arch/sparc/kernel/process.c

   1 /*  linux/arch/sparc/kernel/process.c
   2  *
   3  *  Copyright (C) 1995, 2008 David S. Miller (davem@davemloft.net)
   4  *  Copyright (C) 1996 Eddie C. Dost   (ecd@skynet.be)
   5  */
   6
   7 /*
   8  * This file handles the architecture-dependent parts of process handling..
   9  */
  10
  11 #include <stdarg.h>
  12
  13 #include <linux/errno.h>
  14 #include <linux/module.h>
  15 #include <linux/sched.h>
  16 #include <linux/kernel.h>
  17 #include <linux/mm.h>
  18 #include <linux/stddef.h>
  19 #include <linux/ptrace.h>
  20 #include <linux/slab.h>
  21 #include <linux/user.h>
  22 #include <linux/smp.h>
  23 #include <linux/reboot.h>
  24 #include <linux/delay.h>
  25 #include <linux/pm.h>
  26 #include <linux/init.h>
  27
  28 #include <asm/auxio.h>
  29 #include <asm/oplib.h>
  30 #include <asm/uaccess.h>
  31 #include <asm/system.h>
  32 #include <asm/page.h>
  33 #include <asm/pgalloc.h>
  34 #include <asm/pgtable.h>
  35 #include <asm/delay.h>
  36 #include <asm/processor.h>
  37 #include <asm/psr.h>
  38 #include <asm/elf.h>
  39 #include <asm/prom.h>
  40 #include <asm/unistd.h>
  41
  42 /*
  43  * Power management idle function
  44  * Set in pm platform drivers (apc.c and pmc.c)
  45  */
  46 void (*pm_idle)(void);
  47
  48 /*
  49  * Power-off handler instantiation for pm.h compliance
  50  * This is done via auxio, but could be used as a fallback
  51  * handler when auxio is not present-- unused for now...
  52  */
  53 void (*pm_power_off)(void) = machine_power_off;
  54 EXPORT_SYMBOL(pm_power_off);
  55
  56 /*
  57  * sysctl - toggle power-off restriction for serial console
  58  * systems in machine_power_off()
  59  */
  60 int scons_pwroff = 1;
  61
  62 extern void fpsave(unsigned long *, unsigned long *, void *, unsigned long *);
  63
  64 struct task_struct *last_task_used_math = NULL;
  65 struct thread_info *current_set[NR_CPUS];
  66
  67 #ifndef CONFIG_SMP
  68
  69 #define SUN4C_FAULT_HIGH 100
  70
  71 /*
  72  * the idle loop on a Sparc... ;)
  73  */
  74 void cpu_idle(void)
  75 {
  76         /* endless idle loop with no priority at all */
  77         for (;;) {
  78                 if (ARCH_SUN4C_SUN4) {
  79                         static int count = HZ;
  80                         static unsigned long last_jiffies;
  81                         static unsigned long last_faults;
  82                         static unsigned long fps;
  83                         unsigned long now;
  84                         unsigned long faults;
  85
  86                         extern unsigned long sun4c_kernel_faults;
  87                         extern void sun4c_grow_kernel_ring(void);
  88
  89                         local_irq_disable();
  90                         now = jiffies;
  91                         count -= (now - last_jiffies);
  92                         last_jiffies = now;
  93                         if (count < 0) {
  94                                 count += HZ;
  95                                 faults = sun4c_kernel_faults;
  96                                 fps = (fps + (faults - last_faults)) >> 1;
  97                                 last_faults = faults;
  98 #if 0
  99                                 printk("kernel faults / second = %ld\n", fps);
 100 #endif
 101                                 if (fps >= SUN4C_FAULT_HIGH) {
 102                                         sun4c_grow_kernel_ring();
 103                                 }
 104                         }
 105                         local_irq_enable();
 106                 }
 107
 108                 if (pm_idle) {
 109                         while (!need_resched())
 110                                 (*pm_idle)();
 111                 } else {
 112                         while (!need_resched())
 113                                 cpu_relax();
 114                 }
