gdb: add target displaced stepping support

The amd-dbgapi library, used in the AMD GPU port, has the capability to
prepare and cleanup displaced step operations.  In order to use it, add
the following target_ops methods:

 - supports_displaced_step
 - displaced_step_prepare
 - displaced_step_finish
 - displaced_step_restore_all_in_ptid

Prior to this patch, displaced stepping preparation and cleanup is done
solely by gdbarches.  Update infrun to use these new target methods
instead of gdbarch hooks.  To keep the behavior for other architectures
unchanged, make the default implementations of the new target_ops method
forward to the thread's gdbarch.

displaced_step_restore_all_in_ptid won't be needed for the AMD GPU port,
but was added for completeness.  It would be weird for infrun displaced
stepping code to call target methods except for that one thing where it
calls a gdbarch method.

Since this patch only adds infrastructure, no behavior change is
expected.

Change-Id: I07c68dddb5759a55cd137a711d2679eedc0d9285

0 files changed, 0 insertions, 0 deletions