ptrace.c

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/*
 * 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/capability.h>
#include <linux/export.h>
#include <linux/sched.h>
#include <linux/errno.h>
#include <linux/mm.h>
#include <linux/highmem.h>
#include <linux/pagemap.h>
#include <linux/ptrace.h>
#include <linux/security.h>
#include <linux/signal.h>
#include <linux/audit.h>
#include <linux/pid_namespace.h>
#include <linux/syscalls.h>
#include <linux/uaccess.h>
#include <linux/regset.h>
#include <linux/hw_breakpoint.h>
#include <linux/cn_proc.h>


static int ptrace_trapping_sleep_fn(void *flags)
{
    schedule();
    return 0;
}

/*
 * 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(struct task_struct *child, struct task_struct *new_parent)
{
    BUG_ON(!list_empty(&child->ptrace_entry));
    list_add(&child->ptrace_entry, &new_parent->ptraced);
    child->parent = new_parent;
}

void __ptrace_unlink(struct task_struct *child)
{
    BUG_ON(!child->ptrace);

    child->ptrace = 0;
    child->parent = child->real_parent;
    list_del_init(&child->ptrace_entry);

    spin_lock(&child->sighand->siglock);

    /*
     * Clear all pending traps and TRAPPING.  TRAPPING should be
     * cleared regardless of JOBCTL_STOP_PENDING.  Do it explicitly.
     */
    task_clear_jobctl_pending(child, JOBCTL_TRAP_MASK);
    task_clear_jobctl_trapping(child);

    /*
     * Reinstate JOBCTL_STOP_PENDING if group stop is in effect and
     * @child isn't dead.
     */
    if (!(child->flags & PF_EXITING) &&
        (child->signal->flags & SIGNAL_STOP_STOPPED ||
         child->signal->group_stop_count)) {
        child->jobctl |= JOBCTL_STOP_PENDING;

        /*
         * This is only possible if this thread was cloned by the
         * traced task running in the stopped group, set the signal
         * for the future reports.
         * FIXME: we should change ptrace_init_task() to handle this
         * case.
         */
        if (!(child->jobctl & JOBCTL_STOP_SIGMASK))
            child->jobctl |= SIGSTOP;
    }

    /*
     * If transition to TASK_STOPPED is pending or in TASK_TRACED, kick
     * @child in the butt.  Note that @resume should be used iff @child
     * is in TASK_TRACED; otherwise, we might unduly disrupt
     * TASK_KILLABLE sleeps.
     */
    if (child->jobctl & JOBCTL_STOP_PENDING || task_is_traced(child))
        signal_wake_up(child, task_is_traced(child));

    spin_unlock(&child->sighand->siglock);
}

int ptrace_check_attach(struct task_struct *child, bool ignore_state)
{
    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->sighand can't be NULL, release_task()
         * does ptrace_unlink() before __exit_signal().
         */
        spin_lock_irq(&child->sighand->siglock);
        WARN_ON_ONCE(task_is_stopped(child));
        if (ignore_state || (task_is_traced(child) &&
                     !(child->jobctl & JOBCTL_LISTENING)))
            ret = 0;
        spin_unlock_irq(&child->sighand->siglock);
    }
    read_unlock(&tasklist_lock);

    if (!ret && !ignore_state)
        ret = wait_task_inactive(child, TASK_TRACED) ? 0 : -ESRCH;

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

static int ptrace_has_cap(struct user_namespace *ns, unsigned int mode)
{
    if (mode & PTRACE_MODE_NOAUDIT)
        return has_ns_capability_noaudit(current, ns, CAP_SYS_PTRACE);
    else
        return has_ns_capability(current, ns, CAP_SYS_PTRACE);
}

/* Returns 0 on success, -errno on denial. */
static int __ptrace_may_access(struct task_struct *task, unsigned int mode)
{
    const struct cred *cred = current_cred(), *tcred;

