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Diffstat (limited to 'gdb/lin-lwp.c')
| -rw-r--r-- | gdb/lin-lwp.c | 1550 |
1 files changed, 0 insertions, 1550 deletions
diff --git a/gdb/lin-lwp.c b/gdb/lin-lwp.c deleted file mode 100644 index cd577fb..0000000 --- a/gdb/lin-lwp.c +++ /dev/null @@ -1,1550 +0,0 @@ -/* Multi-threaded debugging support for GNU/Linux (LWP layer). - Copyright 2000, 2001 Free Software Foundation, Inc. - - This file is part of GDB. - - This program is free software; you can redistribute it and/or modify - it under the terms of the GNU General Public License as published by - the Free Software Foundation; either version 2 of the License, or - (at your option) any later version. - - This program is distributed in the hope that it will be useful, - but WITHOUT ANY WARRANTY; without even the implied warranty of - MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the - GNU General Public License for more details. - - You should have received a copy of the GNU General Public License - along with this program; if not, write to the Free Software - Foundation, Inc., 59 Temple Place - Suite 330, - Boston, MA 02111-1307, USA. */ - -#include "defs.h" - -#include "gdb_assert.h" -#include "gdb_string.h" -#include <errno.h> -#include <signal.h> -#include <sys/ptrace.h> -#include "gdb_wait.h" - -#include "gdbthread.h" -#include "inferior.h" -#include "target.h" -#include "regcache.h" -#include "gdbcmd.h" - -static int debug_lin_lwp; -extern const char *strsignal (int sig); - -/* On GNU/Linux there are no real LWP's. The closest thing to LWP's - are processes sharing the same VM space. A multi-threaded process - is basically a group of such processes. However, such a grouping - is almost entirely a user-space issue; the kernel doesn't enforce - such a grouping at all (this might change in the future). In - general, we'll rely on the threads library (i.e. the GNU/Linux - Threads library) to provide such a grouping. - - It is perfectly well possible to write a multi-threaded application - without the assistance of a threads library, by using the clone - system call directly. This module should be able to give some - rudimentary support for debugging such applications if developers - specify the CLONE_PTRACE flag in the clone system call, and are - using the Linux kernel 2.4 or above. - - Note that there are some peculiarities in GNU/Linux that affect - this code: - - - In general one should specify the __WCLONE flag to waitpid in - order to make it report events for any of the cloned processes - (and leave it out for the initial process). However, if a cloned - process has exited the exit status is only reported if the - __WCLONE flag is absent. Linux kernel 2.4 has a __WALL flag, but - we cannot use it since GDB must work on older systems too. - - - When a traced, cloned process exits and is waited for by the - debugger, the kernel reassigns it to the original parent and - keeps it around as a "zombie". Somehow, the GNU/Linux Threads - library doesn't notice this, which leads to the "zombie problem": - When debugged a multi-threaded process that spawns a lot of - threads will run out of processes, even if the threads exit, - because the "zombies" stay around. */ - -/* Structure describing a LWP. */ -struct lwp_info -{ - /* The process id of the LWP. This is a combination of the LWP id - and overall process id. */ - ptid_t ptid; - - /* Non-zero if this LWP is cloned. In this context "cloned" means - that the LWP is reporting to its parent using a signal other than - SIGCHLD. */ - int cloned; - - /* Non-zero if we sent this LWP a SIGSTOP (but the LWP didn't report - it back yet). */ - int signalled; - - /* Non-zero if this LWP is stopped. */ - int stopped; - - /* Non-zero if this LWP will be/has been resumed. Note that an LWP - can be marked both as stopped and resumed at the same time. This - happens if we try to resume an LWP that has a wait status - pending. We shouldn't let the LWP run until that wait status has - been processed, but we should not report that wait status if GDB - didn't try to let the LWP run. */ - int resumed; - - /* If non-zero, a pending wait status. */ - int status; - - /* Non-zero if we were stepping this LWP. */ - int step; - - /* Next LWP in list. */ - struct lwp_info *next; -}; - -/* List of known LWPs. */ -static struct lwp_info *lwp_list; - -/* Number of LWPs in the list. */ -static int num_lwps; - -/* Non-zero if we're running in "threaded" mode. */ -static int threaded; - - -#define GET_LWP(ptid) ptid_get_lwp (ptid) -#define GET_PID(ptid) ptid_get_pid (ptid) -#define is_lwp(ptid) (GET_LWP (ptid) != 0) -#define BUILD_LWP(lwp, pid) ptid_build (pid, lwp, 0) - -/* If the last reported event was a SIGTRAP, this variable is set to - the process id of the LWP/thread that got it. */ -ptid_t trap_ptid; - - -/* This module's target-specific operations. */ -static struct target_ops lin_lwp_ops; - -/* The standard child operations. */ -extern struct target_ops child_ops; - -/* Since we cannot wait (in lin_lwp_wait) for the initial process and - any cloned processes with a single call to waitpid, we