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  1. /*
  2.  * Copyright (c) 2008 Jiri Svoboda
  3.  * All rights reserved.
  4.  *
  5.  * Redistribution and use in source and binary forms, with or without
  6.  * modification, are permitted provided that the following conditions
  7.  * are met:
  8.  *
  9.  * - Redistributions of source code must retain the above copyright
  10.  *   notice, this list of conditions and the following disclaimer.
  11.  * - Redistributions in binary form must reproduce the above copyright
  12.  *   notice, this list of conditions and the following disclaimer in the
  13.  *   documentation and/or other materials provided with the distribution.
  14.  * - The name of the author may not be used to endorse or promote products
  15.  *   derived from this software without specific prior written permission.
  16.  *
  17.  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  18.  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  19.  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  20.  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  21.  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  22.  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  23.  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  24.  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  25.  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  26.  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  27.  */
  28.  
  29. /** @addtogroup generic
  30.  * @{
  31.  */
  32.  
  33. /**
  34.  * @file
  35.  * @brief   Udebug hooks and data structure management.
  36.  *
  37.  * Udebug is an interface that makes userspace debuggers possible.
  38.  */
  39.  
  40. #include <synch/waitq.h>
  41. #include <debug.h>
  42. #include <udebug/udebug.h>
  43. #include <errno.h>
  44. #include <print.h>
  45. #include <arch.h>
  46.  
  47.  
  48. /** Initialize udebug part of task structure.
  49.  *
  50.  * Called as part of task structure initialization.
  51.  * @param ut    Pointer to the structure to initialize.
  52.  */
  53. void udebug_task_init(udebug_task_t *ut)
  54. {
  55.     mutex_initialize(&ut->lock, MUTEX_PASSIVE);
  56.     ut->dt_state = UDEBUG_TS_INACTIVE;
  57.     ut->begin_call = NULL;
  58.     ut->not_stoppable_count = 0;
  59.     ut->evmask = 0;
  60. }
  61.  
  62. /** Initialize udebug part of thread structure.
  63.  *
  64.  * Called as part of thread structure initialization.
  65.  * @param ut    Pointer to the structure to initialize.
  66.  */
  67. void udebug_thread_initialize(udebug_thread_t *ut)
  68. {
  69.     mutex_initialize(&ut->lock, MUTEX_PASSIVE);
  70.     waitq_initialize(&ut->go_wq);
  71.  
  72.     ut->go_call = NULL;
  73.     ut->uspace_state = NULL;
  74.     ut->go = false;
  75.     ut->stoppable = true;
  76.     ut->active = false;
  77.     ut->cur_event = 0; /* none */
  78. }
  79.  
  80. /** Wait for a GO message.
  81.  *
  82.  * When a debugging event occurs in a thread or the thread is stopped,
  83.  * this function is called to block the thread until a GO message
  84.  * is received.
  85.  *
  86.  * @param wq    The wait queue used by the thread to wait for GO messages.
  87.  */
  88. static void udebug_wait_for_go(waitq_t *wq)
  89. {
  90.     int rc;
  91.     ipl_t ipl;
  92.  
  93.     ipl = waitq_sleep_prepare(wq);
  94.  
  95.     wq->missed_wakeups = 0; /* Enforce blocking. */
  96.     rc = waitq_sleep_timeout_unsafe(wq, SYNCH_NO_TIMEOUT, SYNCH_FLAGS_NONE);
  97.  
  98.     waitq_sleep_finish(wq, rc, ipl);
  99. }
  100.  
  101. /** Do a preliminary check that a debugging session is in progress.
  102.  *
  103.  * This only requires the THREAD->udebug.lock mutex (and not TASK->udebug.lock
  104.  * mutex). For an undebugged task, this will never block (while there could be
  105.  * collisions by different threads on the TASK mutex), thus improving SMP
  106.  * perormance for undebugged tasks.
  107.  *
  108.  * @return  True if the thread was in a debugging session when the function
  109.  *      checked, false otherwise.
  110.  */
  111. static bool udebug_thread_precheck(void)
  112. {
  113.     bool res;
  114.  
