xref: /linux/arch/sparc/kernel/process_64.c (revision bdd1a21b52557ea8f61d0a5dc2f77151b576eb70) 
1 // SPDX-License-Identifier: GPL-2.0
2 /*  arch/sparc64/kernel/process.c
3  *
4  *  Copyright (C) 1995, 1996, 2008 David S. Miller (davem@davemloft.net)
5  *  Copyright (C) 1996       Eddie C. Dost   (ecd@skynet.be)
6  *  Copyright (C) 1997, 1998 Jakub Jelinek   (jj@sunsite.mff.cuni.cz)
7  */
8 
9 /*
10  * This file handles the architecture-dependent parts of process handling..
11  */
12 
13 #include <stdarg.h>
14 
15 #include <linux/errno.h>
16 #include <linux/export.h>
17 #include <linux/sched.h>
18 #include <linux/sched/debug.h>
19 #include <linux/sched/task.h>
20 #include <linux/sched/task_stack.h>
21 #include <linux/kernel.h>
22 #include <linux/mm.h>
23 #include <linux/fs.h>
24 #include <linux/smp.h>
25 #include <linux/stddef.h>
26 #include <linux/ptrace.h>
27 #include <linux/slab.h>
28 #include <linux/user.h>
29 #include <linux/delay.h>
30 #include <linux/compat.h>
31 #include <linux/tick.h>
32 #include <linux/init.h>
33 #include <linux/cpu.h>
34 #include <linux/perf_event.h>
35 #include <linux/elfcore.h>
36 #include <linux/sysrq.h>
37 #include <linux/nmi.h>
38 #include <linux/context_tracking.h>
39 #include <linux/signal.h>
40 
41 #include <linux/uaccess.h>
42 #include <asm/page.h>
43 #include <asm/pgalloc.h>
44 #include <asm/processor.h>
45 #include <asm/pstate.h>
46 #include <asm/elf.h>
47 #include <asm/fpumacro.h>
48 #include <asm/head.h>
49 #include <asm/cpudata.h>
50 #include <asm/mmu_context.h>
51 #include <asm/unistd.h>
52 #include <asm/hypervisor.h>
53 #include <asm/syscalls.h>
54 #include <asm/irq_regs.h>
55 #include <asm/smp.h>
56 #include <asm/pcr.h>
57 
58 #include "kstack.h"
59 
60 /* Idle loop support on sparc64. */
61 void arch_cpu_idle(void)
62 {
63 	if (tlb_type != hypervisor) {
64 		touch_nmi_watchdog();
65 		raw_local_irq_enable();
66 	} else {
67 		unsigned long pstate;
68 
69 		raw_local_irq_enable();
70 
71                 /* The sun4v sleeping code requires that we have PSTATE.IE cleared over
72                  * the cpu sleep hypervisor call.
73                  */
74 		__asm__ __volatile__(
75 			"rdpr %%pstate, %0\n\t"
76 			"andn %0, %1, %0\n\t"
77 			"wrpr %0, %%g0, %%pstate"
78 			: "=&r" (pstate)
79 			: "i" (PSTATE_IE));
80 
81 		if (!need_resched() && !cpu_is_offline(smp_processor_id())) {
82 			sun4v_cpu_yield();
83 			/* If resumed by cpu_poke then we need to explicitly
84 			 * call scheduler_ipi().
