned long)ret_from_fork;
 408
 409         p->thread.last_syscall = -1;
 410
 411         return 0;
 412 }
 413
 414 /*
 415  * Set up a thread for executing a new program
 416  */
 417 void start_thread(struct pt_regs *regs, unsigned long nip, unsigned long sp)
 418 {
 419         set_fs(USER_DS);
 420         memset(regs->gpr, 0, sizeof(regs->gpr));
 421         regs->ctr = 0;
 422         regs->link = 0;
 423         regs->xer = 0;
 424         regs->ccr = 0;
 425         regs->mq = 0;
 426         regs->nip = nip;
 427         regs->gpr[1] = sp;
 428         regs->msr = MSR_USER;
 429         if (last_task_used_math == current)
 430                 last_task_used_math = 0;
 431         if (last_task_used_altivec == current)
 432                 last_task_used_altivec = 0;
 433         memset(current->thread.fpr, 0, sizeof(current->thread.fpr));
 434         current->thread.fpscr = 0;
 435 #ifdef CONFIG_ALTIVEC
 436         memset(current->thread.vr, 0, sizeof(current->thread.vr));
 437         memset(&current->thread.vscr, 0, sizeof(current->thread.vscr));
 438         current->thread.vrsave = 0;
 439         current->thread.used_vr = 0;
 440 #endif /* CONFIG_ALTIVEC */
 441 }
 442
 443 int set_fpexc_mode(struct task_struct *tsk, unsigned int val)
 444 {
 445         struct pt_regs *regs = tsk->thread.regs;
 446
 447         if (val > PR_FP_EXC_PRECISE)
 448                 return -EINVAL;
 449         tsk->thread.fpexc_mode = __pack_fe01(val);
 450         if (regs != NULL && (regs->msr & MSR_FP) != 0)
 451                 regs->msr = (regs->msr & ~(MSR_FE0|MSR_FE1))
 452                         | tsk->thread.fpexc_mode;
 453         return 0;
 454 }
 455
 456 int get_fpexc_mode(struct task_struct *tsk, unsigned long adr)
 457 {
 458         unsigned int val;
 459
 460         val = __unpack_fe01(tsk->thread.fpexc_mode);
 461         return put_user(val, (unsigned int *) adr);
 462 }
 463
 464 int sys_clone(unsigned long clone_flags, unsigned long usp,
 465               int __user *parent_tidp, void __user *child_threadptr,
 466               int __user *child_tidp, int p6,
 467               struct pt_regs *regs)
 468 {
 469         CHECK_FULL_REGS(regs);
 470         if (usp == 0)
 471                 usp = regs->gpr[1];     /* stack pointer for child */
 472         return do_fork(clone_flags & ~CLONE_IDLETASK, usp, regs, 0,
 473                         parent_tidp, child_tidp);
 474 }
 475
 476 int sys_fork(int p1, int p2, int p3, int p4, int p5, int p6,
 477              struct pt_regs *regs)
 478 {
 479         CHECK_FULL_REGS(regs);
 480         return do_fork(SIGCHLD, regs->gpr[1], regs, 0, NULL, NULL);
 481 }
 482
 483 int sys_vfork(int p1, int p2, int p3, int p4, int p5, int p6,
 484               struct pt_regs *regs)
 485 {
 486         CHECK_FULL_REGS(regs);
 487         return do_fork(CLONE_VFORK | CLONE_VM | SIGCHLD, regs->gpr[1],
 488                         regs, 0, NULL, NULL);
 489 }
 490
 491 int sys_execve(unsigned long a0, unsigned long a1, unsigned long a2,
 492                unsigned long a3, unsigned long a4, unsigned long a5,
 493                struct pt_regs *regs)
 494 {
 495         int error;
 496         char * filename;
 497
 498         filename = getname((char __user *) a0);
 499         error = PTR_ERR(filename);
 500         if (IS_ERR(filename))
 501                 goto out;
 502         preempt_disable();
 503         if (regs->msr & MSR_FP)
 504                 giveup_fpu(current);
 505 #ifdef CONFIG_ALTIVEC
 506         if (regs->msr & MSR_VEC)
 507                 giveup_altivec(current);
 508 #endif /* CONFIG_ALTIVEC */
 509         preempt_enable();
 510         error = do_execve(filename, (char __user *__user *) a1,
 511                           (char __user *__user *) a2, regs);
 512         if (error == 0)
 513                 current->ptrace &= ~PT_DTRACE;
 514         putname(filename);
 515 out:
 516         return error;
 517 }
 518
 519 void dump_stack(void)
 520 {
 521         show_stack(current, NULL);
 522 }
 523
 524 EXPORT_SYMBOL(dump_stack);
 525
 526 void show_stack(struct task_struct *tsk, unsigned long *stack)
 527 {
 528         unsigned long sp, stack_top, prev_sp, ret;
 529         int count = 0;
 530         unsigned long next_exc = 0;
 531         struct pt_regs *regs;
 532         extern char ret_from_except, ret_from_except_full, ret_from_syscall;
 533
 534         sp = (unsigned long) stack;
 535         if (tsk == NULL)
 536                 tsk = current;
 537         if (sp == 0) {
 538                 if (tsk == current)
 539                         asm("mr %0,1" : "=r" (sp));
 540                 else
 541                         sp = tsk->thread.ksp;
 542         }
 543
 544         prev_sp = (unsigned long) (tsk->thread_info + 1);
 545         stack_top = (unsigned long) tsk->thread_info + THREAD_SIZE;
