tracing: Turn hist_elt_data field_var_str into a flexible array

The field_var_str array was allocated separately via kcalloc() with its
length already known at elt_data allocation time.  Convert it to a
flexible array member and fold the two allocations into a single
kzalloc_flex(), reordering hist_trigger_elt_data_alloc() so n_str is
computed and bounds-checked before the struct allocation.

hist_elt_data is only reached through tracing_map_elt::private_data
(a void *), never embedded, so adding a FAM imposes no tail-position
constraint on any enclosing struct.

Added __counted_by for extra runtime analysis.

Link: https://patch.msgid.link/20260522214407.18120-1-rosenp@gmail.com
Assisted-by: Claude:Opus-4.7
Signed-off-by: Rosen Penev <rosenp@gmail.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

0 files changed, 0 insertions, 0 deletions