[PATCH 0/2] gdb, aarch64: cache pointer authentication masks per inferior

[Luis Machado <luis.machado.foss@gmail.com>]

aarch64_remove_non_address_bits recomputes the pointer authentication
dmask/cmask on every call by walking the current inferior's thread
list, looking up its regcache, and reading the masks from the target.
This function is called from memory_xfer_partial for every memory
transfer GDB performs, as well as from the watchpoint and breakpoint
address-masking hooks, so the lookup happens far more often than the
masks can possibly change (they are fixed for the life of a process
and shared by all of its threads).

Patch 1 caches the computed mask per inferior instead of recomputing
it on every call, only populating the cache when a thread is stopped
so a transient "thread running" state never gets cached as a
permanent answer, and invalidates the cache on inferior exit,
inferior appeared, and exec.

Patch 2 adds a selftest that verifies the cache actually avoids
redundant target register fetches across a simulated resume/stop
cycle.

Tested on aarch64-linux with no regressions, though the testing was
done on a target without PAC support. It would be good to also
validate on a PAC-enabled target to be sure.

Luis Machado (2):
  gdb, aarch64: cache pointer authentication masks per inferior
  gdb, aarch64: add selftest for the pauth mask cache

 gdb/aarch64-tdep.c | 224 ++++++++++++++++++++++++++++++++++++---------
 1 file changed, 182 insertions(+), 42 deletions(-)

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2.43.0