    /* May we inspect the given task?
     * This check is used both for attaching with ptrace
     * and for allowing access to sensitive information in /proc.
     *
     * ptrace_attach denies several cases that /proc allows
     * because setting up the necessary parent/child relationship
     * or halting the specified task is impossible.
     */
    int dumpable = 0;
    /* Don't let security modules deny introspection */
    if (task == current)
        return 0;
    rcu_read_lock();
    tcred = __task_cred(task);
    if (uid_eq(cred->uid, tcred->euid) &&
        uid_eq(cred->uid, tcred->suid) &&
        uid_eq(cred->uid, tcred->uid)  &&
        gid_eq(cred->gid, tcred->egid) &&
        gid_eq(cred->gid, tcred->sgid) &&
        gid_eq(cred->gid, tcred->gid))
        goto ok;
    if (ptrace_has_cap(tcred->user_ns, mode))
        goto ok;
    rcu_read_unlock();
    return -EPERM;
ok:
    rcu_read_unlock();
    smp_rmb();
    if (task->mm)
        dumpable = get_dumpable(task->mm);
    if (!dumpable  && !ptrace_has_cap(task_user_ns(task), mode))
        return -EPERM;

    return security_ptrace_access_check(task, mode);
}

bool ptrace_may_access(struct task_struct *task, unsigned int mode)
{
    int err;
    task_lock(task);
    err = __ptrace_may_access(task, mode);
    task_unlock(task);
    return !err;
}

static int ptrace_attach(struct task_struct *task, long request,
             unsigned long addr,
             unsigned long flags)
{
    bool seize = (request == PTRACE_SEIZE);
    int retval;

    retval = -EIO;
    if (seize) {
        if (addr != 0)
            goto out;
        if (flags & ~(unsigned long)PTRACE_O_MASK)
            goto out;
        flags = PT_PTRACED | PT_SEIZED | (flags << PT_OPT_FLAG_SHIFT);
    } else {
        flags = PT_PTRACED;
    }

    audit_ptrace(task);

    retval = -EPERM;
    if (unlikely(task->flags & PF_KTHREAD))
        goto out;
    if (same_thread_group(task, current))
        goto out;

    /*
     * Protect exec's credential calculations against our interference;
     * SUID, SGID and LSM creds get determined differently
     * under ptrace.
     */
    retval = -ERESTARTNOINTR;
    if (mutex_lock_interruptible(&task->signal->cred_guard_mutex))
        goto out;

    task_lock(task);
    retval = __ptrace_may_access(task, PTRACE_MODE_ATTACH);
    task_unlock(task);
    if (retval)
        goto unlock_creds;

    write_lock_irq(&tasklist_lock);
    retval = -EPERM;
    if (unlikely(task->exit_state))
        goto unlock_tasklist;
    if (task->ptrace)
        goto unlock_tasklist;

    if (seize)
        flags |= PT_SEIZED;
    if (ns_capable(task_user_ns(task), CAP_SYS_PTRACE))
        flags |= PT_PTRACE_CAP;
    task->ptrace = flags;

    __ptrace_link(task, current);

    /* SEIZE doesn't trap tracee on attach */
    if (!seize)
        send_sig_info(SIGSTOP, SEND_SIG_FORCED, task);

    spin_lock(&task->sighand->siglock);

    /*
     * If the task is already STOPPED, set JOBCTL_TRAP_STOP and
     * TRAPPING, and kick it so that it transits to TRACED.  TRAPPING
     * will be cleared if the child completes the transition or any
     * event which clears the group stop states happens.  We'll wait
     * for the transition to complete before returning from this
     * function.
     *
     * This hides STOPPED -> RUNNING -> TRACED transition from the
     * attaching thread but a different thread in the same group can
     * still observe the transient RUNNING state.  IOW, if another
     * thread's WNOHANG wait(2) on the stopped tracee races against
     * ATTACH, the wait(2) may fail due to the transient RUNNING.
     *
     * The following task_is_stopped() test is safe as both transitions
     * in and out of STOPPED are protected by siglock.
     */
    if (task_is_stopped(task) &&
        task_set_jobctl_pending(task, JOBCTL_TRAP_STOP | JOBCTL_TRAPPING))
        signal_wake_up(task, 1);