 115                 preempt_enable_no_resched();
 116                 schedule();
 117                 preempt_disable();
 118                 check_pgt_cache();
 119         }
 120 }
 121
 122 #else
 123
 124 /* This is being executed in task 0 'user space'. */
 125 void cpu_idle(void)
 126 {
 127         set_thread_flag(TIF_POLLING_NRFLAG);
 128         /* endless idle loop with no priority at all */
 129         while(1) {
 130                 while (!need_resched())
 131                         cpu_relax();
 132                 preempt_enable_no_resched();
 133                 schedule();
 134                 preempt_disable();
 135                 check_pgt_cache();
 136         }
 137 }
 138
 139 #endif
 140
 141 /* XXX cli/sti -> local_irq_xxx here, check this works once SMP is fixed. */
 142 void machine_halt(void)
 143 {
 144         local_irq_enable();
 145         mdelay(8);
 146         local_irq_disable();
 147         prom_halt();
 148         panic("Halt failed!");
 149 }
 150
 151 void machine_restart(char * cmd)
 152 {
 153         char *p;
 154
 155         local_irq_enable();
 156         mdelay(8);
 157         local_irq_disable();
 158
 159         p = strchr (reboot_command, '\n');
 160         if (p) *p = 0;
 161         if (cmd)
 162                 prom_reboot(cmd);
 163         if (*reboot_command)
 164                 prom_reboot(reboot_command);
 165         prom_feval ("reset");
 166         panic("Reboot failed!");
 167 }
 168
 169 void machine_power_off(void)
 170 {
 171 #ifdef CONFIG_SUN_AUXIO
 172         if (auxio_power_register &&
 173             (strcmp(of_console_device->type, "serial") || scons_pwroff))
 174                 *auxio_power_register |= AUXIO_POWER_OFF;
 175 #endif
 176         machine_halt();
 177 }
 178
 179 #if 0
 180
 181 static DEFINE_SPINLOCK(sparc_backtrace_lock);
 182
 183 void __show_backtrace(unsigned long fp)
 184 {
 185         struct reg_window *rw;
 186         unsigned long flags;
 187         int cpu = smp_processor_id();
 188
 189         spin_lock_irqsave(&sparc_backtrace_lock, flags);
 190
 191         rw = (struct reg_window *)fp;
 192         while(rw && (((unsigned long) rw) >= PAGE_OFFSET) &&
 193             !(((unsigned long) rw) & 0x7)) {
 194                 printk("CPU[%d]: ARGS[%08lx,%08lx,%08lx,%08lx,%08lx,%08lx] "
 195                        "FP[%08lx] CALLER[%08lx]: ", cpu,
 196                        rw->ins[0], rw->ins[1], rw->ins[2], rw->ins[3],
 197                        rw->ins[4], rw->ins[5],
 198                        rw->ins[6],
 199                        rw->ins[7]);
 200                 printk("%pS\n", (void *) rw->ins[7]);
 201                 rw = (struct reg_window *) rw->ins[6];
 202         }
 203         spin_unlock_irqrestore(&sparc_backtrace_lock, flags);
 204 }
 205
 206 #define __SAVE __asm__ __volatile__("save %sp, -0x40, %sp\n\t")
 207 #define __RESTORE __asm__ __volatile__("restore %g0, %g0, %g0\n\t")
 208 #define __GET_FP(fp) __asm__ __volatile__("mov %%i6, %0" : "=r" (fp))
 209
 210 void show_backtrace(void)
 211 {
 212         unsigned long fp;
 213
 214         __SAVE; __SAVE; __SAVE; __SAVE;
 215         __SAVE; __SAVE; __SAVE; __SAVE;
 216         __RESTORE; __RESTORE; __RESTORE; __RESTORE;
 217         __RESTORE; __RESTORE; __RESTORE; __RESTORE;
 218
 219         __GET_FP(fp);
 220
 221         __show_backtrace(fp);
 222 }
 223
 224 #ifdef CONFIG_SMP
 225 void smp_show_backtrace_all_cpus(void)
 226 {
 227         xc0((smpfunc_t) show_backtrace);
 228         show_backtrace();
 229 }
 230 #endif
 231
 232 void show_stackframe(struct sparc_stackf *sf)
 233 {
 234         unsigned long size;
 235         unsigned long *stk;
 236         int i;
 237
 238         printk("l0: %08lx l1: %08lx l2: %08lx l3: %08lx "
 239                "l4: %08lx l5: %08lx l6: %08lx l7: %08lx\n",
