diff options
Diffstat (limited to 'gdbserver/event-loop.cc')
| -rw-r--r-- | gdbserver/event-loop.cc | 567 |
1 files changed, 567 insertions, 0 deletions
diff --git a/gdbserver/event-loop.cc b/gdbserver/event-loop.cc new file mode 100644 index 00000000000..8827e8a32eb --- /dev/null +++ b/gdbserver/event-loop.cc @@ -0,0 +1,567 @@ +/* Event loop machinery for the remote server for GDB. + Copyright (C) 1999-2020 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 3 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, see <http://www.gnu.org/licenses/>. */ + +/* Based on src/gdb/event-loop.c. */ + +#include "server.h" + +#include <sys/types.h> +#include "gdbsupport/gdb_sys_time.h" + +#ifdef USE_WIN32API +#include <windows.h> +#include <io.h> +#endif + +#include <unistd.h> +#include <queue> + +typedef int (event_handler_func) (gdb_fildes_t); + +/* Tell create_file_handler what events we are interested in. */ + +#define GDB_READABLE (1<<1) +#define GDB_WRITABLE (1<<2) +#define GDB_EXCEPTION (1<<3) + +/* Events are queued by on the event_queue and serviced later + on by do_one_event. An event can be, for instance, a file + descriptor becoming ready to be read. Servicing an event simply + means that the procedure PROC will be called. We have 2 queues, + one for file handlers that we listen to in the event loop, and one + for the file handlers+events that are ready. The procedure PROC + associated with each event is always the same (handle_file_event). + Its duty is to invoke the handler associated with the file + descriptor whose state change generated the event, plus doing other + cleanups and such. */ + +struct gdb_event + { + /* Procedure to call to service this event. */ + event_handler_func *proc; + + /* File descriptor that is ready. */ + gdb_fildes_t fd; + }; + +/* Information about each file descriptor we register with the event + loop. */ + +typedef struct file_handler + { + /* File descriptor. */ + gdb_fildes_t fd; + + /* Events we want to monitor. */ + int mask; + + /* Events that have been seen since the last time. */ + int ready_mask; + + /* Procedure to call when fd is ready. */ + handler_func *proc; + + /* Argument to pass to proc. */ + gdb_client_data client_data; + + /* Was an error detected on this fd? */ + int error; + + /* Next registered file descriptor. */ + struct file_handler *next_file; + } +file_handler; + +typedef gdb::unique_xmalloc_ptr<gdb_event> gdb_event_up; + +static std::queue<gdb_event_up, std::list<gdb_event_up>> event_queue; + +/* Gdb_notifier is just a list of file descriptors gdb is interested + in. These are the input file descriptor, and the target file + descriptor. Each of the elements in the gdb_notifier list is + basically a description of what kind of events gdb is interested + in, for each fd. */ + +static struct + { + /* Ptr to head of file handler list. */ + file_handler *first_file_handler; + + /* Masks to be used in the next call to select. Bits are set in + response to calls to create_file_handler. */ + fd_set check_masks[3]; + + /* What file descriptors were found ready by select. */ + fd_set ready_masks[3]; + + /* Number of valid bits (highest fd value + 1). (for select) */ + int num_fds; + } +gdb_notifier; + +/* Callbacks are just routines that are executed before waiting for the + next event. In GDB this is struct gdb_timer. We don't need timers + so rather than copy all that complexity in gdbserver, we provide what + we need, but we do so in a way that if/when the day comes that we need + that complexity, it'll be easier to add - replace callbacks with timers + and use a delta of zero (which is all gdb currently uses timers for anyway). + + PROC will be executed before gdbserver goes to sleep to wait for the + next event. */ + +struct callback_event + { + int id; + callback_handler_func *proc; + gdb_client_data data; + struct callback_event *next; + }; + +/* Table of registered callbacks. */ + +static struct + { + struct callback_event *first; + struct callback_event *last; + + /* Id of the last callback created. */ + int num_callbacks; + } +callback_list; + +void +initialize_event_loop (void) +{ +} + +/* Process one event. If an event was processed, 1 is returned + otherwise 0 is returned. Scan the queue from head to tail, + processing therefore the high priority events first, by invoking + the associated event handler procedure. */ + +static int +process_event (void) +{ + /* Let's get rid of the event from the event queue. We need to + do this now because while processing the event, since the + proc function could end up jumping out to the caller of this + function. In that case, we would have on the event queue an + event which has been processed, but not deleted. */ + if (!event_queue.empty ()) + { + gdb_event_up event_ptr = std::move (event_queue.front ()); + event_queue.pop (); + + event_handler_func *proc = event_ptr->proc; + gdb_fildes_t fd = event_ptr->fd; + + /* Now call the procedure associated with the event. */ + if ((*proc) (fd)) + return -1; + return 1; + } + + /* This is the case if there are no event on the event queue. */ + return 0; +} + +/* Append PROC to the callback list. + The result is the "id" of the callback that can be passed back to + delete_callback_event. */ + +int +append_callback_event (callback_handler_func *proc, gdb_client_data data) +{ + struct callback_event *event_ptr = XNEW (struct callback_event); + + event_ptr->id = callback_list.num_callbacks++; + event_ptr->proc = proc; + event_ptr->data = data; + event_ptr->next = NULL; + if (callback_list.first == NULL) + callback_list.first = event_ptr; + if (callback_list.last != NULL) + callback_list.last->next = event_ptr; + callback_list.last = event_ptr; + return event_ptr->id; +} + +/* Delete callback ID. + It is not an error callback ID doesn't exist. */ + +void +delete_callback_event (int id) +{ + struct callback_event **p; + + for (p = &callback_list.first; *p != NULL; p = &(*p)->next) + { + struct callback_event *event_ptr = *p; + + if (event_ptr->id == id) + { + *p = event_ptr->next; + if (event_ptr == callback_list.last) + callback_list.last = NULL; + free (event_ptr); + break; + } + } +} + +/* Run the next callback. + The result is 1 if a callback was called and event processing + should continue, -1 if the callback wants the event loop to exit, + and 0 if there are no more callbacks. */ + +static int +process_callback (void) +{ + struct callback_event *event_ptr; + + event_ptr = callback_list.first; + if (event_ptr != NULL) + { + callback_handler_func *proc = event_ptr->proc; + gdb_client_data data = event_ptr->data; + + /* Remove the event before calling PROC, + more events may get added by PROC. */ + callback_list.first = event_ptr->next; + if (callback_list.first == NULL) + callback_list.last = NULL; + free (event_ptr); + if ((*proc) (data)) + return -1; + return 1; + } + + return 0; +} + +/* Add a file handler/descriptor to the list of descriptors we are + interested in. FD is the file descriptor for the file/stream to be + listened to. MASK is a combination of READABLE, WRITABLE, + EXCEPTION. PROC is the procedure that will be called when an event + occurs for FD. CLIENT_DATA is the argument to pass to PROC. */ + +static void +create_file_handler (gdb_fildes_t fd, int mask, handler_func *proc, + gdb_client_data client_data) +{ + file_handler *file_ptr; + + /* Do we already have a file handler for this file? (We may be + changing its associated procedure). */ + for (file_ptr = gdb_notifier.first_file_handler; + file_ptr != NULL; + file_ptr = file_ptr->next_file) + if (file_ptr->fd == fd) + break; + + /* It is a new file descriptor. Add it to the list. Otherwise, + just change the data associated with it. */ + if (file_ptr == NULL) + { + file_ptr = XNEW (struct file_handler); + file_ptr->fd = fd; + file_ptr->ready_mask = 0; + file_ptr->next_file = gdb_notifier.first_file_handler; + gdb_notifier.first_file_handler = file_ptr; + + if (mask & GDB_READABLE) + FD_SET (fd, &gdb_notifier.check_masks[0]); + else + FD_CLR (fd, &gdb_notifier.check_masks[0]); + + if (mask & GDB_WRITABLE) + FD_SET (fd, &gdb_notifier.check_masks[1]); + else + FD_CLR (fd, &gdb_notifier.check_masks[1]); + + if (mask & GDB_EXCEPTION) + FD_SET (fd, &gdb_notifier.check_masks[2]); + else + FD_CLR (fd, &gdb_notifier.check_masks[2]); + + if (gdb_notifier.num_fds <= fd) + gdb_notifier.num_fds = fd + 1; + } + + file_ptr->proc = proc; + file_ptr->client_data = client_data; + file_ptr->mask = mask; +} + +/* Wrapper function for create_file_handler. */ + +void +add_file_handler (gdb_fildes_t fd, + handler_func *proc, gdb_client_data client_data) +{ + create_file_handler (fd, GDB_READABLE | GDB_EXCEPTION, proc, client_data); +} + +/* Remove the file descriptor FD from the list of monitored fd's: + i.e. we don't care anymore about events on the FD. */ + +void +delete_file_handler (gdb_fildes_t fd) +{ + file_handler *file_ptr, *prev_ptr = NULL; + int i; + + /* Find the entry for the given file. */ + + for (file_ptr = gdb_notifier.first_file_handler; + file_ptr != NULL; + file_ptr = file_ptr->next_file) + if (file_ptr->fd == fd) + break; + + if (file_ptr == NULL) + return; + + if (file_ptr->mask & GDB_READABLE) + FD_CLR (fd, &gdb_notifier.check_masks[0]); + if (file_ptr->mask & GDB_WRITABLE) + FD_CLR (fd, &gdb_notifier.check_masks[1]); + if (file_ptr->mask & GDB_EXCEPTION) + FD_CLR (fd, &gdb_notifier.check_masks[2]); + + /* Find current max fd. */ + + if ((fd + 1) == gdb_notifier.num_fds) + { + gdb_notifier.num_fds--; + for (i = gdb_notifier.num_fds; i; i--) + { + if (FD_ISSET (i - 1, &gdb_notifier.check_masks[0]) + || FD_ISSET (i - 1, &gdb_notifier.check_masks[1]) + || FD_ISSET (i - 1, &gdb_notifier.check_masks[2])) + break; + } + gdb_notifier.num_fds = i; + } + + /* Deactivate the file descriptor, by clearing its mask, so that it + will not fire again. */ + + file_ptr->mask = 0; + + /* Get rid of the file handler in the file handler list. */ + if (file_ptr == gdb_notifier.first_file_handler) + gdb_notifier.first_file_handler = file_ptr->next_file; + else + { + for (prev_ptr = gdb_notifier.first_file_handler; + prev_ptr->next_file != file_ptr; + prev_ptr = prev_ptr->next_file) + ; + prev_ptr->next_file = file_ptr->next_file; + } + free (file_ptr); +} + +/* Handle the given event by calling the procedure associated to the + corresponding file handler. Called by process_event indirectly, + through event_ptr->proc. EVENT_FILE_DESC is file descriptor of the + event in the front of the event queue. */ + +static int +handle_file_event (gdb_fildes_t event_file_desc) +{ + file_handler *file_ptr; + int mask; + + /* Search the file handler list to find one that matches the fd in + the event. */ + for (file_ptr = gdb_notifier.first_file_handler; file_ptr != NULL; + file_ptr = file_ptr->next_file) + { + if (file_ptr->fd == event_file_desc) + { + /* See if the desired events (mask) match the received + events (ready_mask). */ + + if (file_ptr->ready_mask & GDB_EXCEPTION) + { + warning ("Exception condition detected on fd %s", + pfildes (file_ptr->fd)); + file_ptr->error = 1; + } + else + file_ptr->error = 0; + mask = file_ptr->ready_mask & file_ptr->mask; + + /* Clear the received events for next time around. */ + file_ptr->ready_mask = 0; + + /* If there was a match, then call the handler. */ + if (mask != 