    spin_unlock(&task->sighand->siglock);

    retval = 0;
unlock_tasklist:
    write_unlock_irq(&tasklist_lock);
unlock_creds:
    mutex_unlock(&task->signal->cred_guard_mutex);
out:
    if (!retval) {
        wait_on_bit(&task->jobctl, JOBCTL_TRAPPING_BIT,
                ptrace_trapping_sleep_fn, TASK_UNINTERRUPTIBLE);
        proc_ptrace_connector(task, PTRACE_ATTACH);
    }

    return retval;
}

static int ptrace_traceme(void)
{
    int ret = -EPERM;

    write_lock_irq(&tasklist_lock);
    /* Are we already being traced? */
    if (!current->ptrace) {
        ret = security_ptrace_traceme(current->parent);
        /*
         * Check PF_EXITING to ensure ->real_parent has not passed
         * exit_ptrace(). Otherwise we don't report the error but
         * pretend ->real_parent untraces us right after return.
         */
        if (!ret && !(current->real_parent->flags & PF_EXITING)) {
            current->ptrace = PT_PTRACED;
            __ptrace_link(current, current->real_parent);
        }
    }
    write_unlock_irq(&tasklist_lock);

    return ret;
}

/*
 * Called with irqs disabled, returns true if childs should reap themselves.
 */
static int ignoring_children(struct sighand_struct *sigh)
{
    int ret;
    spin_lock(&sigh->siglock);
    ret = (sigh->action[SIGCHLD-1].sa.sa_handler == SIG_IGN) ||
          (sigh->action[SIGCHLD-1].sa.sa_flags & SA_NOCLDWAIT);
    spin_unlock(&sigh->siglock);
    return ret;
}

/*
 * Called with tasklist_lock held for writing.
 * Unlink a traced task, and clean it up if it was a traced zombie.
 * Return true if it needs to be reaped with release_task().
 * (We can't call release_task() here because we already hold tasklist_lock.)
 *
 * If it's a zombie, our attachedness prevented normal parent notification
 * or self-reaping.  Do notification now if it would have happened earlier.
 * If it should reap itself, return true.
 *
 * If it's our own child, there is no notification to do. But if our normal
 * children self-reap, then this child was prevented by ptrace and we must
 * reap it now, in that case we must also wake up sub-threads sleeping in
 * do_wait().
 */
static bool __ptrace_detach(struct task_struct *tracer, struct task_struct *p)
{
    bool dead;

    __ptrace_unlink(p);

    if (p->exit_state != EXIT_ZOMBIE)
        return false;

    dead = !thread_group_leader(p);

    if (!dead && thread_group_empty(p)) {
        if (!same_thread_group(p->real_parent, tracer))
            dead = do_notify_parent(p, p->exit_signal);
        else if (ignoring_children(tracer->sighand)) {
            __wake_up_parent(p, tracer);
            dead = true;
        }
    }
    /* Mark it as in the process of being reaped. */
    if (dead)
        p->exit_state = EXIT_DEAD;
    return dead;
}

static int ptrace_detach(struct task_struct *child, unsigned int data)
{
    bool dead = false;

    if (!valid_signal(data))
        return -EIO;

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

    write_lock_irq(&tasklist_lock);
    /*
     * This child can be already killed. Make sure de_thread() or
     * our sub-thread doing do_wait() didn't do release_task() yet.
     */
    if (child->ptrace) {
        child->exit_code = data;
        dead = __ptrace_detach(current, child);
    }
    write_unlock_irq(&tasklist_lock);

    proc_ptrace_connector(child, PTRACE_DETACH);
    if (unlikely(dead))
        release_task(child);

    return 0;
}

/*
 * Detach all tasks we were using ptrace on. Called with tasklist held
 * for writing, and returns with it held too. But note it can release
 * and reacquire the lock.
 */
void exit_ptrace(struct task_struct *tracer)
    __releases(&tasklist_lock)
    __acquires(&tasklist_lock)
{
    struct task_struct *p, *n;
    LIST_HEAD(ptrace_dead);

    if (likely(list_empty(&tracer->ptraced)))
        return;

