262 lines
10 KiB
C
262 lines
10 KiB
C
/* Definitions used by the GDB event loop.
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Copyright 1999 Free Software Foundation, Inc.
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Written by Elena Zannoni <ezannoni@cygnus.com> of Cygnus Solutions.
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This file is part of GDB.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 59 Temple Place - Suite 330,
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Boston, MA 02111-1307, USA. */
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/* An event loop listens for events from multiple event sources. When
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an event arrives, it is queued and processed by calling the
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appropriate event handler. The event loop then continues to listen
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for more events. An event loop completes when there are no event
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sources to listen on. External event sources can be plugged into
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the loop.
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There are 3 main components:
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- a list of file descriptors to be monitored, GDB_NOTIFIER.
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- a list of events that have occurred, EVENT_QUEUE.
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- a list of signal handling functions, SIGHANDLER_LIST.
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GDB_NOTIFIER keeps track of the event sources. Event sources for
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gdb are currently the UI and the target. Gdb communicates with the
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command line user interface via the readline library and usually
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communicates with remote targets via a serial port. Serial ports
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are represented in GDB as file descriptors and select/poll calls.
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For native targets instead, the communication consists of calls to
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ptrace and waits (via signals) or calls to poll/select (via file
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descriptors). In the current gdb, the code handling events related
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to the target resides in the wait_for_inferior function and in
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various target specific files (*-tdep.c).
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EVENT_QUEUE keeps track of the events that have happened during the
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last iteration of the event loop, and need to be processed. An
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event is represented by a procedure to be invoked in order to
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process the event. The queue is scanned head to tail. If the
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event of interest is a change of state in a file descriptor, then a
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call to poll or select will be made to detect it.
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If the events generate signals, they are also queued by special
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functions that are invoked through traditional signal handlers.
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The actions to be taken is response to such events will be executed
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when the SIGHANDLER_LIST is scanned, the next time through the
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infinite loop.
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Corollary tasks are the creation and deletion of event sources. */
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typedef PTR gdb_client_data;
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typedef struct gdb_event gdb_event;
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typedef void (handler_func) PARAMS ((gdb_client_data));
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typedef void (event_handler_func) PARAMS ((int));
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/* Event for the GDB event system. Events are queued by calling
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async_queue_event and serviced later on by gdb_do_one_event. An
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event can be, for instance, a file descriptor becoming ready to be
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read. Servicing an event simply means that the procedure PROC will
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be called. We have 2 queues, one for file handlers that we listen
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to in the event loop, and one for the file handlers+events that are
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ready. The procedure PROC associated with each event is always the
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same (handle_file_event). Its duty is to invoke the handler
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associated with the file descriptor whose state change generated
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the event, plus doing other cleanups adn such. */
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struct gdb_event
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{
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event_handler_func *proc; /* Procedure to call to service this event. */
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int fd; /* File descriptor that is ready. */
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struct gdb_event *next_event; /* Next in list of events or NULL. */
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};
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/* Information about each file descriptor we register with the event
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loop. */
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typedef struct file_handler
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{
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int fd; /* File descriptor. */
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int mask; /* Events we want to monitor: POLLIN, etc. */
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int ready_mask; /* Events that have been seen since
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the last time. */
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handler_func *proc; /* Procedure to call when fd is ready. */
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gdb_client_data client_data; /* Argument to pass to proc. */
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struct file_handler *next_file; /* Next registered file descriptor. */
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}
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file_handler;
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/* PROC is a function to be invoked when the READY flag is set. This
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happens when there has been a signal and the corresponding signal
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handler has 'triggered' this async_signal_handler for
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execution. The actual work to be done in response to a signal will
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be carried out by PROC at a later time, within process_event. This
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provides a deferred execution of signal handlers.
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Async_init_signals takes care of setting up such an
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asyn_signal_handler for each interesting signal. */
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typedef struct async_signal_handler
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{
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int ready; /* If ready, call this handler from the main event loop,
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using invoke_async_handler. */
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struct async_signal_handler *next_handler; /* Ptr to next handler */
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handler_func *proc; /* Function to call to do the work */
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gdb_client_data client_data; /* Argument to async_handler_func */
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}
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async_signal_handler;
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/* Where to add an event onto the event queue, by queue_event. */
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typedef enum
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{
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/* Add at tail of queue. It will be processed in first in first
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out order. */
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TAIL,
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/* Add at head of queue. It will be processed in last in first out
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order. */
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HEAD
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}
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queue_position;
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/* Tell create_file_handler what events we are interested in.
