/*
 * arch/v850/kernel/ptrace.c -- `ptrace' system call
 *
 *  Copyright (C) 2002,03,04  NEC Electronics Corporation
 *  Copyright (C) 2002,03,04  Miles Bader <miles@gnu.org>
 *
 * Derived from arch/mips/kernel/ptrace.c:
 *
 *  Copyright (C) 1992 Ross Biro
 *  Copyright (C) Linus Torvalds
 *  Copyright (C) 1994, 95, 96, 97, 98, 2000 Ralf Baechle
 *  Copyright (C) 1996 David S. Miller
 *  Kevin D. Kissell, kevink@mips.com and Carsten Langgaard, carstenl@mips.com
 *  Copyright (C) 1999 MIPS Technologies, Inc.
 *
 * This file is subject to the terms and conditions of the GNU General
 * Public License.  See the file COPYING in the main directory of this
 * archive for more details.
 */

#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/sched.h>
#include <linux/smp_lock.h>
#include <linux/ptrace.h>
#include <linux/signal.h>

#include <asm/errno.h>
#include <asm/ptrace.h>
#include <asm/processor.h>
#include <asm/uaccess.h>

/* Returns the address where the register at REG_OFFS in P is stashed away.  */
static v850_reg_t *reg_save_addr (unsigned reg_offs, struct task_struct *t)
{
	struct pt_regs *regs;

	/* Three basic cases:

	   (1) A register normally saved before calling the scheduler, is
	       available in the kernel entry pt_regs structure at the top
	       of the kernel stack.  The kernel trap/irq exit path takes
	       care to save/restore almost all registers for ptrace'd
	       processes.

	   (2) A call-clobbered register, where the process P entered the
	       kernel via [syscall] trap, is not stored anywhere; that's
	       OK, because such registers are not expected to be preserved
	       when the trap returns anyway (so we don't actually bother to
	       test for this case).

	   (3) A few registers not used at all by the kernel, and so
	       normally never saved except by context-switches, are in the
	       context switch state.  */

	if (reg_offs == PT_CTPC || reg_offs == PT_CTPSW || reg_offs == PT_CTBP)
		/* Register saved during context switch.  */
		regs = thread_saved_regs (t);
	else
		/* Register saved during kernel entry (or not available).  */
		regs = task_regs (t);

	return (v850_reg_t *)((char *)regs + reg_offs);
}

/* Set the bits SET and clear the bits CLEAR in the v850e DIR
   (`debug information register').  Returns the new value of DIR.  */
static inline v850_reg_t set_dir (v850_reg_t set, v850_reg_t clear)
{
	register v850_reg_t rval asm ("r10");
	register v850_reg_t arg0 asm ("r6") = set;
	register v850_reg_t arg1 asm ("r7") = clear;

	/* The dbtrap handler has exactly this functionality when called
	   from kernel mode.  0xf840 is a `dbtrap' insn.  */
	asm (".short 0xf840" : "=r" (rval) : "r" (arg0), "r" (arg1));

	return rval;
}

/* Makes sure hardware single-stepping is (globally) enabled.
   Returns true if successful.  */
static inline int enable_single_stepping (void)
{
	static int enabled = 0;	/* Remember whether we already did it.  */
	if (! enabled) {
		/* Turn on the SE (`single-step enable') bit, 0x100, in the
		   DIR (`debug information register').  This may fail if a
		   processor doesn't support it or something.  We also try
		   to clear bit 0x40 (`INI'), which is necessary to use the
		   debug stuff on the v850e2; on the v850e, clearing 0x40
		   shouldn't cause any problem.  */
		v850_reg_t dir = set_dir (0x100, 0x40);
		/* Make sure it really got set.  */
		if (dir & 0x100)
			enabled = 1;
	}
	return enabled;
}

/* Try to set CHILD's single-step flag to VAL.  Returns true if successful.  */
static int set_single_step (struct task_struct *t, int val)
{
	v850_reg_t *psw_addr = reg_save_addr(PT_PSW, t);
	if (val) {
		/* Make sure single-stepping is enabled.  */
		if (! enable_single_stepping ())
			return 0;
		/* Set T's single-step flag.  */
		*psw_addr |= 0x800;
	} else
		*psw_addr &= ~0x800;
	return 1;
}

long sys_ptrace(long request, long pid, long addr, long data)
{
	struct task_struct *child;
	int rval;

	lock_kernel();