85 			 */
86 			scheduler_poke();
87 		}
88 
89 		/* Re-enable interrupts. */
90 		__asm__ __volatile__(
91 			"rdpr %%pstate, %0\n\t"
92 			"or %0, %1, %0\n\t"
93 			"wrpr %0, %%g0, %%pstate"
94 			: "=&r" (pstate)
95 			: "i" (PSTATE_IE));
96 	}
97 }
98 
99 #ifdef CONFIG_HOTPLUG_CPU
100 void arch_cpu_idle_dead(void)
101 {
102 	sched_preempt_enable_no_resched();
103 	cpu_play_dead();
104 }
105 #endif
106 
107 #ifdef CONFIG_COMPAT
108 static void show_regwindow32(struct pt_regs *regs)
109 {
110 	struct reg_window32 __user *rw;
111 	struct reg_window32 r_w;
112 	mm_segment_t old_fs;
113 
114 	__asm__ __volatile__ ("flushw");
115 	rw = compat_ptr((unsigned int)regs->u_regs[14]);
116 	old_fs = get_fs();
117 	set_fs (USER_DS);
118 	if (copy_from_user (&r_w, rw, sizeof(r_w))) {
119 		set_fs (old_fs);
120 		return;
121 	}
122 
123 	set_fs (old_fs);
124 	printk("l0: %08x l1: %08x l2: %08x l3: %08x "
125 	       "l4: %08x l5: %08x l6: %08x l7: %08x\n",
126 	       r_w.locals[0], r_w.locals[1], r_w.locals[2], r_w.locals[3],
127 	       r_w.locals[4], r_w.locals[5], r_w.locals[6], r_w.locals[7]);
128 	printk("i0: %08x i1: %08x i2: %08x i3: %08x "
129 	       "i4: %08x i5: %08x i6: %08x i7: %08x\n",
130 	       r_w.ins[0], r_w.ins[1], r_w.ins[2], r_w.ins[3],
131 	       r_w.ins[4], r_w.ins[5], r_w.ins[6], r_w.ins[7]);
132 }
133 #else
134 #define show_regwindow32(regs)	do { } while (0)
135 #endif
136 
137 static void show_regwindow(struct pt_regs *regs)
138 {
139 	struct reg_window __user *rw;
140 	struct reg_window *rwk;
141 	struct reg_window r_w;
142 	mm_segment_t old_fs;
143 
144 	if ((regs->tstate & TSTATE_PRIV) || !(test_thread_flag(TIF_32BIT))) {
145 		__asm__ __volatile__ ("flushw");
146 		rw = (struct reg_window __user *)
147 			(regs->u_regs[14] + STACK_BIAS);
148 		rwk = (struct reg_window *)
149 			(regs->u_regs[14] + STACK_BIAS);
150 		if (!(regs->tstate & TSTATE_PRIV)) {
151 			old_fs = get_fs();
152 			set_fs (USER_DS);
153 			if (copy_from_user (&r_w, rw, sizeof(r_w))) {
154 				set_fs (old_fs);
155 				return;
156 			}
157 			rwk = &r_w;
158 			set_fs (old_fs);
159 		}
160 	} else {
161 		show_regwindow32(regs);
162 		return;
163 	}
164 	printk("l0: %016lx l1: %016lx l2: %016lx l3: %016lx\n",
165 	       rwk->locals[0], rwk->locals[1], rwk->locals[2], rwk->locals[3]);
166 	printk("l4: %016lx l5: %016lx l6: %016lx l7: %016lx\n",
167 	       rwk->locals[4], rwk->locals[5], rwk->locals[6], rwk->locals[7]);
168 	printk("i0: %016lx i1: %016lx i2: %016lx i3: %016lx\n",
169 	       rwk->ins[0], rwk->ins[1], rwk->ins[2], rwk->ins[3]);
170 	printk("i4: %016lx i5: %016lx i6: %016lx i7: %016lx\n",
171 	       rwk->ins[4], rwk->ins[5], rwk->ins[6], rwk->ins[7]);
172 	if (regs->tstate & TSTATE_PRIV)
173 		printk("I7: <%pS>\n", (void *) rwk->ins[7]);
174 }
175 
176 void show_regs(struct pt_regs *regs)
177 {
178 	show_regs_print_info(KERN_DEFAULT);
179 
180 	printk("TSTATE: %016lx TPC: %016lx TNPC: %016lx Y: %08x    %s\n", regs->tstate,