 546         while (count < 16 && sp > prev_sp && sp < stack_top && (sp & 3) == 0) {
 547                 if (count == 0) {
 548                         printk("Call trace:");
 549 #ifdef CONFIG_KALLSYMS
 550                         printk("\n");
 551 #endif
 552                 } else {
 553                         if (next_exc) {
 554                                 ret = next_exc;
 555                                 next_exc = 0;
 556                         } else
 557                                 ret = *(unsigned long *)(sp + 4);
 558                         printk(" [%08lx] ", ret);
 559 #ifdef CONFIG_KALLSYMS
 560                         print_symbol("%s", ret);
 561                         printk("\n");
 562 #endif
 563                         if (ret == (unsigned long) &ret_from_except
 564                             || ret == (unsigned long) &ret_from_except_full
 565                             || ret == (unsigned long) &ret_from_syscall) {
 566                                 /* sp + 16 points to an exception frame */
 567                                 regs = (struct pt_regs *) (sp + 16);
 568                                 if (sp + 16 + sizeof(*regs) <= stack_top)
 569                                         next_exc = regs->nip;
 570                         }
 571                 }
 572                 ++count;
 573                 sp = *(unsigned long *)sp;
 574         }
 575 #if !CONFIG_KALLSYMS
 576         if (count > 0)
 577                 printk("\n");
 578 #endif
 579 }
 580
 581 #if 0
 582 /*
 583  * Low level print for debugging - Cort
 584  */
 585 int __init ll_printk(const char *fmt, ...)
 586 {
 587         va_list args;
 588         char buf[256];
 589         int i;
 590
 591         va_start(args, fmt);
 592         i=vsprintf(buf,fmt,args);
 593         ll_puts(buf);
 594         va_end(args);
 595         return i;
 596 }
 597
 598 int lines = 24, cols = 80;
 599 int orig_x = 0, orig_y = 0;
 600
 601 void puthex(unsigned long val)
 602 {
 603         unsigned char buf[10];
 604         int i;
 605         for (i = 7;  i >= 0;  i--)
 606         {
 607                 buf[i] = "0123456789ABCDEF"[val & 0x0F];
 608                 val >>= 4;
 609         }
 610         buf[8] = '\0';
 611         prom_print(buf);
 612 }
 613
 614 void __init ll_puts(const char *s)
 615 {
 616         int x,y;
 617         char *vidmem = (char *)/*(_ISA_MEM_BASE + 0xB8000) */0xD00B8000;
 618         char c;
 619         extern int mem_init_done;
 620
 621         if ( mem_init_done ) /* assume this means we can printk */
 622         {
 623                 printk(s);
 624                 return;
 625         }
 626
 627 #if 0
 628         if ( have_of )
 629         {
 630                 prom_print(s);
 631                 return;
 632         }
 633 #endif
 634
 635         /*
 636          * can't ll_puts on chrp without openfirmware yet.
 637          * vidmem just needs to be setup for it.
 638          * -- Cort
 639          */
 640         if ( _machine != _MACH_prep )
 641                 return;
 642         x = orig_x;
 643         y = orig_y;
 644
 645         while ( ( c = *s++ ) != '\0' ) {
 646                 if ( c == '\n' ) {
 647                         x = 0;
 648                         if ( ++y >= lines ) {
 649                                 /*scroll();*/
 650                                 /*y--;*/
 651                                 y = 0;
 652                         }
 653                 } else {
 654                         vidmem [ ( x + cols * y ) * 2 ] = c;
 655                         if ( ++x >= cols ) {
 656                                 x = 0;
 657                                 if ( ++y >= lines ) {
 658                                         /*scroll();*/
 659                                         /*y--;*/
 660                                         y = 0;
 661                                 }
 662                         }
 663                 }
 664         }
 665
 666         orig_x = x;
 667         orig_y = y;
 668 }
 669 #endif
 670
 671 unsigned long get_wchan(struct task_struct *p)
 672 {
 673         unsigned long ip, sp;
 674         unsigned long stack_page = (unsigned long) p->thread_info;
 675         int count = 0;
 676         if (!p || p == current || p->state == TASK_RUNNING)
 677                 return 0;
 678         sp = p->thread.ksp;
 679         do {
 680                 sp = *(unsigned long *)sp;
 681                 if (sp < stack_page || sp >= stack_page + 8188)
 682                         return 0;
 683                 if (count > 0) {
 684                         ip = *(unsigned long *)(sp + 4);
 685                         if (!in_sched_functions(ip))
 686                                 return ip;
 687                 }
 688         } while (count++ < 16);
 689         return 0;
 690 }