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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 <arch.h>
  45.  
  46.  
  47. /** Initialize udebug part of task structure.
  48.  *
  49.  * Called as part of task structure initialization.
  50.  * @param ut    Pointer to the structure to initialize.
  51.  */
  52. void udebug_task_init(udebug_task_t *ut)
  53. {
  54.     mutex_initialize(&ut->lock, MUTEX_PASSIVE);
  55.     ut->dt_state = UDEBUG_TS_INACTIVE;
  56.     ut->begin_call = NULL;
  57.     ut->not_stoppable_count = 0;
  58.     ut->evmask = 0;
  59. }
  60.  
  61. /** Initialize udebug part of thread structure.
  62.  *
  63.  * Called as part of thread structure initialization.
  64.  * @param ut    Pointer to the structure to initialize.
  65.  */
  66. void udebug_thread_initialize(udebug_thread_t *ut)
  67. {
  68.     mutex_initialize(&ut->lock, MUTEX_PASSIVE);
  69.     waitq_initialize(&ut->go_wq);
  70.  
  71.     ut->go_call = NULL;
  72.     ut->uspace_state = NULL;
  73.     ut->go = false;
  74.     ut->stoppable = true;
  75.     ut->debug_active = false;
  76.     ut->cur_event = 0; /* none */
  77. }
  78.  
  79. /** Wait for a GO message.
  80.  *
  81.  * When a debugging event occurs in a thread or the thread is stopped,
  82.  * this function is called to block the thread until a GO message
  83.  * is received.
  84.  *
  85.  * @param wq    The wait queue used by the thread to wait for GO messages.
  86.  */
  87. static void udebug_wait_for_go(waitq_t *wq)
  88. {
  89.     int rc;
  90.     ipl_t ipl;
  91.  
  92.     ipl = waitq_sleep_prepare(wq);
  93.  
  94.     wq->missed_wakeups = 0; /* Enforce blocking. */
  95.     rc = waitq_sleep_timeout_unsafe(wq, SYNCH_NO_TIMEOUT, SYNCH_FLAGS_NONE);
  96.  
  97.     waitq_sleep_finish(wq, rc, ipl);
  98. }
  99.  
  100. /** Do a preliminary check that a debugging session is in progress.
  101.  *
  102.  * This only requires the THREAD->udebug.lock mutex (and not TASK->udebug.lock
  103.  * mutex). For an undebugged task, this will never block (while there could be
  104.  * collisions by different threads on the TASK mutex), thus improving SMP
  105.  * perormance for undebugged tasks.
  106.  *
  107.  * @return  True if the thread was in a debugging session when the function
  108.  *      checked, false otherwise.
  109.  */
  110. static bool udebug_thread_precheck(void)
  111. {
  112.     bool res;
  113.  
  114.     mutex_lock(&THREAD->udebug.lock);
  115.     res = THREAD->udebug.debug_active;
  116.     mutex_unlock(&THREAD->udebug.lock);
  117.  
  118.     return res;
  119. }
  120.  
  121. /** Start of stoppable section.
  122.  *
  123.  * A stoppable section is a section of code where if the thread can be stoped. In other words,
  124.  * if a STOP operation is issued, the thread is guaranteed not to execute
  125.  * any userspace instructions until the thread is resumed.
  126.  *
  127.  * Having stoppable sections is better than having stopping points, since
  128.  * a thread can be stopped even when it is blocked indefinitely in a system
  129.  * call (whereas it would not reach any stopping point).
  130.  */
  131. void udebug_stoppable_begin(void)
  132. {
  133.     int nsc;
  134.     call_t *db_call, *go_call;
  135.  
  136.     ASSERT(THREAD);
  137.     ASSERT(TASK);
  138.  
  139.     /* Early check for undebugged tasks */
  140.     if (!udebug_thread_precheck()) {
  141.         return;
  142.     }
  143.  
  144.     mutex_lock(&TASK->udebug.lock);
  145.  
  146.     nsc = --TASK->udebug.not_stoppable_count;
  147.  
  148.     /* Lock order OK, THREAD->udebug.lock is after TASK->udebug.lock */
  149.     mutex_lock(&THREAD->udebug.lock);
  150.     ASSERT(THREAD->udebug.stoppable == false);
  151.     THREAD->udebug.stoppable = true;
  152.  