    list_for_each_entry_safe(p, n, &tracer->ptraced, ptrace_entry) {
        if (__ptrace_detach(tracer, p))
            list_add(&p->ptrace_entry, &ptrace_dead);
    }

    write_unlock_irq(&tasklist_lock);
    BUG_ON(!list_empty(&tracer->ptraced));

    list_for_each_entry_safe(p, n, &ptrace_dead, ptrace_entry) {
        list_del_init(&p->ptrace_entry);
        release_task(p);
    }

    write_lock_irq(&tasklist_lock);
}

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, unsigned long data)
{
    unsigned flags;

    if (data & ~(unsigned long)PTRACE_O_MASK)
        return -EINVAL;

    /* Avoid intermediate state when all opts are cleared */
    flags = child->ptrace;
    flags &= ~(PTRACE_O_MASK << PT_OPT_FLAG_SHIFT);
    flags |= (data << PT_OPT_FLAG_SHIFT);
    child->ptrace = flags;

    return 0;
}

static int ptrace_getsiginfo(struct task_struct *child, siginfo_t *info)
{
    unsigned long flags;
    int error = -ESRCH;

    if (lock_task_sighand(child, &flags)) {
        error = -EINVAL;
        if (likely(child->last_siginfo != NULL)) {
            *info = *child->last_siginfo;
            error = 0;
        }
        unlock_task_sighand(child, &flags);
    }
    return error;
}

static int ptrace_setsiginfo(struct task_struct *child, const siginfo_t *info)
{
    unsigned long flags;
    int error = -ESRCH;

    if (lock_task_sighand(child, &flags)) {
        error = -EINVAL;
        if (likely(child->last_siginfo != NULL)) {
            *child->last_siginfo = *info;
            error = 0;
        }
        unlock_task_sighand(child, &flags);
    }
    return error;
}


#ifdef PTRACE_SINGLESTEP
#define is_singlestep(request)      ((request) == PTRACE_SINGLESTEP)
#else
#define is_singlestep(request)      0
#endif

#ifdef PTRACE_SINGLEBLOCK
#define is_singleblock(request)     ((request) == PTRACE_SINGLEBLOCK)
#else
#define is_singleblock(request)     0
#endif

#ifdef PTRACE_SYSEMU
#define is_sysemu_singlestep(request)   ((request) == PTRACE_SYSEMU_SINGLESTEP)
#else
#define is_sysemu_singlestep(request)   0
#endif

static int ptrace_resume(struct task_struct *child, long request,
             unsigned long data)
{
    if (!valid_signal(data))
        return -EIO;

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

#ifdef TIF_SYSCALL_EMU
    if (request == PTRACE_SYSEMU || request == PTRACE_SYSEMU_SINGLESTEP)
        set_tsk_thread_flag(child, TIF_SYSCALL_EMU);
    else
        clear_tsk_thread_flag(child, TIF_SYSCALL_EMU);
#endif

    if (is_singleblock(request)) {
        if (unlikely(!arch_has_block_step()))
            return -EIO;
        user_enable_block_step(child);
    } else if (is_singlestep(request) || is_sysemu_singlestep(request)) {
        if (unlikely(!arch_has_single_step()))
            return -EIO;
        user_enable_single_step(child);
    } else {
        user_disable_single_step(child);
    }

    child->exit_code = data;
    wake_up_state(child, __TASK_TRACED);

    return 0;
}

#ifdef CONFIG_HAVE_ARCH_TRACEHOOK

static const struct user_regset *
find_regset(const struct user_regset_view *view, unsigned int type)
{
    const struct user_regset *regset;
    int n;

    for (n = 0; n < view->n; ++n) {
        regset = view->regsets + n;
        if (regset->core_note_type == type)
            return regset;
    }

    return NULL;
}

static int ptrace_regset(struct task_struct *task, int req, unsigned int type,
             struct iovec *kiov)
{
    const struct user_regset_view *view = task_user_regset_view(task);
    const struct user_regset *regset = find_regset(view, type);
    int regset_no;

    if (!regset || (kiov->iov_len % regset->size) != 0)
        return -EINVAL;

    regset_no = regset - view->regsets;
    kiov->iov_len = min(kiov->iov_len,
                (__kernel_size_t) (regset->n * regset->size));

    if (req == PTRACE_GETREGSET)
        return copy_regset_to_user(task, view, regset_no, 0,
                       kiov->iov_len, kiov->iov_base);
    else
        return copy_regset_from_user(task, view, regset_no, 0,
                         kiov->iov_len, kiov->iov_base);
}

