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process.c

/*
 *  linux/arch/arm26/kernel/process.c
 *
 *  Copyright (C) 2003 Ian Molton - adapted for ARM26
 *  Copyright (C) 1996-2000 Russell King - Converted to ARM.
 *  Origional Copyright (C) 1995  Linus Torvalds
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */
#include <stdarg.h>

#include <linux/module.h>
#include <linux/sched.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/stddef.h>
#include <linux/unistd.h>
#include <linux/ptrace.h>
#include <linux/slab.h>
#include <linux/user.h>
#include <linux/a.out.h>
#include <linux/delay.h>
#include <linux/reboot.h>
#include <linux/interrupt.h>
#include <linux/init.h>

#include <asm/system.h>
#include <asm/io.h>
#include <asm/leds.h>
#include <asm/processor.h>
#include <asm/uaccess.h>

extern const char *processor_modes[];
extern void setup_mm_for_reboot(char mode);

static volatile int hlt_counter;

void disable_hlt(void)
{
      hlt_counter++;
}

EXPORT_SYMBOL(disable_hlt);

void enable_hlt(void)
{
      hlt_counter--;
}

EXPORT_SYMBOL(enable_hlt);

static int __init nohlt_setup(char *__unused)
{
      hlt_counter = 1;
      return 1;
}

static int __init hlt_setup(char *__unused)
{
      hlt_counter = 0;
      return 1;
}

__setup("nohlt", nohlt_setup);
__setup("hlt", hlt_setup);

/*
 * This is our default idle handler.  We need to disable
 * interrupts here to ensure we don't miss a wakeup call.
 */
void cpu_idle(void)
{
      /* endless idle loop with no priority at all */
      while (1) {
            while (!need_resched())
                  cpu_relax();
            preempt_enable_no_resched();
            schedule();
            preempt_disable();
      }
}

static char reboot_mode = 'h';

int __init reboot_setup(char *str)
{
      reboot_mode = str[0];
      return 1;
}

__setup("reboot=", reboot_setup);

/* ARM26 cant do these but we still need to define them. */
void machine_halt(void)
{
}
void machine_power_off(void)
{
}

void machine_restart(char * __unused)
{
      /*
       * Clean and disable cache, and turn off interrupts
       */
      cpu_proc_fin();

      /*
       * Tell the mm system that we are going to reboot -
       * we may need it to insert some 1:1 mappings so that
       * soft boot works.
       */
      setup_mm_for_reboot(reboot_mode);

      /*
         * copy branch instruction to reset location and call it
         */

        *(unsigned long *)0 = *(unsigned long *)0x03800000;
        ((void(*)(void))0)();

      /*
       * Whoops - the architecture was unable to reboot.
       * Tell the user! Should never happen...
       */
      mdelay(1000);
      printk("Reboot failed -- System halted\n");
      while (1);
}

void show_regs(struct pt_regs * regs)
{
      unsigned long flags;

      flags = condition_codes(regs);

      printk("pc : [<%08lx>]    lr : [<%08lx>]    %s\n"
             "sp : %08lx  ip : %08lx  fp : %08lx\n",
            instruction_pointer(regs),
            regs->ARM_lr, print_tainted(), regs->ARM_sp,
            regs->ARM_ip, regs->ARM_fp);
      printk("r10: %08lx  r9 : %08lx  r8 : %08lx\n",
            regs->ARM_r10, regs->ARM_r9,
            regs->ARM_r8);
      printk("r7 : %08lx  r6 : %08lx  r5 : %08lx  r4 : %08lx\n",
            regs->ARM_r7, regs->ARM_r6,
            regs->ARM_r5, regs->ARM_r4);
      printk("r3 : %08lx  r2 : %08lx  r1 : %08lx  r0 : %08lx\n",
            regs->ARM_r3, regs->ARM_r2,
            regs->ARM_r1, regs->ARM_r0);
      printk("Flags: %c%c%c%c",
            flags & PSR_N_BIT ? 'N' : 'n',
            flags & PSR_Z_BIT ? 'Z' : 'z',
            flags & PSR_C_BIT ? 'C' : 'c',
            flags & PSR_V_BIT ? 'V' : 'v');
      printk("  IRQs o%s  FIQs o%s  Mode %s  Segment %s\n",
            interrupts_enabled(regs) ? "n" : "ff",
            fast_interrupts_enabled(regs) ? "n" : "ff",
            processor_modes[processor_mode(regs)],
            get_fs() == get_ds() ? "kernel" : "user");
}

