1// SPDX-License-Identifier: GPL-2.0
2/*
3 *  linux/arch/alpha/kernel/process.c
4 *
5 *  Copyright (C) 1995  Linus Torvalds
6 */
7
8/*
9 * This file handles the architecture-dependent parts of process handling.
10 */
11
12#include <linux/cpu.h>
13#include <linux/errno.h>
14#include <linux/module.h>
15#include <linux/sched.h>
16#include <linux/sched/debug.h>
17#include <linux/sched/task.h>
18#include <linux/sched/task_stack.h>
19#include <linux/kernel.h>
20#include <linux/mm.h>
21#include <linux/smp.h>
22#include <linux/stddef.h>
23#include <linux/unistd.h>
24#include <linux/ptrace.h>
25#include <linux/user.h>
26#include <linux/time.h>
27#include <linux/major.h>
28#include <linux/stat.h>
29#include <linux/vt.h>
30#include <linux/mman.h>
31#include <linux/elfcore.h>
32#include <linux/reboot.h>
33#include <linux/tty.h>
34#include <linux/console.h>
35#include <linux/slab.h>
36#include <linux/rcupdate.h>
37
38#include <asm/reg.h>
39#include <linux/uaccess.h>
40#include <asm/io.h>
41#include <asm/hwrpb.h>
42#include <asm/fpu.h>
43
44#include "proto.h"
45#include "pci_impl.h"
46
47/*
48 * Power off function, if any
49 */
50void (*pm_power_off)(void) = machine_power_off;
51EXPORT_SYMBOL(pm_power_off);
52
53#ifdef CONFIG_ALPHA_WTINT
54/*
55 * Sleep the CPU.
56 * EV6, LCA45 and QEMU know how to power down, skipping N timer interrupts.
57 */
58void arch_cpu_idle(void)
59{
60	wtint(0);
61}
62
63void __noreturn arch_cpu_idle_dead(void)
64{
65	wtint(INT_MAX);
66	BUG();
67}
68#endif /* ALPHA_WTINT */
69
70struct halt_info {
71	int mode;
72	char *restart_cmd;
73};
74
75static void
76common_shutdown_1(void *generic_ptr)
77{
78	struct halt_info *how = generic_ptr;
79	struct percpu_struct *cpup;
80	unsigned long *pflags, flags;
81	int cpuid = smp_processor_id();
82
83	/* No point in taking interrupts anymore. */
84	local_irq_disable();
85
86	cpup = (struct percpu_struct *)
87			((unsigned long)hwrpb + hwrpb->processor_offset
88			 + hwrpb->processor_size * cpuid);
89	pflags = &cpup->flags;
90	flags = *pflags;
91
92	/* Clear reason to "default"; clear "bootstrap in progress". */
93	flags &= ~0x00ff0001UL;
94
95#ifdef CONFIG_SMP
96	/* Secondaries halt here. */
97	if (cpuid != boot_cpuid) {
98		flags |= 0x00040000UL; /* "remain halted" */
99		*pflags = flags;
100		set_cpu_present(cpuid, false);
101		set_cpu_possible(cpuid, false);
102		halt();
103	}
104#endif
105
106	if (how->mode == LINUX_REBOOT_CMD_RESTART) {
107		if (!how->restart_cmd) {
108			flags |= 0x00020000UL; /* "cold bootstrap" */
109		} else {
110			/* For SRM, we could probably set environment
111			   variables to get this to work.  We'd have to
112			   delay this until after srm_paging_stop unless
113			   we ever got srm_fixup working.
