| 1 | /* Definitions used by the GDB event loop. |
| 2 | Copyright 1999 Free Software Foundation, Inc. |
| 3 | Written by Elena Zannoni <ezannoni@cygnus.com> of Cygnus Solutions. |
| 4 | |
| 5 | This file is part of GDB. |
| 6 | |
| 7 | This program is free software; you can redistribute it and/or modify |
| 8 | it under the terms of the GNU General Public License as published by |
| 9 | the Free Software Foundation; either version 2 of the License, or |
| 10 | (at your option) any later version. |
| 11 | |
| 12 | This program is distributed in the hope that it will be useful, |
| 13 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 14 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 15 | GNU General Public License for more details. |
| 16 | |
| 17 | You should have received a copy of the GNU General Public License |
| 18 | along with this program; if not, write to the Free Software |
| 19 | Foundation, Inc., 59 Temple Place - Suite 330, |
| 20 | Boston, MA 02111-1307, USA. */ |
| 21 | |
| 22 | /* An event loop listens for events from multiple event sources. When |
| 23 | an event arrives, it is queued and processed by calling the |
| 24 | appropriate event handler. The event loop then continues to listen |
| 25 | for more events. An event loop completes when there are no event |
| 26 | sources to listen on. External event sources can be plugged into |
| 27 | the loop. |
| 28 | |
| 29 | There are 3 main components: |
| 30 | - a list of file descriptors to be monitored, GDB_NOTIFIER. |
| 31 | - a list of events that have occurred, EVENT_QUEUE. |
| 32 | - a list of signal handling functions, SIGHANDLER_LIST. |
| 33 | |
| 34 | GDB_NOTIFIER keeps track of the event sources. Event sources for |
| 35 | gdb are currently the UI and the target. Gdb communicates with the |
| 36 | command line user interface via the readline library and usually |
| 37 | communicates with remote targets via a serial port. Serial ports |
| 38 | are represented in GDB as file descriptors and select/poll calls. |
| 39 | For native targets instead, the communication consists of calls to |
| 40 | ptrace and waits (via signals) or calls to poll/select (via file |
| 41 | descriptors). In the current gdb, the code handling events related |
| 42 | to the target resides in the wait_for_inferior function and in |
| 43 | various target specific files (*-tdep.c). |
| 44 | |
| 45 | EVENT_QUEUE keeps track of the events that have happened during the |
| 46 | last iteration of the event loop, and need to be processed. An |
| 47 | event is represented by a procedure to be invoked in order to |
| 48 | process the event. The queue is scanned head to tail. If the |
| 49 | event of interest is a change of state in a file descriptor, then a |
| 50 | call to poll or select will be made to detect it. |
| 51 | |
| 52 | If the events generate signals, they are also queued by special |
| 53 | functions that are invoked through traditional signal handlers. |
| 54 | The actions to be taken is response to such events will be executed |
| 55 | when the SIGHANDLER_LIST is scanned, the next time through the |
| 56 | infinite loop. |
| 57 | |
| 58 | Corollary tasks are the creation and deletion of event sources. */ |
| 59 | |
| 60 | typedef PTR gdb_client_data; |
| 61 | typedef struct gdb_event gdb_event; |
| 62 | |
| 63 | typedef void (handler_func) PARAMS ((gdb_client_data)); |
| 64 | typedef void (event_handler_func) PARAMS ((int)); |
| 65 | |
| 66 | /* Event for the GDB event system. Events are queued by calling |
| 67 | async_queue_event and serviced later on by gdb_do_one_event. An |
| 68 | event can be, for instance, a file descriptor becoming ready to be |
| 69 | read. Servicing an event simply means that the procedure PROC will |
| 70 | be called. We have 2 queues, one for file handlers that we listen |
| 71 | to in the event loop, and one for the file handlers+events that are |
| 72 | ready. The procedure PROC associated with each event is always the |
| 73 | same (handle_file_event). Its duty is to invoke the handler |
| 74 | associated with the file descriptor whose state change generated |
