arch/alpha/kernel/process.c

   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 }