/*
 * ptrace.c
 * By Ross Biro 1/23/92
 * edited by Linus Torvalds
 *
 * This file is subject to the terms and conditions of the GNU General Public
 * License.  See the file README.legal in the main directory of this archive
 * for more details.
 */

#include <linux/head.h>
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/mm.h>
#include <linux/errno.h>
#include <linux/ptrace.h>
#include <linux/user.h>

#include <asm/segment.h>
#include <asm/system.h>
#include <linux/debugreg.h>

/*
 * does not yet catch signals sent when the child dies.
 * in exit.c or in signal.c.
 */

/* change a pid into a task struct. */
static inline struct task_struct * get_task(int pid)
{
	int i;

	for (i = 1; i < NR_TASKS; i++) {
		if (task[i] != NULL && (task[i]->pid == pid))
			return task[i];
	}
	return NULL;
}

/*
 * this routine will get a word off of the processes priviledged stack.
 * the offset is how far from the base addr as stored in the TSS.
 * this routine assumes that all the priviledged stacks are in our
 * data space.
 */
int ptrace_get_stack_long(struct task_struct *task, int offset)
{
	unsigned char *stack;

	stack = (unsigned char *)task->tss.esp0;
	stack += offset;
	return (*((int *)stack));
}

/*
 * this routine will put a word on the processes priviledged stack.
 * the offset is how far from the base addr as stored in the TSS.
 * this routine assumes that all the priviledged stacks are in our
 * data space.
 */
int ptrace_put_stack_long(struct task_struct *task, int offset,
			  unsigned long data)
{
	unsigned char * stack;
	
	stack = (unsigned char *) task->tss.esp0;
	stack += offset;
	*(unsigned long *) stack = data;
	return 0;
}

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

	if (request == PTRACE_TRACEME) {
		/* are we already being traced? */
		if (current->flags & PF_PTRACED)
			return -EPERM;
		/* set the ptrace bit in the proccess flags. */
		current->flags |= PF_PTRACED;
		return 0;
	}
	if (pid == 1)           /* you may not mess with init */
		return -EPERM;
	if (!(child = get_task(pid)))
		return -ESRCH;
	if (request == PTRACE_ATTACH) {
		if (child == current)
			return -EPERM;
		if ((!child->dumpable || (current->uid != child->euid) ||
		    (current->gid != child->egid)) && !suser())
			return -EPERM;
		/* the same process cannot be attached many times */
		if (child->flags & PF_PTRACED)
			return -EPERM;
		child->flags |= PF_PTRACED;
		if (child->p_pptr != current) {
			REMOVE_LINKS(child);
			child->p_pptr = current;
			SET_LINKS(child);
		}
		send_sig(SIGSTOP, child, 1);
		return 0;
	}
	if (!(child->flags & PF_PTRACED))
		return -ESRCH;
	if (child->state != TASK_STOPPED) {
		if (request != PTRACE_KILL && request != PTRACE_DETACH)
			return -ESRCH;
	}
	if (child->p_pptr != current)
		return -ESRCH;

	switch (request) {
	/* when I and D space are seperate, these will need to be fixed. */
		case PTRACE_PEEKTEXT: /* read word at location addr. */
		case PTRACE_PEEKDATA: {
			unsigned long tmp;
			int res;

			res = ptrace_read_long(child, addr, &tmp);
			if (res < 0)
				return res;
			res = verify_area(VERIFY_WRITE, (void *) data, sizeof(long));
			if (!res)
				put_fs_long(tmp,(unsigned long *) data);
			return res;
		}

	/* read the word at location addr in the USER area. */
		case PTRACE_PEEKUSR:
			return ptrace_peekusr (child, addr, data);

      /* when I and D space are seperate, this will have to be fixed. */
		case PTRACE_POKETEXT: /* write the word at location addr. */
		case PTRACE_POKEDATA:
			return ptrace_write_long(child,addr,data);

		case PTRACE_POKEUSR: /* write the word at location addr in the USER area */
			return ptrace_pokeusr (child, addr, data);

		case PTRACE_SYSCALL: /* continue and stop at next (return from) syscall */
		case PTRACE_CONT: { /* restart after signal. */
			if ((unsigned long) data > NSIG)
				return -EIO;
			if (request == PTRACE_SYSCALL)
				child->flags |= PF_TRACESYS;
			else
				child->flags &= ~PF_TRACESYS;
			child->exit_code = data;
			child->state = TASK_RUNNING;
	/* make sure the single step bit is not set. */
			ptrace_clrsingle(child);
			return 0;
		}

/*
 * make the child exit.  Best I can do is send it a sigkill.
 * perhaps it should be put in the status that it want's to
 * exit.
 */
		case PTRACE_KILL: {
			child->state = TASK_RUNNING;
			child->exit_code = SIGKILL;
	/* make sure the single step bit is not set. */
			ptrace_clrsingle (child);
			return 0;
		}

		case PTRACE_SINGLESTEP: {  /* set the trap flag. */
			if ((unsigned long) data > NSIG)
				return -EIO;
			child->flags &= ~PF_TRACESYS;
			ptrace_setsingle (child);
			child->state = TASK_RUNNING;
			child->exit_code = data;
	/* give it a chance to run. */
			return 0;
		}

		case PTRACE_DETACH: { /* detach a process that was attached. */
			if ((unsigned long) data > NSIG)
				return -EIO;
			child->flags &= ~(PF_PTRACED|PF_TRACESYS);
			child->state = TASK_RUNNING;
			child->exit_code = data;
			REMOVE_LINKS(child);
			child->p_pptr = child->p_opptr;
			SET_LINKS(child);
			/* make sure the single step bit is not set. */
			ptrace_clrsingle(child);
			return 0;
		}

		default:
			return -EIO;
	}
	return -EIO;
}


asmlinkage void syscall_trace(void)
{
	if ((current->flags & (PF_PTRACED|PF_TRACESYS))
			!= (PF_PTRACED|PF_TRACESYS))
		return;
	current->exit_code = SIGTRAP;
	current->state = TASK_STOPPED;
	notify_parent(current);
	schedule();
	/*
	 * 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)
		current->signal |= (1 << (current->exit_code - 1));
	current->exit_code = 0;
	return;
}