OpenE2K/binutils-gdb
12
0
Fork 0
Code Issues Pull Requests Releases Wiki Activity

Fix problems with finishing a dummy function call on simulators.

Browse Source 
Some simulators don't handle permanent breakpoints properly and will
sometimes terminate when hitting such a breakpoint instruction or have
unwanted effects.

When a permanent breakpoint is inserted, GDB will not attempt to insert
other breakpoint locations on top of it, leading to the problem described
above.

By not marking permanent breakpoint locations as inserted, we allow the
insertion of breakpoint locations on top of the permanent ones, preventing
the simulators from running into that situation.

gdb/ChangeLog:

2015-06-17  Luis Machado  <lgustavo@codesourcery.com>

	* breakpoint.c (add_location_to_breakpoint): Don't mark permanent
	locations as inserted.
	Update and expand comment about permanent locations.
	(bp_loc_is_permanent): Don't return 0 for bp_call_dummy.
	Move comment to add_location_to_breakpoint.
	(update_global_location_list): Don't error out if a permanent
	breakpoint is not marked inserted.
	Don't error out if a non-permanent breakpoint location is inserted on
	top of a permanent breakpoint.
This commit is contained in:
Luis Machado 2015-06-17 16:50:57 -03:00
parent da4616f69f
commit 6ae8866180
2 changed files with 26 additions and 30 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

12
gdb/ChangeLog
View File

@ -1,3 +1,15 @@
2015-06-17 Luis Machado <lgustavo@codesourcery.com>
* breakpoint.c (add_location_to_breakpoint): Don't mark permanent
locations as inserted.
Update and expand comment about permanent locations.
(bp_loc_is_permanent): Don't return 0 for bp_call_dummy.
Move comment to add_location_to_breakpoint.
(update_global_location_list): Don't error out if a permanent
breakpoint is not marked inserted.
Don't error out if a non-permanent breakpoint location is inserted on
top of a permanent breakpoint.
2015-06-17 Luis Machado <lgustavo@codesourcery.com>
* breakpoint.c (make_breakpoint_permanent): Remove unused

44
gdb/breakpoint.c
View File

@ -8898,11 +8898,21 @@ add_location_to_breakpoint (struct breakpoint *b,
set_breakpoint_location_function (loc,
sal->explicit_pc || sal->explicit_line);
/* While by definition, permanent breakpoints are already present in the
code, we don't mark the location as inserted. Normally one would expect
that GDB could rely on that breakpoint instruction to stop the program,
thus removing the need to insert its own breakpoint, except that executing
the breakpoint instruction can kill the target instead of reporting a
SIGTRAP. E.g., on SPARC, when interrupts are disabled, executing the
instruction resets the CPU, so QEMU 2.0.0 for SPARC correspondingly dies
with "Trap 0x02 while interrupts disabled, Error state". Letting the
breakpoint be inserted normally results in QEMU knowing about the GDB
breakpoint, and thus trap before the breakpoint instruction is executed.
(If GDB later needs to continue execution past the permanent breakpoint,
it manually increments the PC, thus avoiding executing the breakpoint
instruction.) */
if (bp_loc_is_permanent (loc))
{
loc->inserted = 1;
loc->permanent = 1;
}
loc->permanent = 1;
return loc;
}
@ -8954,20 +8964,6 @@ bp_loc_is_permanent (struct bp_location *loc)
gdb_assert (loc != NULL);
/* bp_call_dummy breakpoint locations are usually memory locations
where GDB just wrote a breakpoint instruction, making it look
as if there is a permanent breakpoint at that location. Considering
it permanent makes GDB rely on that breakpoint instruction to stop
the program, thus removing the need to insert its own breakpoint
there. This is normally expected to work, except that some versions
of QEMU (Eg: QEMU 2.0.0 for SPARC) just report a fatal problem (Trap
0x02 while interrupts disabled, Error state) instead of reporting
a SIGTRAP. QEMU should probably be fixed, but in the interest of
compatibility with versions that behave this way, we always consider
bp_call_dummy breakpoint locations as non-permanent. */
if (loc->owner->type == bp_call_dummy)
return 0;
cleanup = save_current_space_and_thread ();
switch_to_program_space_and_thread (loc->pspace);
@ -12419,12 +12415,6 @@ update_global_location_list (enum ugll_insert_mode insert_mode)
continue;
}
/* Permanent breakpoint should always be inserted. */
if (loc->permanent && ! loc->inserted)
internal_error (__FILE__, __LINE__,
_("allegedly permanent breakpoint is not "
"actually inserted"));
if (b->type == bp_hardware_watchpoint)
loc_first_p = &wp_loc_first;
else if (b->type == bp_read_watchpoint)
@ -12460,12 +12450,6 @@ update_global_location_list (enum ugll_insert_mode insert_mode)
/* Clear the condition modification flag. */
loc->condition_changed = condition_unchanged;
if (loc->inserted && !loc->permanent
&& (*loc_first_p)->permanent)
internal_error (__FILE__, __LINE__,
_("another breakpoint was inserted on top of "
"a permanent breakpoint"));
}
if (insert_mode == UGLL_INSERT || breakpoints_should_be_inserted_now ())