ptrace.c

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    1 /*
    2  * linux/kernel/ptrace.c
    3  *
    4  * (C) Copyright 1999 Linus Torvalds
    5  *
    6  * Common interfaces for "ptrace()" which we do not want
    7  * to continually duplicate across every architecture.
    8  */
    9 
   10 #include <linux/capability.h>
   11 #include <linux/export.h>
   12 #include <linux/sched.h>
   13 #include <linux/errno.h>
   14 #include <linux/mm.h>
   15 #include <linux/highmem.h>
   16 #include <linux/pagemap.h>
   17 #include <linux/ptrace.h>
   18 #include <linux/security.h>
   19 #include <linux/signal.h>
   20 #include <linux/audit.h>
   21 #include <linux/pid_namespace.h>
   22 #include <linux/syscalls.h>
   23 #include <linux/uaccess.h>
   24 #include <linux/regset.h>
   25 #include <linux/hw_breakpoint.h>
   26 #include <linux/cn_proc.h>
   27 
   28 
   29 static int ptrace_trapping_sleep_fn(void *flags)
   30 {
   31         schedule();
   32         return 0;
   33 }
   34 
   35 /*
   36  * ptrace a task: make the debugger its new parent and
   37  * move it to the ptrace list.
   38  *
   39  * Must be called with the tasklist lock write-held.
   40  */
   41 void __ptrace_link(struct task_struct *child, struct task_struct *new_parent)
   42 {
   43         BUG_ON(!list_empty(&child->ptrace_entry));
   44         list_add(&child->ptrace_entry, &new_parent->ptraced);
   45         child->parent = new_parent;
   46 }
   47 
   48 /**
   49  * __ptrace_unlink - unlink ptracee and restore its execution state
   50  * @child: ptracee to be unlinked
   51  *
   52  * Remove @child from the ptrace list, move it back to the original parent,
   53  * and restore the execution state so that it conforms to the group stop
   54  * state.
   55  *
   56  * Unlinking can happen via two paths - explicit PTRACE_DETACH or ptracer
   57  * exiting.  For PTRACE_DETACH, unless the ptracee has been killed between
   58  * ptrace_check_attach() and here, it's guaranteed to be in TASK_TRACED.
   59  * If the ptracer is exiting, the ptracee can be in any state.
   60  *
   61  * After detach, the ptracee should be in a state which conforms to the
   62  * group stop.  If the group is stopped or in the process of stopping, the
   63  * ptracee should be put into TASK_STOPPED; otherwise, it should be woken
   64  * up from TASK_TRACED.
   65  *
   66  * If the ptracee is in TASK_TRACED and needs to be moved to TASK_STOPPED,
   67  * it goes through TRACED -> RUNNING -> STOPPED transition which is similar
   68  * to but in the opposite direction of what happens while attaching to a
   69  * stopped task.  However, in this direction, the intermediate RUNNING
   70  * state is not hidden even from the current ptracer and if it immediately
   71  * re-attaches and performs a WNOHANG wait(2), it may fail.
   72  *
   73  * CONTEXT:
   74  * write_lock_irq(tasklist_lock)
   75  */
   76 void __ptrace_unlink(struct task_struct *child)
   77 {
   78         BUG_ON(!child->ptrace);
   79 
   80         child->ptrace = 0;
   81         child->parent = child->real_parent;
   82         list_del_init(&child->ptrace_entry);
   83 
   84         spin_lock(&child->sighand->siglock);
   85 
   86         /*
   87          * Clear all pending traps and TRAPPING.  TRAPPING should be
   88          * cleared regardless of JOBCTL_STOP_PENDING.  Do it explicitly.
   89          */
   90         task_clear_jobctl_pending(child, JOBCTL_TRAP_MASK);
   91         task_clear_jobctl_trapping(child);
   92 
   93         /*
   94          * Reinstate JOBCTL_STOP_PENDING if group stop is in effect and
   95          * @child isn't dead.
   96          */
   97         if (!(child->flags & PF_EXITING) &&
   98             (child->signal->flags & SIGNAL_STOP_STOPPED ||
   99              child->signal->group_stop_count)) {
  100                 child->jobctl |= JOBCTL_STOP_PENDING;
  101 
  102                 /*
  103                  * This is only possible if this thread was cloned by the
  104                  * traced task running in the stopped group, set the signal
  105                  * for the future reports.
  106                  * FIXME: we should change ptrace_init_task() to handle this
  107                  * case.
  108                  */
  109                 if (!(child->jobctl & JOBCTL_STOP_SIGMASK))
  110                         child->jobctl |= SIGSTOP;
  111         }
  112 
  113         /*
  114          * If transition to TASK_STOPPED is pending or in TASK_TRACED, kick
  115          * @child in the butt.  Note that @resume should be used iff @child
  116          * is in TASK_TRACED; otherwise, we might unduly disrupt
  117          * TASK_KILLABLE sleeps.