114
115			   At the moment, SRM will use the last boot device,
116			   but the file and flags will be the defaults, when
117			   doing a "warm" bootstrap.  */
118			flags |= 0x00030000UL; /* "warm bootstrap" */
119		}
120	} else {
121		flags |= 0x00040000UL; /* "remain halted" */
122	}
123	*pflags = flags;
124
125#ifdef CONFIG_SMP
126	/* Wait for the secondaries to halt. */
127	set_cpu_present(boot_cpuid, false);
128	set_cpu_possible(boot_cpuid, false);
129	while (!cpumask_empty(cpu_present_mask))
130		barrier();
131#endif
132
133	/* If booted from SRM, reset some of the original environment. */
134	if (alpha_using_srm) {
135#ifdef CONFIG_DUMMY_CONSOLE
136		/* If we've gotten here after SysRq-b, leave interrupt
137		   context before taking over the console. */
138		if (in_hardirq())
139			irq_exit();
140		/* This has the effect of resetting the VGA video origin.  */
141		console_lock();
142		do_take_over_console(&dummy_con, 0, MAX_NR_CONSOLES-1, 1);
143		console_unlock();
144#endif
145		pci_restore_srm_config();
146		set_hae(srm_hae);
147	}
148
149	if (alpha_mv.kill_arch)
150		alpha_mv.kill_arch(how->mode);
151
152	if (! alpha_using_srm && how->mode != LINUX_REBOOT_CMD_RESTART) {
153		/* Unfortunately, since MILO doesn't currently understand
154		   the hwrpb bits above, we can't reliably halt the
155		   processor and keep it halted.  So just loop.  */
156		return;
157	}
158
159	if (alpha_using_srm)
160		srm_paging_stop();
161
162	halt();
163}
164
165static void
166common_shutdown(int mode, char *restart_cmd)
167{
168	struct halt_info args;
169	args.mode = mode;
170	args.restart_cmd = restart_cmd;
171	on_each_cpu(common_shutdown_1, &args, 0);
172}
173
174void
175machine_restart(char *restart_cmd)
176{
177	common_shutdown(LINUX_REBOOT_CMD_RESTART, restart_cmd);
178}
179
180
181void
182machine_halt(void)
183{
184	common_shutdown(LINUX_REBOOT_CMD_HALT, NULL);
185}
186
187
188void
189machine_power_off(void)
190{
191	common_shutdown(LINUX_REBOOT_CMD_POWER_OFF, NULL);
192}
193
194
195/* Used by sysrq-p, among others.  I don't believe r9-r15 are ever
196   saved in the context it's used.  */
197
198void
199show_regs(struct pt_regs *regs)
200{
201	show_regs_print_info(KERN_DEFAULT);
202	dik_show_regs(regs, NULL);
203}
204
205/*
206 * Re-start a thread when doing execve()
207 */
208void
209start_thread(struct pt_regs * regs, unsigned long pc, unsigned long sp)
210{
211	regs->pc = pc;
212	regs->ps = 8;
213	wrusp(sp);
214}
215EXPORT_SYMBOL(start_thread);
216
217void
218flush_thread(void)
219{
220	/* Arrange for each exec'ed process to start off with a clean slate
221	   with respect to the FPU.  This is all exceptions disabled.  */
222	current_thread_info()->ieee_state = 0;
223	wrfpcr(FPCR_DYN_NORMAL | ieee_swcr_to_fpcr(0));
224
225	/* Clean slate for TLS.  */
226	current_thread_info()->pcb.unique = 0;
227}
228
229/*
230 * Copy architecture-specific thread state
231 */
232int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
233{
234	unsigned long clone_flags = args->flags;
235	unsigned long usp = args->stack;
236	unsigned long tls = args->tls;
237	extern void ret_from_fork(void);
238	extern void ret_from_kernel_thread(void);
239
240	struct thread_info *childti = task_thread_info(p);
241	struct pt_regs *childregs = task_pt_regs(p);
242	struct pt_regs *regs = current_pt_regs();
243	struct switch_stack *childstack, *stack;
244
245	childstack = ((struct switch_stack *) childregs) - 1;
246	childti->pcb.ksp = (unsigned long) childstack;
247	childti->pcb.flags = 1;	/* set FEN, clear everything else */
248	childti->status |= TS_SAVED_FP | TS_RESTORE_FP;
249
250	if (unlikely(args->fn)) {
251		/* kernel thread */
252		memset(childstack, 0,
253			sizeof(struct switch_stack) + sizeof(struct pt_regs));
254		childstack->r26 = (unsigned long) ret_from_kernel_thread;
255		childstack->r9 = (unsigned long) args->fn;
256		childstack->r10 = (unsigned long) args->fn_arg;
257		childregs->hae = alpha_mv.hae_cache;
258		memset(childti->fp, '\0', sizeof(childti->fp));
259		childti->pcb.usp = 0;
260		return 0;
261	}
262	/* Note: if CLONE_SETTLS is not set, then we must inherit the
263	   value from the parent, which will have been set by the block
264	   copy in dup_task_struct.  This is non-intuitive, but is
265	   required for proper operation in the case of a threaded
266	   application calling fork.  */
267	if (clone_flags & CLONE_SETTLS)
268		childti->pcb.unique = tls;
269	else
270		regs->r20 = 0;	/* OSF/1 has some strange fork() semantics.  */
271	childti->pcb.usp = usp ?: rdusp();
272	*childregs = *regs;
273	childregs->r0 = 0;
274	childregs->r19 = 0;
275	childregs->r20 = 1;	/* OSF/1 has some strange fork() semantics.  */
276	stack = ((struct switch_stack *) regs) - 1;
277	*childstack = *stack;
278	childstack->r26 = (unsigned long) ret_from_fork;
279	return 0;
280}
281
282/*
283 * Fill in the user structure for a ELF core dump.
