+/*
+ * proc_exec_switch_task
+ *
+ * Parameters: p proc
+ * old_task task before exec
+ * new_task task after exec
+ * new_thread thread in new task
+ *
+ * Returns: proc.
+ *
+ * Note: The function will switch the task pointer of proc
+ * from old task to new task. The switch needs to happen
+ * after draining all proc refs and inside a proc translock.
+ * In the case of failure to switch the task, which might happen
+ * if the process received a SIGKILL or jetsam killed it, it will make
+ * sure that the new tasks terminates. User proc ref returned
+ * to caller.
+ *
+ * This function is called after point of no return, in the case
+ * failure to switch, it will terminate the new task and swallow the
+ * error and let the terminated process complete exec and die.
+ */
+proc_t
+proc_exec_switch_task(proc_t p, task_t old_task, task_t new_task, thread_t new_thread)
+{
+ int error = 0;
+ boolean_t task_active;
+ boolean_t proc_active;
+ boolean_t thread_active;
+ thread_t old_thread = current_thread();
+
+ /*
+ * Switch the task pointer of proc to new task.
+ * Before switching the task, wait for proc_refdrain.
+ * After the switch happens, the proc can disappear,
+ * take a ref before it disappears. Waiting for
+ * proc_refdrain in exec will block all other threads
+ * trying to take a proc ref, boost the current thread
+ * to avoid priority inversion.
+ */
+ thread_set_exec_promotion(old_thread);
+ p = proc_refdrain_with_refwait(p, TRUE);
+ /* extra proc ref returned to the caller */
+
+ assert(get_threadtask(new_thread) == new_task);
+ task_active = task_is_active(new_task);
+
+ /* Take the proc_translock to change the task ptr */
+ proc_lock(p);
+ proc_active = !(p->p_lflag & P_LEXIT);
+
+ /* Check if the current thread is not aborted due to SIGKILL */
+ thread_active = thread_is_active(old_thread);
+
+ /*
+ * Do not switch the task if the new task or proc is already terminated
+ * as a result of error in exec past point of no return
+ */
+ if (proc_active && task_active && thread_active) {
+ error = proc_transstart(p, 1, 0);
+ if (error == 0) {
+ uthread_t new_uthread = get_bsdthread_info(new_thread);
+ uthread_t old_uthread = get_bsdthread_info(current_thread());
+
+ /*
+ * bsd_info of old_task will get cleared in execve and posix_spawn
+ * after firing exec-success/error dtrace probe.
+ */
+ p->task = new_task;
+
+ /* Clear dispatchqueue and workloop ast offset */
+ p->p_dispatchqueue_offset = 0;
+ p->p_dispatchqueue_serialno_offset = 0;
+ p->p_return_to_kernel_offset = 0;
+
+ /* Copy the signal state, dtrace state and set bsd ast on new thread */
+ act_set_astbsd(new_thread);
+ new_uthread->uu_siglist = old_uthread->uu_siglist;
+ new_uthread->uu_sigwait = old_uthread->uu_sigwait;
+ new_uthread->uu_sigmask = old_uthread->uu_sigmask;
+ new_uthread->uu_oldmask = old_uthread->uu_oldmask;
+ new_uthread->uu_vforkmask = old_uthread->uu_vforkmask;
+ new_uthread->uu_exit_reason = old_uthread->uu_exit_reason;
+#if CONFIG_DTRACE
+ new_uthread->t_dtrace_sig = old_uthread->t_dtrace_sig;
+ new_uthread->t_dtrace_stop = old_uthread->t_dtrace_stop;
+ new_uthread->t_dtrace_resumepid = old_uthread->t_dtrace_resumepid;
+ assert(new_uthread->t_dtrace_scratch == NULL);
+ new_uthread->t_dtrace_scratch = old_uthread->t_dtrace_scratch;
+
+ old_uthread->t_dtrace_sig = 0;
+ old_uthread->t_dtrace_stop = 0;
+ old_uthread->t_dtrace_resumepid = 0;
+ old_uthread->t_dtrace_scratch = NULL;
+#endif
+ /* Copy the resource accounting info */
+ thread_copy_resource_info(new_thread, current_thread());
+
+ /* Clear the exit reason and signal state on old thread */
+ old_uthread->uu_exit_reason = NULL;
+ old_uthread->uu_siglist = 0;
+
+ /* Add the new uthread to proc uthlist and remove the old one */
+ TAILQ_INSERT_TAIL(&p->p_uthlist, new_uthread, uu_list);
+ TAILQ_REMOVE(&p->p_uthlist, old_uthread, uu_list);
+
+ task_set_did_exec_flag(old_task);
+ task_clear_exec_copy_flag(new_task);
+
+ task_copy_fields_for_exec(new_task, old_task);
+
+ proc_transend(p, 1);
+ }
+ }
+
+ proc_unlock(p);
+ proc_refwake(p);
+ thread_clear_exec_promotion(old_thread);
+
+ if (error != 0 || !task_active || !proc_active || !thread_active) {
+ task_terminate_internal(new_task);
+ }
+
+ return p;
+}
projects / apple / xnu.git / blobdiff