  118          */
  119         if (child->jobctl & JOBCTL_STOP_PENDING || task_is_traced(child))
  120                 ptrace_signal_wake_up(child, true);
  121 
  122         spin_unlock(&child->sighand->siglock);
  123 }
  124 
  125 /* Ensure that nothing can wake it up, even SIGKILL */
  126 static bool ptrace_freeze_traced(struct task_struct *task)
  127 {
  128         bool ret = false;
  129 
  130         /* Lockless, nobody but us can set this flag */
  131         if (task->jobctl & JOBCTL_LISTENING)
  132                 return ret;
  133 
  134         spin_lock_irq(&task->sighand->siglock);
  135         if (task_is_traced(task) && !__fatal_signal_pending(task)) {
  136                 task->state = __TASK_TRACED;
  137                 ret = true;
  138         }
  139         spin_unlock_irq(&task->sighand->siglock);
  140 
  141         return ret;
  142 }
  143 
  144 static void ptrace_unfreeze_traced(struct task_struct *task)
  145 {
  146         if (task->state != __TASK_TRACED)
  147                 return;
  148 
  149         WARN_ON(!task->ptrace || task->parent != current);
  150 
  151         spin_lock_irq(&task->sighand->siglock);
  152         if (__fatal_signal_pending(task))
  153                 wake_up_state(task, __TASK_TRACED);
  154         else
  155                 task->state = TASK_TRACED;
  156         spin_unlock_irq(&task->sighand->siglock);
  157 }
  158 
  159 /**
  160  * ptrace_check_attach - check whether ptracee is ready for ptrace operation
  161  * @child: ptracee to check for
  162  * @ignore_state: don't check whether @child is currently %TASK_TRACED
  163  *
  164  * Check whether @child is being ptraced by %current and ready for further
  165  * ptrace operations.  If @ignore_state is %false, @child also should be in
  166  * %TASK_TRACED state and on return the child is guaranteed to be traced
  167  * and not executing.  If @ignore_state is %true, @child can be in any
  168  * state.
  169  *
  170  * CONTEXT:
  171  * Grabs and releases tasklist_lock and @child->sighand->siglock.
  172  *
  173  * RETURNS:
  174  * 0 on success, -ESRCH if %child is not ready.
  175  */
  176 static int ptrace_check_attach(struct task_struct *child, bool ignore_state)
  177 {
  178         int ret = -ESRCH;
  179 
  180         /*
  181          * We take the read lock around doing both checks to close a
  182          * possible race where someone else was tracing our child and
  183          * detached between these two checks.  After this locked check,
  184          * we are sure that this is our traced child and that can only
  185          * be changed by us so it's not changing right after this.
  186          */
  187         read_lock(&tasklist_lock);
  188         if (child->ptrace && child->parent == current) {
  189                 WARN_ON(child->state == __TASK_TRACED);
  190                 /*
  191                  * child->sighand can't be NULL, release_task()
  192                  * does ptrace_unlink() before __exit_signal().
  193                  */
  194                 if (ignore_state || ptrace_freeze_traced(child))
  195                         ret = 0;
  196         }
  197         read_unlock(&tasklist_lock);
  198 
  199         if (!ret && !ignore_state) {
  200                 if (!wait_task_inactive(child, __TASK_TRACED)) {
  201                         /*
  202                          * This can only happen if may_ptrace_stop() fails and
  203                          * ptrace_stop() changes ->state back to TASK_RUNNING,
  204                          * so we should not worry about leaking __TASK_TRACED.
  205                          */
  206                         WARN_ON(child->state == __TASK_TRACED);
  207                         ret = -ESRCH;
  208                 }
  209         }
  210 
  211         return ret;
  212 }
  213 
  214 static int ptrace_has_cap(struct user_namespace *ns, unsigned int mode)
  215 {
  216         if (mode & PTRACE_MODE_NOAUDIT)
  217                 return has_ns_capability_noaudit(current, ns, CAP_SYS_PTRACE);
  218         else
  219                 return has_ns_capability(current, ns, CAP_SYS_PTRACE);
  220 }
  221 
  222 /* Returns 0 on success, -errno on denial. */
  223 static int __ptrace_may_access(struct task_struct *task, unsigned int mode)
  224 {
  225         const struct cred *cred = current_cred(), *tcred;
  226 
  227         /* May we inspect the given task?
  228          * This check is used both for attaching with ptrace
  229          * and for allowing access to sensitive information in /proc.
  230          *
  231          * ptrace_attach denies several cases that /proc allows
  232          * because setting up the necessary parent/child relationship
  233          * or halting the specified task is impossible.