284 */
285void
286dump_elf_thread(elf_greg_t *dest, struct pt_regs *pt, struct thread_info *ti)
287{
288	/* switch stack follows right below pt_regs: */
289	struct switch_stack * sw = ((struct switch_stack *) pt) - 1;
290
291	dest[ 0] = pt->r0;
292	dest[ 1] = pt->r1;
293	dest[ 2] = pt->r2;
294	dest[ 3] = pt->r3;
295	dest[ 4] = pt->r4;
296	dest[ 5] = pt->r5;
297	dest[ 6] = pt->r6;
298	dest[ 7] = pt->r7;
299	dest[ 8] = pt->r8;
300	dest[ 9] = sw->r9;
301	dest[10] = sw->r10;
302	dest[11] = sw->r11;
303	dest[12] = sw->r12;
304	dest[13] = sw->r13;
305	dest[14] = sw->r14;
306	dest[15] = sw->r15;
307	dest[16] = pt->r16;
308	dest[17] = pt->r17;
309	dest[18] = pt->r18;
310	dest[19] = pt->r19;
311	dest[20] = pt->r20;
312	dest[21] = pt->r21;
313	dest[22] = pt->r22;
314	dest[23] = pt->r23;
315	dest[24] = pt->r24;
316	dest[25] = pt->r25;
317	dest[26] = pt->r26;
318	dest[27] = pt->r27;
319	dest[28] = pt->r28;
320	dest[29] = pt->gp;
321	dest[30] = ti == current_thread_info() ? rdusp() : ti->pcb.usp;
322	dest[31] = pt->pc;
323
324	/* Once upon a time this was the PS value.  Which is stupid
325	   since that is always 8 for usermode.  Usurped for the more
326	   useful value of the thread's UNIQUE field.  */
327	dest[32] = ti->pcb.unique;
328}
329EXPORT_SYMBOL(dump_elf_thread);
330
331int
332dump_elf_task(elf_greg_t *dest, struct task_struct *task)
333{
334	dump_elf_thread(dest, task_pt_regs(task), task_thread_info(task));
335	return 1;
336}
337EXPORT_SYMBOL(dump_elf_task);
338
339int elf_core_copy_task_fpregs(struct task_struct *t, elf_fpregset_t *fpu)
340{
341	memcpy(fpu, task_thread_info(t)->fp, 32 * 8);
342	return 1;
343}
344
345/*
346 * Return saved PC of a blocked thread.  This assumes the frame
347 * pointer is the 6th saved long on the kernel stack and that the
348 * saved return address is the first long in the frame.  This all
349 * holds provided the thread blocked through a call to schedule() ($15
350 * is the frame pointer in schedule() and $15 is saved at offset 48 by
351 * entry.S:do_switch_stack).
352 *
353 * Under heavy swap load I've seen this lose in an ugly way.  So do
354 * some extra sanity checking on the ranges we expect these pointers
355 * to be in so that we can fail gracefully.  This is just for ps after
356 * all.  -- r~
357 */
358
359static unsigned long
360thread_saved_pc(struct task_struct *t)
361{
362	unsigned long base = (unsigned long)task_stack_page(t);
363	unsigned long fp, sp = task_thread_info(t)->pcb.ksp;
364
365	if (sp > base && sp+6*8 < base + 16*1024) {
366		fp = ((unsigned long*)sp)[6];
367		if (fp > sp && fp < base + 16*1024)
368			return *(unsigned long *)fp;
369	}
370
371	return 0;
372}
373
374unsigned long
375__get_wchan(struct task_struct *p)
376{
377	unsigned long schedule_frame;
378	unsigned long pc;
379
380	/*
381	 * This one depends on the frame size of schedule().  Do a
382	 * "disass schedule" in gdb to find the frame size.  Also, the
383	 * code assumes that sleep_on() follows immediately after
384	 * interruptible_sleep_on() and that add_timer() follows
385	 * immediately after interruptible_sleep().  Ugly, isn't it?
386	 * Maybe adding a wchan field to task_struct would be better,
387	 * after all...
388	 */
389
390	pc = thread_saved_pc(p);
391	if (in_sched_functions(pc)) {
392		schedule_frame = ((unsigned long *)task_thread_info(p)->pcb.ksp)[6];
393		return ((unsigned long *)schedule_frame)[12];
394	}
395	return pc;
396}
397