xref: /openbmc/linux/arch/alpha/kernel/process.c (revision 071c44e4)
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  */
50 void (*pm_power_off)(void) = machine_power_off;
51 EXPORT_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  */
arch_cpu_idle(void)58 void arch_cpu_idle(void)
59 {
60 	wtint(0);
61 }
62 
arch_cpu_idle_dead(void)63 void __noreturn arch_cpu_idle_dead(void)
64 {
65 	wtint(INT_MAX);
66 	BUG();
67 }
68 #endif /* ALPHA_WTINT */
69 
70 struct halt_info {
71 	int mode;
72 	char *restart_cmd;
73 };
74 
75 static void
common_shutdown_1(void * generic_ptr)76 common_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 
165 static void
common_shutdown(int mode,char * restart_cmd)166 common_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 
174 void
machine_restart(char * restart_cmd)175 machine_restart(char *restart_cmd)
176 {
177 	common_shutdown(LINUX_REBOOT_CMD_RESTART, restart_cmd);
178 }
179 
180 
181 void
machine_halt(void)182 machine_halt(void)
183 {
184 	common_shutdown(LINUX_REBOOT_CMD_HALT, NULL);
185 }
186 
187 
188 void
machine_power_off(void)189 machine_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 
198 void
show_regs(struct pt_regs * regs)199 show_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  */
208 void
start_thread(struct pt_regs * regs,unsigned long pc,unsigned long sp)209 start_thread(struct pt_regs * regs, unsigned long pc, unsigned long sp)
210 {
211 	regs->pc = pc;
212 	regs->ps = 8;
213 	wrusp(sp);
214 }
215 EXPORT_SYMBOL(start_thread);
216 
217 void
flush_thread(void)218 flush_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  */
copy_thread(struct task_struct * p,const struct kernel_clone_args * args)232 int 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  */
285 void
dump_elf_thread(elf_greg_t * dest,struct pt_regs * pt,struct thread_info * ti)286 dump_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 }
329 EXPORT_SYMBOL(dump_elf_thread);
330 
331 int
dump_elf_task(elf_greg_t * dest,struct task_struct * task)332 dump_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 }
337 EXPORT_SYMBOL(dump_elf_task);
338 
elf_core_copy_task_fpregs(struct task_struct * t,elf_fpregset_t * fpu)339 int 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 
359 static unsigned long
thread_saved_pc(struct task_struct * t)360 thread_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 
374 unsigned long
__get_wchan(struct task_struct * p)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