  153.     if (TASK->udebug.dt_state == UDEBUG_TS_BEGINNING && nsc == 0) {
  154.         /*
  155.          * This was the last non-stoppable thread. Reply to
  156.          * DEBUG_BEGIN call.
  157.          */
  158.  
  159.         db_call = TASK->udebug.begin_call;
  160.         ASSERT(db_call);
  161.  
  162.         TASK->udebug.dt_state = UDEBUG_TS_ACTIVE;
  163.         TASK->udebug.begin_call = NULL;
  164.  
  165.         IPC_SET_RETVAL(db_call->data, 0);
  166.         ipc_answer(&TASK->answerbox, db_call);     
  167.  
  168.     } else if (TASK->udebug.dt_state == UDEBUG_TS_ACTIVE) {
  169.         /*
  170.          * Active debugging session
  171.          */
  172.  
  173.         if (THREAD->udebug.debug_active == true &&
  174.             THREAD->udebug.go == false) {
  175.             /*
  176.              * Thread was requested to stop - answer go call
  177.              */
  178.  
  179.             /* Make sure nobody takes this call away from us */
  180.             go_call = THREAD->udebug.go_call;
  181.             THREAD->udebug.go_call = NULL;
  182.             ASSERT(go_call);
  183.  
  184.             IPC_SET_RETVAL(go_call->data, 0);
  185.             IPC_SET_ARG1(go_call->data, UDEBUG_EVENT_STOP);
  186.  
  187.             THREAD->udebug.cur_event = UDEBUG_EVENT_STOP;
  188.  
  189.                 ipc_answer(&TASK->answerbox, go_call);
  190.         }
  191.     }
  192.  
  193.     mutex_unlock(&THREAD->udebug.lock);
  194.         mutex_unlock(&TASK->udebug.lock);
  195. }
  196.  
  197. /** End of a stoppable section.
  198.  *
  199.  * This is the point where the thread will block if it is stopped.
  200.  * (As, by definition, a stopped thread must not leave its stoppable section).
  201.  */
  202. void udebug_stoppable_end(void)
  203. {
  204.     /* Early check for undebugged tasks */
  205.     if (!udebug_thread_precheck()) {
  206.         return;
  207.     }
  208.  
  209. restart:
  210.     mutex_lock(&TASK->udebug.lock);
  211.     mutex_lock(&THREAD->udebug.lock);
  212.  
  213.     if (THREAD->udebug.debug_active &&
  214.         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.debug_active != true ||
  268.         THREAD->udebug.go == false ||
  269.         (TASK->udebug.evmask & UDEBUG_EVMASK(etype)) == 0) {
  270.         mutex_unlock(&THREAD->udebug.lock);
  271.         mutex_unlock(&TASK->udebug.lock);
  272.         return;
  273.     }
  274.  
  275.     //printf("udebug_syscall_event\n");
  276.     call = THREAD->udebug.go_call;
  277.     THREAD->udebug.go_call = NULL;
  278.  
  279.     IPC_SET_RETVAL(call->data, 0);
  280.     IPC_SET_ARG1(call->data, etype);
  281.     IPC_SET_ARG2(call->data, id);
  282.     IPC_SET_ARG3(call->data, rc);
  283.     //printf("udebug_syscall_event/ipc_answer\n");
  284.  
  285.     THREAD->udebug.syscall_args[0] = a1;
  286.     THREAD->udebug.syscall_args[1] = a2;
  287.     THREAD->udebug.syscall_args[2] = a3;
  288.     THREAD->udebug.syscall_args[3] = a4;
  289.     THREAD->udebug.syscall_args[4] = a5;
  290.     THREAD->udebug.syscall_args[5] = a6;
  291.  
  292.     /*
  293.      * Make sure udebug.go is false when going to sleep
  294.      * in case we get woken up by DEBUG_END. (At which
  295.      * point it must be back to the initial true value).
  296.      */
  297.     THREAD->udebug.go = false;
  298.     THREAD->udebug.cur_event = etype;
  299.  
  300.     ipc_answer(&TASK->answerbox, call);
  301.  
