/*
 * 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/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 <linux/signal.h>
#include <linux/audit.h>
#include <linux/pid_namespace.h>
#include <linux/syscalls.h>
#include <linux/uaccess.h>


/*
 * Initialize a new task whose father had been ptraced.
 *
 * Called from copy_process().
 */
void ptrace_fork(struct task_struct *child, unsigned long clone_flags)
{
        arch_ptrace_fork(child, clone_flags);
}

/*
 * 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;
}

/*
 * 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.
 * Requires that irqs be disabled.
 */
static void ptrace_untrace(struct task_struct *child)
{
        spin_lock(&child->sighand->siglock);
        if (task_is_traced(child)) {
                /*
                 * If the group stop is completed or in progress,
                 * this thread was already counted as stopped.
                 */
                if (child->signal->flags & SIGNAL_STOP_STOPPED ||
                    child->signal->group_stop_count)
                        __set_task_state(child, TASK_STOPPED);
                else
                        signal_wake_up(child, 1);
        }
        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(struct task_struct *child)
{
        BUG_ON(!child->ptrace);

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

        arch_ptrace_untrace(child);
        if (task_is_traced(child))
                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) {
                ret = 0;
                /*
                 * child->sighand can't be NULL, release_task()
                 * does ptrace_unlink() before __exit_signal().
                 */
                spin_lock_irq(&child->sighand->siglock);
                if (task_is_stopped(child))
                        child->state = TASK_TRACED;
                else if (!task_is_traced(child) && !kill)
                        ret = -ESRCH;
                spin_unlock_irq(&child->sighand->siglock);
        }
        read_unlock(&tasklist_lock);

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

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

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 ((cred->uid != tcred->euid ||
             cred->uid != tcred->suid ||
             cred->uid != tcred->uid  ||
             cred->gid != tcred->egid ||
             cred->gid != tcred->sgid ||
             cred->gid != tcred->gid) &&
            !capable(CAP_SYS_PTRACE)) {
                rcu_read_unlock();
                return -EPERM;
        }
        rcu_read_unlock();
        smp_rmb();
        if (task->mm)
                dumpable = get_dumpable(task->mm);
        if (!dumpable && !capable(CAP_SYS_PTRACE))
                return -EPERM;

        return security_ptrace_may_access(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;
}

int ptrace_attach(struct task_struct *task)
{
        int retval;
        unsigned long flags;

        audit_ptrace(task);

        retval = -EPERM;
        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 = mutex_lock_interruptible(&task->cred_exec_mutex);
        if (retval  < 0)
                goto out;

        retval = -EPERM;
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);
        if (!write_trylock_irqsave(&tasklist_lock, flags)) {
                task_unlock(task);
                do {
                        cpu_relax();
                } while (!write_can_lock(&tasklist_lock));
                goto repeat;
        }

        if (!task->mm)
                goto bad;
        /* the same process cannot be attached many times */
        if (task->ptrace & PT_PTRACED)
                goto bad;
        retval = __ptrace_may_access(task, PTRACE_MODE_ATTACH);
        if (retval)
                goto bad;

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

        __ptrace_link(task, current);

        send_sig_info(SIGSTOP, SEND_SIG_FORCED, task);
bad:
        write_unlock_irqrestore(&tasklist_lock, flags);
        task_unlock(task);
        mutex_unlock(&task->cred_exec_mutex);
out:
        return retval;
}

/*
 * 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.
 */
static bool __ptrace_detach(struct task_struct *tracer, struct task_struct *p)
{
        __ptrace_unlink(p);

        if (p->exit_state == EXIT_ZOMBIE) {
                if (!task_detached(p) && thread_group_empty(p)) {
                        if (!same_thread_group(p->real_parent, tracer))
                                do_notify_parent(p, p->exit_signal);
                        else if (ignoring_children(tracer->sighand))
                                p->exit_signal = -1;
                }
                if (task_detached(p)) {
                        /* Mark it as in the process of being reaped. */
                        p->exit_state = EXIT_DEAD;
                        return true;
                }
        }

        return false;
}

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);
                if (!child->exit_state)
                        wake_up_process(child);
        }
        write_unlock_irq(&tasklist_lock);

        if (unlikely(dead))
                release_task(child);

        return 0;
}

/*
 * Detach all tasks we were using ptrace on.
 */
void exit_ptrace(struct task_struct *tracer)
{
        struct task_struct *p, *n;
        LIST_HEAD(ptrace_dead);

        write_lock_irq(&tasklist_lock);
        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);
        }
}

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 *info)
{
        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)) {
                        *info = *child->last_siginfo;
                        error = 0;
                }
                spin_unlock_irq(&child->sighand->siglock);
        }
        read_unlock(&tasklist_lock);
        return error;
}

static int ptrace_setsiginfo(struct task_struct *child, const siginfo_t *info)
{
        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)) {
                        *child->last_siginfo = *info;
                        error = 0;
                }
                spin_unlock_irq(&child->sighand->siglock);
        }
        read_unlock(&tasklist_lock);
        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, 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_process(child);

        return 0;
}

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

        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, (unsigned long __user *) data);
                break;

        case PTRACE_GETSIGINFO:
                ret = ptrace_getsiginfo(child, &siginfo);
                if (!ret)
                        ret = copy_siginfo_to_user((siginfo_t __user *) data,
                                                   &siginfo);
                break;

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

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

#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);

        default:
                break;
        }

        return ret;
}

/**
 * ptrace_traceme  --  helper for PTRACE_TRACEME
 *
 * Performs checks and sets PT_PTRACED.
 * Should be used by all ptrace implementations for PTRACE_TRACEME.
 */
int ptrace_traceme(void)
{
        int ret = -EPERM;

        /*
         * Are we already being traced?
         */
repeat:
        task_lock(current);
        if (!(current->ptrace & PT_PTRACED)) {
                /*
                 * See ptrace_attach() comments about the locking here.
                 */
                unsigned long flags;
                if (!write_trylock_irqsave(&tasklist_lock, flags)) {
                        task_unlock(current);
                        do {
                                cpu_relax();
                        } while (!write_can_lock(&tasklist_lock));
                        goto repeat;
                }

                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_irqrestore(&tasklist_lock, flags);
        }
        task_unlock(current);
        return ret;
}

/**
 * ptrace_get_task_struct  --  grab a task struct reference for ptrace
 * @pid:       process id to grab a task_struct reference of
 *
 * This function is a helper for ptrace implementations.  It checks
 * permissions and then grabs a task struct for use of the actual
 * ptrace implementation.
 *
 * Returns the task_struct for @pid or an ERR_PTR() on failure.
 */
struct task_struct *ptrace_get_task_struct(pid_t pid)
{
        struct task_struct *child;

        read_lock(&tasklist_lock);
        child = find_task_by_vpid(pid);
        if (child)
                get_task_struct(child);

        read_unlock(&tasklist_lock);
        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, long, addr, long, data)
{
        struct task_struct *child;
        long ret;

        /*
         * This lock_kernel fixes a subtle race with suid exec
         */
        lock_kernel();
        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) {
                ret = ptrace_attach(child);
                /*
                 * 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);
        if (ret < 0)
                goto out_put_task_struct;

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

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

int generic_ptrace_peekdata(struct task_struct *tsk, long addr, 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, long addr, 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;

        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;

        /*
         * This lock_kernel fixes a subtle race with suid exec
         */
        lock_kernel();
        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) {
                ret = ptrace_attach(child);
                /*
                 * 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);
        if (!ret)
                ret = compat_arch_ptrace(child, request, addr, data);

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