 240                sf->locals[0], sf->locals[1], sf->locals[2], sf->locals[3],
 241                sf->locals[4], sf->locals[5], sf->locals[6], sf->locals[7]);
 242         printk("i0: %08lx i1: %08lx i2: %08lx i3: %08lx "
 243                "i4: %08lx i5: %08lx fp: %08lx i7: %08lx\n",
 244                sf->ins[0], sf->ins[1], sf->ins[2], sf->ins[3],
 245                sf->ins[4], sf->ins[5], (unsigned long)sf->fp, sf->callers_pc);
 246         printk("sp: %08lx x0: %08lx x1: %08lx x2: %08lx "
 247                "x3: %08lx x4: %08lx x5: %08lx xx: %08lx\n",
 248                (unsigned long)sf->structptr, sf->xargs[0], sf->xargs[1],
 249                sf->xargs[2], sf->xargs[3], sf->xargs[4], sf->xargs[5],
 250                sf->xxargs[0]);
 251         size = ((unsigned long)sf->fp) - ((unsigned long)sf);
 252         size -= STACKFRAME_SZ;
 253         stk = (unsigned long *)((unsigned long)sf + STACKFRAME_SZ);
 254         i = 0;
 255         do {
 256                 printk("s%d: %08lx\n", i++, *stk++);
 257         } while ((size -= sizeof(unsigned long)));
 258 }
 259 #endif
 260
 261 void show_regs(struct pt_regs *r)
 262 {
 263         struct reg_window *rw = (struct reg_window *) r->u_regs[14];
 264
 265         printk("PSR: %08lx PC: %08lx NPC: %08lx Y: %08lx    %s\n",
 266                r->psr, r->pc, r->npc, r->y, print_tainted());
 267         printk("PC: <%pS>\n", (void *) r->pc);
 268         printk("%%G: %08lx %08lx  %08lx %08lx  %08lx %08lx  %08lx %08lx\n",
 269                r->u_regs[0], r->u_regs[1], r->u_regs[2], r->u_regs[3],
 270                r->u_regs[4], r->u_regs[5], r->u_regs[6], r->u_regs[7]);
 271         printk("%%O: %08lx %08lx  %08lx %08lx  %08lx %08lx  %08lx %08lx\n",
 272                r->u_regs[8], r->u_regs[9], r->u_regs[10], r->u_regs[11],
 273                r->u_regs[12], r->u_regs[13], r->u_regs[14], r->u_regs[15]);
 274         printk("RPC: <%pS>\n", (void *) r->u_regs[15]);
 275
 276         printk("%%L: %08lx %08lx  %08lx %08lx  %08lx %08lx  %08lx %08lx\n",
 277                rw->locals[0], rw->locals[1], rw->locals[2], rw->locals[3],
 278                rw->locals[4], rw->locals[5], rw->locals[6], rw->locals[7]);
 279         printk("%%I: %08lx %08lx  %08lx %08lx  %08lx %08lx  %08lx %08lx\n",
 280                rw->ins[0], rw->ins[1], rw->ins[2], rw->ins[3],
 281                rw->ins[4], rw->ins[5], rw->ins[6], rw->ins[7]);
 282 }
 283
 284 /*
 285  * The show_stack is an external API which we do not use ourselves.
 286  * The oops is printed in die_if_kernel.
 287  */
 288 void show_stack(struct task_struct *tsk, unsigned long *_ksp)
 289 {
 290         unsigned long pc, fp;
 291         unsigned long task_base;
 292         struct reg_window *rw;
 293         int count = 0;
 294
 295         if (tsk != NULL)
 296                 task_base = (unsigned long) task_stack_page(tsk);
 297         else
 298                 task_base = (unsigned long) current_thread_info();
 299
 300         fp = (unsigned long) _ksp;
 301         do {
 302                 /* Bogus frame pointer? */
 303                 if (fp < (task_base + sizeof(struct thread_info)) ||
 304                     fp >= (task_base + (PAGE_SIZE << 1)))
 305                         break;
 306                 rw = (struct reg_window *) fp;
 307                 pc = rw->ins[7];
 308                 printk("[%08lx : ", pc);
 309                 printk("%pS ] ", (void *) pc);
 310                 fp = rw->ins[6];
 311         } while (++count < 16);
 312         printk("\n");
 313 }
 314
 315 void dump_stack(void)
 316 {
 317         unsigned long *ksp;
 318
 319         __asm__ __volatile__("mov       %%fp, %0"
 320                              : "=r" (ksp));
 321         show_stack(current, ksp);
 322 }
 323
 324 EXPORT_SYMBOL(dump_stack);
 325
 326 /*
 327  * Note: sparc64 has a pretty intricated thread_saved_pc, check it out.
