/*
 * 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/module.h>
#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 <linux/security.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);
}
 
static inline int pending_resume_signal(struct sigpending *pending)
{
#define M(sig) (1UL << ((sig)-1))
        return sigtestsetmask(&pending->signal, M(SIGCONT) | M(SIGKILL));
}

/*
 * Turn a tracing stop into a normal stop now, since with no tracer there
 * would be no way to wake it up with SIGCONT or SIGKILL.  If there was a
 * signal sent that would resume the child, but didn't because it was in
 * TASK_TRACED, resume it now.
 */
void ptrace_untrace(task_t *child)
{
        spin_lock(&child->sighand->siglock);
        if (child->state == TASK_TRACED) {
                if (pending_resume_signal(&child->pending) ||
                    pending_resume_signal(&child->signal->shared_pending)) {
                        signal_wake_up(child, 1);
                } else {
                        child->state = TASK_STOPPED;
                }
        }
        spin_unlock(&child->sighand->siglock);
}

/*
 * 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)) {
                list_del_init(&child->ptrace_list);
                REMOVE_LINKS(child);
                child->parent = child->real_parent;
                SET_LINKS(child);
        }

        if (child->state == TASK_TRACED)
                ptrace_untrace(child);
}

/*
 * Check that we have indeed attached to the thing..
 */
int ptrace_check_attach(struct task_struct *child, int kill)
{
        int ret = -ESRCH;

        /*
         * We take the read lock around doing both checks to close a
         * possible race where someone else was tracing our child and
         * detached between these two checks.  After this locked check,
         * we are sure that this is our traced child and that can only
         * be changed by us so it's not changing right after this.
         */
        read_lock(&tasklist_lock);
        if ((child->ptrace & PT_PTRACED) && child->parent == current &&
            (!(child->ptrace & PT_ATTACHED) || child->real_parent != current)
            && child->signal != NULL) {
                ret = 0;
                spin_lock_irq(&child->sighand->siglock);
                if (child->state == TASK_STOPPED) {
                        child->state = TASK_TRACED;
                } else if (child->state != TASK_TRACED && !kill) {
                        ret = -ESRCH;
                }
                spin_unlock_irq(&child->sighand->siglock);
        }
        read_unlock(&tasklist_lock);

        if (!ret && !kill) {
                wait_task_inactive(child);
        }

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

int ptrace_attach(struct task_struct *task)
{
        int retval;

        retval = -EPERM;
        if (task->pid <= 1)
                goto out;
        if (task == current)
                goto out;

repeat:
        /*
         * Nasty, nasty.
         *
         * We want to hold both the task-lock and the
         * tasklist_lock for writing at the same time.
         * But that's against the rules (tasklist_lock
         * is taken for reading by interrupts on other
         * cpu's that may have task_lock).
         */
        task_lock(task);
        local_irq_disable();
        if (!write_trylock(&tasklist_lock)) {
                local_irq_enable();
                task_unlock(task);
                do {
                        cpu_relax();
                } while (rwlock_is_locked(&tasklist_lock));
                goto repeat;
        }

        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_ptrace(current, task);
        if (retval)
                goto bad;

        /* Go */
        task->ptrace |= PT_PTRACED | ((task->real_parent != current)
                                      ? PT_ATTACHED : 0);
        if (capable(CAP_SYS_PTRACE))
                task->ptrace |= PT_PTRACE_CAP;

        __ptrace_link(task, current);

        force_sig_specific(SIGSTOP, task);

bad:
        write_unlock_irq(&tasklist_lock);
        task_unlock(task);
out:
        return retval;
}

void __ptrace_detach(struct task_struct *child, unsigned int data)
{
        /* .. re-parent .. */
        child->exit_code = data;
        __ptrace_unlink(child);
        /* .. and wake it up. */
        if (child->exit_state != EXIT_ZOMBIE)
                wake_up_process(child);
}

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

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

        write_lock_irq(&tasklist_lock);
        /* protect against de_thread()->release_task() */
        if (child->ptrace)
                __ptrace_detach(child, data);
        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(tsk, 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;

                maddr = kmap(page);
                if (write) {
                        copy_to_user_page(vma, page, addr,
                                          maddr + offset, buf, bytes);
                        if (!PageCompound(page))
                                set_page_dirty_lock(page);
                } else {
                        copy_from_user_page(vma, page, addr,
                                            buf, maddr + offset, bytes);
                }
                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 __user *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 __user *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;
}

static int ptrace_setoptions(struct task_struct *child, long data)
{
        child->ptrace &= ~PT_TRACE_MASK;

        if (data & PTRACE_O_TRACESYSGOOD)
                child->ptrace |= PT_TRACESYSGOOD;

        if (data & PTRACE_O_TRACEFORK)
                child->ptrace |= PT_TRACE_FORK;

        if (data & PTRACE_O_TRACEVFORK)
                child->ptrace |= PT_TRACE_VFORK;

        if (data & PTRACE_O_TRACECLONE)
                child->ptrace |= PT_TRACE_CLONE;

        if (data & PTRACE_O_TRACEEXEC)
                child->ptrace |= PT_TRACE_EXEC;

        if (data & PTRACE_O_TRACEVFORKDONE)
                child->ptrace |= PT_TRACE_VFORK_DONE;

        if (data & PTRACE_O_TRACEEXIT)
                child->ptrace |= PT_TRACE_EXIT;

        return (data & ~PTRACE_O_MASK) ? -EINVAL : 0;
}

static int ptrace_getsiginfo(struct task_struct *child, siginfo_t __user * data)
{
        siginfo_t lastinfo;
        int error = -ESRCH;

        read_lock(&tasklist_lock);
        if (likely(child->sighand != NULL)) {
                error = -EINVAL;
                spin_lock_irq(&child->sighand->siglock);
                if (likely(child->last_siginfo != NULL)) {
                        lastinfo = *child->last_siginfo;
                        error = 0;
                }
                spin_unlock_irq(&child->sighand->siglock);
        }
        read_unlock(&tasklist_lock);
        if (!error)
                return copy_siginfo_to_user(data, &lastinfo);
        return error;
}

static int ptrace_setsiginfo(struct task_struct *child, siginfo_t __user * data)
{
        siginfo_t newinfo;
        int error = -ESRCH;

        if (copy_from_user(&newinfo, data, sizeof (siginfo_t)))
                return -EFAULT;

        read_lock(&tasklist_lock);
        if (likely(child->sighand != NULL)) {
                error = -EINVAL;
                spin_lock_irq(&child->sighand->siglock);
                if (likely(child->last_siginfo != NULL)) {
                        *child->last_siginfo = newinfo;
                        error = 0;
                }
                spin_unlock_irq(&child->sighand->siglock);
        }
        read_unlock(&tasklist_lock);
        return error;
}

int ptrace_request(struct task_struct *child, long request,
                   long addr, long data)
{
        int ret = -EIO;

        switch (request) {
#ifdef PTRACE_OLDSETOPTIONS
        case PTRACE_OLDSETOPTIONS:
#endif
        case PTRACE_SETOPTIONS:
                ret = ptrace_setoptions(child, data);
                break;
        case PTRACE_GETEVENTMSG:
                ret = put_user(child->ptrace_message, (unsigned long __user *) data);
                break;
        case PTRACE_GETSIGINFO:
                ret = ptrace_getsiginfo(child, (siginfo_t __user *) data);
                break;
        case PTRACE_SETSIGINFO:
                ret = ptrace_setsiginfo(child, (siginfo_t __user *) data);
                break;
        default:
                break;
        }

        return ret;
}