181 	       regs->tpc, regs->tnpc, regs->y, print_tainted());
182 	printk("TPC: <%pS>\n", (void *) regs->tpc);
183 	printk("g0: %016lx g1: %016lx g2: %016lx g3: %016lx\n",
184 	       regs->u_regs[0], regs->u_regs[1], regs->u_regs[2],
185 	       regs->u_regs[3]);
186 	printk("g4: %016lx g5: %016lx g6: %016lx g7: %016lx\n",
187 	       regs->u_regs[4], regs->u_regs[5], regs->u_regs[6],
188 	       regs->u_regs[7]);
189 	printk("o0: %016lx o1: %016lx o2: %016lx o3: %016lx\n",
190 	       regs->u_regs[8], regs->u_regs[9], regs->u_regs[10],
191 	       regs->u_regs[11]);
192 	printk("o4: %016lx o5: %016lx sp: %016lx ret_pc: %016lx\n",
193 	       regs->u_regs[12], regs->u_regs[13], regs->u_regs[14],
194 	       regs->u_regs[15]);
195 	printk("RPC: <%pS>\n", (void *) regs->u_regs[15]);
196 	show_regwindow(regs);
197 	show_stack(current, (unsigned long *)regs->u_regs[UREG_FP], KERN_DEFAULT);
198 }
199 
200 union global_cpu_snapshot global_cpu_snapshot[NR_CPUS];
201 static DEFINE_SPINLOCK(global_cpu_snapshot_lock);
202 
203 static void __global_reg_self(struct thread_info *tp, struct pt_regs *regs,
204 			      int this_cpu)
205 {
206 	struct global_reg_snapshot *rp;
207 
208 	flushw_all();
209 
210 	rp = &global_cpu_snapshot[this_cpu].reg;
211 
212 	rp->tstate = regs->tstate;
213 	rp->tpc = regs->tpc;
214 	rp->tnpc = regs->tnpc;
215 	rp->o7 = regs->u_regs[UREG_I7];
216 
217 	if (regs->tstate & TSTATE_PRIV) {
218 		struct reg_window *rw;
219 
220 		rw = (struct reg_window *)
221 			(regs->u_regs[UREG_FP] + STACK_BIAS);
222 		if (kstack_valid(tp, (unsigned long) rw)) {
223 			rp->i7 = rw->ins[7];
224 			rw = (struct reg_window *)
225 				(rw->ins[6] + STACK_BIAS);
226 			if (kstack_valid(tp, (unsigned long) rw))
227 				rp->rpc = rw->ins[7];
228 		}
229 	} else {
230 		rp->i7 = 0;
231 		rp->rpc = 0;
232 	}
233 	rp->thread = tp;
234 }
235 
236 /* In order to avoid hangs we do not try to synchronize with the
237  * global register dump client cpus.  The last store they make is to
238  * the thread pointer, so do a short poll waiting for that to become
239  * non-NULL.
240  */
241 static void __global_reg_poll(struct global_reg_snapshot *gp)
242 {
243 	int limit = 0;
244 
245 	while (!gp->thread && ++limit < 100) {
246 		barrier();
247 		udelay(1);
248 	}
249 }
250 
251 void arch_trigger_cpumask_backtrace(const cpumask_t *mask, bool exclude_self)
252 {
253 	struct thread_info *tp = current_thread_info();
254 	struct pt_regs *regs = get_irq_regs();
255 	unsigned long flags;
256 	int this_cpu, cpu;
257 
258 	if (!regs)
259 		regs = tp->kregs;
260 
261 	spin_lock_irqsave(&global_cpu_snapshot_lock, flags);
262 
263 	this_cpu = raw_smp_processor_id();
264 
265 	memset(global_cpu_snapshot, 0, sizeof(global_cpu_snapshot));
266 
267 	if (cpumask_test_cpu(this_cpu, mask) && !exclude_self)
268 		__global_reg_self(tp, regs, this_cpu);
269 
270 	smp_fetch_global_regs();
271 
272 	for_each_cpu(cpu, mask) {