  115.     mutex_lock(&THREAD->udebug.lock);
  116.     res = THREAD->udebug.active;
  117.     mutex_unlock(&THREAD->udebug.lock);
  118.  
  119.     return res;
  120. }
  121.  
  122. /** Start of stoppable section.
  123.  *
  124.  * A stoppable section is a section of code where if the thread can be stoped. In other words,
  125.  * if a STOP operation is issued, the thread is guaranteed not to execute
  126.  * any userspace instructions until the thread is resumed.
  127.  *
  128.  * Having stoppable sections is better than having stopping points, since
  129.  * a thread can be stopped even when it is blocked indefinitely in a system
  130.  * call (whereas it would not reach any stopping point).
  131.  */
  132. void udebug_stoppable_begin(void)
  133. {
  134.     int nsc;
  135.     call_t *db_call, *go_call;
  136.  
  137.     ASSERT(THREAD);
  138.     ASSERT(TASK);
  139.  
  140.     /* Early check for undebugged tasks */
  141.     if (!udebug_thread_precheck()) {
  142.         return;
  143.     }
  144.  
  145.     mutex_lock(&TASK->udebug.lock);
  146.  
  147.     nsc = --TASK->udebug.not_stoppable_count;
  148.  
  149.     /* Lock order OK, THREAD->udebug.lock is after TASK->udebug.lock */
  150.     mutex_lock(&THREAD->udebug.lock);
  151.     ASSERT(THREAD->udebug.stoppable == false);
  152.     THREAD->udebug.stoppable = true;
  153.  
  154.     if (TASK->udebug.dt_state == UDEBUG_TS_BEGINNING && nsc == 0) {
  155.         /*
  156.          * This was the last non-stoppable thread. Reply to
  157.          * DEBUG_BEGIN call.
  158.          */
  159.  
  160.         db_call = TASK->udebug.begin_call;
  161.         ASSERT(db_call);
  162.  
  163.         TASK->udebug.dt_state = UDEBUG_TS_ACTIVE;
  164.         TASK->udebug.begin_call = NULL;
  165.  
  166.         IPC_SET_RETVAL(db_call->data, 0);
  167.         ipc_answer(&TASK->answerbox, db_call);     
  168.  
  169.     } else if (TASK->udebug.dt_state == UDEBUG_TS_ACTIVE) {
  170.         /*
  171.          * Active debugging session
  172.          */
  173.  
  174.         if (THREAD->udebug.active == true &&
  175.             THREAD->udebug.go == false) {
  176.             /*
  177.              * Thread was requested to stop - answer go call
  178.              */
  179.  
  180.             /* Make sure nobody takes this call away from us */
  181.             go_call = THREAD->udebug.go_call;
  182.             THREAD->udebug.go_call = NULL;
  183.             ASSERT(go_call);
  184.  
  185.             IPC_SET_RETVAL(go_call->data, 0);
  186.             IPC_SET_ARG1(go_call->data, UDEBUG_EVENT_STOP);
  187.  
  188.             THREAD->udebug.cur_event = UDEBUG_EVENT_STOP;
  189.  
  190.                 ipc_answer(&TASK->answerbox, go_call);
  191.         }
  192.     }
  193.  
  194.     mutex_unlock(&THREAD->udebug.lock);
  195.         mutex_unlock(&TASK->udebug.lock);
  196. }
  197.  
  198. /** End of a stoppable section.
  199.  *
  200.  * This is the point where the thread will block if it is stopped.
  201.  * (As, by definition, a stopped thread must not leave its stoppable section).
  202.  */
  203. void udebug_stoppable_end(void)
  204. {
  205.     /* Early check for undebugged tasks */
  206.     if (!udebug_thread_precheck()) {
  207.         return;
  208.     }
  209.  
  210. restart:
  211.     mutex_lock(&TASK->udebug.lock);
  212.     mutex_lock(&THREAD->udebug.lock);
  213.  