#endif

int ptrace_request(struct task_struct *child, long request,
           unsigned long addr, unsigned long data)
{
    bool seized = child->ptrace & PT_SEIZED;
    int ret = -EIO;
    siginfo_t siginfo, *si;
    void __user *datavp = (void __user *) data;
    unsigned long __user *datalp = datavp;
    unsigned long flags;

    switch (request) {
    case PTRACE_PEEKTEXT:
    case PTRACE_PEEKDATA:
        return generic_ptrace_peekdata(child, addr, data);
    case PTRACE_POKETEXT:
    case PTRACE_POKEDATA:
        return generic_ptrace_pokedata(child, addr, data);

#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, datalp);
        break;

    case PTRACE_GETSIGINFO:
        ret = ptrace_getsiginfo(child, &siginfo);
        if (!ret)
            ret = copy_siginfo_to_user(datavp, &siginfo);
        break;

    case PTRACE_SETSIGINFO:
        if (copy_from_user(&siginfo, datavp, sizeof siginfo))
            ret = -EFAULT;
        else
            ret = ptrace_setsiginfo(child, &siginfo);
        break;

    case PTRACE_INTERRUPT:
        /*
         * Stop tracee without any side-effect on signal or job
         * control.  At least one trap is guaranteed to happen
         * after this request.  If @child is already trapped, the
         * current trap is not disturbed and another trap will
         * happen after the current trap is ended with PTRACE_CONT.
         *
         * The actual trap might not be PTRACE_EVENT_STOP trap but
         * the pending condition is cleared regardless.
         */
        if (unlikely(!seized || !lock_task_sighand(child, &flags)))
            break;

        /*
         * INTERRUPT doesn't disturb existing trap sans one
         * exception.  If ptracer issued LISTEN for the current
         * STOP, this INTERRUPT should clear LISTEN and re-trap
         * tracee into STOP.
         */
        if (likely(task_set_jobctl_pending(child, JOBCTL_TRAP_STOP)))
            signal_wake_up(child, child->jobctl & JOBCTL_LISTENING);

        unlock_task_sighand(child, &flags);
        ret = 0;
        break;

    case PTRACE_LISTEN:
        /*
         * Listen for events.  Tracee must be in STOP.  It's not
         * resumed per-se but is not considered to be in TRACED by
         * wait(2) or ptrace(2).  If an async event (e.g. group
         * stop state change) happens, tracee will enter STOP trap
         * again.  Alternatively, ptracer can issue INTERRUPT to
         * finish listening and re-trap tracee into STOP.
         */
        if (unlikely(!seized || !lock_task_sighand(child, &flags)))
            break;

        si = child->last_siginfo;
        if (likely(si && (si->si_code >> 8) == PTRACE_EVENT_STOP)) {
            child->jobctl |= JOBCTL_LISTENING;
            /*
             * If NOTIFY is set, it means event happened between
             * start of this trap and now.  Trigger re-trap.
             */
            if (child->jobctl & JOBCTL_TRAP_NOTIFY)
                signal_wake_up(child, true);
            ret = 0;
        }
        unlock_task_sighand(child, &flags);
        break;

    case PTRACE_DETACH:  /* detach a process that was attached. */
        ret = ptrace_detach(child, data);
        break;

