bpftool: Generate skeleton for global percpu data

Enhance bpftool to generate skeletons that properly handle global percpu
variables. The generated skeleton now includes a dedicated structure for
percpu data, allowing users to initialize and access percpu variables more
efficiently.

For global percpu variables, the skeleton now includes a nested
structure, e.g.:

struct test_global_percpu_data {
	struct bpf_object_skeleton *skeleton;
	struct bpf_object *obj;
	struct {
		struct bpf_map *percpu;
	} maps;
	// ...
	struct test_global_percpu_data__percpu {
		int data;
		char run;
		struct {
			char set;
			int i;
			int nums[7];
		} struct_data;
		int nums[7];
	} *percpu;

	// ...
};

  * The "struct test_global_percpu_data__percpu *percpu" points to
    initialized data, which is actually "maps.percpu->mmaped".
  * Before loading the skeleton, updating the
    "struct test_global_percpu_data__percpu *percpu" modifies the initial
    value of the corresponding global percpu variables.
  * After loading the skeleton, "maps.percpu->mmaped" has been marked as
    read-only in libbpf. If users want to update the global percpu
    variables, they have to update the "maps.percpu" map instead.
  * For lightweight skeleton, "lskel->percpu" will be protected by
    "mprotect(p, sz, PROT_READ)".
  * For subskeleton, those variables of global percpu data will be
    skipped.

Assisted-by: Codex:gpt-5.5-xhigh
Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Quentin Monnet <qmo@kernel.org>
Link: https://lore.kernel.org/bpf/20260813152324.97937-7-leon.hwang@linux.dev

0 files changed, 0 insertions, 0 deletions