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Linux/arch/alpha/kernel/process.c

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  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/errno.h>
 13 #include <linux/module.h>
 14 #include <linux/sched.h>
 15 #include <linux/sched/debug.h>
 16 #include <linux/sched/task.h>
 17 #include <linux/sched/task_stack.h>
 18 #include <linux/kernel.h>
 19 #include <linux/mm.h>
 20 #include <linux/smp.h>
 21 #include <linux/stddef.h>
 22 #include <linux/unistd.h>
 23 #include <linux/ptrace.h>
 24 #include <linux/user.h>
 25 #include <linux/time.h>
 26 #include <linux/major.h>
 27 #include <linux/stat.h>
 28 #include <linux/vt.h>
 29 #include <linux/mman.h>
 30 #include <linux/elfcore.h>
 31 #include <linux/reboot.h>
 32 #include <linux/tty.h>
 33 #include <linux/console.h>
 34 #include <linux/slab.h>
 35 #include <linux/rcupdate.h>
 36 
 37 #include <asm/reg.h>
 38 #include <linux/uaccess.h>
 39 #include <asm/io.h>
 40 #include <asm/pgtable.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  */
 58 void arch_cpu_idle(void)
 59 {
 60         wtint(0);
 61         local_irq_enable();
 62 }
 63 
 64 void arch_cpu_idle_dead(void)
 65 {
 66         wtint(INT_MAX);
 67 }
 68 #endif /* ALPHA_WTINT */
 69 
 70 struct halt_info {
 71         int mode;
 72         char *restart_cmd;
 73 };
 74 
 75 static void
 76 common_shutdown_1(void *generic_ptr)
 77 {
 78         struct halt_info *how = (struct halt_info *)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_weight(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_interrupt())
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
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
175 machine_restart(char *restart_cmd)
176 {
177         common_shutdown(LINUX_REBOOT_CMD_RESTART, restart_cmd);
178 }
179 
180 
181 void
182 machine_halt(void)
183 {
184         common_shutdown(LINUX_REBOOT_CMD_HALT, NULL);
185 }
186 
187 
188 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
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
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
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 void
230 release_thread(struct task_struct *dead_task)
231 {
232 }
233 
234 /*
235  * Copy architecture-specific thread state
236  */
237 int
238 copy_thread(unsigned long clone_flags, unsigned long usp,
239             unsigned long kthread_arg,
240             struct task_struct *p)
241 {
242         extern void ret_from_fork(void);
243         extern void ret_from_kernel_thread(void);
244 
245         struct thread_info *childti = task_thread_info(p);
246         struct pt_regs *childregs = task_pt_regs(p);
247         struct pt_regs *regs = current_pt_regs();
248         struct switch_stack *childstack, *stack;
249 
250         childstack = ((struct switch_stack *) childregs) - 1;
251         childti->pcb.ksp = (unsigned long) childstack;
252         childti->pcb.flags = 1; /* set FEN, clear everything else */
253 
254         if (unlikely(p->flags & PF_KTHREAD)) {
255                 /* kernel thread */
256                 memset(childstack, 0,
257                         sizeof(struct switch_stack) + sizeof(struct pt_regs));
258                 childstack->r26 = (unsigned long) ret_from_kernel_thread;
259                 childstack->r9 = usp;   /* function */
260                 childstack->r10 = kthread_arg;
261                 childregs->hae = alpha_mv.hae_cache,
262                 childti->pcb.usp = 0;
263                 return 0;
264         }
265         /* Note: if CLONE_SETTLS is not set, then we must inherit the
266            value from the parent, which will have been set by the block
267            copy in dup_task_struct.  This is non-intuitive, but is
268            required for proper operation in the case of a threaded
269            application calling fork.  */
270         if (clone_flags & CLONE_SETTLS)
271                 childti->pcb.unique = regs->r20;
272         else
273                 regs->r20 = 0;  /* OSF/1 has some strange fork() semantics.  */
274         childti->pcb.usp = usp ?: rdusp();
275         *childregs = *regs;
276         childregs->r0 = 0;
277         childregs->r19 = 0;
278         childregs->r20 = 1;     /* OSF/1 has some strange fork() semantics.  */
279         stack = ((struct switch_stack *) regs) - 1;
280         *childstack = *stack;
281         childstack->r26 = (unsigned long) ret_from_fork;
282         return 0;
283 }
284 
285 /*
286  * Fill in the user structure for a ELF core dump.