have to use - the WNOHANG flag and call waitpid in a loop. To optimize - things a bit we use `sigsuspend' to wake us up when a process has - something to report (it will send us a SIGCHLD if it has). To make - this work we have to juggle with the signal mask. We save the - original signal mask such that we can restore it before creating a - new process in order to avoid blocking certain signals in the - inferior. We then block SIGCHLD during the waitpid/sigsuspend - loop. */ - -/* Original signal mask. */ -static sigset_t normal_mask; - -/* Signal mask for use with sigsuspend in lin_lwp_wait, initialized in - _initialize_lin_lwp. */ -static sigset_t suspend_mask; - -/* Signals to block to make that sigsuspend work. */ -static sigset_t blocked_mask; - - -/* Prototypes for local functions. */ -static int stop_wait_callback (struct lwp_info *lp, void *data); - -/* Convert wait status STATUS to a string. Used for printing debug - messages only. */ - -static char * -status_to_str (int status) -{ - static char buf[64]; - - if (WIFSTOPPED (status)) - snprintf (buf, sizeof (buf), "%s (stopped)", - strsignal (WSTOPSIG (status))); - else if (WIFSIGNALED (status)) - snprintf (buf, sizeof (buf), "%s (terminated)", - strsignal (WSTOPSIG (status))); - else - snprintf (buf, sizeof (buf), "%d (exited)", - WEXITSTATUS (status)); - - return buf; -} - -/* Initialize the list of LWPs. Note that this module, contrary to - what GDB's generic threads layer does for its thread list, - re-initializes the LWP lists whenever we mourn or detach (which - doesn't involve mourning) the inferior. */ - -static void -init_lwp_list (void) -{ - struct lwp_info *lp, *lpnext; - - for (lp = lwp_list; lp; lp = lpnext) - { - lpnext = lp->next; - xfree (lp); - } - - lwp_list = NULL; - num_lwps = 0; - threaded = 0; -} - -/* Add the LWP specified by PID to the list. If this causes the - number of LWPs to become larger than one, go into "threaded" mode. - Return a pointer to the structure describing the new LWP. */ - -static struct lwp_info * -add_lwp (ptid_t ptid) -{ - struct lwp_info *lp; - - gdb_assert (is_lwp (ptid)); - - lp = (struct lwp_info *) xmalloc (sizeof (struct lwp_info)); - - memset (lp, 0, sizeof (struct lwp_info)); - - lp->ptid = ptid; - - lp->next = lwp_list; - lwp_list = lp; - if (++num_lwps > 1) - threaded = 1; - - return lp; -} - -/* Remove the LWP specified by PID from the list. */ - -static void -delete_lwp (ptid_t ptid) -{ - struct lwp_info *lp, *lpprev; - - lpprev = NULL; - - for (lp = lwp_list; lp; lpprev = lp, lp = lp->next) - if (ptid_equal (lp->ptid, ptid)) - break; - - if (!lp) - return; - - /* We don't go back to "non-threaded" mode if the number of threads - becomes less than two. */ - num_lwps--; - - if (lpprev) - lpprev->next = lp->next; - else - lwp_list = lp->next; - - xfree (lp); -} - -/* Return a pointer to the structure describing the LWP corresponding - to PID. If no corresponding LWP could be found, return NULL. */ - -static struct lwp_info * -find_lwp_pid (ptid_t ptid) -{ - struct lwp_info *lp; - int lwp; - - if (is_lwp (ptid)) - lwp = GET_LWP (ptid); - else - lwp = GET_PID (ptid); - - for (lp = lwp_list; lp; lp = lp->next) - if (lwp == GET_LWP (lp->ptid)) - return lp; - - return NULL; -} - -/* Call CALLBACK with its second argument set to DATA for every LWP in - the list. If CALLBACK returns 1 for a particular LWP, return a - pointer to the structure describing that LWP immediately. - Otherwise return NULL. */ - -struct lwp_info * -iterate_over_lwps (int (*callback) (struct lwp_info *, void *), void *data) -{ - struct lwp_info *lp, *lpnext; - - for (lp = lwp_list; lp; lp = lpnext) - { - lpnext = lp->next; - if ((*callback) (lp, data)) - return lp; - } - - return NULL; -} - - -/* Implementation of the PREPARE_TO_PROCEED hook for the GNU/Linux LWP - layer. - - Note that this implementation is potentially redundant now that - default_prepare_to_proceed() has been added. - - FIXME This may not support switching threads after Ctrl-C - correctly. The default implementation does support this. */ - -int -lin_lwp_prepare_to_proceed (void) -{ - if (! ptid_equal (trap_ptid, null_ptid) - && ! ptid_equal (inferior_ptid, trap_ptid)) - { - /* Switched over from TRAP_PID. */ - CORE_ADDR stop_pc = read_pc (); - CORE_ADDR trap_pc; - - /* Avoid switching where it wouldn't do any good, i.e. if both - threads are at the same breakpoint. */ - trap_pc = read_pc_pid (trap_ptid); - if (trap_pc != stop_pc && breakpoint_here_p (trap_pc)) - { - /* User hasn't deleted the breakpoint. Return non-zero, and - switch back to TRAP_PID. */ - inferior_ptid = trap_ptid; - - /* FIXME: Is this stuff really necessary? */ - flush_cached_frames (); - registers_changed (); - - return 1; - } - } - - return 0; -} - - -#if 0 -static void -lin_lwp_open (char *args, int from_tty) -{ - push_target (&lin_lwp_ops); -} -#endif - -/* Attach to the LWP specified by PID. If VERBOSE is non-zero, print - a message telling the user that a new LWP has been added to the - process. */ - -void -lin_lwp_attach_lwp (ptid_t ptid, int verbose) -{ - struct lwp_info *lp; - - gdb_assert (is_lwp (ptid)); - - /* Make sure SIGCHLD is blocked. We don't want SIGCHLD events - to interrupt either the ptrace() or waitpid() calls below. */ - if (! sigismember (&blocked_mask, SIGCHLD)) - { - sigaddset (&blocked_mask, SIGCHLD); - sigprocmask (SIG_BLOCK, &blocked_mask, NULL); - } - - if (verbose) - printf_filtered ("[New %s]\n", target_pid_to_str (ptid)); - - lp = find_lwp_pid (ptid); - if (lp == NULL) - lp = add_lwp (ptid); - - /* We assume that we're already attached to any LWP that has an - id equal to the overall process id. */ - if (GET_LWP (ptid) != GET_PID (ptid)) - { - pid_t pid; - int status; - - if (ptrace (PTRACE_ATTACH, GET_LWP (ptid), 0, 0) < 0) - error ("Can't attach %s: %s", target_pid_to_str (ptid), - safe_strerror (errno)); - - pid = waitpid (GET_LWP (ptid), &status, 0); - if (pid == -1 && errno == ECHILD) - { - /* Try again with __WCLONE to check cloned processes. */ - pid = waitpid (GET_LWP (ptid), &status, __WCLONE); - lp->cloned = 1; - } - - gdb_assert (pid == GET_LWP (ptid) - && WIFSTOPPED (status) && WSTOPSIG (status)); - - lp->stopped = 1; - } - else - { - /* We assume that the LWP representing the original process - is already stopped. Mark it as stopped in the data structure - that the lin-lwp layer uses to keep track of threads. Note - that this won't have already been done since the main thread - will have, we assume, been stopped by an attach from a - different layer. */ - lp->stopped = 1; - } -} - -static void -lin_lwp_attach (char *args, int from_tty) -{ - struct lwp_info *lp; - pid_t pid; - int status; - - /* FIXME: We should probably accept a list of process id's, and - attach all of them. */ - child_ops.to_attach (args, from_tty); - - /* Add the initial process as the first LWP to the list. */ - lp = add_lwp (BUILD_LWP (GET_PID (inferior_ptid), GET_PID (inferior_ptid))); - - /* Make sure the initial process is stopped. The user-level threads - layer might want to poke around in the inferior, and that won't - work if things haven't stabilized yet. */ - pid = waitpid (GET_PID (inferior_ptid), &status, 0); - if (pid == -1 && errno == ECHILD) - { - warning ("%s is a cloned process", target_pid_to_str (inferior_ptid)); - - /* Try again with __WCLONE to check cloned processes. */ - pid = waitpid (GET_PID (inferior_ptid), &status, __WCLONE); - lp->cloned = 1; - } - - gdb_assert (pid == GET_PID (inferior_ptid) - && WIFSTOPPED (status) && WSTOPSIG (status) == SIGSTOP); - - lp->stopped = 1; - - /* Fake the SIGSTOP that core GDB expects. */ - lp->status = W_STOPCODE (SIGSTOP); - lp->resumed = 1; -} - -static int -detach_callback (struct lwp_info *lp, void *data) -{ - gdb_assert (lp->status == 0 || WIFSTOPPED (lp->status)); - - if (debug_lin_lwp && lp->status) - fprintf_unfiltered (gdb_stdlog, "Pending %s for LWP %ld on detach.\n", - strsignal (WSTOPSIG (lp->status)), GET_LWP (lp->ptid)); - - while (lp->signalled && lp->stopped) - { - if (ptrace (PTRACE_CONT, GET_LWP (lp->ptid), 0, - WSTOPSIG (lp->status)) < 0) - error ("Can't continue %s: %s", target_pid_to_str (lp->ptid), - safe_strerror (errno)); - - lp->stopped = 0; - lp->signalled = 0; - lp->status = 0; - stop_wait_callback (lp, NULL); - - gdb_assert (lp->status == 0 || WIFSTOPPED (lp->status)); - } - - /* We don't actually detach from the LWP that has an id equal to the - overall process id just yet. */ - if (GET_LWP (lp->ptid) != GET_PID (lp->ptid)) - { - if (ptrace (PTRACE_DETACH, GET_LWP (lp->ptid), 0, - WSTOPSIG (lp->status)) < 0) - error ("Can't detach %s: %s", target_pid_to_str (lp->ptid), - safe_strerror (errno)); - - delete_lwp (lp->ptid); - } - - return 0; -} - -static void -lin_lwp_detach (char *args, int from_tty) -{ - iterate_over_lwps (detach_callback, NULL); - - /* Only the initial process should be left right now. */ - gdb_assert (num_lwps == 1); - - trap_ptid = null_ptid; - - /* Destroy LWP info; it's no longer valid. */ - init_lwp_list (); - - /* Restore the original signal mask. */ - sigprocmask (SIG_SETMASK, &normal_mask, NULL); - sigemptyset (&blocked_mask); - - inferior_ptid = pid_to_ptid (GET_PID (inferior_ptid)); - child_ops.to_detach (args, from_tty); -} - - -struct private_thread_info -{ - int lwpid; -}; - -/* Return non-zero if TP corresponds to the LWP specified by DATA - (which is assumed to be a pointer to a `struct lwp_info'. */ - -static int -find_lwp_callback (struct thread_info *tp, void *data) -{ - struct lwp_info *lp = data; - - if (tp->private->lwpid == GET_LWP (lp->ptid)) - return 1; - - return 0; -} - -/* Resume LP. */ - -static int -resume_callback (struct lwp_info *lp, void *data) -{ - if (lp->stopped && lp->status == 0) - { - struct thread_info *tp; - -#if 0 - /* FIXME: kettenis/2000-08-26: This should really be handled - properly by core GDB. */ - - tp = find_thread_pid (lp->ptid); - if (tp == NULL) - tp = iterate_over_threads (find_lwp_callback, lp); - gdb_assert (tp); - - /* If we were previously stepping the thread, and now continue - the thread we must invalidate the stepping range. However, - if there is a step_resume breakpoint for this thread, we must - preserve the stepping range to make it possible to continue - stepping once we hit it. */ - if (tp->step_range_end && tp->step_resume_breakpoint == NULL) - { - gdb_assert (lp->step); - tp->step_range_start = tp->step_range_end = 0; - } -#endif - - child_resume (pid_to_ptid (GET_LWP (lp->ptid)), 0, TARGET_SIGNAL_0); - lp->stopped = 0; - lp->step = 0; - } - - return 0; -} - -static int -resume_clear_callback (struct lwp_info *lp, void *data) -{ - lp->resumed = 0; - return 0; -} - -static int -resume_set_callback (struct lwp_info *lp, void *data) -{ - lp->resumed = 1; - return 0; -} - -static void -lin_lwp_resume (ptid_t ptid, int step, enum target_signal signo) -{ - struct lwp_info *lp; - int resume_all; - - /* Apparently the interpretation of PID is dependent on STEP: If - STEP is non-zero, a specific PID means `step only this process - id'. But if STEP is zero, then PID means `continue *all* - processes, but give the signal only to this one'. */ - resume_all = (PIDGET (ptid) == -1) || !step; - - if (resume_all) - iterate_over_lwps (resume_set_callback, NULL); - else - iterate_over_lwps (resume_clear_callback, NULL); - - /* If PID is -1, it's the current inferior that should be - handled specially. */ - if (PIDGET (ptid) == -1) - ptid = inferior_ptid; - - lp = find_lwp_pid (ptid); - if (lp) - { - ptid = pid_to_ptid (GET_LWP (lp->ptid)); - - /* Remember if we're stepping. */ - lp->step = step; - - /* Mark this LWP as resumed. */ - lp->resumed = 1; - - /* If we have a pending wait status for this thread, there is no - point in resuming the process. */ - if (lp->status) - { - /* FIXME: What should we do if we are supposed to continue - this thread with a signal? */ - gdb_assert (signo == TARGET_SIGNAL_0); - return; - } - - /* Mark LWP as not stopped to prevent it from being continued by - resume_callback. */ - lp->stopped = 0; - } - - if (resume_all) - iterate_over_lwps (resume_callback, NULL); - - child_resume (ptid, step, signo); -} - - -/* Send a SIGSTOP to LP. */ - -static int -stop_callback (struct lwp_info *lp, void *data) -{ - if (! lp->stopped && ! lp->signalled) - { - int ret; - - ret = kill (GET_LWP (lp->ptid), SIGSTOP); - gdb_assert (ret == 0); - - lp->signalled = 1; - gdb_assert (lp->status == 0); - } - - return 0; -} - -/* Wait until LP is stopped. If DATA is non-null it is interpreted as - a pointer to a set of signals to be flushed immediately. */ - -static int -stop_wait_callback (struct lwp_info *lp, void *data) -{ - sigset_t *flush_mask = data; - - if (! lp->stopped && lp->signalled) - { - pid_t pid; - int status; - - gdb_assert (lp->status == 0); - - pid = waitpid (GET_LWP (lp->ptid), &status, lp->cloned ? __WCLONE : 0); - if (pid == -1 && errno == ECHILD) - /* OK, the proccess has disappeared. We'll catch the actual - exit event in lin_lwp_wait. */ - return 0; - - gdb_assert (pid == GET_LWP (lp->ptid)); - - if (WIFEXITED (status) || WIFSIGNALED (status)) - { - gdb_assert (num_lwps > 1); - - if (in_thread_list (lp->ptid)) - { - /* Core GDB cannot deal with us deleting the current - thread. */ - if (!ptid_equal (lp->ptid, inferior_ptid)) - delete_thread (lp->ptid); - printf_unfiltered ("[%s exited]\n", - target_pid_to_str (lp->ptid)); - } - if (debug_lin_lwp) - fprintf_unfiltered (gdb_stdlog, - "%s exited.\n", target_pid_to_str (lp->ptid)); - - delete_lwp (lp->ptid); - return 0; - } - - gdb_assert (WIFSTOPPED (status)); - - /* Ignore any signals in FLUSH_MASK. */ - if (flush_mask && sigismember (flush_mask, WSTOPSIG (status))) - { - ptrace (PTRACE_CONT, GET_LWP (lp->ptid), 0, 0); - return stop_wait_callback (lp, flush_mask); - } - - if (WSTOPSIG (status) != SIGSTOP) - { - if (WSTOPSIG (status) == SIGTRAP) - { - /* If a LWP other than the LWP that we're reporting an - event for has hit a GDB breakpoint (as opposed to - some random trap signal), then just arrange for it to - hit it again later. We don't keep the SIGTRAP status - and don't forward the SIGTRAP signal to the LWP. We - will handle the current event, eventually we will - resume all LWPs, and this one will get its breakpoint - trap again. - - If we do not do this, then we run the risk that the - user will delete or disable the breakpoint, but the - thread will have already tripped on it. */ - - /* Now resume this LWP and get the SIGSTOP event. */ - ptrace (PTRACE_CONT, GET_LWP (lp->ptid), 0, 0); - if (debug_lin_lwp) - { - fprintf_unfiltered (gdb_stderr, - "SWC: Candidate SIGTRAP event in %ld\n", - GET_LWP (lp->ptid)); - } - /* Hold the SIGTRAP for handling by lin_lwp_wait. */ - stop_wait_callback (lp, data); - /* If there's another event, throw it back into the queue. */ - if (lp->status) - kill (GET_LWP (lp->ptid), WSTOPSIG (lp->status)); - /* Save the sigtrap event. */ - lp->status = status; - return 0; - } - else - { - /* The thread was stopped with a signal other than - SIGSTOP, and didn't accidentally trip a breakpoint. */ - - if (debug_lin_lwp) - { - fprintf_unfiltered (gdb_stderr, - "SWC: Pending event %d in %ld\n", - WSTOPSIG (status), GET_LWP (lp->ptid)); - } - /* Now resume this LWP and get the SIGSTOP event. */ - ptrace (PTRACE_CONT, GET_LWP (lp->ptid), 0, 0); - - /* Hold this event/waitstatus while we check