/* ptrace.c */
/* By Ross Biro 1/23/92 */
/* edited by Linus Torvalds */

#include <linux/head.h>
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/mm.h>
#include <errno.h>
#include <asm/segment.h>
#include <asm/system.h>
#include <sys/ptrace.h>

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

/* determines which flags the user has access to. */
/* 1 = access 0 = no access */
#define FLAG_MASK 0x00000dd9

/* set's the trap flag. */
#define TRAP_FLAG 0x100

/*
 * this is the number to subtract from the top of the stack. To find
 * the local frame.
 */
#define MAGICNUMBER 68

void do_no_page(unsigned long, unsigned long, struct task_struct *, unsigned long);
void write_verify(unsigned long);

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

	for (i = 0; i < NR_TASKS; i++) {
		if (task[i] != NULL && (task[i]->pid == pid))
			return i;
	}
	return -1;
}

/*
 * 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.
 */   
static inline int 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.
 */
static inline int 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;
}

/*
 * This routine gets a long from any process space by following the page
 * tables. NOTE! You should check that the long isn't on a page boundary,
 * and that it is in the task area before calling this: this routine does
 * no checking.
 *
 * NOTE2! This uses "tsk->tss.cr3" even though we know it's currently always
 * zero. This routine shouldn't have to change when we make a better mm.
 */
static unsigned long get_long(struct task_struct * tsk,
	unsigned long addr)
{
	unsigned long page;

	addr += tsk->start_code;
repeat:
	page = tsk->tss.cr3 + ((addr >> 20) & 0xffc);
	page = *(unsigned long *) page;
	if (page & PAGE_PRESENT) {
		page &= 0xfffff000;
		page += (addr >> 10) & 0xffc;
		page = *((unsigned long *) page);
	}
	if (!(page & PAGE_PRESENT)) {
		do_no_page(0,addr,tsk,0);
		goto repeat;
	}
	page &= 0xfffff000;
	page += addr & 0xfff;
	return *(unsigned long *) page;
}

/*
 * This routine puts a long into any process space by following the page
 * tables. NOTE! You should check that the long isn't on a page boundary,
 * and that it is in the task area before calling this: this routine does
 * no checking.
 */
static void put_long(struct task_struct * tsk, unsigned long addr,
	unsigned long data)
{
	unsigned long page;

	addr += tsk->start_code;
repeat:
	page = tsk->tss.cr3 + ((addr >> 20) & 0xffc);
	page = *(unsigned long *) page;
	if (page & PAGE_PRESENT) {
		page &= 0xfffff000;
		page += (addr >> 10) & 0xffc;
		page = *((unsigned long *) page);
	}
	if (!(page & PAGE_PRESENT)) {
		do_no_page(0,addr,tsk,0);
		goto repeat;
	}
	if (!(page & PAGE_RW)) {
		write_verify(addr);
		goto repeat;
	}
	page &= 0xfffff000;
	page += addr & 0xfff;
	*(unsigned long *) page = data;
}

/*
 * This routine checks the page boundaries, and that the offset is
 * within the task area. It then calls get_long() to read a long.
 */
static int read_long(struct task_struct * tsk, unsigned long addr,
	unsigned long * result)
{
	unsigned long low,high;

	if (addr > TASK_SIZE-4)
		return -EIO;
	if ((addr & 0xfff) > PAGE_SIZE-4) {
		low = get_long(tsk,addr & 0xfffffffc);
		high = get_long(tsk,(addr+4) & 0xfffffffc);
		switch (addr & 3) {
			case 1:
				low >>= 8;
				low |= high << 24;
				break;
			case 2:
				low >>= 16;
				low |= high << 16;
				break;
			case 3:
				low >>= 24;
				low |= high << 8;
				break;
		}
		*result = low;
	} else
		*result = get_long(tsk,addr);
	return 0;
}

