arch/v850/kernel/process.c

   1 /*
   2  * arch/v850/kernel/process.c -- Arch-dependent process handling
   3  *
   4  *  Copyright (C) 2001,02,03  NEC Electronics Corporation
   5  *  Copyright (C) 2001,02,03  Miles Bader <miles@gnu.org>
   6  *
   7  * This file is subject to the terms and conditions of the GNU General
   8  * Public License.  See the file COPYING in the main directory of this
   9  * archive for more details.
  10  *
  11  * Written by Miles Bader <miles@gnu.org>
  12  */
  13
  14 #include <linux/errno.h>
  15 #include <linux/sched.h>
  16 #include <linux/kernel.h>
  17 #include <linux/mm.h>
  18 #include <linux/smp.h>
  19 #include <linux/stddef.h>
  20 #include <linux/unistd.h>
  21 #include <linux/ptrace.h>
  22 #include <linux/slab.h>
  23 #include <linux/user.h>
  24 #include <linux/a.out.h>
  25 #include <linux/reboot.h>
  26
  27 #include <asm/uaccess.h>
  28 #include <asm/system.h>
  29 #include <asm/pgtable.h>
  30
  31 void (*pm_power_off)(void) = NULL;
  32 EXPORT_SYMBOL(pm_power_off);
  33
  34 extern void ret_from_fork (void);
  35
  36
  37 /* The idle loop.  */
  38 static void default_idle (void)
  39 {
  40         while (! need_resched ())
  41                 asm ("halt; nop; nop; nop; nop; nop" ::: "cc");
  42 }
  43
  44 void (*idle)(void) = default_idle;
  45
  46 /*
  47  * The idle thread. There's no useful work to be
  48  * done, so just try to conserve power and have a
  49  * low exit latency (ie sit in a loop waiting for
  50  * somebody to say that they'd like to reschedule)
  51  */
  52 void cpu_idle (void)
  53 {
  54         /* endless idle loop with no priority at all */
  55         while (1) {
  56                 while (!need_resched())
  57                         (*idle) ();
  58
  59                 preempt_enable_no_resched();
  60                 schedule();
  61                 preempt_disable();
  62         }
  63 }
  64
  65 /*
  66  * This is the mechanism for creating a new kernel thread.
  67  *
  68  * NOTE! Only a kernel-only process (ie the swapper or direct descendants who
  69  * haven't done an "execve()") should use this: it will work within a system
  70  * call from a "real" process, but the process memory space will not be free'd
  71  * until both the parent and the child have exited.
  72  */
  73 int kernel_thread (int (*fn)(void *), void *arg, unsigned long flags)
  74 {
  75         register mm_segment_t fs = get_fs ();
  76         register unsigned long syscall asm (SYSCALL_NUM);
  77         register unsigned long arg0 asm (SYSCALL_ARG0);
  78         register unsigned long ret asm (SYSCALL_RET);
  79
  80         set_fs (KERNEL_DS);
  81
  82         /* Clone this thread.  Note that we don't pass the clone syscall's
  83            second argument -- it's ignored for calls from kernel mode (the
  84            child's SP is always set to the top of the kernel stack).  */
  85         arg0 = flags | CLONE_VM;
  86         syscall = __NR_clone;
  87         asm volatile ("trap " SYSCALL_SHORT_TRAP
  88                       : "=r" (ret), "=r" (syscall)
  89                       : "1" (syscall), "r" (arg0)
  90                       : SYSCALL_SHORT_CLOBBERS);
  91
  92         if (ret == 0) {
  93                 /* In child thread, call FN and exit.  */
  94                 arg0 = (*fn) (arg);
  95                 syscall = __NR_exit;
  96                 asm volatile ("trap " SYSCALL_SHORT_TRAP
  97                               : "=r" (ret), "=r" (syscall)
  98                               : "1" (syscall), "r" (arg0)
  99                               : SYSCALL_SHORT_CLOBBERS);
 100         }
 101
 102         /* In parent.  */
 103         set_fs (fs);
 104
 105         return ret;
 106 }
 107
 108 void flush_thread (void)
 109 {
 110         set_fs (USER_DS);
 111 }
 112
 113 int copy_thread (int nr, unsigned long clone_flags,
 114                  unsigned long stack_start, unsigned long stack_size,
 115                  struct task_struct *p, struct pt_regs *regs)
 116 {
 117         /* Start pushing stuff from the top of the child's kernel stack.  */
 118         unsigned long orig_ksp = task_tos(p);
 119         unsigned long ksp = orig_ksp;
 120         /* We push two `state save' stack fames (see entry.S) on the new
 121            kernel stack:
 122              1) The innermost one is what switch_thread would have
 123                 pushed, and is used when we context switch to the child
 124                 thread for the first time.  It's set up to return to
 125                 ret_from_fork in entry.S.