  234          */
  235         int dumpable = 0;
  236         /* Don't let security modules deny introspection */
  237         if (task == current)
  238                 return 0;
  239         rcu_read_lock();
  240         tcred = __task_cred(task);
  241         if (uid_eq(cred->uid, tcred->euid) &&
  242             uid_eq(cred->uid, tcred->suid) &&
  243             uid_eq(cred->uid, tcred->uid)  &&
  244             gid_eq(cred->gid, tcred->egid) &&
  245             gid_eq(cred->gid, tcred->sgid) &&
  246             gid_eq(cred->gid, tcred->gid))
  247                 goto ok;
  248         if (ptrace_has_cap(tcred->user_ns, mode))
  249                 goto ok;
  250         rcu_read_unlock();
  251         return -EPERM;
  252 ok:
  253         rcu_read_unlock();
  254         smp_rmb();
  255         if (task->mm)
  256                 dumpable = get_dumpable(task->mm);
  257         rcu_read_lock();
  258         if (!dumpable && !ptrace_has_cap(__task_cred(task)->user_ns, mode)) {
  259                 rcu_read_unlock();
  260                 return -EPERM;
  261         }
  262         rcu_read_unlock();
  263 
  264         return security_ptrace_access_check(task, mode);
  265 }
  266 
  267 bool ptrace_may_access(struct task_struct *task, unsigned int mode)
  268 {
  269         int err;
  270         task_lock(task);
  271         err = __ptrace_may_access(task, mode);
  272         task_unlock(task);
  273         return !err;
  274 }
  275 
  276 static int ptrace_attach(struct task_struct *task, long request,
  277                          unsigned long addr,
  278                          unsigned long flags)
  279 {
  280         bool seize = (request == PTRACE_SEIZE);
  281         int retval;
  282 
  283         retval = -EIO;
  284         if (seize) {
  285                 if (addr != 0)
  286                         goto out;
  287                 if (flags & ~(unsigned long)PTRACE_O_MASK)
  288                         goto out;
  289                 flags = PT_PTRACED | PT_SEIZED | (flags << PT_OPT_FLAG_SHIFT);
  290         } else {
  291                 flags = PT_PTRACED;
  292         }
  293 
  294         audit_ptrace(task);
  295 
  296         retval = -EPERM;
  297         if (unlikely(task->flags & PF_KTHREAD))
  298                 goto out;
  299         if (same_thread_group(task, current))
  300                 goto out;
  301 
  302         /*
  303          * Protect exec's credential calculations against our interference;
  304          * SUID, SGID and LSM creds get determined differently
  305          * under ptrace.
  306          */
  307         retval = -ERESTARTNOINTR;
  308         if (mutex_lock_interruptible(&task->signal->cred_guard_mutex))
  309                 goto out;
  310 
  311         task_lock(task);
  312         retval = __ptrace_may_access(task, PTRACE_MODE_ATTACH);
  313         task_unlock(task);
  314         if (retval)
  315                 goto unlock_creds;
  316 
  317         write_lock_irq(&tasklist_lock);
  318         retval = -EPERM;
  319         if (unlikely(task->exit_state))
  320                 goto unlock_tasklist;
  321         if (task->ptrace)
  322                 goto unlock_tasklist;
  323 
  324         if (seize)
  325                 flags |= PT_SEIZED;
  326         rcu_read_lock();
  327         if (ns_capable(__task_cred(task)->user_ns, CAP_SYS_PTRACE))
  328                 flags |= PT_PTRACE_CAP;
  329         rcu_read_unlock();
  330         task->ptrace = flags;
  331 
  332         __ptrace_link(task, current);
  333 
  334         /* SEIZE doesn't trap tracee on attach */
  335         if (!seize)
  336                 send_sig_info(SIGSTOP, SEND_SIG_FORCED, task);
  337 
  338         spin_lock(&task->sighand->siglock);
  339 
  340         /*
  341          * If the task is already STOPPED, set JOBCTL_TRAP_STOP and
  342          * TRAPPING, and kick it so that it transits to TRACED.  TRAPPING
  343          * will be cleared if the child completes the transition or any
  344          * event which clears the group stop states happens.  We'll wait
  345          * for the transition to complete before returning from this
  346          * function.
  347          *
  348          * This hides STOPPED -> RUNNING -> TRACED transition from the
  349          * attaching thread but a different thread in the same group can
  350          * still observe the transient RUNNING state.  IOW, if another
  351          * thread's WNOHANG wait(2) on the stopped tracee races against
  352          * ATTACH, the wait(2) may fail due to the transient RUNNING.
  353          *
  354          * The following task_is_stopped() test is safe as both transitions
  355          * in and out of STOPPED are protected by siglock.
  356          */
  357         if (task_is_stopped(task) &&
  358             task_set_jobctl_pending(task, JOBCTL_TRAP_STOP | JOBCTL_TRAPPING))
  359                 signal_wake_up_state(task, __TASK_STOPPED);
  360 
  361         spin_unlock(&task->sighand->siglock);
  362 
  363         retval = 0;
  364 unlock_tasklist:
  365         write_unlock_irq(&tasklist_lock);
  366 unlock_creds:
  367         mutex_unlock(&task->signal->cred_guard_mutex);
  368 out:
  369         if (!retval) {
  370                 wait_on_bit(&task->jobctl, JOBCTL_TRAPPING_BIT,
  371                             ptrace_trapping_sleep_fn, TASK_UNINTERRUPTIBLE);
  372                 proc_ptrace_connector(task, PTRACE_ATTACH);
  373         }
  374 
  375         return retval;
  376 }
  377 
  378 /**
  379  * ptrace_traceme  --  helper for PTRACE_TRACEME
  380  *
  381  * Performs checks and sets PT_PTRACED.
  382  * Should be used by all ptrace implementations for PTRACE_TRACEME.
  383  */
  384 static int ptrace_traceme(void)
  385 {
  386         int ret = -EPERM;
  387 
  388         write_lock_irq(&tasklist_lock);
  389         /* Are we already being traced? */
  390         if (!current->ptrace) {
  391                 ret = security_ptrace_traceme(current->parent);
  392                 /*
  393                  * Check PF_EXITING to ensure ->real_parent has not passed
  394                  * exit_ptrace(). Otherwise we don't report the error but
  395                  * pretend ->real_parent untraces us right after return.
  396                  */
  397                 if (!ret && !(current->real_parent->flags & PF_EXITING)) {
  398                         current->ptrace = PT_PTRACED;
  399                         __ptrace_link(current, current->real_parent);
  400                 }
  401         }
  402         write_unlock_irq(&tasklist_lock);
  403 
  404         return ret;
  405 }
  406 
  407 /*
  408  * Called with irqs disabled, returns true if childs should reap themselves.