/*
 * This routine checks the page boundaries, and that the offset is
 * within the task area. It then calls put_long() to write a long.
 */
static int write_long(struct task_struct * tsk, unsigned long addr,
	unsigned long data)
{
	unsigned long low,high;

	if (addr > TASK_SIZE-4)
		return -EIO;
	if ((addr & 0xfff) > PAGE_SIZE-4) {
		low = get_long(tsk,addr & 0xfffffffc);
		high = get_long(tsk,(addr+4) & 0xfffffffc);
		switch (addr & 3) {
			case 0: /* shouldn't happen, but safety first */
				low = data;
				break;
			case 1:
				low &= 0x000000ff;
				low |= data << 8;
				high &= 0xffffff00;
				high |= data >> 24;
				break;
			case 2:
				low &= 0x0000ffff;
				low |= data << 16;
				high &= 0xffff0000;
				high |= data >> 16;
				break;
			case 3:
				low &= 0x00ffffff;
				low |= data << 24;
				high &= 0xff000000;
				high |= data >> 8;
				break;
		}
		put_long(tsk,addr & 0xfffffffc,low);
		put_long(tsk,(addr+4) & 0xfffffffc,high);
	} else
		put_long(tsk,addr,data);
	return 0;
}

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

	if (request == 0) {
		/* set the ptrace bit in the proccess flags. */
		current->flags |= PF_PTRACED;
		return 0;
	}

	childno = get_task(pid);

	if (childno < 0)
		return -ESRCH;
	else
		child = task[childno];

	if (child->p_pptr != current || !(child->flags & PF_PTRACED) ||
	    child->state != TASK_STOPPED)
		return -ESRCH;

	switch (request) {
	/* when I and D space are seperate, these will need to be fixed. */
		case 1: /* read word at location addr. */ 
		case 2: {
			int tmp,res;

			res = read_long(task[childno], addr, &tmp);
			if (res < 0)
				return res;
			verify_area((void *) data, 4);
			put_fs_long(tmp,(unsigned long *) data);
			return 0;
		}

	/* read the word at location addr in the USER area. */
		case 3: {
			int tmp;
			addr = addr >> 2; /* temporary hack. */
			if (addr < 0 || addr >= 17)
				return -EIO;
			verify_area((void *) data, 4);
			tmp = get_stack_long(child, 4*addr - MAGICNUMBER);
			put_fs_long(tmp,(unsigned long *) data);
			return 0;
		}

      /* when I and D space are seperate, this will have to be fixed. */
		case 4: /* write the word at location addr. */
		case 5:
			return write_long(task[childno],addr,data);

		case 6: /* write the word at location addr in the USER area */
			addr = addr >> 2; /* temproary hack. */
			if (addr < 0 || addr >= 17)
				return -EIO;
			if (addr == ORIG_EAX)
				return -EIO;
			if (addr == EFL) {   /* flags. */
				data &= FLAG_MASK;
				data |= get_stack_long(child, EFL*4-MAGICNUMBER)  & ~FLAG_MASK;
			}
			if (put_stack_long(child, 4*addr-MAGICNUMBER, data))
				return -EIO;
			return 0;

		case 7: { /* restart after signal. */
			long tmp;

			child->signal=0;
			if (data > 0 && data <= NSIG)
				child->signal = 1<<(data-1);
			child->state = 0;
	/* make sure the single step bit is not set. */
			tmp = get_stack_long(child, 4*EFL-MAGICNUMBER) & ~TRAP_FLAG;
			put_stack_long(child, 4*EFL-MAGICNUMBER,tmp);
			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 8: {
			long tmp;

			child->state = 0;
			child->signal = 1 << (SIGKILL-1);
	/* make sure the single step bit is not set. */
			tmp = get_stack_long(child, 4*EFL-MAGICNUMBER) & ~TRAP_FLAG;
			put_stack_long(child, 4*EFL-MAGICNUMBER,tmp);
			return 0;
		}

		case 9: {  /* set the trap flag. */
			long tmp;

			tmp = get_stack_long(child, 4*EFL-MAGICNUMBER) | TRAP_FLAG;
			put_stack_long(child, 4*EFL-MAGICNUMBER,tmp);
			child->state = 0;
			child->signal = 0;
			if (data > 0 && data <NSIG)
				child->signal= 1<<(data-1);
	/* give it a chance to run. */
			return 0;
		}

		default:
			return -EIO;
	}
}