273 		struct global_reg_snapshot *gp;
274 
275 		if (exclude_self && cpu == this_cpu)
276 			continue;
277 
278 		gp = &global_cpu_snapshot[cpu].reg;
279 
280 		__global_reg_poll(gp);
281 
282 		tp = gp->thread;
283 		printk("%c CPU[%3d]: TSTATE[%016lx] TPC[%016lx] TNPC[%016lx] TASK[%s:%d]\n",
284 		       (cpu == this_cpu ? '*' : ' '), cpu,
285 		       gp->tstate, gp->tpc, gp->tnpc,
286 		       ((tp && tp->task) ? tp->task->comm : "NULL"),
287 		       ((tp && tp->task) ? tp->task->pid : -1));
288 
289 		if (gp->tstate & TSTATE_PRIV) {
290 			printk("             TPC[%pS] O7[%pS] I7[%pS] RPC[%pS]\n",
291 			       (void *) gp->tpc,
292 			       (void *) gp->o7,
293 			       (void *) gp->i7,
294 			       (void *) gp->rpc);
295 		} else {
296 			printk("             TPC[%lx] O7[%lx] I7[%lx] RPC[%lx]\n",
297 			       gp->tpc, gp->o7, gp->i7, gp->rpc);
298 		}
299 
300 		touch_nmi_watchdog();
301 	}
302 
303 	memset(global_cpu_snapshot, 0, sizeof(global_cpu_snapshot));
304 
305 	spin_unlock_irqrestore(&global_cpu_snapshot_lock, flags);
306 }
307 
308 #ifdef CONFIG_MAGIC_SYSRQ
309 
310 static void sysrq_handle_globreg(int key)
311 {
312 	trigger_all_cpu_backtrace();
313 }
314 
315 static const struct sysrq_key_op sparc_globalreg_op = {
316 	.handler	= sysrq_handle_globreg,
317 	.help_msg	= "global-regs(y)",
318 	.action_msg	= "Show Global CPU Regs",
319 };
320 
321 static void __global_pmu_self(int this_cpu)
322 {
323 	struct global_pmu_snapshot *pp;
324 	int i, num;
325 
326 	if (!pcr_ops)
327 		return;
328 
329 	pp = &global_cpu_snapshot[this_cpu].pmu;
330 
331 	num = 1;
332 	if (tlb_type == hypervisor &&
333 	    sun4v_chip_type >= SUN4V_CHIP_NIAGARA4)
334 		num = 4;
335 
336 	for (i = 0; i < num; i++) {
337 		pp->pcr[i] = pcr_ops->read_pcr(i);
338 		pp->pic[i] = pcr_ops->read_pic(i);
339 	}
340 }
341 
342 static void __global_pmu_poll(struct global_pmu_snapshot *pp)
343 {
344 	int limit = 0;
345 
346 	while (!pp->pcr[0] && ++limit < 100) {
347 		barrier();
348 		udelay(1);
349 	}
350 }
351 
352 static void pmu_snapshot_all_cpus(void)
353 {
354 	unsigned long flags;
355 	int this_cpu, cpu;
356 
357 	spin_lock_irqsave(&global_cpu_snapshot_lock, flags);
358 
359 	memset(global_cpu_snapshot, 0, sizeof(global_cpu_snapshot));
360 
361 	this_cpu = raw_smp_processor_id();
362 
363 	__global_pmu_self(this_cpu);
364 
365 	smp_fetch_global_pmu();
366 
367 	for_each_online_cpu(cpu) {
368 		struct global_pmu_snapshot *pp = &global_cpu_snapshot[cpu].pmu;
369 
370 		__global_pmu_poll(pp);
371 
372 		printk("%c CPU[%3d]: PCR[%08lx:%08lx:%08lx:%08lx] PIC[%08lx:%08lx:%08lx:%08lx]\n",
373 		       (cpu == this_cpu ? '*' : ' '), cpu,
374 		       pp->pcr[0], pp->pcr[1], pp->pcr[2], pp->pcr[3],
375 		       pp->pic[0], pp->pic[1], pp->pic[2], pp->pic[3]);
376 
377 		touch_nmi_watchdog();
378 	}
379 
380 	memset(global_cpu_snapshot, 0, sizeof(global_cpu_snapshot));
381 
382 	spin_unlock_irqrestore(&global_cpu_snapshot_lock, flags);
383 }
384 
