binutils-gdb/gdb/annotate.c
Pedro Alves 6fdebc3d1c PR gdb/17472: With annotations, input while executing in the foreground crashes readline/GDB
Jan caught an intermittent GDB crash with the annota1.exp test:

 Starting program: .../gdb/testsuite/gdb.base/annota1 ^M
 [...]
 FAIL: gdb.base/annota1.exp: run until main breakpoint (timeout)
 [...]
 readline: readline_callback_read_char() called with no handler!^M
 ERROR: Process no longer exists

All we need to is to continue the inferior in the foreground, and type
a command while the inferior is running.  E.g.:

 (gdb) set annotate 2

 ▒▒pre-prompt
 (gdb)
 ▒▒prompt
 c

 ▒▒post-prompt
 Continuing.

 ▒▒starting

 ▒▒frames-invalid

 *inferior is running now*

 p 1<ret>

 readline: readline_callback_read_char() called with no handler!
 Aborted (core dumped)
 $


When we run a foreground execution command we call
target_terminal_inferior to stop GDB from processing input, and to put
the inferior's terminal settings in effect.  Then we tell readline to
hide the prompt with display_gdb_prompt, which clears readline's input
callback too.  When the target stops, we call target_terminal_ours,
which re-installs stdin in the event loop, and then we redisplay the
prompt, reinstalling the readline callbacks.

However, when annotations are in effect, the "frames-invalid"
annotation code calls target_terminal_ours after 'resume' had already
called target_terminal_inferior:

 (top-gdb) bt
 #0  0x000000000056b82f in annotate_frames_invalid () at gdb/annotate.c:219
 #1  0x000000000072e6cc in reinit_frame_cache () at gdb/frame.c:1705
 #2  0x0000000000594bb9 in registers_changed_ptid (ptid=...) at gdb/regcache.c:612
 #3  0x000000000064cca1 in target_resume (ptid=..., step=1, signal=GDB_SIGNAL_0) at gdb/target.c:2136
 #4  0x00000000005f57af in resume (step=1, sig=GDB_SIGNAL_0) at gdb/infrun.c:2263
 #5  0x00000000005f6051 in proceed (addr=18446744073709551615, siggnal=GDB_SIGNAL_DEFAULT, step=1) at gdb/infrun.c:2613

And then once we hide the prompt and remove readline's input handler
callback, we're in a bad state.  We end up with the target running
supposedly in the foreground, but with stdin still installed on the
event loop.  Any input then calls into readline, which aborts because
no rl_linefunc callback handler is installed:

 Program received signal SIGABRT, Aborted.
 0x0000003b36a35877 in __GI_raise (sig=sig@entry=6) at ../nptl/sysdeps/unix/sysv/linux/raise.c:56
 56        return INLINE_SYSCALL (tgkill, 3, pid, selftid, sig);

 (top-gdb) bt
 #0  0x0000003b36a35877 in __GI_raise (sig=sig@entry=6) at ../nptl/sysdeps/unix/sysv/linux/raise.c:56
 #1  0x0000003b36a36f68 in __GI_abort () at abort.c:89
 During symbol reading, debug info gives source 9 included from file at zero line 0.
 During symbol reading, debug info gives command-line macro definition with non-zero line 19: _STDC_PREDEF_H 1.
 #2  0x0000000000784a25 in rl_callback_read_char () at src/readline/callback.c:116
 #3  0x0000000000619111 in rl_callback_read_char_wrapper (client_data=0x0) at src/gdb/event-top.c:167
 #4  0x00000000006194e7 in stdin_event_handler (error=0, client_data=0x0) at src/gdb/event-top.c:373
 #5  0x00000000006180da in handle_file_event (data=...) at src/gdb/event-loop.c:763
 #6  0x00000000006175c1 in process_event () at src/gdb/event-loop.c:340
 #7  0x0000000000617688 in gdb_do_one_event () at src/gdb/event-loop.c:404
 #8  0x00000000006176d8 in start_event_loop () at src/gdb/event-loop.c:429
 #9  0x0000000000619143 in cli_command_loop (data=0x0) at src/gdb/event-top.c:182
 #10 0x000000000060f4c8 in current_interp_command_loop () at src/gdb/interps.c:318
 #11 0x0000000000610691 in captured_command_loop (data=0x0) at src/gdb/main.c:323
 #12 0x000000000060c385 in catch_errors (func=0x610676 <captured_command_loop>, func_args=0x0, errstring=0x900241 "", mask=RETURN_MASK_ALL)
     at src/gdb/exceptions.c:237
 #13 0x0000000000611b8f in captured_main (data=0x7fffffffd7b0) at src/gdb/main.c:1151
 #14 0x000000000060c385 in catch_errors (func=0x610a8e <captured_main>, func_args=0x7fffffffd7b0, errstring=0x900241 "", mask=RETURN_MASK_ALL)
     at src/gdb/exceptions.c:237
 #15 0x0000000000611bb8 in gdb_main (args=0x7fffffffd7b0) at src/gdb/main.c:1159
 #16 0x000000000045ef57 in main (argc=3, argv=0x7fffffffd8b8) at src/gdb/gdb.c:32

The fix is to make the annotation code call target_terminal_inferior
again after printing, if the inferior's settings were in effect.