	if (request == PTRACE_TRACEME) {
		/* are we already being traced? */
		if (current->ptrace & PT_PTRACED) {
			rval = -EPERM;
			goto out;
		}
		/* set the ptrace bit in the process flags. */
		current->ptrace |= PT_PTRACED;
		rval = 0;
		goto out;
	}
	rval = -ESRCH;
	read_lock(&tasklist_lock);
	child = find_task_by_pid(pid);
	if (child)
		get_task_struct(child);
	read_unlock(&tasklist_lock);
	if (!child)
		goto out;

	rval = -EPERM;
	if (pid == 1)		/* you may not mess with init */
		goto out_tsk;

	if (request == PTRACE_ATTACH) {
		rval = ptrace_attach(child);
		goto out_tsk;
	}
	rval = ptrace_check_attach(child, request == PTRACE_KILL);
	if (rval < 0)
		goto out_tsk;

	switch (request) {
		unsigned long val, copied;

	case PTRACE_PEEKTEXT: /* read word at location addr. */
	case PTRACE_PEEKDATA:
		copied = access_process_vm(child, addr, &val, sizeof(val), 0);
		rval = -EIO;
		if (copied != sizeof(val))
			break;
		rval = put_user(val, (unsigned long *)data);
		goto out;

	case PTRACE_POKETEXT: /* write the word at location addr. */
	case PTRACE_POKEDATA:
		rval = 0;
		if (access_process_vm(child, addr, &data, sizeof(data), 1)
		    == sizeof(data))
			break;
		rval = -EIO;
		goto out;

	/* Read/write the word at location ADDR in the registers.  */
	case PTRACE_PEEKUSR:
	case PTRACE_POKEUSR:
		rval = 0;
		if (addr >= PT_SIZE && request == PTRACE_PEEKUSR) {
			/* Special requests that don't actually correspond
			   to offsets in struct pt_regs.  */
			if (addr == PT_TEXT_ADDR)
				val = child->mm->start_code;
			else if (addr == PT_DATA_ADDR)
				val = child->mm->start_data;
			else if (addr == PT_TEXT_LEN)
				val = child->mm->end_code
					- child->mm->start_code;
			else
				rval = -EIO;
		} else if (addr >= 0 && addr < PT_SIZE && (addr & 0x3) == 0) {
			v850_reg_t *reg_addr = reg_save_addr(addr, child);
			if (request == PTRACE_PEEKUSR)
				val = *reg_addr;
			else
				*reg_addr = data;
		} else
			rval = -EIO;

		if (rval == 0 && request == PTRACE_PEEKUSR)
			rval = put_user (val, (unsigned long *)data);
		goto out;

	/* Continue and stop at next (return from) syscall */
	case PTRACE_SYSCALL:
	/* Restart after a signal.  */
	case PTRACE_CONT:
	/* Execute a single instruction. */
	case PTRACE_SINGLESTEP:
		rval = -EIO;
		if (!valid_signal(data))
			break;

		/* Turn CHILD's single-step flag on or off.  */
		if (! set_single_step (child, request == PTRACE_SINGLESTEP))
			break;

		if (request == PTRACE_SYSCALL)
			set_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
		else
			clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);

		child->exit_code = data;
		wake_up_process(child);
		rval = 0;
		break;

	/*
	 * make the child exit.  Best I can do is send it a sigkill.
	 * perhaps it should be put in the status that it wants to
	 * exit.
	 */
	case PTRACE_KILL:
		rval = 0;
		if (child->exit_state == EXIT_ZOMBIE)	/* already dead */
			break;
		child->exit_code = SIGKILL;
		wake_up_process(child);
		break;

	case PTRACE_DETACH: /* detach a process that was attached. */
		set_single_step (child, 0);  /* Clear single-step flag */
		rval = ptrace_detach(child, data);
		break;

	default:
		rval = -EIO;
		goto out;
	}

out_tsk:
	put_task_struct(child);
out:
	unlock_kernel();
	return rval;
}

asmlinkage void syscall_trace(void)
{
	if (!test_thread_flag(TIF_SYSCALL_TRACE))
		return;
	if (!(current->ptrace & PT_PTRACED))
		return;
	/* The 0x80 provides a way for the tracing parent to distinguish
	   between a syscall stop and SIGTRAP delivery */
	ptrace_notify(SIGTRAP | ((current->ptrace & PT_TRACESYSGOOD)
				 ? 0x80 : 0));
	/*
	 * this isn't the same as continuing with a signal, but it will do
	 * for normal use.  strace only continues with a signal if the
	 * stopping signal is not SIGTRAP.  -brl
	 */
	if (current->exit_code) {
		send_sig(current->exit_code, current, 1);
		current->exit_code = 0;
	}
}

void ptrace_disable (struct task_struct *child)
{
	/* nothing to do */
}