  214.     if (THREAD->udebug.active && THREAD->udebug.go == false) {
  215.         TASK->udebug.begin_call = NULL;
  216.         mutex_unlock(&THREAD->udebug.lock);
  217.         mutex_unlock(&TASK->udebug.lock);
  218.  
  219.         udebug_wait_for_go(&THREAD->udebug.go_wq);
  220.  
  221.         goto restart;
  222.         /* Must try again - have to lose stoppability atomically. */
  223.     } else {
  224.         ++TASK->udebug.not_stoppable_count;
  225.         ASSERT(THREAD->udebug.stoppable == true);
  226.         THREAD->udebug.stoppable = false;
  227.  
  228.         mutex_unlock(&THREAD->udebug.lock);
  229.         mutex_unlock(&TASK->udebug.lock);
  230.     }
  231. }
  232.  
  233. /** Upon being scheduled to run, check if the current thread should stop.
  234.  *
  235.  * This function is called from clock().
  236.  */
  237. void udebug_before_thread_runs(void)
  238. {
  239.     /* Check if we're supposed to stop */
  240.     udebug_stoppable_begin();
  241.     udebug_stoppable_end();
  242. }
  243.  
  244. /** Syscall event hook.
  245.  *
  246.  * Must be called before and after servicing a system call. This generates
  247.  * a SYSCALL_B or SYSCALL_E event, depending on the value of @a end_variant.
  248.  */
  249. void udebug_syscall_event(unative_t a1, unative_t a2, unative_t a3,
  250.     unative_t a4, unative_t a5, unative_t a6, unative_t id, unative_t rc,
  251.     bool end_variant)
  252. {
  253.     call_t *call;
  254.     udebug_event_t etype;
  255.  
  256.     etype = end_variant ? UDEBUG_EVENT_SYSCALL_E : UDEBUG_EVENT_SYSCALL_B;
  257.  
  258.     /* Early check for undebugged tasks */
  259.     if (!udebug_thread_precheck()) {
  260.         return;
  261.     }
  262.  
  263.     mutex_lock(&TASK->udebug.lock);
  264.     mutex_lock(&THREAD->udebug.lock);
  265.  
  266.     /* Must only generate events when in debugging session and is go. */
  267.     if (THREAD->udebug.active != true || THREAD->udebug.go == false ||
  268.         (TASK->udebug.evmask & UDEBUG_EVMASK(etype)) == 0) {
  269.         mutex_unlock(&THREAD->udebug.lock);
  270.         mutex_unlock(&TASK->udebug.lock);
  271.         return;
  272.     }
  273.  
  274.     //printf("udebug_syscall_event\n");
  275.     call = THREAD->udebug.go_call;
  276.     THREAD->udebug.go_call = NULL;
  277.  
  278.     IPC_SET_RETVAL(call->data, 0);
  279.     IPC_SET_ARG1(call->data, etype);
  280.     IPC_SET_ARG2(call->data, id);
  281.     IPC_SET_ARG3(call->data, rc);
  282.     //printf("udebug_syscall_event/ipc_answer\n");
  283.  
  284.     THREAD->udebug.syscall_args[0] = a1;
  285.     THREAD->udebug.syscall_args[1] = a2;
  286.     THREAD->udebug.syscall_args[2] = a3;
  287.     THREAD->udebug.syscall_args[3] = a4;
  288.     THREAD->udebug.syscall_args[4] = a5;
  289.     THREAD->udebug.syscall_args[5] = a6;
  290.  
  291.     /*
  292.      * Make sure udebug.go is false when going to sleep
  293.      * in case we get woken up by DEBUG_END. (At which
  294.      * point it must be back to the initial true value).
  295.      */
  296.     THREAD->udebug.go = false;
  297.     THREAD->udebug.cur_event = etype;
  298.  
  299.     ipc_answer(&TASK->answerbox, call);
  300.  
  301.     mutex_unlock(&THREAD->udebug.lock);
  302.     mutex_unlock(&TASK->udebug.lock);
  303.  
  304.     udebug_wait_for_go(&THREAD->udebug.go_wq);
  305. }
  306.  
  307. /** Thread-creation event hook combined with attaching the thread.
