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gdb: restore displaced step buffer bytes when another thread forks

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In handle_inferior_event, where we handle forks, we make sure to restore
the bytes of the displaced stepping buffer in the child's address
space.  However, we only do it when the forking thread was the one
doing a displaced step.  It could happen that a thread forks while
another one is doing a displaced step.  In this case, we also need to
restore the bytes in the child.

Move the byte-restoring code outside of the condition that checks
whether the event thread was displaced stepping.

gdb/ChangeLog:

	* infrun.c (handle_inferior_event): Restore displaced step
	buffer bytes in child process when handling fork, even if fork
	happened in another thread than the displaced-stepping one.

Change-Id: Ibb0daaeb123aba03f4fb4b4d820754eb2436bc69
This commit is contained in:
Simon Marchi 2020-12-04 16:43:52 -05:00 committed by Simon Marchi
parent 3b7a962dec
commit c0aba012ed
2 changed files with 21 additions and 13 deletions
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6
gdb/ChangeLog
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@ -1,3 +1,9 @@
2020-12-04 Simon Marchi <simon.marchi@polymtl.ca>
* infrun.c (handle_inferior_event): Restore displaced step
buffer bytes in child process when handling fork, even if fork
happened in another thread than the displaced-stepping one.
2020-12-04 Simon Marchi <simon.marchi@efficios.com>
* infrun.c (infrun_inferior_execd): New function.

28
gdb/infrun.c
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@ -5302,25 +5302,27 @@ handle_inferior_event (struct execution_control_state *ecs)
{
struct regcache *regcache = get_thread_regcache (ecs->event_thread);
struct gdbarch *gdbarch = regcache->arch ();
inferior *parent_inf = find_inferior_ptid (ecs->target, ecs->ptid);
/* If checking displaced stepping is supported, and thread
ecs->ptid is displaced stepping. */
/* If this is a fork (child gets its own address space copy) and the
displaced step buffer was in use at the time of the fork, restore
displaced step buffer bytes in the child process. */
if (ecs->ws.kind == TARGET_WAITKIND_FORKED)
{
displaced_step_inferior_state *displaced
= get_displaced_stepping_state (parent_inf);
if (displaced->step_thread != nullptr)
displaced_step_restore (displaced, ecs->ws.value.related_pid);
}
/* If displaced stepping is supported, and thread ecs->ptid is
displaced stepping. */
if (displaced_step_in_progress_thread (ecs->event_thread))
{
struct inferior *parent_inf
= find_inferior_ptid (ecs->target, ecs->ptid);
struct regcache *child_regcache;
CORE_ADDR parent_pc;
if (ecs->ws.kind == TARGET_WAITKIND_FORKED)
{
struct displaced_step_inferior_state *displaced
= get_displaced_stepping_state (parent_inf);
/* Restore scratch pad for child process. */
displaced_step_restore (displaced, ecs->ws.value.related_pid);
}
/* GDB has got TARGET_WAITKIND_FORKED or TARGET_WAITKIND_VFORKED,
indicating that the displaced stepping of syscall instruction
has been done. Perform cleanup for parent process here. Note