| 75 | the event, plus doing other cleanups adn such. */ |
| 76 | |
| 77 | struct gdb_event |
| 78 | { |
| 79 | event_handler_func *proc; /* Procedure to call to service this event. */ |
| 80 | int fd; /* File descriptor that is ready. */ |
| 81 | struct gdb_event *next_event; /* Next in list of events or NULL. */ |
| 82 | }; |
| 83 | |
| 84 | /* Information about each file descriptor we register with the event |
| 85 | loop. */ |
| 86 | |
| 87 | typedef struct file_handler |
| 88 | { |
| 89 | int fd; /* File descriptor. */ |
| 90 | int mask; /* Events we want to monitor: POLLIN, etc. */ |
| 91 | int ready_mask; /* Events that have been seen since |
| 92 | the last time. */ |
| 93 | handler_func *proc; /* Procedure to call when fd is ready. */ |
| 94 | gdb_client_data client_data; /* Argument to pass to proc. */ |
| 95 | struct file_handler *next_file; /* Next registered file descriptor. */ |
| 96 | } |
| 97 | file_handler; |
| 98 | |
| 99 | /* PROC is a function to be invoked when the READY flag is set. This |
| 100 | happens when there has been a signal and the corresponding signal |
| 101 | handler has 'triggered' this async_signal_handler for |
| 102 | execution. The actual work to be done in response to a signal will |
| 103 | be carried out by PROC at a later time, within process_event. This |
| 104 | provides a deferred execution of signal handlers. |
| 105 | Async_init_signals takes care of setting up such an |
| 106 | asyn_signal_handler for each interesting signal. */ |
| 107 | |
| 108 | typedef struct async_signal_handler |
| 109 | { |
| 110 | int ready; /* If ready, call this handler from the main event loop, |
| 111 | using invoke_async_handler. */ |
| 112 | struct async_signal_handler *next_handler; /* Ptr to next handler */ |
| 113 | handler_func *proc; /* Function to call to do the work */ |
| 114 | gdb_client_data client_data; /* Argument to async_handler_func */ |
| 115 | } |
| 116 | async_signal_handler; |
| 117 | |
| 118 | /* Where to add an event onto the event queue, by queue_event. */ |
| 119 | typedef enum |
| 120 | { |
| 121 | /* Add at tail of queue. It will be processed in first in first |
| 122 | out order. */ |
| 123 | TAIL, |
| 124 | /* Add at head of queue. It will be processed in last in first out |
| 125 | order. */ |
| 126 | HEAD |
| 127 | } |
| 128 | queue_position; |
| 129 | |
| 130 | /* Tell create_file_handler what events we are interested in. |
| 131 | This is used by the select version of the event loop. */ |
| 132 | |
| 133 | #define GDB_READABLE (1<<1) |
| 134 | #define GDB_WRITABLE (1<<2) |
| 135 | #define GDB_EXCEPTION (1<<3) |
| 136 | |
| 137 | /* Type of the mask arguments to select. */ |
| 138 | |
| 139 | #ifndef NO_FD_SET |
| 140 | #define SELECT_MASK fd_set |
| 141 | #else |
| 142 | #ifndef _AIX |
| 143 | typedef long fd_mask; |
| 144 | #endif |
| 145 | #if defined(_IBMR2) |
| 146 | #define SELECT_MASK void |
| 147 | #else |
| 148 | #define SELECT_MASK int |
| 149 | #endif |
| 150 | #endif |
| 151 | |
| 152 | /* Define "NBBY" (number of bits per byte) if it's not already defined. */ |
| 153 | |
| 154 | #ifndef NBBY |
| 155 | #define NBBY 8 |
| 156 | #endif |
| 157 | |
| 158 | |
| 159 | /* Define the number of fd_masks in an fd_set */ |
| 160 | |
| 161 | #ifndef FD_SETSIZE |
| 162 | #ifdef OPEN_MAX |
| 163 | #define FD_SETSIZE OPEN_MAX |
| 164 | #else |
| 165 | #define FD_SETSIZE 256 |
| 166 | #endif |
| 167 | #endif |
| 168 | #if !defined(howmany) |
| 169 | #define howmany(x, y) (((x)+((y)-1))/(y)) |
| 170 | #endif |
| 171 | #ifndef NFDBITS |
| 172 | #define NFDBITS NBBY*sizeof(fd_mask) |
| 173 | #endif |
| 174 | #define MASK_SIZE howmany(FD_SETSIZE, NFDBITS) |
| 175 | |
| 176 | |
| 177 | /* Stack for prompts. Each prompt is composed as a prefix, a prompt |
| 178 | and a suffix. The prompt to be displayed at any given time is the |
| 179 | one on top of the stack. A stack is necessary because of cases in |
| 180 | which the execution of a gdb command requires further input from |
| 181 | the user, like for instance 'commands' for breakpoints and |