  308.  *
  309.  * Must be called when a new userspace thread is created in the debugged
  310.  * task. Generates a THREAD_B event. Also attaches the thread @a t
  311.  * to the task @a ta.
  312.  *
  313.  * This is necessary to avoid a race condition where the BEGIN and THREAD_READ
  314.  * requests would be handled inbetween attaching the thread and checking it
  315.  * for being in a debugging session to send the THREAD_B event. We could then
  316.  * either miss threads or get some threads both in the thread list
  317.  * and get a THREAD_B event for them.
  318.  *
  319.  * @param t Structure of the thread being created. Not locked, as the
  320.  *      thread is not executing yet.
  321.  * @param ta    Task to which the thread should be attached.
  322.  */
  323. void udebug_thread_b_event_attach(struct thread *t, struct task *ta)
  324. {
  325.     call_t *call;
  326.  
  327.     mutex_lock(&TASK->udebug.lock);
  328.     mutex_lock(&THREAD->udebug.lock);
  329.  
  330.     thread_attach(t, ta);
  331.  
  332.     LOG("udebug_thread_b_event\n");
  333.     LOG("- check state\n");
  334.  
  335.     /* Must only generate events when in debugging session */
  336.     if (THREAD->udebug.active != true) {
  337.         LOG("- udebug.active: %s, udebug.go: %s\n",
  338.             THREAD->udebug.active ? "yes(+)" : "no(-)",
  339.             THREAD->udebug.go ? "yes(-)" : "no(+)");
  340.         mutex_unlock(&THREAD->udebug.lock);
  341.         mutex_unlock(&TASK->udebug.lock);
  342.         return;
  343.     }
  344.  
  345.     LOG("- trigger event\n");
  346.  
  347.     call = THREAD->udebug.go_call;
  348.     THREAD->udebug.go_call = NULL;
  349.     IPC_SET_RETVAL(call->data, 0);
  350.     IPC_SET_ARG1(call->data, UDEBUG_EVENT_THREAD_B);
  351.     IPC_SET_ARG2(call->data, (unative_t)t);
  352.  
  353.     /*
  354.      * Make sure udebug.go is false when going to sleep
  355.      * in case we get woken up by DEBUG_END. (At which
  356.      * point it must be back to the initial true value).
  357.      */
  358.     THREAD->udebug.go = false;
  359.     THREAD->udebug.cur_event = UDEBUG_EVENT_THREAD_B;
  360.  
  361.     ipc_answer(&TASK->answerbox, call);
  362.  
  363.     mutex_unlock(&THREAD->udebug.lock);
  364.     mutex_unlock(&TASK->udebug.lock);
  365.  
  366.     LOG("- sleep\n");
  367.     udebug_wait_for_go(&THREAD->udebug.go_wq);
  368. }
  369.  
  370. /** Thread-termination event hook.
  371.  *
  372.  * Must be called when the current thread is terminating.
  373.  * Generates a THREAD_E event.
  374.  */
  375. void udebug_thread_e_event(void)
  376. {
  377.     call_t *call;
  378.  
  379.     mutex_lock(&TASK->udebug.lock);
  380.     mutex_lock(&THREAD->udebug.lock);
  381.  
  382.     LOG("udebug_thread_e_event\n");
  383.     LOG("- check state\n");
  384.  
  385.     /* Must only generate events when in debugging session. */
  386.     if (THREAD->udebug.active != true) {
  387. /*      printf("- udebug.active: %s, udebug.go: %s\n",
  388.             THREAD->udebug.active ? "yes(+)" : "no(-)",
  389.             THREAD->udebug.go ? "yes(-)" : "no(+)");*/
  390.         mutex_unlock(&THREAD->udebug.lock);
  391.         mutex_unlock(&TASK->udebug.lock);
  392.         return;
  393.     }
  394.  
  395.     LOG("- trigger event\n");
  396.  
  397.     call = THREAD->udebug.go_call;
  398.     THREAD->udebug.go_call = NULL;
  399.     IPC_SET_RETVAL(call->data, 0);
  400.     IPC_SET_ARG1(call->data, UDEBUG_EVENT_THREAD_E);
  401.  