While at it, when we're doing output only, instead of
target_terminal_ours, we should call target_terminal_ours_for_output.
The latter doesn't actually remove stdin from the event loop, and also
leaves SIGINT forwarded to the target.

New test included.

Tested on x86_64 Fedora 20, native and gdbserver.

gdb/
2014-10-17  Pedro Alves  <palves@redhat.com>

	PR gdb/17472
	* annotate.c (annotate_breakpoints_invalid): Use
	target_terminal_our_for_output instead of target_terminal_ours.
	Give back the terminal to the target.
	(annotate_frames_invalid): Likewise.

gdb/testsuite/
2014-10-17  Pedro Alves  <palves@redhat.com>

	PR gdb/17472
	* gdb.base/annota-input-while-running.c: New file.
	* gdb.base/annota-input-while-running.exp: New file.
2014-10-17 13:32:26 +01:00

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/* Annotation routines for GDB.
Copyright (C) 1986-2014 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/>. */
#include "defs.h"
#include "annotate.h"
#include "value.h"
#include "target.h"
#include "gdbtypes.h"
#include "breakpoint.h"
#include "observer.h"
#include "inferior.h"
#include "infrun.h"
/* Prototypes for local functions. */
extern void _initialize_annotate (void);
static void print_value_flags (struct type *);
static void breakpoint_changed (struct breakpoint *b);
void (*deprecated_annotate_signalled_hook) (void);
void (*deprecated_annotate_signal_hook) (void);
/* Booleans indicating whether we've emitted certain notifications.
Used to suppress useless repeated notifications until the next time
we're ready to accept more commands. Reset whenever a prompt is
displayed. */
static int frames_invalid_emitted;
static int breakpoints_invalid_emitted;
/* True if the target can async, and a synchronous execution command
is not in progress. If true, input is accepted, so don't suppress
annotations. */
static int
async_background_execution_p (void)
{
return (target_can_async_p () && !sync_execution);
}
static void
print_value_flags (struct type *t)
{
if (can_dereference (t))
printf_filtered (("*"));
else
printf_filtered (("-"));
}
static void
annotate_breakpoints_invalid (void)
{
if (annotation_level == 2
&& (!breakpoints_invalid_emitted
|| async_background_execution_p ()))
{
/* If the inferior owns the terminal (e.g., we're resuming),
make sure to leave with the inferior still owning it. */
int was_inferior = target_terminal_is_inferior ();
target_terminal_ours_for_output ();
printf_unfiltered (("\n\032\032breakpoints-invalid\n"));
if (was_inferior)
target_terminal_inferior ();
breakpoints_invalid_emitted = 1;
}
}
void
annotate_breakpoint (int num)
{
if (annotation_level > 1)
printf_filtered (("\n\032\032breakpoint %d\n"), num);
}
void
annotate_catchpoint (int num)
{
if (annotation_level > 1)
printf_filtered (("\n\032\032catchpoint %d\n"), num);
}
void
annotate_watchpoint (int num)
{
if (annotation_level > 1)
printf_filtered (("\n\032\032watchpoint %d\n"), num);
}
void
annotate_starting (void)
{
if (annotation_level > 1)
printf_filtered (("\n\032\032starting\n"));
}
void
annotate_stopped (void)
{
if (annotation_level > 1)
printf_filtered (("\n\032\032stopped\n"));
}
void
annotate_exited (int exitstatus)
{
if (annotation_level > 1)
printf_filtered (("\n\032\032exited %d\n"), exitstatus);
}
void
annotate_signalled (void)
{
if (deprecated_annotate_signalled_hook)
deprecated_annotate_signalled_hook ();
if (annotation_level > 1)
printf_filtered (("\n\032\032signalled\n"));
}
void
annotate_signal_name (void)
{
if (annotation_level == 2)
printf_filtered (("\n\032\032signal-name\n"));
}
void
annotate_signal_name_end (void)
{
if (annotation_level == 2)
printf_filtered (("\n\032\032signal-name-end\n"));
}
void
annotate_signal_string (void)
{
if (annotation_level == 2)
printf_filtered (("\n\032\032signal-string\n"));
}
void
annotate_signal_string_end (void)
{
if (annotation_level == 2)