  409  */
  410 static int ignoring_children(struct sighand_struct *sigh)
  411 {
  412         int ret;
  413         spin_lock(&sigh->siglock);
  414         ret = (sigh->action[SIGCHLD-1].sa.sa_handler == SIG_IGN) ||
  415               (sigh->action[SIGCHLD-1].sa.sa_flags & SA_NOCLDWAIT);
  416         spin_unlock(&sigh->siglock);
  417         return ret;
  418 }
  419 
  420 /*
  421  * Called with tasklist_lock held for writing.
  422  * Unlink a traced task, and clean it up if it was a traced zombie.
  423  * Return true if it needs to be reaped with release_task().
  424  * (We can't call release_task() here because we already hold tasklist_lock.)
  425  *
  426  * If it's a zombie, our attachedness prevented normal parent notification
  427  * or self-reaping.  Do notification now if it would have happened earlier.
  428  * If it should reap itself, return true.
  429  *
  430  * If it's our own child, there is no notification to do. But if our normal
  431  * children self-reap, then this child was prevented by ptrace and we must
  432  * reap it now, in that case we must also wake up sub-threads sleeping in
  433  * do_wait().
  434  */
  435 static bool __ptrace_detach(struct task_struct *tracer, struct task_struct *p)
  436 {
  437         bool dead;
  438 
  439         __ptrace_unlink(p);
  440 
  441         if (p->exit_state != EXIT_ZOMBIE)
  442                 return false;
  443 
  444         dead = !thread_group_leader(p);
  445 
  446         if (!dead && thread_group_empty(p)) {
  447                 if (!same_thread_group(p->real_parent, tracer))
  448                         dead = do_notify_parent(p, p->exit_signal);
  449                 else if (ignoring_children(tracer->sighand)) {
  450                         __wake_up_parent(p, tracer);
  451                         dead = true;
  452                 }
  453         }
  454         /* Mark it as in the process of being reaped. */
  455         if (dead)
  456                 p->exit_state = EXIT_DEAD;
  457         return dead;
  458 }
  459 
  460 static int ptrace_detach(struct task_struct *child, unsigned int data)
  461 {
  462         bool dead = false;
  463 
  464         if (!valid_signal(data))
  465                 return -EIO;
  466 
  467         /* Architecture-specific hardware disable .. */
  468         ptrace_disable(child);
  469         clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
  470 
  471         write_lock_irq(&tasklist_lock);
  472         /*
  473          * This child can be already killed. Make sure de_thread() or
  474          * our sub-thread doing do_wait() didn't do release_task() yet.
  475          */
  476         if (child->ptrace) {
  477                 child->exit_code = data;
  478                 dead = __ptrace_detach(current, child);
  479         }
  480         write_unlock_irq(&tasklist_lock);
  481 
  482         proc_ptrace_connector(child, PTRACE_DETACH);
  483         if (unlikely(dead))
  484                 release_task(child);
  485 
  486         return 0;
  487 }
  488 
  489 /*
  490  * Detach all tasks we were using ptrace on. Called with tasklist held
  491  * for writing, and returns with it held too. But note it can release
  492  * and reacquire the lock.
  493  */
  494 void exit_ptrace(struct task_struct *tracer)
  495         __releases(&tasklist_lock)
  496         __acquires(&tasklist_lock)
  497 {
  498         struct task_struct *p, *n;
  499         LIST_HEAD(ptrace_dead);
  500 
  501         if (likely(list_empty(&tracer->ptraced)))
  502                 return;
  503 
  504         list_for_each_entry_safe(p, n, &tracer->ptraced, ptrace_entry) {
  505                 if (unlikely(p->ptrace & PT_EXITKILL))
  506                         send_sig_info(SIGKILL, SEND_SIG_FORCED, p);
  507 
  508                 if (__ptrace_detach(tracer, p))
  509                         list_add(&p->ptrace_entry, &ptrace_dead);
  510         }
  511 
  512         write_unlock_irq(&tasklist_lock);
  513         BUG_ON(!list_empty(&tracer->ptraced));
  514 
  515         list_for_each_entry_safe(p, n, &ptrace_dead, ptrace_entry) {
  516                 list_del_init(&p->ptrace_entry);
  517                 release_task(p);
  518         }
  519 
  520         write_lock_irq(&tasklist_lock);
  521 }
  522 
  523 int ptrace_readdata(struct task_struct *tsk, unsigned long src, char __user *dst, int len)
  524 {
  525         int copied = 0;
  526 
  527         while (len > 0) {
  528                 char buf[128];
  529                 int this_len, retval;
  530 
  531                 this_len = (len > sizeof(buf)) ? sizeof(buf) : len;
  532                 retval = access_process_vm(tsk, src, buf, this_len, 0);
  533                 if (!retval) {
  534                         if (copied)
  535                                 break;
  536                         return -EIO;
  537                 }
  538                 if (copy_to_user(dst, buf, retval))
  539                         return -EFAULT;
  540                 copied += retval;
  541                 src += retval;
  542                 dst += retval;
  543                 len -= retval;
