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gdb: protect some 'regcache_read_pc' calls

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It possible that a thread whose PC we attempt to read is already dead.
In this case, 'regcache_read_pc' errors out.  This impacts the
"proceed" execution flow, where GDB quits early before having a chance
to check if there exists a pending event.  To remedy, keep going with
a 0 value for the PC if 'regcache_read_pc' fails.  Because the value
of PC before resuming a thread is mostly used for storing and checking
the next time the thread stops, this tolerance is expected to be
harmless for a dead thread/process.

gdb/ChangeLog:
2020-05-14  Tankut Baris Aktemur  <tankut.baris.aktemur@intel.com>

	* regcache.c (regcache_read_pc_protected): New function
	implementation that returns 0 if the PC cannot read via
	'regcache_read_pc'.
	* infrun.c (proceed): Call 'regcache_read_pc_protected'
	instead of 'regcache_read_pc'.
	(keep_going_pass_signal): Ditto.

gdbsupport/ChangeLog:
2020-05-14  Tankut Baris Aktemur  <tankut.baris.aktemur@intel.com>

	* common-regcache.h (regcache_read_pc_protected): New function
	declaration.
This commit is contained in:
Tankut Baris Aktemur 2020-05-14 13:59:53 +02:00
parent 9d95b8e9d6
commit fc75c28ba1
5 changed files with 41 additions and 3 deletions
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9
gdb/ChangeLog
View File

@ -1,3 +1,12 @@
2020-05-14 Tankut Baris Aktemur <tankut.baris.aktemur@intel.com>
* regcache.c (regcache_read_pc_protected): New function
implementation that returns 0 if the PC cannot read via
'regcache_read_pc'.
* infrun.c (proceed): Call 'regcache_read_pc_protected'
instead of 'regcache_read_pc'.
(keep_going_pass_signal): Ditto.
2020-05-13 Tom Tromey <tromey@adacore.com>
* ada-lang.c (align_value): Remove.

7
gdb/infrun.c
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@ -2995,7 +2995,8 @@ proceed (CORE_ADDR addr, enum gdb_signal siggnal)
gdbarch = regcache->arch ();
const address_space *aspace = regcache->aspace ();
pc = regcache_read_pc (regcache);
pc = regcache_read_pc_protected (regcache);
thread_info *cur_thr = inferior_thread ();
/* Fill in with reasonable starting values. */
@ -3122,7 +3123,7 @@ proceed (CORE_ADDR addr, enum gdb_signal siggnal)
advanced. Must do this before resuming any thread, as in
all-stop/remote, once we resume we can't send any other packet
until the target stops again. */
cur_thr->prev_pc = regcache_read_pc (regcache);
cur_thr->prev_pc = regcache_read_pc_protected (regcache);
{
scoped_restore save_defer_tc = make_scoped_defer_target_commit_resume ();
@ -7929,7 +7930,7 @@ keep_going_pass_signal (struct execution_control_state *ecs)
/* Save the pc before execution, to compare with pc after stop. */
ecs->event_thread->prev_pc
= regcache_read_pc (get_thread_regcache (ecs->event_thread));
= regcache_read_pc_protected (get_thread_regcache (ecs->event_thread));
if (ecs->event_thread->control.trap_expected)
{

18
gdb/regcache.c
View File

@ -1220,6 +1220,24 @@ regcache_read_pc (struct regcache *regcache)
return pc_val;
}
/* See gdbsupport/common-regcache.h. */
CORE_ADDR
regcache_read_pc_protected (regcache *regcache)
{
CORE_ADDR pc;
try
{
pc = regcache_read_pc (regcache);
}
catch (const gdb_exception_error &ex)
{
pc = 0;
}
return pc;
}
void
regcache_write_pc (struct regcache *regcache, CORE_ADDR pc)
{

5
gdbsupport/ChangeLog
View File

@ -1,3 +1,8 @@
2020-05-14 Tankut Baris Aktemur <tankut.baris.aktemur@intel.com>
* common-regcache.h (regcache_read_pc_protected): New function
declaration.
2020-04-28 Tankut Baris Aktemur <tankut.baris.aktemur@intel.com>
* gdb-sigmask.h: Fix typo (pthead_sigmask -> pthread_sigmask).

5
gdbsupport/common-regcache.h
View File

@ -56,6 +56,11 @@ extern int regcache_register_size (const struct regcache *regcache, int n);
extern CORE_ADDR regcache_read_pc (struct regcache *regcache);
/* Read the PC register. If PC cannot be read, return 0.
This is a wrapper around 'regcache_read_pc'. */
extern CORE_ADDR regcache_read_pc_protected (regcache *regcache);
/* Read a raw register into a unsigned integer. */
extern enum register_status regcache_raw_read_unsigned
(struct regcache *regcache, int regnum, ULONGEST *val);