287  */
288 void
289 dump_elf_thread(elf_greg_t *dest, struct pt_regs *pt, struct thread_info *ti)
290 {
291         /* switch stack follows right below pt_regs: */
292         struct switch_stack * sw = ((struct switch_stack *) pt) - 1;
293 
294         dest[ 0] = pt->r0;
295         dest[ 1] = pt->r1;
296         dest[ 2] = pt->r2;
297         dest[ 3] = pt->r3;
298         dest[ 4] = pt->r4;
299         dest[ 5] = pt->r5;
300         dest[ 6] = pt->r6;
301         dest[ 7] = pt->r7;
302         dest[ 8] = pt->r8;
303         dest[ 9] = sw->r9;
304         dest[10] = sw->r10;
305         dest[11] = sw->r11;
306         dest[12] = sw->r12;
307         dest[13] = sw->r13;
308         dest[14] = sw->r14;
309         dest[15] = sw->r15;
310         dest[16] = pt->r16;
311         dest[17] = pt->r17;
312         dest[18] = pt->r18;
313         dest[19] = pt->r19;
314         dest[20] = pt->r20;
315         dest[21] = pt->r21;
316         dest[22] = pt->r22;
317         dest[23] = pt->r23;
318         dest[24] = pt->r24;
319         dest[25] = pt->r25;
320         dest[26] = pt->r26;
321         dest[27] = pt->r27;
322         dest[28] = pt->r28;
323         dest[29] = pt->gp;
324         dest[30] = ti == current_thread_info() ? rdusp() : ti->pcb.usp;
325         dest[31] = pt->pc;
326 
327         /* Once upon a time this was the PS value.  Which is stupid
328            since that is always 8 for usermode.  Usurped for the more
329            useful value of the thread's UNIQUE field.  */
330         dest[32] = ti->pcb.unique;
331 }
332 EXPORT_SYMBOL(dump_elf_thread);
333 
334 int
335 dump_elf_task(elf_greg_t *dest, struct task_struct *task)
336 {
337         dump_elf_thread(dest, task_pt_regs(task), task_thread_info(task));
338         return 1;
339 }
340 EXPORT_SYMBOL(dump_elf_task);
341 
342 int
343 dump_elf_task_fp(elf_fpreg_t *dest, struct task_struct *task)
344 {
345         struct switch_stack *sw = (struct switch_stack *)task_pt_regs(task) - 1;
346         memcpy(dest, sw->fp, 32 * 8);
347         return 1;
348 }
349 EXPORT_SYMBOL(dump_elf_task_fp);
350 
351 /*
352  * Return saved PC of a blocked thread.  This assumes the frame
353  * pointer is the 6th saved long on the kernel stack and that the
354  * saved return address is the first long in the frame.  This all
355  * holds provided the thread blocked through a call to schedule() ($15
356  * is the frame pointer in schedule() and $15 is saved at offset 48 by
357  * entry.S:do_switch_stack).
358  *
359  * Under heavy swap load I've seen this lose in an ugly way.  So do
360  * some extra sanity checking on the ranges we expect these pointers
361  * to be in so that we can fail gracefully.  This is just for ps after
362  * all.  -- r~
363  */
364 
365 static unsigned long
366 thread_saved_pc(struct task_struct *t)
367 {
368         unsigned long base = (unsigned long)task_stack_page(t);
369         unsigned long fp, sp = task_thread_info(t)->pcb.ksp;
370 
371         if (sp > base && sp+6*8 < base + 16*1024) {
372                 fp = ((unsigned long*)sp)[6];
373                 if (fp > sp && fp < base + 16*1024)
374                         return *(unsigned long *)fp;
375         }
376 
377         return 0;
378 }
379 
380 unsigned long
381 get_wchan(struct task_struct *p)
382 {
383         unsigned long schedule_frame;
384         unsigned long pc;
385         if (!p || p == current || p->state == TASK_RUNNING)
386                 return 0;
387         /*
388          * This one depends on the frame size of schedule().  Do a
389          * "disass schedule" in gdb to find the frame size.  Also, the
390          * code assumes that sleep_on() follows immediately after
391          * interruptible_sleep_on() and that add_timer() follows
392          * immediately after interruptible_sleep().  Ugly, isn't it?
393          * Maybe adding a wchan field to task_struct would be better,
394          * after all...
395          */
396 
397         pc = thread_saved_pc(p);
398         if (in_sched_functions(pc)) {
399                 schedule_frame = ((unsigned long *)task_thread_info(p)->pcb.ksp)[6];
400                 return ((unsigned long *)schedule_frame)[12];
401         }
402         return pc;
403 }
404 

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