arch/mn10300/kernel/process.c

   1 /* MN10300  Process handling code
   2  *
   3  * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
   4  * Written by David Howells (dhowells@redhat.com)
   5  *
   6  * This program is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU General Public Licence
   8  * as published by the Free Software Foundation; either version
   9  * 2 of the Licence, or (at your option) any later version.
  10  */
  11 #include <linux/module.h>
  12 #include <linux/errno.h>
  13 #include <linux/sched.h>
  14 #include <linux/kernel.h>
  15 #include <linux/mm.h>
  16 #include <linux/smp.h>
  17 #include <linux/stddef.h>
  18 #include <linux/unistd.h>
  19 #include <linux/ptrace.h>
  20 #include <linux/user.h>
  21 #include <linux/interrupt.h>
  22 #include <linux/delay.h>
  23 #include <linux/reboot.h>
  24 #include <linux/percpu.h>
  25 #include <linux/err.h>
  26 #include <linux/fs.h>
  27 #include <linux/slab.h>
  28 #include <linux/rcupdate.h>
  29 #include <asm/uaccess.h>
  30 #include <asm/pgtable.h>
  31 #include <asm/io.h>
  32 #include <asm/processor.h>
  33 #include <asm/mmu_context.h>
  34 #include <asm/fpu.h>
  35 #include <asm/reset-regs.h>
  36 #include <asm/gdb-stub.h>
  37 #include "internal.h"
  38
  39 /*
  40  * return saved PC of a blocked thread.
  41  */
  42 unsigned long thread_saved_pc(struct task_struct *tsk)
  43 {
  44         return ((unsigned long *) tsk->thread.sp)[3];
  45 }
  46
  47 /*
  48  * power off function, if any
  49  */
  50 void (*pm_power_off)(void);
  51 EXPORT_SYMBOL(pm_power_off);
  52
  53 #if !defined(CONFIG_SMP) || defined(CONFIG_HOTPLUG_CPU)
  54 /*
  55  * we use this if we don't have any better idle routine
  56  */
  57 static void default_idle(void)
  58 {
  59         local_irq_disable();
  60         if (!need_resched())
  61                 safe_halt();
  62         else
  63                 local_irq_enable();
  64 }
  65
  66 #else /* !CONFIG_SMP || CONFIG_HOTPLUG_CPU  */
  67 /*
  68  * On SMP it's slightly faster (but much more power-consuming!)
  69  * to poll the ->work.need_resched flag instead of waiting for the
  70  * cross-CPU IPI to arrive. Use this option with caution.
  71  */
  72 static inline void poll_idle(void)
  73 {
  74         int oldval;
  75
  76         local_irq_enable();
  77
  78         /*
  79          * Deal with another CPU just having chosen a thread to
  80          * run here:
  81          */
  82         oldval = test_and_clear_thread_flag(TIF_NEED_RESCHED);
  83
  84         if (!oldval) {
  85                 set_thread_flag(TIF_POLLING_NRFLAG);
  86                 while (!need_resched())
  87                         cpu_relax();
  88                 clear_thread_flag(TIF_POLLING_NRFLAG);
  89         } else {
  90                 set_need_resched();
  91         }
  92 }
  93 #endif /* !CONFIG_SMP || CONFIG_HOTPLUG_CPU */
  94
  95 /*
  96  * the idle thread
  97  * - there's no useful work to be done, so just try to conserve power and have
  98  *   a low exit latency (ie sit in a loop waiting for somebody to say that
  99  *   they'd like to reschedule)
 100  */
 101 void cpu_idle(void)
 102 {
 103         /* endless idle loop with no priority at all */
 104         for (;;) {
 105                 rcu_idle_enter();
 106                 while (!need_resched()) {
 107                         void (*idle)(void);
 108
 109                         smp_rmb();
 110                         if (!idle) {
 111 #if defined(CONFIG_SMP) && !defined(CONFIG_HOTPLUG_CPU)
 112                                 idle = poll_idle;
 113 #else  /* CONFIG_SMP && !CONFIG_HOTPLUG_CPU */
 114                                 idle = default_idle;
 115 #endif /* CONFIG_SMP && !CONFIG_HOTPLUG_CPU */
 116                         }
 117                         idle();
 118                 }
 119                 rcu_idle_exit();
 120
 121                 schedule_preempt_disabled();
 122         }
 123 }
 124
 125 void release_segments(struct mm_struct *mm)
 126 {
 127 }
 128
 129 void machine_restart(char *cmd)
 130 {
 131 #ifdef CONFIG_KERNEL_DEBUGGER
 132         gdbstub_exit(0);
 133 #endif
 134
 135 #ifdef mn10300_unit_hard_reset
 136         mn10300_unit_hard_reset();
 137 #else
 138         mn10300_proc_hard_reset();
 139 #endif
 140 }
 141
 142 void machine_halt(void)
 143 {
 144 #ifdef CONFIG_KERNEL_DEBUGGER
 145         gdbstub_exit(0);
 146 #endif
 147 }
 148
 149 void machine_power_off(void)
 150 {
 151 #ifdef CONFIG_KERNEL_DEBUGGER
 152         gdbstub_exit(0);
 153 #endif
 154 }
 155
 156 void show_regs(struct pt_regs *regs)
 157 {
 158 }
 159
 160 /*
 161  * free current thread data structures etc..