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This is used by the select version of the event loop. */
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#define GDB_READABLE (1<<1)
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#define GDB_WRITABLE (1<<2)
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#define GDB_EXCEPTION (1<<3)
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/* Type of the mask arguments to select. */
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#ifndef NO_FD_SET
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#define SELECT_MASK fd_set
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#else
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#ifndef _AIX
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typedef long fd_mask;
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#endif
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#if defined(_IBMR2)
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#define SELECT_MASK void
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#else
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#define SELECT_MASK int
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#endif
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#endif
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/* Define "NBBY" (number of bits per byte) if it's not already defined. */
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#ifndef NBBY
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#define NBBY 8
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#endif
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/* Define the number of fd_masks in an fd_set */
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#ifndef FD_SETSIZE
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#ifdef OPEN_MAX
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#define FD_SETSIZE OPEN_MAX
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#else
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#define FD_SETSIZE 256
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#endif
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#endif
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#if !defined(howmany)
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#define howmany(x, y) (((x)+((y)-1))/(y))
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#endif
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#ifndef NFDBITS
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#define NFDBITS NBBY*sizeof(fd_mask)
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#endif
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#define MASK_SIZE howmany(FD_SETSIZE, NFDBITS)
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/* Stack for prompts. Each prompt is composed as a prefix, a prompt
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and a suffix. The prompt to be displayed at any given time is the
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one on top of the stack. A stack is necessary because of cases in
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which the execution of a gdb command requires further input from
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the user, like for instance 'commands' for breakpoints and
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'actions' for tracepoints. In these cases, the prompt is '>' and
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gdb should process input using the asynchronous readline interface
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and the event loop. In order to achieve this, we need to save
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somewhere the state of GDB, i.e. that it is processing user input
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as part of a command and not as part of the top level command loop.
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The prompt stack represents part of the saved state. Another part
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would be the function that readline would invoke after a whole line
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of input has ben entered. This second piece would be something
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like, for instance, where to return within the code for the actions
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commands after a line has been read. This latter portion has not
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beeen implemented yet. The need for a 3-part prompt arises from
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the annotation level. When this is set to 2, the prompt is actually
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composed of a prefix, the prompt itself and a suffix. */
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/* At any particular time there will be always at least one prompt on
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the stack, the one being currently displayed by gdb. If gdb is
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using annotation level equal 2, there will be 2 prompts on the
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stack: the usual one, w/o prefix and suffix (at top - 1), and the
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'composite' one with prefix and suffix added (at top). At this
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time, this is the only use of the prompt stack. Resetting annotate
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to 0 or 1, pops the top of the stack, resetting its size to one
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element. The MAXPROMPTS limit is safe, for now. Once other cases
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are dealt with (like the different prompts used for 'commands' or
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'actions') this array implementation of the prompt stack may have
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to change. */
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#define MAXPROMPTS 10
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struct prompts
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{
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struct
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{
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char *prefix;
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char *prompt;
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char *suffix;
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}
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prompt_stack[MAXPROMPTS];
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int top;
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};
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#define PROMPT(X) the_prompts.prompt_stack[the_prompts.top + X].prompt
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#define PREFIX(X) the_prompts.prompt_stack[the_prompts.top + X].prefix
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#define SUFFIX(X) the_prompts.prompt_stack[the_prompts.top + X].suffix
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/* Exported functions from event-loop.c */
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extern void start_event_loop PARAMS ((void));
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extern void delete_file_handler PARAMS ((int));
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extern void add_file_handler PARAMS ((int, void (*) (void), gdb_client_data));
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extern void mark_async_signal_handler PARAMS ((async_signal_handler *));
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extern async_signal_handler *
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create_async_signal_handler PARAMS ((handler_func *, gdb_client_data));
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extern void delete_async_signal_handler PARAMS ((async_signal_handler ** async_handler_ptr));
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/* Exported functions from event-top.c.
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FIXME: these should really go into top.h. */
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extern void display_gdb_prompt PARAMS ((char *));
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extern void async_init_signals PARAMS ((void));
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extern void set_async_editing_command PARAMS ((char *, int, struct cmd_list_element *));
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extern void set_async_annotation_level PARAMS ((char *, int, struct cmd_list_element *));
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extern void set_async_prompt PARAMS ((char *, int, struct cmd_list_element *));
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extern void handle_stop_sig PARAMS ((int));
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extern void handle_sigint PARAMS ((int));
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extern void pop_prompt PARAMS ((void));
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extern void push_prompt PARAMS ((char *, char *, char *));
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extern void gdb_readline2 PARAMS ((void));
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/* Exported variables and functions from event-top.c.
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FIXME: these should really go into top.h. */
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extern int async_command_editing_p;
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extern int exec_done_display_p;
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extern char *async_annotation_suffix;
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extern char *new_async_prompt;
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extern struct prompts the_prompts;
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extern void (*call_readline) PARAMS ((void));
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extern void (*input_handler) PARAMS ((char *));
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extern int input_fd;
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void mark_async_signal_handler_wrapper (void *);
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void async_request_quit (gdb_client_data);
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