 328  */
 329 unsigned long thread_saved_pc(struct task_struct *tsk)
 330 {
 331         return task_thread_info(tsk)->kpc;
 332 }
 333
 334 /*
 335  * Free current thread data structures etc..
 336  */
 337 void exit_thread(void)
 338 {
 339 #ifndef CONFIG_SMP
 340         if(last_task_used_math == current) {
 341 #else
 342         if (test_thread_flag(TIF_USEDFPU)) {
 343 #endif
 344                 /* Keep process from leaving FPU in a bogon state. */
 345                 put_psr(get_psr() | PSR_EF);
 346                 fpsave(&current->thread.float_regs[0], &current->thread.fsr,
 347                        &current->thread.fpqueue[0], &current->thread.fpqdepth);
 348 #ifndef CONFIG_SMP
 349                 last_task_used_math = NULL;
 350 #else
 351                 clear_thread_flag(TIF_USEDFPU);
 352 #endif
 353         }
 354 }
 355
 356 void flush_thread(void)
 357 {
 358         current_thread_info()->w_saved = 0;
 359
 360 #ifndef CONFIG_SMP
 361         if(last_task_used_math == current) {
 362 #else
 363         if (test_thread_flag(TIF_USEDFPU)) {
 364 #endif
 365                 /* Clean the fpu. */
 366                 put_psr(get_psr() | PSR_EF);
 367                 fpsave(&current->thread.float_regs[0], &current->thread.fsr,
 368                        &current->thread.fpqueue[0], &current->thread.fpqdepth);
 369 #ifndef CONFIG_SMP
 370                 last_task_used_math = NULL;
 371 #else
 372                 clear_thread_flag(TIF_USEDFPU);
 373 #endif
 374         }
 375
 376         /* Now, this task is no longer a kernel thread. */
 377         current->thread.current_ds = USER_DS;
 378         if (current->thread.flags & SPARC_FLAG_KTHREAD) {
 379                 current->thread.flags &= ~SPARC_FLAG_KTHREAD;
 380
 381                 /* We must fixup kregs as well. */
 382                 /* XXX This was not fixed for ti for a while, worked. Unused? */
 383                 current->thread.kregs = (struct pt_regs *)
 384                     (task_stack_page(current) + (THREAD_SIZE - TRACEREG_SZ));
 385         }
 386 }
 387
 388 static inline struct sparc_stackf __user *
 389 clone_stackframe(struct sparc_stackf __user *dst,
 390                  struct sparc_stackf __user *src)
 391 {
 392         unsigned long size, fp;
 393         struct sparc_stackf *tmp;
 394         struct sparc_stackf __user *sp;
 395
 396         if (get_user(tmp, &src->fp))
 397                 return NULL;
 398
 399         fp = (unsigned long) tmp;
 400         size = (fp - ((unsigned long) src));
 401         fp = (unsigned long) dst;
 402         sp = (struct sparc_stackf __user *)(fp - size);
 403
 404         /* do_fork() grabs the parent semaphore, we must release it
 405          * temporarily so we can build the child clone stack frame
 406          * without deadlocking.