to see if - there are any more (we still want to get that SIGSTOP). */ - stop_wait_callback (lp, data); - /* If the lp->status field is still empty, use it to hold - this event. If not, then this event must be returned - to the event queue of the LWP. */ - if (lp->status == 0) - lp->status = status; - else - kill (GET_LWP (lp->ptid), WSTOPSIG (status)); - return 0; - } - } - else - { - /* We caught the SIGSTOP that we intended to catch, so - there's no SIGSTOP pending. */ - lp->stopped = 1; - lp->signalled = 0; - } - } - - return 0; -} - -/* Return non-zero if LP has a wait status pending. */ - -static int -status_callback (struct lwp_info *lp, void *data) -{ - /* Only report a pending wait status if we pretend that this has - indeed been resumed. */ - return (lp->status != 0 && lp->resumed); -} - -/* Return non-zero if LP isn't stopped. */ - -static int -running_callback (struct lwp_info *lp, void *data) -{ - return (lp->stopped == 0); -} - -/* Count the LWP's that have had events. */ - -static int -count_events_callback (struct lwp_info *lp, void *data) -{ - int *count = data; - - gdb_assert (count != NULL); - - /* Count only LWPs that have a SIGTRAP event pending. */ - if (lp->status != 0 - && WIFSTOPPED (lp->status) && WSTOPSIG (lp->status) == SIGTRAP) - (*count)++; - - return 0; -} - -/* Select the LWP (if any) that is currently being single-stepped. */ - -static int -select_singlestep_lwp_callback (struct lwp_info *lp, void *data) -{ - if (lp->step && lp->status != 0) - return 1; - else - return 0; -} - -/* Select the Nth LWP that has had a SIGTRAP event. */ - -static int -select_event_lwp_callback (struct lwp_info *lp, void *data) -{ - int *selector = data; - - gdb_assert (selector != NULL); - - /* Select only LWPs that have a SIGTRAP event pending. */ - if (lp->status != 0 - && WIFSTOPPED (lp->status) && WSTOPSIG (lp->status) == SIGTRAP) - if ((*selector)-- == 0) - return 1; - - return 0; -} - -static int -cancel_breakpoints_callback (struct lwp_info *lp, void *data) -{ - struct lwp_info *event_lp = data; - - /* Leave the LWP that has been elected to receive a SIGTRAP alone. */ - if (lp == event_lp) - return 0; - - /* If a LWP other than the LWP that we're reporting an event for has - hit a GDB breakpoint (as opposed to some random trap signal), - then just arrange for it to hit it again later. We don't keep - the SIGTRAP status and don't forward the SIGTRAP signal to the - LWP. We will handle the current event, eventually we will resume - all LWPs, and this one will get its breakpoint trap again. - - If we do not do this, then we run the risk that the user will - delete or disable the breakpoint, but the LWP will have already - tripped on it. */ - - if (lp->status != 0 - && WIFSTOPPED (lp->status) && WSTOPSIG (lp->status) == SIGTRAP - && breakpoint_inserted_here_p (read_pc_pid (lp->ptid) - - DECR_PC_AFTER_BREAK)) - { - if (debug_lin_lwp) - fprintf_unfiltered (gdb_stdlog, - "Push back breakpoint for LWP %ld\n", - GET_LWP (lp->ptid)); - - /* Back up the PC if necessary. */ - if (DECR_PC_AFTER_BREAK) - write_pc_pid (read_pc_pid (lp->ptid) - DECR_PC_AFTER_BREAK, lp->ptid); - - /* Throw away the SIGTRAP. */ - lp->status = 0; - } - - return 0; -} - -/* Select one LWP out of those that have events pending. */ - -static void -select_event_lwp (struct lwp_info **orig_lp, int *status) -{ - int num_events = 0; - int random_selector; - struct lwp_info *event_lp; - - /* Record the wait status for the origional LWP. */ - (*orig_lp)->status = *status; - - /* Give preference to any LWP that is being single-stepped. */ - event_lp = iterate_over_lwps (select_singlestep_lwp_callback, NULL); - if (event_lp != NULL) - { - if (debug_lin_lwp) - fprintf_unfiltered (gdb_stdlog, - "Select single-step LWP %ld\n", - GET_LWP (event_lp->ptid)); - } - else - { - /* No single-stepping LWP. Select one at random, out of those - which have had SIGTRAP events. */ - - /* First see how many SIGTRAP events we have. */ - iterate_over_lwps (count_events_callback, &num_events); - - /* Now randomly pick a LWP out of those that have had a SIGTRAP. */ - random_selector = (int) - ((num_events * (double) rand ()) / (RAND_MAX + 1.0)); - - if (debug_lin_lwp && num_events > 1) - fprintf_unfiltered (gdb_stdlog, - "Found %d SIGTRAP events, selecting #%d\n", - num_events, random_selector); - - event_lp = iterate_over_lwps (select_event_lwp_callback, - &random_selector); - } - - if (event_lp != NULL) - { - /* Switch the event LWP. */ - *orig_lp = event_lp; - *status = event_lp->status; - } - - /* Flush the wait status for the event LWP. */ - (*orig_lp)->status = 0; -} - -/* Return non-zero if LP has been resumed. */ - -static int -resumed_callback (struct lwp_info *lp, void *data) -{ - return lp->resumed; -} - -#ifdef CHILD_WAIT - -/* We need to override child_wait to support attaching to cloned - processes, since a normal wait (as done by the default version) - ignores those processes. */ - -/* Wait for child PTID to do something. Return id of the child, - minus_one_ptid in case of error; store status into *OURSTATUS. */ - -ptid_t -child_wait (ptid_t ptid, struct target_waitstatus *ourstatus) -{ - int save_errno; - int status; - pid_t pid; - - do - { - set_sigint_trap (); /* Causes SIGINT to be passed on to the - attached process. */ - set_sigio_trap (); - - pid = waitpid (GET_PID (ptid), &status, 0); - if (pid == -1 && errno == ECHILD) - /* Try again with __WCLONE to check cloned processes. */ - pid = waitpid (GET_PID (ptid), &status, __WCLONE); - save_errno = errno; - - clear_sigio_trap (); - clear_sigint_trap (); - } - while (pid == -1 && save_errno == EINTR); - - if (pid == -1) - { - warning ("Child process unexpectedly missing: %s", safe_strerror (errno)); - - /* Claim it exited with unknown signal. */ - ourstatus->kind = TARGET_WAITKIND_SIGNALLED; - ourstatus->value.sig = TARGET_SIGNAL_UNKNOWN; - return minus_one_ptid; - } - - store_waitstatus (ourstatus, status); - return pid_to_ptid (pid); -} - -#endif - -static ptid_t -lin_lwp_wait (ptid_t ptid, struct target_waitstatus *ourstatus) -{ - struct lwp_info *lp = NULL; - int options = 0; - int status = 0; - pid_t pid = PIDGET (ptid); - sigset_t flush_mask; - - sigemptyset (&flush_mask); - - /* Make sure SIGCHLD is blocked. */ - if (! sigismember (&blocked_mask, SIGCHLD)) - { - sigaddset (&blocked_mask, SIGCHLD); - sigprocmask (SIG_BLOCK, &blocked_mask, NULL); - } - - retry: - - /* Make sure there is at least one LWP that has been resumed, at - least if there are any LWPs at all. */ - gdb_assert (num_lwps == 0 || iterate_over_lwps (resumed_callback, NULL)); - - /* First check if there is a LWP with a wait status pending. */ - if (pid == -1) - { - /* Any LWP that's been resumed will do. */ - lp = iterate_over_lwps (status_callback, NULL); - if (lp) - { - status = lp->status; - lp->status = 0; - - if (debug_lin_lwp && status) - fprintf_unfiltered (gdb_stdlog, - "Using pending wait status %s for LWP %ld.\n", - status_to_str (status), GET_LWP (lp->ptid)); - } - - /* But if we don't fine one, we'll have to wait, and check both - cloned and uncloned processes. We start with the cloned - processes. */ - options = __WCLONE | WNOHANG; - } - else if (is_lwp (ptid)) - { - if (debug_lin_lwp) - fprintf_unfiltered (gdb_stdlog, - "Waiting for specific LWP %ld.\n", - GET_LWP (ptid)); - - /* We have a specific LWP to check. */ - lp = find_lwp_pid (ptid); - gdb_assert (lp); - status = lp->status; - lp->status = 0; - - if (debug_lin_lwp && status) - fprintf_unfiltered (gdb_stdlog, - "Using pending wait status %s for LWP %ld.\n", - status_to_str (status), GET_LWP (lp->ptid)); - - /* If we have to wait, take into account whether PID is a cloned - process or not. And we have to convert it to something that - the layer beneath us can understand. */ - options = lp->cloned ? __WCLONE : 0; - pid = GET_LWP (ptid); - } - - if (status && lp->signalled) - { - /* A pending SIGSTOP may interfere with the normal stream of - events. In a typical case where interference is a problem, - we have a SIGSTOP signal pending for LWP A while - single-stepping it, encounter an event in LWP B, and take the - pending SIGSTOP while trying to stop LWP A. After processing - the event in LWP B, LWP A is continued, and we'll never see - the SIGTRAP associated with the last time we were - single-stepping LWP A. */ - - /* Resume the thread. It should halt immediately returning the - pending SIGSTOP. */ - child_resume (pid_to_ptid (GET_LWP (lp->ptid)), lp->step, - TARGET_SIGNAL_0); - lp->stopped = 0; - gdb_assert (lp->resumed); - - /* This should catch the pending SIGSTOP. */ - stop_wait_callback (lp, NULL); - } - - set_sigint_trap (); /* Causes SIGINT to be passed on to the - attached process. */ - set_sigio_trap (); - - while (status == 0) - { - pid_t lwpid; - - lwpid = waitpid (pid, &status, options); - if (lwpid > 0) - { - gdb_assert (pid == -1 || lwpid == pid); - - lp = find_lwp_pid (pid_to_ptid (lwpid)); - if (! lp) - { - lp = add_lwp (BUILD_LWP (lwpid, GET_PID (inferior_ptid))); - if (options & __WCLONE) - lp->cloned = 1; - - if (threaded) - { - gdb_assert (WIFSTOPPED (status) - && WSTOPSIG (status) == SIGSTOP); - lp->signalled = 1; - - if (! in_thread_list (inferior_ptid)) - { - inferior_ptid = BUILD_LWP (GET_PID (inferior_ptid), - GET_PID (inferior_ptid)); - add_thread (inferior_ptid); - } - - add_thread (lp->ptid); - printf_unfiltered ("[New %s]\n", - target_pid_to_str (lp->ptid)); - } - } - - /* Make sure we don't report a TARGET_WAITKIND_EXITED or - TARGET_WAITKIND_SIGNALLED event if there are still LWP's - left in the process. */ - if ((WIFEXITED (status) || WIFSIGNALED (status)) && num_lwps > 1) - { - if (in_thread_list (lp->ptid)) - { - /* Core GDB cannot deal with us deleting the current - thread. */ - if (! ptid_equal (lp->ptid, inferior_ptid)) - delete_thread (lp->ptid); - printf_unfiltered ("[%s exited]\n", - target_pid_to_str (lp->ptid)); - } - if (debug_lin_lwp) - fprintf_unfiltered (gdb_stdlog, - "%s exited.\n", - target_pid_to_str (lp->ptid)); - - delete_lwp (lp->ptid); - - /* Make sure there is at least one thread running. */ - gdb_assert (iterate_over_lwps (running_callback, NULL)); - - /* Discard the event. */ - status = 0; - continue; - } - - /* Make sure we don't report a SIGSTOP that we sent - ourselves in an attempt to stop an LWP. */ - if (lp->signalled && WIFSTOPPED (status) - && WSTOPSIG (status) == SIGSTOP) - { - if (debug_lin_lwp) - fprintf_unfiltered (gdb_stdlog, - "Delayed SIGSTOP caught for %s.