 162  */
 163 void exit_thread(void)
 164 {
 165         exit_fpu();
 166 }
 167
 168 void flush_thread(void)
 169 {
 170         flush_fpu();
 171 }
 172
 173 void release_thread(struct task_struct *dead_task)
 174 {
 175 }
 176
 177 /*
 178  * we do not have to muck with descriptors here, that is
 179  * done in switch_mm() as needed.
 180  */
 181 void copy_segments(struct task_struct *p, struct mm_struct *new_mm)
 182 {
 183 }
 184
 185 /*
 186  * this gets called so that we can store lazy state into memory and copy the
 187  * current task into the new thread.
 188  */
 189 int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src)
 190 {
 191         unlazy_fpu(src);
 192         *dst = *src;
 193         return 0;
 194 }
 195
 196 /*
 197  * set up the kernel stack for a new thread and copy arch-specific thread
 198  * control information
 199  */
 200 int copy_thread(unsigned long clone_flags,
 201                 unsigned long c_usp, unsigned long ustk_size,
 202                 struct task_struct *p)
 203 {
 204         struct thread_info *ti = task_thread_info(p);
 205         struct pt_regs *c_regs;
 206         unsigned long c_ksp;
 207
 208         c_ksp = (unsigned long) task_stack_page(p) + THREAD_SIZE;
 209
 210         /* allocate the userspace exception frame and set it up */
 211         c_ksp -= sizeof(struct pt_regs);
 212         c_regs = (struct pt_regs *) c_ksp;
 213         c_ksp -= 12; /* allocate function call ABI slack */
 214
 215         /* set up things up so the scheduler can start the new task */
 216         p->thread.uregs = c_regs;
 217         ti->frame       = c_regs;
 218         p->thread.a3    = (unsigned long) c_regs;
 219         p->thread.sp    = c_ksp;
 220         p->thread.wchan = p->thread.pc;
 221         p->thread.usp   = c_usp;
 222
 223         if (unlikely(p->flags & PF_KTHREAD)) {
 224                 memset(c_regs, 0, sizeof(struct pt_regs));
 225                 c_regs->a0 = c_usp; /* function */
 226                 c_regs->d0 = ustk_size; /* argument */
 227                 local_save_flags(c_regs->epsw);
 228                 c_regs->epsw |= EPSW_IE | EPSW_IM_7;
 229                 p->thread.pc    = (unsigned long) ret_from_kernel_thread;
 230                 return 0;
 231         }
 232         *c_regs = *current_pt_regs();
 233         if (c_usp)
 234                 c_regs->sp = c_usp;
 235         c_regs->epsw &= ~EPSW_FE; /* my FPU */
 236
 237         /* the new TLS pointer is passed in as arg #5 to sys_clone() */
 238         if (clone_flags & CLONE_SETTLS)
 239                 c_regs->e2 = current_frame()->d3;
 240
 241         p->thread.pc    = (unsigned long) ret_from_fork;
 242
 243         return 0;
 244 }
 245
 246 unsigned long get_wchan(struct task_struct *p)
 247 {
 248         return p->thread.wchan;
 249 }