385 static void sysrq_handle_globpmu(int key)
386 {
387 	pmu_snapshot_all_cpus();
388 }
389 
390 static const struct sysrq_key_op sparc_globalpmu_op = {
391 	.handler	= sysrq_handle_globpmu,
392 	.help_msg	= "global-pmu(x)",
393 	.action_msg	= "Show Global PMU Regs",
394 };
395 
396 static int __init sparc_sysrq_init(void)
397 {
398 	int ret = register_sysrq_key('y', &sparc_globalreg_op);
399 
400 	if (!ret)
401 		ret = register_sysrq_key('x', &sparc_globalpmu_op);
402 	return ret;
403 }
404 
405 core_initcall(sparc_sysrq_init);
406 
407 #endif
408 
409 /* Free current thread data structures etc.. */
410 void exit_thread(struct task_struct *tsk)
411 {
412 	struct thread_info *t = task_thread_info(tsk);
413 
414 	if (t->utraps) {
415 		if (t->utraps[0] < 2)
416 			kfree (t->utraps);
417 		else
418 			t->utraps[0]--;
419 	}
420 }
421 
422 void flush_thread(void)
423 {
424 	struct thread_info *t = current_thread_info();
425 	struct mm_struct *mm;
426 
427 	mm = t->task->mm;
428 	if (mm)
429 		tsb_context_switch(mm);
430 
431 	set_thread_wsaved(0);
432 
433 	/* Clear FPU register state. */
434 	t->fpsaved[0] = 0;
435 }
436 
437 /* It's a bit more tricky when 64-bit tasks are involved... */
438 static unsigned long clone_stackframe(unsigned long csp, unsigned long psp)
439 {
440 	bool stack_64bit = test_thread_64bit_stack(psp);
441 	unsigned long fp, distance, rval;
442 
443 	if (stack_64bit) {
444 		csp += STACK_BIAS;
445 		psp += STACK_BIAS;
446 		__get_user(fp, &(((struct reg_window __user *)psp)->ins[6]));
447 		fp += STACK_BIAS;
448 		if (test_thread_flag(TIF_32BIT))
449 			fp &= 0xffffffff;
450 	} else
451 		__get_user(fp, &(((struct reg_window32 __user *)psp)->ins[6]));
452 
453 	/* Now align the stack as this is mandatory in the Sparc ABI
454 	 * due to how register windows work.  This hides the
455 	 * restriction from thread libraries etc.
456 	 */
457 	csp &= ~15UL;
458 
459 	distance = fp - psp;
460 	rval = (csp - distance);
461 	if (copy_in_user((void __user *) rval, (void __user *) psp, distance))
462 		rval = 0;
463 	else if (!stack_64bit) {
464 		if (put_user(((u32)csp),
465 			     &(((struct reg_window32 __user *)rval)->ins[6])))
466 			rval = 0;
467 	} else {
468 		if (put_user(((u64)csp - STACK_BIAS),
469 			     &(((struct reg_window __user *)rval)->ins[6])))
470 			rval = 0;
471 		else
472 			rval = rval - STACK_BIAS;
473 	}
474 
475 	return rval;
476 }
477 
478 /* Standard stuff. */
479 static inline void shift_window_buffer(int first_win, int last_win,
480 				       struct thread_info *t)
481 {
482 	int i;
483 
484 	for (i = first_win; i < last_win; i++) {
485 		t->rwbuf_stkptrs[i] = t->rwbuf_stkptrs[i+1];
486 		memcpy(&t->reg_window[i], &t->reg_window[i+1],
487 		       sizeof(struct reg_window));
488 	}
489 }
490 
491 void synchronize_user_stack(void)
492 {
493 	struct thread_info *t = current_thread_info();
494 	unsigned long window;
495 
496 	flush_user_windows();
497 	if ((window = get_thread_wsaved()) != 0) {