 407          */
 408         if (__copy_user(sp, src, size))
 409                 sp = NULL;
 410         else if (put_user(fp, &sp->fp))
 411                 sp = NULL;
 412
 413         return sp;
 414 }
 415
 416 asmlinkage int sparc_do_fork(unsigned long clone_flags,
 417                              unsigned long stack_start,
 418                              struct pt_regs *regs,
 419                              unsigned long stack_size)
 420 {
 421         unsigned long parent_tid_ptr, child_tid_ptr;
 422         unsigned long orig_i1 = regs->u_regs[UREG_I1];
 423         long ret;
 424
 425         parent_tid_ptr = regs->u_regs[UREG_I2];
 426         child_tid_ptr = regs->u_regs[UREG_I4];
 427
 428         ret = do_fork(clone_flags, stack_start,
 429                       regs, stack_size,
 430                       (int __user *) parent_tid_ptr,
 431                       (int __user *) child_tid_ptr);
 432
 433         /* If we get an error and potentially restart the system
 434          * call, we're screwed because copy_thread() clobbered
 435          * the parent's %o1.  So detect that case and restore it
 436          * here.
 437          */
 438         if ((unsigned long)ret >= -ERESTART_RESTARTBLOCK)
 439                 regs->u_regs[UREG_I1] = orig_i1;
 440
 441         return ret;
 442 }
 443
 444 /* Copy a Sparc thread.  The fork() return value conventions
 445  * under SunOS are nothing short of bletcherous:
 446  * Parent -->  %o0 == childs  pid, %o1 == 0
 447  * Child  -->  %o0 == parents pid, %o1 == 1
 448  *
 449  * NOTE: We have a separate fork kpsr/kwim because
 450  *       the parent could change these values between
 451  *       sys_fork invocation and when we reach here
 452  *       if the parent should sleep while trying to
 453  *       allocate the task_struct and kernel stack in
 454  *       do_fork().
 455  * XXX See comment above sys_vfork in sparc64. todo.
 456  */
 457 extern void ret_from_fork(void);
 458
 459 int copy_thread(int nr, unsigned long clone_flags, unsigned long sp,
 460                 unsigned long unused,
 461                 struct task_struct *p, struct pt_regs *regs)
 462 {
 463         struct thread_info *ti = task_thread_info(p);
 464         struct pt_regs *childregs;
 465         char *new_stack;
 466
 467 #ifndef CONFIG_SMP
 468         if(last_task_used_math == current) {
 469 #else
 470         if (test_thread_flag(TIF_USEDFPU)) {
 471 #endif
 472                 put_psr(get_psr() | PSR_EF);
 473                 fpsave(&p->thread.float_regs[0], &p->thread.fsr,
 474                        &p->thread.fpqueue[0], &p->thread.fpqdepth);
 475 #ifdef CONFIG_SMP
 476                 clear_thread_flag(TIF_USEDFPU);
 477 #endif
 478         }
 479
 480         /*
 481          *  p->thread_info         new_stack   childregs
 482          *  !                      !           !             {if(PSR_PS) }
 483          *  V                      V (stk.fr.) V  (pt_regs)  { (stk.fr.) }
 484          *  +----- - - - - - ------+===========+============={+==========}+
 485          */
 486         new_stack = task_stack_page(p) + THREAD_SIZE;
 487         if (regs->psr & PSR_PS)
 488                 new_stack -= STACKFRAME_SZ;
 489         new_stack -= STACKFRAME_SZ + TRACEREG_SZ;
 490         memcpy(new_stack, (char *)regs - STACKFRAME_SZ, STACKFRAME_SZ + TRACEREG_SZ);
 491         childregs = (struct pt_regs *) (new_stack + STACKFRAME_SZ);
 492
 493         /*
 494          * A new process must start with interrupts closed in 2.5,
 495          * because this is how Mingo's scheduler works (see schedule_tail
 496          * and finish_arch_switch). If we do not do it, a timer interrupt hits
 497          * before we unlock, attempts to re-take the rq->lock, and then we die.
 498          * Thus, kpsr|=PSR_PIL.