  302.     mutex_unlock(&THREAD->udebug.lock);
  303.     mutex_unlock(&TASK->udebug.lock);
  304.  
  305.     udebug_wait_for_go(&THREAD->udebug.go_wq);
  306. }
  307.  
  308. /** Thread-creation event hook combined with attaching the thread.
  309.  *
  310.  * Must be called when a new userspace thread is created in the debugged
  311.  * task. Generates a THREAD_B event. Also attaches the thread @a t
  312.  * to the task @a ta.
  313.  *
  314.  * This is necessary to avoid a race condition where the BEGIN and THREAD_READ
  315.  * requests would be handled inbetween attaching the thread and checking it
  316.  * for being in a debugging session to send the THREAD_B event. We could then
  317.  * either miss threads or get some threads both in the thread list
  318.  * and get a THREAD_B event for them.
  319.  *
  320.  * @param t Structure of the thread being created. Not locked, as the
  321.  *      thread is not executing yet.
  322.  * @param ta    Task to which the thread should be attached.
  323.  */
  324. void udebug_thread_b_event_attach(struct thread *t, struct task *ta)
  325. {
  326.     call_t *call;
  327.  
  328.     mutex_lock(&TASK->udebug.lock);
  329.     mutex_lock(&THREAD->udebug.lock);
  330.  
  331.     thread_attach(t, ta);
  332.  
  333.     LOG("udebug_thread_b_event\n");
  334.     LOG("- check state\n");
  335.  
  336.     /* Must only generate events when in debugging session */
  337.     if (THREAD->udebug.debug_active != true) {
  338.         LOG("- debug_active: %s, udebug.go: %s\n",
  339.             THREAD->udebug.debug_active ? "yes(+)" : "no(-)",
  340.             THREAD->udebug.go ? "yes(-)" : "no(+)");
  341.         mutex_unlock(&THREAD->udebug.lock);
  342.         mutex_unlock(&TASK->udebug.lock);
  343.         return;
  344.     }
  345.  
  346.     LOG("- trigger event\n");
  347.  
  348.     call = THREAD->udebug.go_call;
  349.     THREAD->udebug.go_call = NULL;
  350.     IPC_SET_RETVAL(call->data, 0);
  351.     IPC_SET_ARG1(call->data, UDEBUG_EVENT_THREAD_B);
  352.     IPC_SET_ARG2(call->data, (unative_t)t);
  353.  
  354.     /*
  355.      * Make sure udebug.go is false when going to sleep
  356.      * in case we get woken up by DEBUG_END. (At which
  357.      * point it must be back to the initial true value).
  358.      */
  359.     THREAD->udebug.go = false;
  360.     THREAD->udebug.cur_event = UDEBUG_EVENT_THREAD_B;
  361.  
  362.     ipc_answer(&TASK->answerbox, call);
  363.  
  364.     mutex_unlock(&THREAD->udebug.lock);
  365.     mutex_unlock(&TASK->udebug.lock);
  366.  
  367.     LOG("- sleep\n");
  368.     udebug_wait_for_go(&THREAD->udebug.go_wq);
  369. }
  370.  
  371. /** Thread-termination event hook.
  372.  *
  373.  * Must be called when the current thread is terminating.
  374.  * Generates a THREAD_E event.
  375.  */
  376. void udebug_thread_e_event(void)
  377. {
  378.     call_t *call;
  379.  
  380.     mutex_lock(&TASK->udebug.lock);
  381.     mutex_lock(&THREAD->udebug.lock);
  382.  
  383.     LOG("udebug_thread_e_event\n");
  384.     LOG("- check state\n");
  385.  
  386.     /* Must only generate events when in debugging session. */
  387.     if (THREAD->udebug.debug_active != true) {
  388. /*      printf("- debug_active: %s, udebug.go: %s\n",
  389.             THREAD->udebug.debug_active ? "yes(+)" : "no(-)",
  390.             THREAD->udebug.go ? "yes(-)" : "no(+)");*/
  391.         mutex_unlock(&THREAD->udebug.lock);
  392.         mutex_unlock(&TASK->udebug.lock);
  393.         return;
  394.     }
  395.  
  396.     LOG("- trigger event\n");
  397.  