  544         }
  545         return copied;
  546 }
  547 
  548 int ptrace_writedata(struct task_struct *tsk, char __user *src, unsigned long dst, int len)
  549 {
  550         int copied = 0;
  551 
  552         while (len > 0) {
  553                 char buf[128];
  554                 int this_len, retval;
  555 
  556                 this_len = (len > sizeof(buf)) ? sizeof(buf) : len;
  557                 if (copy_from_user(buf, src, this_len))
  558                         return -EFAULT;
  559                 retval = access_process_vm(tsk, dst, buf, this_len, 1);
  560                 if (!retval) {
  561                         if (copied)
  562                                 break;
  563                         return -EIO;
  564                 }
  565                 copied += retval;
  566                 src += retval;
  567                 dst += retval;
  568                 len -= retval;
  569         }
  570         return copied;
  571 }
  572 
  573 static int ptrace_setoptions(struct task_struct *child, unsigned long data)
  574 {
  575         unsigned flags;
  576 
  577         if (data & ~(unsigned long)PTRACE_O_MASK)
  578                 return -EINVAL;
  579 
  580         /* Avoid intermediate state when all opts are cleared */
  581         flags = child->ptrace;
  582         flags &= ~(PTRACE_O_MASK << PT_OPT_FLAG_SHIFT);
  583         flags |= (data << PT_OPT_FLAG_SHIFT);
  584         child->ptrace = flags;
  585 
  586         return 0;
  587 }
  588 
  589 static int ptrace_getsiginfo(struct task_struct *child, siginfo_t *info)
  590 {
  591         unsigned long flags;
  592         int error = -ESRCH;
  593 
  594         if (lock_task_sighand(child, &flags)) {
  595                 error = -EINVAL;
  596                 if (likely(child->last_siginfo != NULL)) {
  597                         *info = *child->last_siginfo;
  598                         error = 0;
  599                 }
  600                 unlock_task_sighand(child, &flags);
  601         }
  602         return error;
  603 }
  604 
  605 static int ptrace_setsiginfo(struct task_struct *child, const siginfo_t *info)
  606 {
  607         unsigned long flags;
  608         int error = -ESRCH;
  609 
  610         if (lock_task_sighand(child, &flags)) {
  611                 error = -EINVAL;
  612                 if (likely(child->last_siginfo != NULL)) {
  613                         *child->last_siginfo = *info;
  614                         error = 0;
  615                 }
  616                 unlock_task_sighand(child, &flags);
  617         }
  618         return error;
  619 }
  620 
  621 
  622 #ifdef PTRACE_SINGLESTEP
  623 #define is_singlestep(request)          ((request) == PTRACE_SINGLESTEP)
  624 #else
  625 #define is_singlestep(request)          0
  626 #endif
  627 
  628 #ifdef PTRACE_SINGLEBLOCK
  629 #define is_singleblock(request)         ((request) == PTRACE_SINGLEBLOCK)
  630 #else
  631 #define is_singleblock(request)         0
  632 #endif
  633 
  634 #ifdef PTRACE_SYSEMU
  635 #define is_sysemu_singlestep(request)   ((request) == PTRACE_SYSEMU_SINGLESTEP)
  636 #else
  637 #define is_sysemu_singlestep(request)   0
  638 #endif
  639 
  640 static int ptrace_resume(struct task_struct *child, long request,
  641                          unsigned long data)
  642 {
  643         if (!valid_signal(data))
  644                 return -EIO;
  645 
  646         if (request == PTRACE_SYSCALL)
  647                 set_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
  648         else
  649                 clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
  650 
  651 #ifdef TIF_SYSCALL_EMU
  652         if (request == PTRACE_SYSEMU || request == PTRACE_SYSEMU_SINGLESTEP)
  653                 set_tsk_thread_flag(child, TIF_SYSCALL_EMU);
  654         else
  655                 clear_tsk_thread_flag(child, TIF_SYSCALL_EMU);
  656 #endif
  657 
  658         if (is_singleblock(request)) {
  659                 if (unlikely(!arch_has_block_step()))
  660                         return -EIO;
  661                 user_enable_block_step(child);
  662         } else if (is_singlestep(request) || is_sysemu_singlestep(request)) {
  663                 if (unlikely(!arch_has_single_step()))
  664                         return -EIO;
  665                 user_enable_single_step(child);
  666         } else {
  667                 user_disable_single_step(child);
  668         }
  669 
  670         child->exit_code = data;
  671         wake_up_state(child, __TASK_TRACED);
  672 
  673         return 0;
  674 }
  675 
  676 #ifdef CONFIG_HAVE_ARCH_TRACEHOOK
  677 
  678 static const struct user_regset *
  679 find_regset(const struct user_regset_view *view, unsigned int type)
  680 {
  681         const struct user_regset *regset;
  682         int n;
  683 
  684         for (n = 0; n < view->n; ++n) {
  685                 regset = view->regsets + n;
  686                 if (regset->core_note_type == type)
  687                         return regset;
  688         }
  689 
  690         return NULL;
  691 }
  692 