void show_fpregs(struct user_fp *regs)
{
      int i;

      for (i = 0; i < 8; i++) {
            unsigned long *p;
            char type;

            p = (unsigned long *)(regs->fpregs + i);

            switch (regs->ftype[i]) {
                  case 1: type = 'f'; break;
                  case 2: type = 'd'; break;
                  case 3: type = 'e'; break;
                  default: type = '?'; break;
            }
            if (regs->init_flag)
                  type = '?';

            printk("  f%d(%c): %08lx %08lx %08lx%c",
                  i, type, p[0], p[1], p[2], i & 1 ? '\n' : ' ');
      }
                  

      printk("FPSR: %08lx FPCR: %08lx\n",
            (unsigned long)regs->fpsr,
            (unsigned long)regs->fpcr);
}

/*
 * Task structure and kernel stack allocation.
 */
static unsigned long *thread_info_head;
static unsigned int nr_thread_info;

extern unsigned long get_page_8k(int priority);
extern void free_page_8k(unsigned long page);

// FIXME - is this valid?
#define EXTRA_TASK_STRUCT     0
#define ll_alloc_task_struct()      ((struct thread_info *)get_page_8k(GFP_KERNEL))
#define ll_free_task_struct(p)  free_page_8k((unsigned long)(p))

//FIXME - do we use *task param below looks like we dont, which is ok?
//FIXME - if EXTRA_TASK_STRUCT is zero we can optimise the below away permanently. *IF* its supposed to be zero.
struct thread_info *alloc_thread_info(struct task_struct *task)
{
      struct thread_info *thread = NULL;

      if (EXTRA_TASK_STRUCT) {
            unsigned long *p = thread_info_head;

            if (p) {
                  thread_info_head = (unsigned long *)p[0];
                  nr_thread_info -= 1;
            }
            thread = (struct thread_info *)p;
      }

      if (!thread)
            thread = ll_alloc_task_struct();

#ifdef CONFIG_MAGIC_SYSRQ
      /*
       * The stack must be cleared if you want SYSRQ-T to
       * give sensible stack usage information
       */
      if (thread) {
            char *p = (char *)thread;
            memzero(p+KERNEL_STACK_SIZE, KERNEL_STACK_SIZE);
      }
#endif
      return thread;
}

void free_thread_info(struct thread_info *thread)
{
      if (EXTRA_TASK_STRUCT && nr_thread_info < EXTRA_TASK_STRUCT) {
            unsigned long *p = (unsigned long *)thread;
            p[0] = (unsigned long)thread_info_head;
            thread_info_head = p;
            nr_thread_info += 1;
      } else
            ll_free_task_struct(thread);
}

/*
 * Free current thread data structures etc..
 */
void exit_thread(void)
{
}

void flush_thread(void)
{
      struct thread_info *thread = current_thread_info();
      struct task_struct *tsk = current;

      memset(&tsk->thread.debug, 0, sizeof(struct debug_info));
      memset(&thread->fpstate, 0, sizeof(union fp_state));

      clear_used_math();
}

void release_thread(struct task_struct *dead_task)
{
}

asmlinkage void ret_from_fork(void) __asm__("ret_from_fork");

int
copy_thread(int nr, unsigned long clone_flags, unsigned long stack_start,
          unsigned long unused, struct task_struct *p, struct pt_regs *regs)
{
      struct thread_info *thread = task_thread_info(p);
      struct pt_regs *childregs = task_pt_regs(p);