  398.     call = THREAD->udebug.go_call;
  399.     THREAD->udebug.go_call = NULL;
  400.     IPC_SET_RETVAL(call->data, 0);
  401.     IPC_SET_ARG1(call->data, UDEBUG_EVENT_THREAD_E);
  402.  
  403.     /* Prevent any further debug activity in thread. */
  404.     THREAD->udebug.debug_active = false;
  405.     THREAD->udebug.cur_event = 0;       /* none */
  406.     THREAD->udebug.go = false;  /* set to initial value */
  407.  
  408.     ipc_answer(&TASK->answerbox, call);
  409.  
  410.     mutex_unlock(&THREAD->udebug.lock);
  411.     mutex_unlock(&TASK->udebug.lock);
  412.  
  413.     /*
  414.      * This event does not sleep - debugging has finished
  415.      * in this thread.
  416.      */
  417. }
  418.  
  419. /**
  420.  * Terminate task debugging session.
  421.  *
  422.  * Gracefully terminates the debugging session for a task. If the debugger
  423.  * is still waiting for events on some threads, it will receive a
  424.  * FINISHED event for each of them.
  425.  *
  426.  * @param ta    Task structure. ta->udebug.lock must be already locked.
  427.  * @return  Zero on success or negative error code.
  428.  */
  429. int udebug_task_cleanup(struct task *ta)
  430. {
  431.     thread_t *t;
  432.     link_t *cur;
  433.     int flags;
  434.     ipl_t ipl;
  435.  
  436.     LOG("udebug_task_cleanup()\n");
  437.     LOG("task %" PRIu64 "\n", ta->taskid);
  438.  
  439.     if (ta->udebug.dt_state != UDEBUG_TS_BEGINNING &&
  440.         ta->udebug.dt_state != UDEBUG_TS_ACTIVE) {
  441.         LOG("udebug_task_cleanup(): task not being debugged\n");
  442.         return EINVAL;
  443.     }
  444.  
  445.     /* Finish debugging of all userspace threads */
  446.     for (cur = ta->th_head.next; cur != &ta->th_head; cur = cur->next) {
  447.         t = list_get_instance(cur, thread_t, th_link);
  448.  
  449.         mutex_lock(&t->udebug.lock);
  450.  
  451.         ipl = interrupts_disable();
  452.         spinlock_lock(&t->lock);
  453.  
  454.         flags = t->flags;
  455.  
  456.         spinlock_unlock(&t->lock);
  457.         interrupts_restore(ipl);
  458.  
  459.         /* Only process userspace threads. */
  460.         if ((flags & THREAD_FLAG_USPACE) != 0) {
  461.             /* Prevent any further debug activity in thread. */
  462.             t->udebug.debug_active = false;
  463.             t->udebug.cur_event = 0;    /* none */
  464.  
  465.             /* Is the thread still go? */
  466.             if (t->udebug.go == true) {
  467.                 /*
  468.                 * Yes, so clear go. As debug_active == false,
  469.                  * this doesn't affect anything.
  470.                  */
  471.                 t->udebug.go = false;  
  472.  
  473.                 /* Answer GO call */
  474.                 LOG("answer GO call with EVENT_FINISHED\n");
  475.                 IPC_SET_RETVAL(t->udebug.go_call->data, 0);
  476.                 IPC_SET_ARG1(t->udebug.go_call->data,
  477.                     UDEBUG_EVENT_FINISHED);
  478.  
  479.                 ipc_answer(&ta->answerbox, t->udebug.go_call);
  480.                 t->udebug.go_call = NULL;
  481.             } else {
  482.                 /*
  483.                  * Debug_stop is already at initial value.
  484.                  * Yet this means the thread needs waking up.
  485.                  */
  486.  
  487.                 /*
  488.                  * t's lock must not be held when calling
  489.                  * waitq_wakeup.
  490.                  */
  491.                 waitq_wakeup(&t->udebug.go_wq, WAKEUP_FIRST);
  492.             }
  493.         }
  494.         mutex_unlock(&t->udebug.lock);
  495.     }
  496.  
  497.     ta->udebug.dt_state = UDEBUG_TS_INACTIVE;
  498.     ta->udebug.debugger = NULL;
  499.  
  500.     return 0;
  501. }
  502.  
  503.  
  504. /** @}
  505.  */
  506.