#ifdef CONFIG_BINFMT_ELF_FDPIC
    case PTRACE_GETFDPIC: {
        struct mm_struct *mm = get_task_mm(child);
        unsigned long tmp = 0;

        ret = -ESRCH;
        if (!mm)
            break;

        switch (addr) {
        case PTRACE_GETFDPIC_EXEC:
            tmp = mm->context.exec_fdpic_loadmap;
            break;
        case PTRACE_GETFDPIC_INTERP:
            tmp = mm->context.interp_fdpic_loadmap;
            break;
        default:
            break;
        }
        mmput(mm);

        ret = put_user(tmp, datalp);
        break;
    }
#endif

#ifdef PTRACE_SINGLESTEP
    case PTRACE_SINGLESTEP:
#endif
#ifdef PTRACE_SINGLEBLOCK
    case PTRACE_SINGLEBLOCK:
#endif
#ifdef PTRACE_SYSEMU
    case PTRACE_SYSEMU:
    case PTRACE_SYSEMU_SINGLESTEP:
#endif
    case PTRACE_SYSCALL:
    case PTRACE_CONT:
        return ptrace_resume(child, request, data);

    case PTRACE_KILL:
        if (child->exit_state)  /* already dead */
            return 0;
        return ptrace_resume(child, request, SIGKILL);

#ifdef CONFIG_HAVE_ARCH_TRACEHOOK
    case PTRACE_GETREGSET:
    case PTRACE_SETREGSET:
    {
        struct iovec kiov;
        struct iovec __user *uiov = datavp;

        if (!access_ok(VERIFY_WRITE, uiov, sizeof(*uiov)))
            return -EFAULT;

        if (__get_user(kiov.iov_base, &uiov->iov_base) ||
            __get_user(kiov.iov_len, &uiov->iov_len))
            return -EFAULT;

        ret = ptrace_regset(child, request, addr, &kiov);
        if (!ret)
            ret = __put_user(kiov.iov_len, &uiov->iov_len);
        break;
    }
#endif
    default:
        break;
    }

    return ret;
}

static struct task_struct *ptrace_get_task_struct(pid_t pid)
{
    struct task_struct *child;

    rcu_read_lock();
    child = find_task_by_vpid(pid);
    if (child)
        get_task_struct(child);
    rcu_read_unlock();

    if (!child)
        return ERR_PTR(-ESRCH);
    return child;
}

#ifndef arch_ptrace_attach
#define arch_ptrace_attach(child)   do { } while (0)
#endif

SYSCALL_DEFINE4(ptrace, long, request, long, pid, unsigned long, addr,
        unsigned long, data)
{
    struct task_struct *child;
    long ret;

    if (request == PTRACE_TRACEME) {
        ret = ptrace_traceme();
        if (!ret)
            arch_ptrace_attach(current);
        goto out;
    }

    child = ptrace_get_task_struct(pid);
    if (IS_ERR(child)) {
        ret = PTR_ERR(child);
        goto out;
    }

    if (request == PTRACE_ATTACH || request == PTRACE_SEIZE) {
        ret = ptrace_attach(child, request, addr, data);
        /*
         * Some architectures need to do book-keeping after
         * a ptrace attach.
         */
        if (!ret)
            arch_ptrace_attach(child);
        goto out_put_task_struct;
    }

    ret = ptrace_check_attach(child, request == PTRACE_KILL ||
                  request == PTRACE_INTERRUPT);
    if (ret < 0)
        goto out_put_task_struct;

    ret = arch_ptrace(child, request, addr, data);

 out_put_task_struct:
    put_task_struct(child);
 out:
    return ret;
}

int generic_ptrace_peekdata(struct task_struct *tsk, unsigned long addr,
                unsigned long data)
{
    unsigned long tmp;
    int copied;

    copied = access_process_vm(tsk, addr, &tmp, sizeof(tmp), 0);
    if (copied != sizeof(tmp))
        return -EIO;
    return put_user(tmp, (unsigned long __user *)data);
}

int generic_ptrace_pokedata(struct task_struct *tsk, unsigned long addr,
                unsigned long data)
{
    int copied;

    copied = access_process_vm(tsk, addr, &data, sizeof(data), 1);
    return (copied == sizeof(data)) ? 0 : -EIO;
}