 499          */
 500         ti->ksp = (unsigned long) new_stack;
 501         ti->kpc = (((unsigned long) ret_from_fork) - 0x8);
 502         ti->kpsr = current->thread.fork_kpsr | PSR_PIL;
 503         ti->kwim = current->thread.fork_kwim;
 504
 505         if(regs->psr & PSR_PS) {
 506                 extern struct pt_regs fake_swapper_regs;
 507
 508                 p->thread.kregs = &fake_swapper_regs;
 509                 new_stack += STACKFRAME_SZ + TRACEREG_SZ;
 510                 childregs->u_regs[UREG_FP] = (unsigned long) new_stack;
 511                 p->thread.flags |= SPARC_FLAG_KTHREAD;
 512                 p->thread.current_ds = KERNEL_DS;
 513                 memcpy(new_stack, (void *)regs->u_regs[UREG_FP], STACKFRAME_SZ);
 514                 childregs->u_regs[UREG_G6] = (unsigned long) ti;
 515         } else {
 516                 p->thread.kregs = childregs;
 517                 childregs->u_regs[UREG_FP] = sp;
 518                 p->thread.flags &= ~SPARC_FLAG_KTHREAD;
 519                 p->thread.current_ds = USER_DS;
 520
 521                 if (sp != regs->u_regs[UREG_FP]) {
 522                         struct sparc_stackf __user *childstack;
 523                         struct sparc_stackf __user *parentstack;
 524
 525                         /*
 526                          * This is a clone() call with supplied user stack.
 527                          * Set some valid stack frames to give to the child.
 528                          */
 529                         childstack = (struct sparc_stackf __user *)
 530                                 (sp & ~0x7UL);
 531                         parentstack = (struct sparc_stackf __user *)
 532                                 regs->u_regs[UREG_FP];
 533
 534 #if 0
 535                         printk("clone: parent stack:\n");
 536                         show_stackframe(parentstack);
 537 #endif
 538
 539                         childstack = clone_stackframe(childstack, parentstack);
 540                         if (!childstack)
 541                                 return -EFAULT;
 542
 543 #if 0
 544                         printk("clone: child stack:\n");
 545                         show_stackframe(childstack);
 546 #endif
 547
 548                         childregs->u_regs[UREG_FP] = (unsigned long)childstack;
 549                 }
 550         }
 551
 552 #ifdef CONFIG_SMP
 553         /* FPU must be disabled on SMP. */
 554         childregs->psr &= ~PSR_EF;
 555 #endif
 556
 557         /* Set the return value for the child. */
 558         childregs->u_regs[UREG_I0] = current->pid;
 559         childregs->u_regs[UREG_I1] = 1;
 560
 561         /* Set the return value for the parent. */
 562         regs->u_regs[UREG_I1] = 0;
 563
 564         if (clone_flags & CLONE_SETTLS)
 565                 childregs->u_regs[UREG_G7] = regs->u_regs[UREG_I3];
 566
 567         return 0;
 568 }
 569
 570 /*
 571  * fill in the fpu structure for a core dump.
 572  */
 573 int dump_fpu (struct pt_regs * regs, elf_fpregset_t * fpregs)
 574 {
 575         if (used_math()) {
 576                 memset(fpregs, 0, sizeof(*fpregs));
 577                 fpregs->pr_q_entrysize = 8;
 578                 return 1;
 579         }
 580 #ifdef CONFIG_SMP
 581         if (test_thread_flag(TIF_USEDFPU)) {
 582                 put_psr(get_psr() | PSR_EF);
 583                 fpsave(&current->thread.float_regs[0], &current->thread.fsr,
 584                        &current->thread.fpqueue[0], &current->thread.fpqdepth);
 585                 if (regs != NULL) {
 586                         regs->psr &= ~(PSR_EF);
 587                         clear_thread_flag(TIF_USEDFPU);
 588                 }
 589         }
 590 #else
 591         if (current == last_task_used_math) {
 592                 put_psr(get_psr() | PSR_EF);
 593                 fpsave(&current->thread.float_regs[0], &current->thread.fsr,
 594                        &current->thread.fpqueue[0], &current->thread.fpqdepth);
 595                 if (regs != NULL) {
 596                         regs->psr &= ~(PSR_EF);
 597                         last_task_used_math = NULL;
 598                 }
 599         }
 600 #endif
 601         memcpy(&fpregs->pr_fr.pr_regs[0],
 602                &current->thread.float_regs[0],
 603                (sizeof(unsigned long) * 32));
 604         fpregs->pr_fsr = current->thread.fsr;
 605         fpregs->pr_qcnt = current->thread.fpqdepth;
 606         fpregs->pr_q_entrysize = 8;
 607         fpregs->pr_en = 1;
 608         if(fpregs->pr_qcnt != 0) {
 609                 memcpy(&fpregs->pr_q[0],
 610                        &current->thread.fpqueue[0],
 611                        sizeof(struct fpq) * fpregs->pr_qcnt);
 612         }
 613         /* Zero out the rest. */
 614         memset(&fpregs->pr_q[fpregs->pr_qcnt], 0,
 615                sizeof(struct fpq) * (32 - fpregs->pr_qcnt));
 616         return 1;
 617 }
 618
 619 /*
 620  * sparc_execve() executes a new program after the asm stub has set
 621  * things up for us.  This should basically do what I want it to.