498 		window -= 1;
499 		do {
500 			struct reg_window *rwin = &t->reg_window[window];
501 			int winsize = sizeof(struct reg_window);
502 			unsigned long sp;
503 
504 			sp = t->rwbuf_stkptrs[window];
505 
506 			if (test_thread_64bit_stack(sp))
507 				sp += STACK_BIAS;
508 			else
509 				winsize = sizeof(struct reg_window32);
510 
511 			if (!copy_to_user((char __user *)sp, rwin, winsize)) {
512 				shift_window_buffer(window, get_thread_wsaved() - 1, t);
513 				set_thread_wsaved(get_thread_wsaved() - 1);
514 			}
515 		} while (window--);
516 	}
517 }
518 
519 static void stack_unaligned(unsigned long sp)
520 {
521 	force_sig_fault(SIGBUS, BUS_ADRALN, (void __user *) sp, 0);
522 }
523 
524 static const char uwfault32[] = KERN_INFO \
525 	"%s[%d]: bad register window fault: SP %08lx (orig_sp %08lx) TPC %08lx O7 %08lx\n";
526 static const char uwfault64[] = KERN_INFO \
527 	"%s[%d]: bad register window fault: SP %016lx (orig_sp %016lx) TPC %08lx O7 %016lx\n";
528 
529 void fault_in_user_windows(struct pt_regs *regs)
530 {
531 	struct thread_info *t = current_thread_info();
532 	unsigned long window;
533 
534 	flush_user_windows();
535 	window = get_thread_wsaved();
536 
537 	if (likely(window != 0)) {
538 		window -= 1;
539 		do {
540 			struct reg_window *rwin = &t->reg_window[window];
541 			int winsize = sizeof(struct reg_window);
542 			unsigned long sp, orig_sp;
543 
544 			orig_sp = sp = t->rwbuf_stkptrs[window];
545 
546 			if (test_thread_64bit_stack(sp))
547 				sp += STACK_BIAS;
548 			else
549 				winsize = sizeof(struct reg_window32);
550 
551 			if (unlikely(sp & 0x7UL))
552 				stack_unaligned(sp);
553 
554 			if (unlikely(copy_to_user((char __user *)sp,
555 						  rwin, winsize))) {
556 				if (show_unhandled_signals)
557 					printk_ratelimited(is_compat_task() ?
558 							   uwfault32 : uwfault64,
559 							   current->comm, current->pid,
560 							   sp, orig_sp,
561 							   regs->tpc,
562 							   regs->u_regs[UREG_I7]);
563 				goto barf;
564 			}
565 		} while (window--);
566 	}
567 	set_thread_wsaved(0);
568 	return;
569 
570 barf:
571 	set_thread_wsaved(window + 1);
572 	force_sig(SIGSEGV);
573 }
574 
575 /* Copy a Sparc thread.  The fork() return value conventions
576  * under SunOS are nothing short of bletcherous:
577  * Parent -->  %o0 == childs  pid, %o1 == 0
578  * Child  -->  %o0 == parents pid, %o1 == 1
579  */
580 int copy_thread(unsigned long clone_flags, unsigned long sp, unsigned long arg,
581 		struct task_struct *p, unsigned long tls)
582 {
583 	struct thread_info *t = task_thread_info(p);
584 	struct pt_regs *regs = current_pt_regs();
585 	struct sparc_stackf *parent_sf;
586 	unsigned long child_stack_sz;
587 	char *child_trap_frame;
588 
589 	/* Calculate offset to stack_frame & pt_regs */
590 	child_stack_sz = (STACKFRAME_SZ + TRACEREG_SZ);
591 	child_trap_frame = (task_stack_page(p) +
592 			    (THREAD_SIZE - child_stack_sz));
593 