  693 static int ptrace_regset(struct task_struct *task, int req, unsigned int type,
  694                          struct iovec *kiov)
  695 {
  696         const struct user_regset_view *view = task_user_regset_view(task);
  697         const struct user_regset *regset = find_regset(view, type);
  698         int regset_no;
  699 
  700         if (!regset || (kiov->iov_len % regset->size) != 0)
  701                 return -EINVAL;
  702 
  703         regset_no = regset - view->regsets;
  704         kiov->iov_len = min(kiov->iov_len,
  705                             (__kernel_size_t) (regset->n * regset->size));
  706 
  707         if (req == PTRACE_GETREGSET)
  708                 return copy_regset_to_user(task, view, regset_no, 0,
  709                                            kiov->iov_len, kiov->iov_base);
  710         else
  711                 return copy_regset_from_user(task, view, regset_no, 0,
  712                                              kiov->iov_len, kiov->iov_base);
  713 }
  714 
  715 #endif
  716 
  717 int ptrace_request(struct task_struct *child, long request,
  718                    unsigned long addr, unsigned long data)
  719 {
  720         bool seized = child->ptrace & PT_SEIZED;
  721         int ret = -EIO;
  722         siginfo_t siginfo, *si;
  723         void __user *datavp = (void __user *) data;
  724         unsigned long __user *datalp = datavp;
  725         unsigned long flags;
  726 
  727         switch (request) {
  728         case PTRACE_PEEKTEXT:
  729         case PTRACE_PEEKDATA:
  730                 return generic_ptrace_peekdata(child, addr, data);
  731         case PTRACE_POKETEXT:
  732         case PTRACE_POKEDATA:
  733                 return generic_ptrace_pokedata(child, addr, data);
  734 
  735 #ifdef PTRACE_OLDSETOPTIONS
  736         case PTRACE_OLDSETOPTIONS:
  737 #endif
  738         case PTRACE_SETOPTIONS:
  739                 ret = ptrace_setoptions(child, data);
  740                 break;
  741         case PTRACE_GETEVENTMSG:
  742                 ret = put_user(child->ptrace_message, datalp);
  743                 break;
  744 
  745         case PTRACE_GETSIGINFO:
  746                 ret = ptrace_getsiginfo(child, &siginfo);
  747                 if (!ret)
  748                         ret = copy_siginfo_to_user(datavp, &siginfo);
  749                 break;
  750 
  751         case PTRACE_SETSIGINFO:
  752                 if (copy_from_user(&siginfo, datavp, sizeof siginfo))
  753                         ret = -EFAULT;
  754                 else
  755                         ret = ptrace_setsiginfo(child, &siginfo);
  756                 break;
  757 
  758         case PTRACE_INTERRUPT:
  759                 /*
  760                  * Stop tracee without any side-effect on signal or job
  761                  * control.  At least one trap is guaranteed to happen
  762                  * after this request.  If @child is already trapped, the
  763                  * current trap is not disturbed and another trap will
  764                  * happen after the current trap is ended with PTRACE_CONT.
  765                  *
  766                  * The actual trap might not be PTRACE_EVENT_STOP trap but
  767                  * the pending condition is cleared regardless.
  768                  */
  769                 if (unlikely(!seized || !lock_task_sighand(child, &flags)))
  770                         break;
  771 
  772                 /*
  773                  * INTERRUPT doesn't disturb existing trap sans one
  774                  * exception.  If ptracer issued LISTEN for the current
  775                  * STOP, this INTERRUPT should clear LISTEN and re-trap
  776                  * tracee into STOP.
  777                  */
  778                 if (likely(task_set_jobctl_pending(child, JOBCTL_TRAP_STOP)))
  779                         ptrace_signal_wake_up(child, child->jobctl & JOBCTL_LISTENING);
  780 
  781                 unlock_task_sighand(child, &flags);
  782                 ret = 0;
  783                 break;
  784 
  785         case PTRACE_LISTEN:
  786                 /*
  787                  * Listen for events.  Tracee must be in STOP.  It's not
  788                  * resumed per-se but is not considered to be in TRACED by
  789                  * wait(2) or ptrace(2).  If an async event (e.g. group
  790                  * stop state change) happens, tracee will enter STOP trap
  791                  * again.  Alternatively, ptracer can issue INTERRUPT to
  792                  * finish listening and re-trap tracee into STOP.
  793                  */
  794                 if (unlikely(!seized || !lock_task_sighand(child, &flags)))
  795                         break;
  796 
  797                 si = child->last_siginfo;
  798                 if (likely(si && (si->si_code >> 8) == PTRACE_EVENT_STOP)) {
  799                         child->jobctl |= JOBCTL_LISTENING;
  800                         /*
  801                          * If NOTIFY is set, it means event happened between
  802                          * start of this trap and now.  Trigger re-trap.