      *childregs = *regs;
      childregs->ARM_r0 = 0;
      childregs->ARM_sp = stack_start;

      memset(&thread->cpu_context, 0, sizeof(struct cpu_context_save));
      thread->cpu_context.sp = (unsigned long)childregs;
      thread->cpu_context.pc = (unsigned long)ret_from_fork | MODE_SVC26 | PSR_I_BIT;

      return 0;
}

/*
 * fill in the fpe structure for a core dump...
 */
int dump_fpu (struct pt_regs *regs, struct user_fp *fp)
{
      struct thread_info *thread = current_thread_info();
      int used_math = !!used_math();

      if (used_math)
            memcpy(fp, &thread->fpstate.soft, sizeof (*fp));

      return used_math;
}

/*
 * fill in the user structure for a core dump..
 */
void dump_thread(struct pt_regs * regs, struct user * dump)
{
      struct task_struct *tsk = current;

      dump->magic = CMAGIC;
      dump->start_code = tsk->mm->start_code;
      dump->start_stack = regs->ARM_sp & ~(PAGE_SIZE - 1);

      dump->u_tsize = (tsk->mm->end_code - tsk->mm->start_code) >> PAGE_SHIFT;
      dump->u_dsize = (tsk->mm->brk - tsk->mm->start_data + PAGE_SIZE - 1) >> PAGE_SHIFT;
      dump->u_ssize = 0;

      dump->u_debugreg[0] = tsk->thread.debug.bp[0].address;
      dump->u_debugreg[1] = tsk->thread.debug.bp[1].address;
      dump->u_debugreg[2] = tsk->thread.debug.bp[0].insn;
      dump->u_debugreg[3] = tsk->thread.debug.bp[1].insn;
      dump->u_debugreg[4] = tsk->thread.debug.nsaved;

      if (dump->start_stack < 0x04000000)
            dump->u_ssize = (0x04000000 - dump->start_stack) >> PAGE_SHIFT;

      dump->regs = *regs;
      dump->u_fpvalid = dump_fpu (regs, &dump->u_fp);
}

/*
 * Shuffle the argument into the correct register before calling the
 * thread function.  r1 is the thread argument, r2 is the pointer to
 * the thread function, and r3 points to the exit function.
 * FIXME - make sure this is right - the older code used to zero fp
 * and cause the parent to call sys_exit (do_exit in this version)
 */
extern void kernel_thread_helper(void);

asm(    ".section .text\n"
"       .align\n"
"       .type   kernel_thread_helper, #function\n"
"kernel_thread_helper:\n"
"       mov     r0, r1\n"
"       mov     lr, r3\n"
"       mov     pc, r2\n"
"       .size   kernel_thread_helper, . - kernel_thread_helper\n"
"       .previous");

/*
 * Create a kernel thread.
 */
pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags)
{
        struct pt_regs regs;

        memset(&regs, 0, sizeof(regs));

        regs.ARM_r1 = (unsigned long)arg;
        regs.ARM_r2 = (unsigned long)fn;
        regs.ARM_r3 = (unsigned long)do_exit;
        regs.ARM_pc = (unsigned long)kernel_thread_helper | MODE_SVC26;

        return do_fork(flags|CLONE_VM|CLONE_UNTRACED, 0, &regs, 0, NULL, NULL);
}
EXPORT_SYMBOL(kernel_thread);


unsigned long get_wchan(struct task_struct *p)
{
      unsigned long fp, lr;
      unsigned long stack_page;
      int count = 0;
      if (!p || p == current || p->state == TASK_RUNNING)
            return 0;

      stack_page = 4096 + (unsigned long)p;
      fp = thread_saved_fp(p);
      do {
            if (fp < stack_page || fp > 4092+stack_page)
                  return 0;
            lr = pc_pointer (((unsigned long *)fp)[-1]);
            if (!in_sched_functions(lr))
                  return lr;
            fp = *(unsigned long *) (fp - 12);
      } while (count ++ < 16);
      return 0;
}

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