594 	t->new_child = 1;
595 	t->ksp = ((unsigned long) child_trap_frame) - STACK_BIAS;
596 	t->kregs = (struct pt_regs *) (child_trap_frame +
597 				       sizeof(struct sparc_stackf));
598 	t->fpsaved[0] = 0;
599 
600 	if (unlikely(p->flags & (PF_KTHREAD | PF_IO_WORKER))) {
601 		memset(child_trap_frame, 0, child_stack_sz);
602 		__thread_flag_byte_ptr(t)[TI_FLAG_BYTE_CWP] =
603 			(current_pt_regs()->tstate + 1) & TSTATE_CWP;
604 		t->current_ds = ASI_P;
605 		t->kregs->u_regs[UREG_G1] = sp; /* function */
606 		t->kregs->u_regs[UREG_G2] = arg;
607 		return 0;
608 	}
609 
610 	parent_sf = ((struct sparc_stackf *) regs) - 1;
611 	memcpy(child_trap_frame, parent_sf, child_stack_sz);
612 	if (t->flags & _TIF_32BIT) {
613 		sp &= 0x00000000ffffffffUL;
614 		regs->u_regs[UREG_FP] &= 0x00000000ffffffffUL;
615 	}
616 	t->kregs->u_regs[UREG_FP] = sp;
617 	__thread_flag_byte_ptr(t)[TI_FLAG_BYTE_CWP] =
618 		(regs->tstate + 1) & TSTATE_CWP;
619 	t->current_ds = ASI_AIUS;
620 	if (sp != regs->u_regs[UREG_FP]) {
621 		unsigned long csp;
622 
623 		csp = clone_stackframe(sp, regs->u_regs[UREG_FP]);
624 		if (!csp)
625 			return -EFAULT;
626 		t->kregs->u_regs[UREG_FP] = csp;
627 	}
628 	if (t->utraps)
629 		t->utraps[0]++;
630 
631 	/* Set the return value for the child. */
632 	t->kregs->u_regs[UREG_I0] = current->pid;
633 	t->kregs->u_regs[UREG_I1] = 1;
634 
635 	/* Set the second return value for the parent. */
636 	regs->u_regs[UREG_I1] = 0;
637 
638 	if (clone_flags & CLONE_SETTLS)
639 		t->kregs->u_regs[UREG_G7] = tls;
640 
641 	return 0;
642 }
643 
644 /* TIF_MCDPER in thread info flags for current task is updated lazily upon
645  * a context switch. Update this flag in current task's thread flags
646  * before dup so the dup'd task will inherit the current TIF_MCDPER flag.
647  */
648 int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src)
649 {
650 	if (adi_capable()) {
651 		register unsigned long tmp_mcdper;
652 
653 		__asm__ __volatile__(
654 			".word 0x83438000\n\t"	/* rd  %mcdper, %g1 */
655 			"mov %%g1, %0\n\t"
656 			: "=r" (tmp_mcdper)
657 			:
658 			: "g1");
659 		if (tmp_mcdper)
660 			set_thread_flag(TIF_MCDPER);
661 		else
662 			clear_thread_flag(TIF_MCDPER);
663 	}
664 
665 	*dst = *src;
666 	return 0;
667 }
668 
669 unsigned long get_wchan(struct task_struct *task)
670 {
671 	unsigned long pc, fp, bias = 0;
672 	struct thread_info *tp;
673 	struct reg_window *rw;
674         unsigned long ret = 0;
675 	int count = 0;
676 
677 	if (!task || task == current || task_is_running(task))
678 		goto out;
679 
680 	tp = task_thread_info(task);
681 	bias = STACK_BIAS;
682 	fp = task_thread_info(task)->ksp + bias;
683 
684 	do {
685 		if (!kstack_valid(tp, fp))
686 			break;
687 		rw = (struct reg_window *) fp;
688 		pc = rw->ins[7];
689 		if (!in_sched_functions(pc)) {
690 			ret = pc;
691 			goto out;
692 		}
693 		fp = rw->ins[6] + bias;
694 	} while (++count < 16);
695 
696 out:
697 	return ret;
698 }
699