[PATCH] perf/x86/intel/uncore: Use struct_size() in kzalloc_node()

[PATCH] perf/x86/intel/uncore: Use struct_size() in kzalloc_node()

[Gustavo A. R. Silva]

One of the more common cases of allocation size calculations is finding
the size of a structure that has a zero-sized array at the end, along
with memory for some number of elements for that array. For example:

struct intel_uncore_box {
        ...
        struct intel_uncore_extra_reg shared_regs[0];
};

size = sizeof(struct intel_uncore_box) + count * sizeof(struct intel_uncore_extra_reg);
instance = kzalloc_node(size, GFP_KERNEL, node);

Instead of leaving these open-coded and prone to type mistakes, we can
now use the new struct_size() helper:

instance = kzalloc_node(struct_size(instance, shared_regs, count), GFP_KERNEL,
node);

Notice that, in this case, variable size is not necessary, hence it
is removed.

This code was detected with the help of Coccinelle.

Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
---
 arch/x86/events/intel/uncore.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/arch/x86/events/intel/uncore.c b/arch/x86/events/intel/uncore.c
index 3694a5d0703d..013768dc8f37 100644
--- a/arch/x86/events/intel/uncore.c
+++ b/arch/x86/events/intel/uncore.c
@@ -313,12 +313,11 @@ static void uncore_pmu_init_hrtimer(struct intel_uncore_box *box)
 static struct intel_uncore_box *uncore_alloc_box(struct intel_uncore_type *type,
 						 int node)
 {
-	int i, size, numshared = type->num_shared_regs ;
+	int i, numshared = type->num_shared_regs;
 	struct intel_uncore_box *box;
 
-	size = sizeof(*box) + numshared * sizeof(struct intel_uncore_extra_reg);
-
-	box = kzalloc_node(size, GFP_KERNEL, node);
+	box = kzalloc_node(struct_size(box, shared_regs, numshared), GFP_KERNEL,
+			   node);
 	if (!box)
 		return NULL;
 
-- 
2.22.0