\n", - target_pid_to_str (lp->ptid)); - - /* This is a delayed SIGSTOP. */ - lp->signalled = 0; - - child_resume (pid_to_ptid (GET_LWP (lp->ptid)), lp->step, - TARGET_SIGNAL_0); - lp->stopped = 0; - gdb_assert (lp->resumed); - - /* Discard the event. */ - status = 0; - continue; - } - - break; - } - - if (pid == -1) - { - /* Alternate between checking cloned and uncloned processes. */ - options ^= __WCLONE; - - /* And suspend every time we have checked both. */ - if (options & __WCLONE) - sigsuspend (&suspend_mask); - } - - /* We shouldn't end up here unless we want to try again. */ - gdb_assert (status == 0); - } - - clear_sigio_trap (); - clear_sigint_trap (); - - gdb_assert (lp); - - /* Don't report signals that GDB isn't interested in, such as - signals that are neither printed nor stopped upon. Stopping all - threads can be a bit time-consuming so if we want decent - performance with heavily multi-threaded programs, especially when - they're using a high frequency timer, we'd better avoid it if we - can. */ - - if (WIFSTOPPED (status)) - { - int signo = target_signal_from_host (WSTOPSIG (status)); - - if (signal_stop_state (signo) == 0 - && signal_print_state (signo) == 0 - && signal_pass_state (signo) == 1) - { - /* FIMXE: kettenis/2001-06-06: Should we resume all threads - here? It is not clear we should. GDB may not expect - other threads to run. On the other hand, not resuming - newly attached threads may cause an unwanted delay in - getting them running. */ - child_resume (pid_to_ptid (GET_LWP (lp->ptid)), lp->step, signo); - lp->stopped = 0; - status = 0; - goto retry; - } - - if (signo == TARGET_SIGNAL_INT - && signal_pass_state (signo) == 0) - { - /* If ^C/BREAK is typed at the tty/console, SIGINT gets - forwarded to the entire process group, that is, all LWP's - will receive it. Since we only want to report it once, - we try to flush it from all LWPs except this one. */ - sigaddset (&flush_mask, SIGINT); - } - } - - /* This LWP is stopped now. */ - lp->stopped = 1; - - if (debug_lin_lwp) - fprintf_unfiltered (gdb_stdlog, "Candidate event %s in LWP %ld.\n", - status_to_str (status), GET_LWP (lp->ptid)); - - /* Now stop all other LWP's ... */ - iterate_over_lwps (stop_callback, NULL); - - /* ... and wait until all of them have reported back that they're no - longer running. */ - iterate_over_lwps (stop_wait_callback, &flush_mask); - - /* If we're not waiting for a specific LWP, choose an event LWP from - among those that have had events. Giving equal priority to all - LWPs that have had events helps prevent starvation. */ - if (pid == -1) - select_event_lwp (&lp, &status); - - /* Now that we've selected our final event LWP, cancel any - breakpoints in other LWPs that have hit a GDB breakpoint. See - the comment in cancel_breakpoints_callback to find out why. */ - iterate_over_lwps (cancel_breakpoints_callback, lp); - - /* If we're not running in "threaded" mode, we'll report the bare - process id. */ - - if (WIFSTOPPED (status) && WSTOPSIG (status) == SIGTRAP) - { - trap_ptid = (threaded ? lp->ptid : pid_to_ptid (GET_LWP (lp->ptid))); - if (debug_lin_lwp) - fprintf_unfiltered (gdb_stdlog, - "LLW: trap_ptid is %ld\n", - GET_LWP (trap_ptid)); - } - else - trap_ptid = null_ptid; - - store_waitstatus (ourstatus, status); - return (threaded ? lp->ptid : pid_to_ptid (GET_LWP (lp->ptid))); -} - -static int -kill_callback (struct lwp_info *lp, void *data) -{ - ptrace (PTRACE_KILL, GET_LWP (lp->ptid), 0, 0); - return 0; -} - -static int -kill_wait_callback (struct lwp_info *lp, void *data) -{ - pid_t pid; - - /* We must make sure that there are no pending events (delayed - SIGSTOPs, pending SIGTRAPs, etc.) to make sure the current - program doesn't interfere with any following debugging session. */ - - /* For cloned processes we must check both with __WCLONE and - without, since the exit status of a cloned process isn't reported - with __WCLONE. */ - if (lp->cloned) - { - do - { - pid = waitpid (GET_LWP (lp->ptid), NULL, __WCLONE); - } - while (pid == GET_LWP (lp->ptid)); - - gdb_assert (pid == -1 && errno == ECHILD); - } - - do - { - pid = waitpid (GET_LWP (lp->ptid), NULL, 0); - } - while (pid == GET_LWP (lp->ptid)); - - gdb_assert (pid == -1 && errno == ECHILD); - return 0; -} - -static void -lin_lwp_kill (void) -{ - /* Kill all LWP's ... */ - iterate_over_lwps (kill_callback, NULL); - - /* ... and wait until we've flushed all events. */ - iterate_over_lwps (kill_wait_callback, NULL); - - target_mourn_inferior (); -} - -static void -lin_lwp_create_inferior (char *exec_file, char *allargs, char **env) -{ - child_ops.to_create_inferior (exec_file, allargs, env); -} - -static void -lin_lwp_mourn_inferior (void) -{ - trap_ptid = null_ptid; - - /* Destroy LWP info; it's no longer valid. */ - init_lwp_list (); - - /* Restore the original signal mask. */ - sigprocmask (SIG_SETMASK, &normal_mask, NULL); - sigemptyset (&blocked_mask); - - child_ops.to_mourn_inferior (); -} - -static void -lin_lwp_fetch_registers (int regno) -{ - struct cleanup *old_chain = save_inferior_ptid (); - - if (is_lwp (inferior_ptid)) - inferior_ptid = pid_to_ptid (GET_LWP (inferior_ptid)); - - fetch_inferior_registers (regno); - - do_cleanups (old_chain); -} - -static void -lin_lwp_store_registers (int regno) -{ - struct cleanup *old_chain = save_inferior_ptid (); - - if (is_lwp (inferior_ptid)) - inferior_ptid = pid_to_ptid (GET_LWP (inferior_ptid)); - - store_inferior_registers (regno); - - do_cleanups (old_chain); -} - -static int -lin_lwp_xfer_memory (CORE_ADDR memaddr, char *myaddr, int len, int write, - struct mem_attrib *attrib, - struct target_ops *target) -{ - struct cleanup *old_chain = save_inferior_ptid (); - int xfer; - - if (is_lwp (inferior_ptid)) - inferior_ptid = pid_to_ptid (GET_LWP (inferior_ptid)); - - xfer = child_xfer_memory (memaddr, myaddr, len, write, attrib, target); - - do_cleanups (old_chain); - return xfer; -} - -static int -lin_lwp_thread_alive (ptid_t ptid) -{ - gdb_assert (is_lwp (ptid)); - - errno = 0; - ptrace (PTRACE_PEEKUSER, GET_LWP (ptid), 0, 0); - if (errno) - return 0; - - return 1; -} - -static char * -lin_lwp_pid_to_str (ptid_t ptid) -{ - static char buf[64]; - - if (is_lwp (ptid)) - { - snprintf (buf, sizeof (buf), "LWP %ld", GET_LWP (ptid)); - return buf; - } - - return normal_pid_to_str (ptid); -} - -static void -init_lin_lwp_ops (void) -{ -#if 0 - lin_lwp_ops.to_open = lin_lwp_open; -#endif - lin_lwp_ops.to_shortname = "lwp-layer"; - lin_lwp_ops.to_longname = "lwp-layer"; - lin_lwp_ops.to_doc = "Low level threads support (LWP layer)"; - lin_lwp_ops.to_attach = lin_lwp_attach; - lin_lwp_ops.to_detach = lin_lwp_detach; - lin_lwp_ops.to_resume = lin_lwp_resume; - lin_lwp_ops.to_wait = lin_lwp_wait; - lin_lwp_ops.to_fetch_registers = lin_lwp_fetch_registers; - lin_lwp_ops.to_store_registers = lin_lwp_store_registers; - lin_lwp_ops.to_xfer_memory = lin_lwp_xfer_memory; - lin_lwp_ops.to_kill = lin_lwp_kill; - lin_lwp_ops.to_create_inferior = lin_lwp_create_inferior; - lin_lwp_ops.to_mourn_inferior = lin_lwp_mourn_inferior; - lin_lwp_ops.to_thread_alive = lin_lwp_thread_alive; - lin_lwp_ops.to_pid_to_str = lin_lwp_pid_to_str; - lin_lwp_ops.to_stratum = thread_stratum; - lin_lwp_ops.to_has_thread_control = tc_schedlock; - lin_lwp_ops.to_magic = OPS_MAGIC; -} - -static void -sigchld_handler (int signo) -{ - /* Do nothing. The only reason for this handler is that it allows - us to use sigsuspend in lin_lwp_wait above to wait for the - arrival of a SIGCHLD. */ -} - -void -_initialize_lin_lwp (void) -{ - struct sigaction action; - - extern void thread_db_init (struct target_ops *); - - init_lin_lwp_ops (); - add_target (&lin_lwp_ops); - thread_db_init (&lin_lwp_ops); - - /* Save the original signal mask. */ - sigprocmask (SIG_SETMASK, NULL, &normal_mask); - - action.sa_handler = sigchld_handler; - sigemptyset (&action.sa_mask); - action.sa_flags = 0; - sigaction (SIGCHLD, &action, NULL); - - /* Make sure we don't block SIGCHLD during a sigsuspend. */ - sigprocmask (SIG_SETMASK, NULL, &suspend_mask); - sigdelset (&suspend_mask, SIGCHLD); - - sigemptyset (&blocked_mask); - - add_show_from_set (add_set_cmd ("lin-lwp", no_class, var_zinteger, - (char *) &debug_lin_lwp, - "Set debugging of GNU/Linux lwp module.\n\ -Enables printf debugging output.\n", - &setdebuglist), - &showdebuglist); -} - - -/* FIXME: kettenis/2000-08-26: The stuff on this page is specific to - the GNU/Linux Threads library and therefore doesn't really belong - here. */ - -/* Read variable NAME in the target and return its value if found. - Otherwise return zero. It is assumed that the type of the variable - is `int'. */ - -static int -get_signo (const char *name) -{ - struct minimal_symbol *ms; - int signo; - - ms = lookup_minimal_symbol (name, NULL, NULL); - if (ms == NULL) - return 0; - - if (target_read_memory (SYMBOL_VALUE_ADDRESS (ms), (char *) &signo, - sizeof (signo)) != 0) - return 0; - - return signo; -} - -/* Return the set of signals used by the threads library in *SET. */ - -void -lin_thread_get_thread_signals (sigset_t *set) -{ - struct sigaction action; - int restart, cancel; - - sigemptyset (set); - - restart = get_signo ("__pthread_sig_restart"); - if (restart == 0) - return; - - cancel = get_signo ("__pthread_sig_cancel"); - if (cancel == 0) - return; - - sigaddset (set, restart); - sigaddset (set, cancel); - - /* The GNU/Linux Threads library makes terminating threads send a - special "cancel" signal instead of SIGCHLD. Make sure we catch - those (to prevent them from terminating GDB itself, which is - likely to be their default action) and treat them the same way as - SIGCHLD. */ - - action.sa_handler = sigchld_handler; - sigemptyset (&action.sa_mask); - action.sa_flags = 0; - sigaction (cancel, &action, NULL); - - /* We block the "cancel" signal throughout this code ... */ - sigaddset (&blocked_mask, cancel); - sigprocmask (SIG_BLOCK, &blocked_mask, NULL); - - /* ... except during a sigsuspend. */ - sigdelset (&suspend_mask, cancel); -} |