  402.     /* Prevent any further debug activity in thread. */
  403.     THREAD->udebug.active = false;
  404.     THREAD->udebug.cur_event = 0;       /* none */
  405.     THREAD->udebug.go = false;  /* set to initial value */
  406.  
  407.     ipc_answer(&TASK->answerbox, call);
  408.  
  409.     mutex_unlock(&THREAD->udebug.lock);
  410.     mutex_unlock(&TASK->udebug.lock);
  411.  
  412.     /*
  413.      * This event does not sleep - debugging has finished
  414.      * in this thread.
  415.      */
  416. }
  417.  
  418. /**
  419.  * Terminate task debugging session.
  420.  *
  421.  * Gracefully terminates the debugging session for a task. If the debugger
  422.  * is still waiting for events on some threads, it will receive a
  423.  * FINISHED event for each of them.
  424.  *
  425.  * @param ta    Task structure. ta->udebug.lock must be already locked.
  426.  * @return  Zero on success or negative error code.
  427.  */
  428. int udebug_task_cleanup(struct task *ta)
  429. {
  430.     thread_t *t;
  431.     link_t *cur;
  432.     int flags;
  433.     ipl_t ipl;
  434.  
  435.     LOG("udebug_task_cleanup()\n");
  436.     LOG("task %" PRIu64 "\n", ta->taskid);
  437.  
  438.     if (ta->udebug.dt_state != UDEBUG_TS_BEGINNING &&
  439.         ta->udebug.dt_state != UDEBUG_TS_ACTIVE) {
  440.         LOG("udebug_task_cleanup(): task not being debugged\n");
  441.         return EINVAL;
  442.     }
  443.  
  444.     /* Finish debugging of all userspace threads */
  445.     for (cur = ta->th_head.next; cur != &ta->th_head; cur = cur->next) {
  446.         t = list_get_instance(cur, thread_t, th_link);
  447.  
  448.         mutex_lock(&t->udebug.lock);
  449.  
  450.         ipl = interrupts_disable();
  451.         spinlock_lock(&t->lock);
  452.  
  453.         flags = t->flags;
  454.  
  455.         spinlock_unlock(&t->lock);
  456.         interrupts_restore(ipl);
  457.  
  458.         /* Only process userspace threads. */
  459.         if ((flags & THREAD_FLAG_USPACE) != 0) {
  460.             /* Prevent any further debug activity in thread. */
  461.             t->udebug.active = false;
  462.             t->udebug.cur_event = 0;    /* none */
  463.  
  464.             /* Is the thread still go? */
  465.             if (t->udebug.go == true) {
  466.                 /*
  467.                 * Yes, so clear go. As active == false,
  468.                  * this doesn't affect anything.
  469.                  */
  470.                 t->udebug.go = false;  
  471.  
  472.                 /* Answer GO call */
  473.                 LOG("answer GO call with EVENT_FINISHED\n");
  474.                 IPC_SET_RETVAL(t->udebug.go_call->data, 0);
  475.                 IPC_SET_ARG1(t->udebug.go_call->data,
  476.                     UDEBUG_EVENT_FINISHED);
  477.  
  478.                 ipc_answer(&ta->answerbox, t->udebug.go_call);
  479.                 t->udebug.go_call = NULL;
  480.             } else {
  481.                 /*
  482.                  * Debug_stop is already at initial value.
  483.                  * Yet this means the thread needs waking up.
  484.                  */
  485.  
  486.                 /*
  487.                  * t's lock must not be held when calling
  488.                  * waitq_wakeup.
  489.                  */
  490.                 waitq_wakeup(&t->udebug.go_wq, WAKEUP_FIRST);
  491.             }
  492.         }
  493.         mutex_unlock(&t->udebug.lock);
  494.     }
  495.  
  496.     ta->udebug.dt_state = UDEBUG_TS_INACTIVE;
  497.     ta->udebug.debugger = NULL;
  498.  
  499.     return 0;
  500. }
  501.  
  502.  
  503. /** @}
  504.  */
  505.