sparc: prepare kernel/ for unification
[linux-2.6.git] / arch / sparc / kernel / process_32.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) {
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