/*
 * linux/kernel/ptrace.c
 *
 * (C) Copyright 1999 Linus Torvalds
 *
 * Common interfaces for "ptrace()" which we do not want
 * to continually duplicate across every architecture.
 */

#include <linux/sched.h>
#include <linux/errno.h>
#include <linux/mm.h>
#include <linux/highmem.h>
#include <linux/pagemap.h>
#include <linux/smp_lock.h>
#include <linux/ptrace.h>

#include <asm/pgtable.h>
#include <asm/uaccess.h>

/*
 * ptrace a task: make the debugger its new parent and
 * move it to the ptrace list.
 *
 * Must be called with the tasklist lock write-held.
 */
void __ptrace_link(task_t *child, task_t *new_parent)
{
        if (!list_empty(&child->ptrace_list))
                BUG();
        if (child->parent == new_parent)
                return;
        list_add(&child->ptrace_list, &child->parent->ptrace_children);
        REMOVE_LINKS(child);
        child->parent = new_parent;
        SET_LINKS(child);
}
 
/*
 * unptrace a task: move it back to its original parent and
 * remove it from the ptrace list.
 *
 * Must be called with the tasklist lock write-held.
 */
void __ptrace_unlink(task_t *child)
{
        if (!child->ptrace)
                BUG();
        child->ptrace = 0;
        if (list_empty(&child->ptrace_list))
                return;
        list_del_init(&child->ptrace_list);
        REMOVE_LINKS(child);
        child->parent = child->real_parent;
        SET_LINKS(child);
}

/*
 * Check that we have indeed attached to the thing..
 */
int ptrace_check_attach(struct task_struct *child, int kill)
{
        if (!(child->ptrace & PT_PTRACED))
                return -ESRCH;

        if (child->parent != current)
                return -ESRCH;

        if (!kill) {
                if (child->state != TASK_STOPPED)
                        return -ESRCH;
                wait_task_inactive(child);
        }

        /* All systems go.. */
        return 0;
}

int ptrace_attach(struct task_struct *task)
{
        int retval;
        task_lock(task);
        retval = -EPERM;
        if (task->pid <= 1)
                goto bad;
        if (task == current)
                goto bad;
        if (!task->mm)
                goto bad;
        if(((current->uid != task->euid) ||
            (current->uid != task->suid) ||
            (current->uid != task->uid) ||
            (current->gid != task->egid) ||
            (current->gid != task->sgid) ||
            (current->gid != task->gid)) && !capable(CAP_SYS_PTRACE))
                goto bad;
        rmb();
        if (!task->mm->dumpable && !capable(CAP_SYS_PTRACE))
                goto bad;
        /* the same process cannot be attached many times */
        if (task->ptrace & PT_PTRACED)
                goto bad;
        retval = security_ops->ptrace(current, task);
        if (retval)
                goto bad;

        /* Go */
        task->ptrace |= PT_PTRACED;
        if (capable(CAP_SYS_PTRACE))
                task->ptrace |= PT_PTRACE_CAP;
        task_unlock(task);

        write_lock_irq(&tasklist_lock);
        __ptrace_link(task, current);
        write_unlock_irq(&tasklist_lock);

        send_sig(SIGSTOP, task, 1);
        return 0;

bad:
        task_unlock(task);
        return retval;
}

int ptrace_detach(struct task_struct *child, unsigned int data)
{
        if ((unsigned long) data > _NSIG)
                return  -EIO;

        /* Architecture-specific hardware disable .. */
        ptrace_disable(child);

        /* .. re-parent .. */
        child->exit_code = data;

        write_lock_irq(&tasklist_lock);
        __ptrace_unlink(child);
        /* .. and wake it up. */
        if (child->state != TASK_ZOMBIE)
                wake_up_process(child);
        write_unlock_irq(&tasklist_lock);

        return 0;
}

/*
 * Access another process' address space.
 * Source/target buffer must be kernel space, 
 * Do not walk the page table directly, use get_user_pages
 */

int access_process_vm(struct task_struct *tsk, unsigned long addr, void *buf, int len, int write)
{
        struct mm_struct *mm;
        struct vm_area_struct *vma;
        struct page *page;
        void *old_buf = buf;

        mm = get_task_mm(tsk);
        if (!mm)
                return 0;

        down_read(&mm->mmap_sem);
        /* ignore errors, just check how much was sucessfully transfered */
        while (len) {
                int bytes, ret, offset;
                void *maddr;

                ret = get_user_pages(current, mm, addr, 1,
                                write, 1, &page, &vma);
                if (ret <= 0)
                        break;

                bytes = len;
                offset = addr & (PAGE_SIZE-1);
                if (bytes > PAGE_SIZE-offset)
                        bytes = PAGE_SIZE-offset;

                flush_cache_page(vma, addr);

                maddr = kmap(page);
                if (write) {
                        memcpy(maddr + offset, buf, bytes);
                        flush_page_to_ram(page);
                        flush_icache_user_range(vma, page, addr, bytes);
                } else {
                        memcpy(buf, maddr + offset, bytes);
                        flush_page_to_ram(page);
                }
                kunmap(page);
                page_cache_release(page);
                len -= bytes;
                buf += bytes;
                addr += bytes;
        }
        up_read(&mm->mmap_sem);
        mmput(mm);
        
        return buf - old_buf;
}

int ptrace_readdata(struct task_struct *tsk, unsigned long src, char *dst, int len)
{
        int copied = 0;

        while (len > 0) {
                char buf[128];
                int this_len, retval;

                this_len = (len > sizeof(buf)) ? sizeof(buf) : len;
                retval = access_process_vm(tsk, src, buf, this_len, 0);
                if (!retval) {
                        if (copied)
                                break;
                        return -EIO;
                }
                if (copy_to_user(dst, buf, retval))
                        return -EFAULT;
                copied += retval;
                src += retval;
                dst += retval;
                len -= retval;                  
        }
        return copied;
}

int ptrace_writedata(struct task_struct *tsk, char * src, unsigned long dst, int len)
{
        int copied = 0;

        while (len > 0) {
                char buf[128];
                int this_len, retval;

                this_len = (len > sizeof(buf)) ? sizeof(buf) : len;
                if (copy_from_user(buf, src, this_len))
                        return -EFAULT;
                retval = access_process_vm(tsk, dst, buf, this_len, 1);
                if (!retval) {
                        if (copied)
                                break;
                        return -EIO;
                }
                copied += retval;
                src += retval;
                dst += retval;
                len -= retval;                  
        }
        return copied;
}