  803                          */
  804                         if (child->jobctl & JOBCTL_TRAP_NOTIFY)
  805                                 ptrace_signal_wake_up(child, true);
  806                         ret = 0;
  807                 }
  808                 unlock_task_sighand(child, &flags);
  809                 break;
  810 
  811         case PTRACE_DETACH:      /* detach a process that was attached. */
  812                 ret = ptrace_detach(child, data);
  813                 break;
  814 
  815 #ifdef CONFIG_BINFMT_ELF_FDPIC
  816         case PTRACE_GETFDPIC: {
  817                 struct mm_struct *mm = get_task_mm(child);
  818                 unsigned long tmp = 0;
  819 
  820                 ret = -ESRCH;
  821                 if (!mm)
  822                         break;
  823 
  824                 switch (addr) {
  825                 case PTRACE_GETFDPIC_EXEC:
  826                         tmp = mm->context.exec_fdpic_loadmap;
  827                         break;
  828                 case PTRACE_GETFDPIC_INTERP:
  829                         tmp = mm->context.interp_fdpic_loadmap;
  830                         break;
  831                 default:
  832                         break;
  833                 }
  834                 mmput(mm);
  835 
  836                 ret = put_user(tmp, datalp);
  837                 break;
  838         }
  839 #endif
  840 
  841 #ifdef PTRACE_SINGLESTEP
  842         case PTRACE_SINGLESTEP:
  843 #endif
  844 #ifdef PTRACE_SINGLEBLOCK
  845         case PTRACE_SINGLEBLOCK:
  846 #endif
  847 #ifdef PTRACE_SYSEMU
  848         case PTRACE_SYSEMU:
  849         case PTRACE_SYSEMU_SINGLESTEP:
  850 #endif
  851         case PTRACE_SYSCALL:
  852         case PTRACE_CONT:
  853                 return ptrace_resume(child, request, data);
  854 
  855         case PTRACE_KILL:
  856                 if (child->exit_state)  /* already dead */
  857                         return 0;
  858                 return ptrace_resume(child, request, SIGKILL);
  859 
  860 #ifdef CONFIG_HAVE_ARCH_TRACEHOOK
  861         case PTRACE_GETREGSET:
  862         case PTRACE_SETREGSET:
  863         {
  864                 struct iovec kiov;
  865                 struct iovec __user *uiov = datavp;
  866 
  867                 if (!access_ok(VERIFY_WRITE, uiov, sizeof(*uiov)))
  868                         return -EFAULT;
  869 
  870                 if (__get_user(kiov.iov_base, &uiov->iov_base) ||
  871                     __get_user(kiov.iov_len, &uiov->iov_len))
  872                         return -EFAULT;
  873 
  874                 ret = ptrace_regset(child, request, addr, &kiov);
  875                 if (!ret)
  876                         ret = __put_user(kiov.iov_len, &uiov->iov_len);
  877                 break;
  878         }
  879 #endif
  880         default:
  881                 break;
  882         }
  883 
  884         return ret;
  885 }
  886 
  887 static struct task_struct *ptrace_get_task_struct(pid_t pid)
  888 {
  889         struct task_struct *child;
  890 
  891         rcu_read_lock();
  892         child = find_task_by_vpid(pid);
  893         if (child)
  894                 get_task_struct(child);
  895         rcu_read_unlock();
  896 
  897         if (!child)
  898                 return ERR_PTR(-ESRCH);
  899         return child;
  900 }
  901 
  902 #ifndef arch_ptrace_attach
  903 #define arch_ptrace_attach(child)       do { } while (0)
  904 #endif
  905 
  906 SYSCALL_DEFINE4(ptrace, long, request, long, pid, unsigned long, addr,
  907                 unsigned long, data)
  908 {
  909         struct task_struct *child;
  910         long ret;
  911 
  912         if (request == PTRACE_TRACEME) {
  913                 ret = ptrace_traceme();
  914                 if (!ret)
  915                         arch_ptrace_attach(current);
  916                 goto out;
  917         }
  918 
  919         child = ptrace_get_task_struct(pid);
  920         if (IS_ERR(child)) {
  921                 ret = PTR_ERR(child);
  922                 goto out;
  923         }
  924 
  925         if (request == PTRACE_ATTACH || request == PTRACE_SEIZE) {
  926                 ret = ptrace_attach(child, request, addr, data);
  927                 /*
  928                  * Some architectures need to do book-keeping after
  929                  * a ptrace attach.
  930                  */
  931                 if (!ret)
  932                         arch_ptrace_attach(child);
  933                 goto out_put_task_struct;
  934         }
  935 
  936         ret = ptrace_check_attach(child, request == PTRACE_KILL ||
  937                                   request == PTRACE_INTERRUPT);
  938         if (ret < 0)
  939                 goto out_put_task_struct;
  940 
  941         ret = arch_ptrace(child, request, addr, data);
  942         if (ret || request != PTRACE_DETACH)
  943                 ptrace_unfreeze_traced(child);
  944 
  945  out_put_task_struct:
  946         put_task_struct(child);
  947  out:
  948         return ret;
  949 }
  950 
  951 int generic_ptrace_peekdata(struct task_struct *tsk, unsigned long addr,
  952                             unsigned long data)
  953 {
  954         unsigned long tmp;
  955         int copied;
  956 
  957         copied = access_process_vm(tsk, addr, &tmp, sizeof(tmp), 0);
  958         if (copied != sizeof(tmp))
  959                 return -EIO;
  960         return put_user(tmp, (unsigned long __user *)data);
  961 }
  962 
  963 int generic_ptrace_pokedata(struct task_struct *tsk, unsigned long addr,
