kmemleak-test: add percpu leak

Add a per-CPU memory leak, which will be reported like:

unreferenced object 0x3efa840195f8 (size 64):
  comm "modprobe", pid 4667, jiffies 4294688677
  hex dump (first 32 bytes on cpu 0):
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  backtrace (crc 0):
    [<ffffffffa7fa87af>] pcpu_alloc+0x3df/0x840
    [<ffffffffc11642d9>] kmemleak_test_init+0x2c9/0x2f0 [kmemleak_test]
    [<ffffffffa7c02264>] do_one_initcall+0x44/0x300
    [<ffffffffa7de9e10>] do_init_module+0x60/0x240
    [<ffffffffa7deb946>] init_module_from_file+0x86/0xc0
    [<ffffffffa7deba99>] idempotent_init_module+0x109/0x2a0
    [<ffffffffa7debd2a>] __x64_sys_finit_module+0x5a/0xb0
    [<ffffffffa88f4f3a>] do_syscall_64+0x7a/0x160
    [<ffffffffa8a0012b>] entry_SYSCALL_64_after_hwframe+0x76/0x7e

Link: https://lkml.kernel.org/r/20240725041223.872472-3-ptikhomirov@virtuozzo.comSigned-off-by: Pavel Tikhomirov <ptikhomirov@virtuozzo.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@canonical.com>
Cc: Chen Jun <chenjun102@huawei.com>
Cc: Wei Yongjun <weiyongjun1@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

samples/kmemleak/kmemleak-test.c

@@ -79,6 +79,8 @@ static int kmemleak_test_init(void)
 			per_cpu(kmemleak_test_pointer, i));
 	}
 
+	pr_info("__alloc_percpu(64, 4) = %p\n", __alloc_percpu(64, 4));
+
 	return 0;
 }
 module_init(kmemleak_test_init);