| 182 | 'actions' for tracepoints. In these cases, the prompt is '>' and |
| 183 | gdb should process input using the asynchronous readline interface |
| 184 | and the event loop. In order to achieve this, we need to save |
| 185 | somewhere the state of GDB, i.e. that it is processing user input |
| 186 | as part of a command and not as part of the top level command loop. |
| 187 | The prompt stack represents part of the saved state. Another part |
| 188 | would be the function that readline would invoke after a whole line |
| 189 | of input has ben entered. This second piece would be something |
| 190 | like, for instance, where to return within the code for the actions |
| 191 | commands after a line has been read. This latter portion has not |
| 192 | beeen implemented yet. The need for a 3-part prompt arises from |
| 193 | the annotation level. When this is set to 2, the prompt is actually |
| 194 | composed of a prefix, the prompt itself and a suffix. */ |
| 195 | |
| 196 | /* At any particular time there will be always at least one prompt on |
| 197 | the stack, the one being currently displayed by gdb. If gdb is |
| 198 | using annotation level equal 2, there will be 2 prompts on the |
| 199 | stack: the usual one, w/o prefix and suffix (at top - 1), and the |
| 200 | 'composite' one with prefix and suffix added (at top). At this |
| 201 | time, this is the only use of the prompt stack. Resetting annotate |
| 202 | to 0 or 1, pops the top of the stack, resetting its size to one |
| 203 | element. The MAXPROMPTS limit is safe, for now. Once other cases |
| 204 | are dealt with (like the different prompts used for 'commands' or |
| 205 | 'actions') this array implementation of the prompt stack may have |
| 206 | to change. */ |
| 207 | |
| 208 | #define MAXPROMPTS 10 |
| 209 | struct prompts |
| 210 | { |
| 211 | struct |
| 212 | { |
| 213 | char *prefix; |
| 214 | char *prompt; |
| 215 | char *suffix; |
| 216 | } |
| 217 | prompt_stack[MAXPROMPTS]; |
| 218 | int top; |
| 219 | }; |
| 220 | |
| 221 | #define PROMPT(X) the_prompts.prompt_stack[the_prompts.top + X].prompt |
| 222 | #define PREFIX(X) the_prompts.prompt_stack[the_prompts.top + X].prefix |
| 223 | #define SUFFIX(X) the_prompts.prompt_stack[the_prompts.top + X].suffix |
| 224 | |
| 225 | /* Exported functions from event-loop.c */ |
| 226 | |
| 227 | extern void start_event_loop PARAMS ((void)); |
| 228 | extern void delete_file_handler PARAMS ((int)); |
| 229 | extern void add_file_handler PARAMS ((int, void (*) (void), gdb_client_data)); |
| 230 | extern void mark_async_signal_handler PARAMS ((async_signal_handler *)); |
| 231 | extern async_signal_handler * |
| 232 | create_async_signal_handler PARAMS ((handler_func *, gdb_client_data)); |
| 233 | extern void delete_async_signal_handler PARAMS ((async_signal_handler ** async_handler_ptr)); |
| 234 | |
| 235 | /* Exported functions from event-top.c. |
| 236 | FIXME: these should really go into top.h. */ |
| 237 | |
| 238 | extern void display_gdb_prompt PARAMS ((char *)); |
| 239 | extern void async_init_signals PARAMS ((void)); |
| 240 | extern void set_async_editing_command PARAMS ((char *, int, struct cmd_list_element *)); |
| 241 | extern void set_async_annotation_level PARAMS ((char *, int, struct cmd_list_element *)); |
| 242 | extern void set_async_prompt PARAMS ((char *, int, struct cmd_list_element *)); |
| 243 | extern void handle_stop_sig PARAMS ((int)); |
| 244 | extern void handle_sigint PARAMS ((int)); |
| 245 | extern void pop_prompt PARAMS ((void)); |
| 246 | extern void push_prompt PARAMS ((char *, char *, char *)); |
| 247 | extern void gdb_readline2 PARAMS ((void)); |
| 248 | |
| 249 | /* Exported variables from event-top.c. |
| 250 | FIXME: these should really go into top.h. */ |
| 251 | |
| 252 | extern int async_command_editing_p; |
| 253 | extern char *async_annotation_suffix; |
| 254 | extern char *new_async_prompt; |
| 255 | extern struct prompts the_prompts; |
| 256 | extern void (*call_readline) PARAMS ((void)); |
| 257 | extern void (*input_handler) PARAMS ((char *)); |
| 258 | extern int input_fd; |