  964                             unsigned long data)
  965 {
  966         int copied;
  967 
  968         copied = access_process_vm(tsk, addr, &data, sizeof(data), 1);
  969         return (copied == sizeof(data)) ? 0 : -EIO;
  970 }
  971 
  972 #if defined CONFIG_COMPAT
  973 #include <linux/compat.h>
  974 
  975 int compat_ptrace_request(struct task_struct *child, compat_long_t request,
  976                           compat_ulong_t addr, compat_ulong_t data)
  977 {
  978         compat_ulong_t __user *datap = compat_ptr(data);
  979         compat_ulong_t word;
  980         siginfo_t siginfo;
  981         int ret;
  982 
  983         switch (request) {
  984         case PTRACE_PEEKTEXT:
  985         case PTRACE_PEEKDATA:
  986                 ret = access_process_vm(child, addr, &word, sizeof(word), 0);
  987                 if (ret != sizeof(word))
  988                         ret = -EIO;
  989                 else
  990                         ret = put_user(word, datap);
  991                 break;
  992 
  993         case PTRACE_POKETEXT:
  994         case PTRACE_POKEDATA:
  995                 ret = access_process_vm(child, addr, &data, sizeof(data), 1);
  996                 ret = (ret != sizeof(data) ? -EIO : 0);
  997                 break;
  998 
  999         case PTRACE_GETEVENTMSG:
 1000                 ret = put_user((compat_ulong_t) child->ptrace_message, datap);
 1001                 break;
 1002 
 1003         case PTRACE_GETSIGINFO:
 1004                 ret = ptrace_getsiginfo(child, &siginfo);
 1005                 if (!ret)
 1006                         ret = copy_siginfo_to_user32(
 1007                                 (struct compat_siginfo __user *) datap,
 1008                                 &siginfo);
 1009                 break;
 1010 
 1011         case PTRACE_SETSIGINFO:
 1012                 memset(&siginfo, 0, sizeof siginfo);
 1013                 if (copy_siginfo_from_user32(
 1014                             &siginfo, (struct compat_siginfo __user *) datap))
 1015                         ret = -EFAULT;
 1016                 else
 1017                         ret = ptrace_setsiginfo(child, &siginfo);
 1018                 break;
 1019 #ifdef CONFIG_HAVE_ARCH_TRACEHOOK
 1020         case PTRACE_GETREGSET:
 1021         case PTRACE_SETREGSET:
 1022         {
 1023                 struct iovec kiov;
 1024                 struct compat_iovec __user *uiov =
 1025                         (struct compat_iovec __user *) datap;
 1026                 compat_uptr_t ptr;
 1027                 compat_size_t len;
 1028 
 1029                 if (!access_ok(VERIFY_WRITE, uiov, sizeof(*uiov)))
 1030                         return -EFAULT;
 1031 
 1032                 if (__get_user(ptr, &uiov->iov_base) ||
 1033                     __get_user(len, &uiov->iov_len))
 1034                         return -EFAULT;
 1035 
 1036                 kiov.iov_base = compat_ptr(ptr);
 1037                 kiov.iov_len = len;
 1038 
 1039                 ret = ptrace_regset(child, request, addr, &kiov);
 1040                 if (!ret)
 1041                         ret = __put_user(kiov.iov_len, &uiov->iov_len);
 1042                 break;
 1043         }
 1044 #endif
 1045 
 1046         default:
 1047                 ret = ptrace_request(child, request, addr, data);
 1048         }
 1049 
 1050         return ret;
 1051 }
 1052 
 1053 asmlinkage long compat_sys_ptrace(compat_long_t request, compat_long_t pid,
 1054                                   compat_long_t addr, compat_long_t data)
 1055 {
 1056         struct task_struct *child;
 1057         long ret;
 1058 
 1059         if (request == PTRACE_TRACEME) {
 1060                 ret = ptrace_traceme();
 1061                 goto out;
 1062         }
 1063 
 1064         child = ptrace_get_task_struct(pid);
 1065         if (IS_ERR(child)) {
 1066                 ret = PTR_ERR(child);
 1067                 goto out;
 1068         }
 1069 
 1070         if (request == PTRACE_ATTACH || request == PTRACE_SEIZE) {
 1071                 ret = ptrace_attach(child, request, addr, data);
 1072                 /*
 1073                  * Some architectures need to do book-keeping after
 1074                  * a ptrace attach.
 1075                  */
 1076                 if (!ret)
 1077                         arch_ptrace_attach(child);
 1078                 goto out_put_task_struct;
 1079         }
 1080 
 1081         ret = ptrace_check_attach(child, request == PTRACE_KILL ||
 1082                                   request == PTRACE_INTERRUPT);
 1083         if (!ret) {
 1084                 ret = compat_arch_ptrace(child, request, addr, data);
 1085                 if (ret || request != PTRACE_DETACH)
 1086                         ptrace_unfreeze_traced(child);
 1087         }
 1088 
 1089  out_put_task_struct:
 1090         put_task_struct(child);
 1091  out:
 1092         return ret;
 1093 }
 1094 #endif  /* CONFIG_COMPAT */
 1095 
 1096 #ifdef CONFIG_HAVE_HW_BREAKPOINT
 1097 int ptrace_get_breakpoints(struct task_struct *tsk)
 1098 {
 1099         if (atomic_inc_not_zero(&tsk->ptrace_bp_refcnt))
 1100                 return 0;
 1101 
 1102         return -1;
 1103 }
 1104 
 1105 void ptrace_put_breakpoints(struct task_struct *tsk)
 1106 {
 1107         if (atomic_dec_and_test(&tsk->ptrace_bp_refcnt))
 1108                 flush_ptrace_hw_breakpoint(tsk);
 1109 }
 1110 #endif /* CONFIG_HAVE_HW_BREAKPOINT */
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FreeBSD/Linux Kernel Cross Reference sys/kernel/ptrace.c

FreeBSD/Linux Kernel Cross Reference
sys/kernel/ptrace.c