 126              2) The outermost one (nearest the top) is what a syscall
 127                 trap would have pushed, and is set up to return to the
 128                 same location as the parent thread, but with a return
 129                 value of 0. */
 130         struct pt_regs *child_switch_regs, *child_trap_regs;
 131
 132         /* Trap frame.  */
 133         ksp -= STATE_SAVE_SIZE;
 134         child_trap_regs = (struct pt_regs *)(ksp + STATE_SAVE_PT_OFFSET);
 135         /* Switch frame.  */
 136         ksp -= STATE_SAVE_SIZE;
 137         child_switch_regs = (struct pt_regs *)(ksp + STATE_SAVE_PT_OFFSET);
 138
 139         /* First copy parent's register state to child.  */
 140         *child_switch_regs = *regs;
 141         *child_trap_regs = *regs;
 142
 143         /* switch_thread returns to the restored value of the lp
 144            register (r31), so we make that the place where we want to
 145            jump when the child thread begins running.  */
 146         child_switch_regs->gpr[GPR_LP] = (v850_reg_t)ret_from_fork;
 147
 148         if (regs->kernel_mode)
 149                 /* Since we're returning to kernel-mode, make sure the child's
 150                    stored kernel stack pointer agrees with what the actual
 151                    stack pointer will be at that point (the trap return code
 152                    always restores the SP, even when returning to
 153                    kernel-mode).  */
 154                 child_trap_regs->gpr[GPR_SP] = orig_ksp;
 155         else
 156                 /* Set the child's user-mode stack-pointer (the name
 157                    `stack_start' is a misnomer, it's just the initial SP
 158                    value).  */
 159                 child_trap_regs->gpr[GPR_SP] = stack_start;
 160
 161         /* Thread state for the child (everything else is on the stack).  */
 162         p->thread.ksp = ksp;
 163
 164         return 0;
 165 }
 166
 167 /*
 168  * sys_execve() executes a new program.
 169  */
 170 int sys_execve (char *name, char **argv, char **envp, struct pt_regs *regs)
 171 {
 172         char *filename = getname (name);
 173         int error = PTR_ERR (filename);
 174
 175         if (! IS_ERR (filename)) {
 176                 error = do_execve (filename, argv, envp, regs);
 177                 putname (filename);
 178         }
 179
 180         return error;
 181 }
 182
 183
 184 /*
 185  * These bracket the sleeping functions..
 186  */
 187 #define first_sched     ((unsigned long)__sched_text_start)
 188 #define last_sched      ((unsigned long)__sched_text_end)
 189
 190 unsigned long get_wchan (struct task_struct *p)
 191 {
 192 #if 0  /* Barf.  Figure out the stack-layout later.  XXX  */
 193         unsigned long fp, pc;
 194         int count = 0;
 195
 196         if (!p || p == current || p->state == TASK_RUNNING)
 197                 return 0;
 198
 199         pc = thread_saved_pc (p);
 200
 201         /* This quite disgusting function walks up the stack, following
 202            saved return address, until it something that's out of bounds
 203            (as defined by `first_sched' and `last_sched').  It then
 204            returns the last PC that was in-bounds.  */
 205         do {
 206                 if (fp < stack_page + sizeof (struct task_struct) ||
 207                     fp >= 8184+stack_page)
 208                         return 0;
 209                 pc = ((unsigned long *)fp)[1];
 210                 if (pc < first_sched || pc >= last_sched)
 211                         return pc;
 212                 fp = *(unsigned long *) fp;
 213         } while (count++ < 16);
 214 #endif
 215
 216         return 0;
 217 }