#if defined CONFIG_COMPAT
#include <linux/compat.h>

int compat_ptrace_request(struct task_struct *child, compat_long_t request,
              compat_ulong_t addr, compat_ulong_t data)
{
    compat_ulong_t __user *datap = compat_ptr(data);
    compat_ulong_t word;
    siginfo_t siginfo;
    int ret;

    switch (request) {
    case PTRACE_PEEKTEXT:
    case PTRACE_PEEKDATA:
        ret = access_process_vm(child, addr, &word, sizeof(word), 0);
        if (ret != sizeof(word))
            ret = -EIO;
        else
            ret = put_user(word, datap);
        break;

    case PTRACE_POKETEXT:
    case PTRACE_POKEDATA:
        ret = access_process_vm(child, addr, &data, sizeof(data), 1);
        ret = (ret != sizeof(data) ? -EIO : 0);
        break;

    case PTRACE_GETEVENTMSG:
        ret = put_user((compat_ulong_t) child->ptrace_message, datap);
        break;

    case PTRACE_GETSIGINFO:
        ret = ptrace_getsiginfo(child, &siginfo);
        if (!ret)
            ret = copy_siginfo_to_user32(
                (struct compat_siginfo __user *) datap,
                &siginfo);
        break;

    case PTRACE_SETSIGINFO:
        memset(&siginfo, 0, sizeof siginfo);
        if (copy_siginfo_from_user32(
                &siginfo, (struct compat_siginfo __user *) datap))
            ret = -EFAULT;
        else
            ret = ptrace_setsiginfo(child, &siginfo);
        break;
#ifdef CONFIG_HAVE_ARCH_TRACEHOOK
    case PTRACE_GETREGSET:
    case PTRACE_SETREGSET:
    {
        struct iovec kiov;
        struct compat_iovec __user *uiov =
            (struct compat_iovec __user *) datap;
        compat_uptr_t ptr;
        compat_size_t len;

        if (!access_ok(VERIFY_WRITE, uiov, sizeof(*uiov)))
            return -EFAULT;

        if (__get_user(ptr, &uiov->iov_base) ||
            __get_user(len, &uiov->iov_len))
            return -EFAULT;

        kiov.iov_base = compat_ptr(ptr);
        kiov.iov_len = len;

        ret = ptrace_regset(child, request, addr, &kiov);
        if (!ret)
            ret = __put_user(kiov.iov_len, &uiov->iov_len);
        break;
    }
#endif

    default:
        ret = ptrace_request(child, request, addr, data);
    }

    return ret;
}

asmlinkage long compat_sys_ptrace(compat_long_t request, compat_long_t pid,
                  compat_long_t addr, compat_long_t data)
{
    struct task_struct *child;
    long ret;

    if (request == PTRACE_TRACEME) {
        ret = ptrace_traceme();
        goto out;
    }

    child = ptrace_get_task_struct(pid);
    if (IS_ERR(child)) {
        ret = PTR_ERR(child);
        goto out;
    }

    if (request == PTRACE_ATTACH || request == PTRACE_SEIZE) {
        ret = ptrace_attach(child, request, addr, data);
        /*
         * Some architectures need to do book-keeping after
         * a ptrace attach.
         */
        if (!ret)
            arch_ptrace_attach(child);
        goto out_put_task_struct;
    }

    ret = ptrace_check_attach(child, request == PTRACE_KILL ||
                  request == PTRACE_INTERRUPT);
    if (!ret)
        ret = compat_arch_ptrace(child, request, addr, data);

 out_put_task_struct:
    put_task_struct(child);
 out:
    return ret;
}
#endif  /* CONFIG_COMPAT */

#ifdef CONFIG_HAVE_HW_BREAKPOINT
int ptrace_get_breakpoints(struct task_struct *tsk)
{
    if (atomic_inc_not_zero(&tsk->ptrace_bp_refcnt))
        return 0;

    return -1;
}

void ptrace_put_breakpoints(struct task_struct *tsk)
{
    if (atomic_dec_and_test(&tsk->ptrace_bp_refcnt))
        flush_ptrace_hw_breakpoint(tsk);
}
#endif /* CONFIG_HAVE_HW_BREAKPOINT */