printf_filtered (("\n\032\032signal-string-end\n"));
}
void
annotate_signal (void)
{
if (deprecated_annotate_signal_hook)
deprecated_annotate_signal_hook ();
if (annotation_level > 1)
printf_filtered (("\n\032\032signal\n"));
}
void
annotate_breakpoints_headers (void)
{
if (annotation_level == 2)
printf_filtered (("\n\032\032breakpoints-headers\n"));
}
void
annotate_field (int num)
{
if (annotation_level == 2)
printf_filtered (("\n\032\032field %d\n"), num);
}
void
annotate_breakpoints_table (void)
{
if (annotation_level == 2)
printf_filtered (("\n\032\032breakpoints-table\n"));
}
void
annotate_record (void)
{
if (annotation_level == 2)
printf_filtered (("\n\032\032record\n"));
}
void
annotate_breakpoints_table_end (void)
{
if (annotation_level == 2)
printf_filtered (("\n\032\032breakpoints-table-end\n"));
}
void
annotate_frames_invalid (void)
{
if (annotation_level == 2
&& (!frames_invalid_emitted
|| async_background_execution_p ()))
{
/* If the inferior owns the terminal (e.g., we're resuming),
make sure to leave with the inferior still owning it. */
int was_inferior = target_terminal_is_inferior ();
target_terminal_ours_for_output ();
printf_unfiltered (("\n\032\032frames-invalid\n"));
if (was_inferior)
target_terminal_inferior ();
frames_invalid_emitted = 1;
}
}
void
annotate_new_thread (void)
{
if (annotation_level > 1)
{
printf_unfiltered (("\n\032\032new-thread\n"));
}
}
void
annotate_thread_changed (void)
{
if (annotation_level > 1)
{
printf_unfiltered (("\n\032\032thread-changed\n"));
}
}
void
annotate_field_begin (struct type *type)
{
if (annotation_level == 2)
{
printf_filtered (("\n\032\032field-begin "));
print_value_flags (type);
printf_filtered (("\n"));
}
}
void
annotate_field_name_end (void)
{
if (annotation_level == 2)
printf_filtered (("\n\032\032field-name-end\n"));
}
void
annotate_field_value (void)
{
if (annotation_level == 2)
printf_filtered (("\n\032\032field-value\n"));
}
void
annotate_field_end (void)
{
if (annotation_level == 2)
printf_filtered (("\n\032\032field-end\n"));
}
void
annotate_quit (void)
{
if (annotation_level > 1)
printf_filtered (("\n\032\032quit\n"));
}
void
annotate_error (void)
{
if (annotation_level > 1)
printf_filtered (("\n\032\032error\n"));
}
void
annotate_error_begin (void)
{
if (annotation_level > 1)
fprintf_filtered (gdb_stderr, "\n\032\032error-begin\n");
}
void
annotate_value_history_begin (int histindex, struct type *type)
{
if (annotation_level == 2)
{
printf_filtered (("\n\032\032value-history-begin %d "), histindex);
print_value_flags (type);
printf_filtered (("\n"));
}
}
void
annotate_value_begin (struct type *type)
{
if (annotation_level == 2)
{
printf_filtered (("\n\032\032value-begin "));
print_value_flags (type);
printf_filtered (("\n"));
}
}
void
annotate_value_history_value (void)
{
if (annotation_level == 2)
printf_filtered (("\n\032\032value-history-value\n"));
}
void
annotate_value_history_end (void)
{
if (annotation_level == 2)
printf_filtered (("\n\032\032value-history-end\n"));
}
void
annotate_value_end (void)
{
if (annotation_level == 2)
printf_filtered (("\n\032\032value-end\n"));
}
void
annotate_display_begin (void)
{
if (annotation_level == 2)
printf_filtered (("\n\032\032display-begin\n"));
}
void
annotate_display_number_end (void)
{
if (annotation_level == 2)
printf_filtered (("\n\032\032display-number-end\n"));
}
void
annotate_display_format (void)
{
if (annotation_level == 2)
printf_filtered (("\n\032\032display-format\n"));
}
void
annotate_display_expression (void)
{
if (annotation_level == 2)
printf_filtered (("\n\032\032display-expression\n"));
}
void
annotate_display_expression_end (void)
{
if (annotation_level == 2)
printf_filtered (("\n\032\032display-expression-end\n"));
}
void
annotate_display_value (void)
{
if (annotation_level == 2)
printf_filtered (("\n\032\032display-value\n"));
}
void
annotate_display_end (void)
{
if (annotation_level == 2)
