1// SPDX-License-Identifier: GPL-2.0
 2/*
 3 * lib/smp_processor_id.c
 4 *
 5 * DEBUG_PREEMPT variant of smp_processor_id().
 6 */
 7#include <linux/export.h>
 8#include <linux/kprobes.h>
 9#include <linux/sched.h>
10
11noinstr static
12unsigned int check_preemption_disabled(const char *what1, const char *what2)
13{
14	int this_cpu = raw_smp_processor_id();
15
16	if (likely(preempt_count()))
17		goto out;
18
19	if (irqs_disabled())
20		goto out;
21
22	/*
23	 * Kernel threads bound to a single CPU can safely use
24	 * smp_processor_id():
25	 */
26	if (current->nr_cpus_allowed == 1)
27		goto out;
28
29	/*
30	 * It is valid to assume CPU-locality during early bootup:
31	 */
32	if (system_state < SYSTEM_SCHEDULING)
33		goto out;
34
35	/*
36	 * Avoid recursion:
37	 */
38	preempt_disable_notrace();
39
40	instrumentation_begin();
41	if (!printk_ratelimit())
42		goto out_enable;
43
44	printk(KERN_ERR "BUG: using %s%s() in preemptible [%08x] code: %s/%d\n",
45		what1, what2, preempt_count() - 1, current->comm, current->pid);
46
47	printk("caller is %pS\n", __builtin_return_address(0));
48	dump_stack();
49	instrumentation_end();
50
51out_enable:
52	preempt_enable_no_resched_notrace();
53out:
54	return this_cpu;
55}
56
57noinstr unsigned int debug_smp_processor_id(void)
58{
59	return check_preemption_disabled("smp_processor_id", "");
60}
61EXPORT_SYMBOL(debug_smp_processor_id);
62
63noinstr void __this_cpu_preempt_check(const char *op)
64{
65	check_preemption_disabled("__this_cpu_", op);
66}
67EXPORT_SYMBOL(__this_cpu_preempt_check);