rust: add a rust helper for krealloc()

Memory allocation profiling is turning krealloc() into a nontrivial macro
- so for now, we need a helper for it.

Until we have proper support on the rust side for memory allocation
profiling this does mean that all Rust allocations will be accounted to
the helper.

Link: https://lkml.kernel.org/r/20240321163705.3067592-25-surenb@google.com
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Acked-by: Miguel Ojeda <ojeda@kernel.org>
Tested-by: Kees Cook <keescook@chromium.org>
Cc: Alex Gaynor <alex.gaynor@gmail.com>
Cc: Wedson Almeida Filho <wedsonaf@gmail.com>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Gary Guo <gary@garyguo.net>
Cc: "Björn Roy Baron" <bjorn3_gh@protonmail.com>
Cc: Benno Lossin <benno.lossin@proton.me>
Cc: Andreas Hindborg <a.hindborg@samsung.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Christoph Lameter <cl@linux.com>
Cc: Dennis Zhou <dennis@kernel.org>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

rust/helpers.c

@@ -28,6 +28,7 @@
 #include <linux/mutex.h>
 #include <linux/refcount.h>
 #include <linux/sched/signal.h>
+#include <linux/slab.h>
 #include <linux/spinlock.h>
 #include <linux/wait.h>
 #include <linux/workqueue.h>
@@ -157,6 +158,13 @@ void rust_helper_init_work_with_key(struct work_struct *work, work_func_t func,
 }
 EXPORT_SYMBOL_GPL(rust_helper_init_work_with_key);
 
+void * __must_check __realloc_size(2)
+rust_helper_krealloc(const void *objp, size_t new_size, gfp_t flags)
+{
+	return krealloc(objp, new_size, flags);
+}
+EXPORT_SYMBOL_GPL(rust_helper_krealloc);
+
 /*
  * `bindgen` binds the C `size_t` type as the Rust `usize` type, so we can
  * use it in contexts where Rust expects a `usize` like slice (array) indices.