printf_filtered (("\n\032\032display-end\n"));
}
void
annotate_arg_begin (void)
{
if (annotation_level == 2)
printf_filtered (("\n\032\032arg-begin\n"));
}
void
annotate_arg_name_end (void)
{
if (annotation_level == 2)
printf_filtered (("\n\032\032arg-name-end\n"));
}
void
annotate_arg_value (struct type *type)
{
if (annotation_level == 2)
{
printf_filtered (("\n\032\032arg-value "));
print_value_flags (type);
printf_filtered (("\n"));
}
}
void
annotate_arg_end (void)
{
if (annotation_level == 2)
printf_filtered (("\n\032\032arg-end\n"));
}
void
annotate_source (char *filename, int line, int character, int mid,
struct gdbarch *gdbarch, CORE_ADDR pc)
{
if (annotation_level > 1)
printf_filtered (("\n\032\032source "));
else
printf_filtered (("\032\032"));
printf_filtered (("%s:%d:%d:%s:%s\n"), filename, line, character,
mid ? "middle" : "beg", paddress (gdbarch, pc));
}
void
annotate_frame_begin (int level, struct gdbarch *gdbarch, CORE_ADDR pc)
{
if (annotation_level > 1)
printf_filtered (("\n\032\032frame-begin %d %s\n"),
level, paddress (gdbarch, pc));
}
void
annotate_function_call (void)
{
if (annotation_level == 2)
printf_filtered (("\n\032\032function-call\n"));
}
void
annotate_signal_handler_caller (void)
{
if (annotation_level == 2)
printf_filtered (("\n\032\032signal-handler-caller\n"));
}
void
annotate_frame_address (void)
{
if (annotation_level == 2)
printf_filtered (("\n\032\032frame-address\n"));
}
void
annotate_frame_address_end (void)
{
if (annotation_level == 2)
printf_filtered (("\n\032\032frame-address-end\n"));
}
void
annotate_frame_function_name (void)
{
if (annotation_level == 2)
printf_filtered (("\n\032\032frame-function-name\n"));
}
void
annotate_frame_args (void)
{
if (annotation_level == 2)
printf_filtered (("\n\032\032frame-args\n"));
}
void
annotate_frame_source_begin (void)
{
if (annotation_level == 2)
printf_filtered (("\n\032\032frame-source-begin\n"));
}
void
annotate_frame_source_file (void)
{
if (annotation_level == 2)
printf_filtered (("\n\032\032frame-source-file\n"));
}
void
annotate_frame_source_file_end (void)
{
if (annotation_level == 2)
printf_filtered (("\n\032\032frame-source-file-end\n"));
}
void
annotate_frame_source_line (void)
{
if (annotation_level == 2)
printf_filtered (("\n\032\032frame-source-line\n"));
}
void
annotate_frame_source_end (void)
{
if (annotation_level == 2)
printf_filtered (("\n\032\032frame-source-end\n"));
}
void
annotate_frame_where (void)
{
if (annotation_level == 2)
printf_filtered (("\n\032\032frame-where\n"));
}
void
annotate_frame_end (void)
{
if (annotation_level == 2)
printf_filtered (("\n\032\032frame-end\n"));
}
void
annotate_array_section_begin (int idx, struct type *elttype)
{
if (annotation_level == 2)
{
printf_filtered (("\n\032\032array-section-begin %d "), idx);
print_value_flags (elttype);
printf_filtered (("\n"));
}
}
void
annotate_elt_rep (unsigned int repcount)
{
if (annotation_level == 2)
printf_filtered (("\n\032\032elt-rep %u\n"), repcount);
}
void
annotate_elt_rep_end (void)
{
if (annotation_level == 2)
printf_filtered (("\n\032\032elt-rep-end\n"));
}
void
annotate_elt (void)
{
if (annotation_level == 2)
printf_filtered (("\n\032\032elt\n"));
}
void
annotate_array_section_end (void)
{
if (annotation_level == 2)
printf_filtered (("\n\032\032array-section-end\n"));
}
/* Called when GDB is about to display the prompt. Used to reset
annotation suppression whenever we're ready to accept new
frontend/user commands. */
void
annotate_display_prompt (void)
{
frames_invalid_emitted = 0;
breakpoints_invalid_emitted = 0;
}
static void
breakpoint_changed (struct breakpoint *b)
{
if (b->number <= 0)
return;
annotate_breakpoints_invalid ();
}
void
_initialize_annotate (void)
{
observer_attach_breakpoint_created (breakpoint_changed);
observer_attach_breakpoint_deleted (breakpoint_changed);
observer_attach_breakpoint_modified (breakpoint_changed);
}