0) + { + if ((*file_ptr->proc) (file_ptr->error, + file_ptr->client_data) < 0) + return -1; + } + break; + } + } + + return 0; +} + +/* Create a file event, to be enqueued in the event queue for + processing. The procedure associated to this event is always + handle_file_event, which will in turn invoke the one that was + associated to FD when it was registered with the event loop. */ + +static gdb_event * +create_file_event (gdb_fildes_t fd) +{ + gdb_event *file_event_ptr; + + file_event_ptr = XNEW (gdb_event); + file_event_ptr->proc = handle_file_event; + file_event_ptr->fd = fd; + + return file_event_ptr; +} + +/* Called by do_one_event to wait for new events on the monitored file + descriptors. Queue file events as they are detected by the poll. + If there are no events, this function will block in the call to + select. Return -1 if there are no files descriptors to monitor, + otherwise return 0. */ + +static int +wait_for_event (void) +{ + file_handler *file_ptr; + int num_found = 0; + + /* Make sure all output is done before getting another event. */ + fflush (stdout); + fflush (stderr); + + if (gdb_notifier.num_fds == 0) + return -1; + + gdb_notifier.ready_masks[0] = gdb_notifier.check_masks[0]; + gdb_notifier.ready_masks[1] = gdb_notifier.check_masks[1]; + gdb_notifier.ready_masks[2] = gdb_notifier.check_masks[2]; + num_found = select (gdb_notifier.num_fds, + &gdb_notifier.ready_masks[0], + &gdb_notifier.ready_masks[1], + &gdb_notifier.ready_masks[2], + NULL); + + /* Clear the masks after an error from select. */ + if (num_found == -1) + { + FD_ZERO (&gdb_notifier.ready_masks[0]); + FD_ZERO (&gdb_notifier.ready_masks[1]); + FD_ZERO (&gdb_notifier.ready_masks[2]); +#ifdef EINTR + /* Dont print anything if we got a signal, let gdb handle + it. */ + if (errno != EINTR) + perror_with_name ("select"); +#endif + } + + /* Enqueue all detected file events. */ + + for (file_ptr = gdb_notifier.first_file_handler; + file_ptr != NULL && num_found > 0; + file_ptr = file_ptr->next_file) + { + int mask = 0; + + if (FD_ISSET (file_ptr->fd, &gdb_notifier.ready_masks[0])) + mask |= GDB_READABLE; + if (FD_ISSET (file_ptr->fd, &gdb_notifier.ready_masks[1])) + mask |= GDB_WRITABLE; + if (FD_ISSET (file_ptr->fd, &gdb_notifier.ready_masks[2])) + mask |= GDB_EXCEPTION; + + if (!mask) + continue; + else + num_found--; + + /* Enqueue an event only if this is still a new event for this + fd. */ + + if (file_ptr->ready_mask == 0) + { + gdb_event *file_event_ptr = create_file_event (file_ptr->fd); + + event_queue.emplace (file_event_ptr); + } + file_ptr->ready_mask = mask; + } + + return 0; +} + +/* Start up the event loop. This is the entry point to the event + loop. */ + +void +start_event_loop (void) +{ + /* Loop until there is nothing to do. This is the entry point to + the event loop engine. If nothing is ready at this time, wait + for something to happen (via wait_for_event), then process it. + Return when there are no longer event sources to wait for. */ + + while (1) + { + /* Any events already waiting in the queue? */ + int res = process_event (); + + /* Did the event handler want the event loop to stop? */ + if (res == -1) + return; + + if (res) + continue; + + /* Process any queued callbacks before we go to sleep. */ + res = process_callback (); + + /* Did the callback want the event loop to stop? */ + if (res == -1) + return; + + if (res) + continue; + + /* Wait for a new event. If wait_for_event returns -1, we + should get out because this means that there are no event + sources left. This will make the event loop stop, and the + application exit. */ + + if (wait_for_event () < 0) + return; + } + + /* We are done with the event loop. There are no more event sources + to listen to. So we exit gdbserver. */ +} |