 622  */
 623 asmlinkage int sparc_execve(struct pt_regs *regs)
 624 {
 625         int error, base = 0;
 626         char *filename;
 627
 628         /* Check for indirect call. */
 629         if(regs->u_regs[UREG_G1] == 0)
 630                 base = 1;
 631
 632         filename = getname((char __user *)regs->u_regs[base + UREG_I0]);
 633         error = PTR_ERR(filename);
 634         if(IS_ERR(filename))
 635                 goto out;
 636         error = do_execve(filename,
 637                           (char __user * __user *)regs->u_regs[base + UREG_I1],
 638                           (char __user * __user *)regs->u_regs[base + UREG_I2],
 639                           regs);
 640         putname(filename);
 641 out:
 642         return error;
 643 }
 644
 645 /*
 646  * This is the mechanism for creating a new kernel thread.
 647  *
 648  * NOTE! Only a kernel-only process(ie the swapper or direct descendants
 649  * who haven't done an "execve()") should use this: it will work within
 650  * a system call from a "real" process, but the process memory space will
 651  * not be freed until both the parent and the child have exited.
 652  */
 653 pid_t kernel_thread(int (*fn)(void *), void * arg, unsigned long flags)
 654 {
 655         long retval;
 656
 657         __asm__ __volatile__("mov %4, %%g2\n\t"    /* Set aside fn ptr... */
 658                              "mov %5, %%g3\n\t"    /* and arg. */
 659                              "mov %1, %%g1\n\t"
 660                              "mov %2, %%o0\n\t"    /* Clone flags. */
 661                              "mov 0, %%o1\n\t"     /* usp arg == 0 */
 662                              "t 0x10\n\t"          /* Linux/Sparc clone(). */
 663                              "cmp %%o1, 0\n\t"
 664                              "be 1f\n\t"           /* The parent, just return. */
 665                              " nop\n\t"            /* Delay slot. */
 666                              "jmpl %%g2, %%o7\n\t" /* Call the function. */
 667                              " mov %%g3, %%o0\n\t" /* Get back the arg in delay. */
 668                              "mov %3, %%g1\n\t"
 669                              "t 0x10\n\t"          /* Linux/Sparc exit(). */
 670                              /* Notreached by child. */
 671                              "1: mov %%o0, %0\n\t" :
 672                              "=r" (retval) :
 673                              "i" (__NR_clone), "r" (flags | CLONE_VM | CLONE_UNTRACED),
 674                              "i" (__NR_exit),  "r" (fn), "r" (arg) :
 675                              "g1", "g2", "g3", "o0", "o1", "memory", "cc");
 676         return retval;
 677 }
 678
 679 unsigned long get_wchan(struct task_struct *task)
 680 {
 681         unsigned long pc, fp, bias = 0;
 682         unsigned long task_base = (unsigned long) task;
 683         unsigned long ret = 0;
 684         struct reg_window *rw;
 685         int count = 0;
 686
 687         if (!task || task == current ||
 688             task->state == TASK_RUNNING)
 689                 goto out;
 690
 691         fp = task_thread_info(task)->ksp + bias;
 692         do {
 693                 /* Bogus frame pointer? */
 694                 if (fp < (task_base + sizeof(struct thread_info)) ||
 695                     fp >= (task_base + (2 * PAGE_SIZE)))
 696                         break;
 697                 rw = (struct reg_window *) fp;
 698                 pc = rw->ins[7];
 699                 if (!in_sched_functions(pc)) {
 700                         ret = pc;
 701                         goto out;
 702                 }
 703                 fp = rw->ins[6] + bias;
 704         } while (++count < 16);
 705
 706 out:
 707         return ret;
 708 }
 709