xref: /kernel/linux/linux-5.10/lib/dump_stack.c (revision 8c2ecf20) 
1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Provide a default dump_stack() function for architectures
4 * which don't implement their own.
5 */
6
7#include <linux/kernel.h>
8#include <linux/export.h>
9#include <linux/sched.h>
10#include <linux/sched/debug.h>
11#include <linux/smp.h>
12#include <linux/atomic.h>
13#include <linux/kexec.h>
14#include <linux/utsname.h>
15
16static char dump_stack_arch_desc_str[128];
17
18/**
19 * dump_stack_set_arch_desc - set arch-specific str to show with task dumps
20 * @fmt: printf-style format string
21 * @...: arguments for the format string
22 *
23 * The configured string will be printed right after utsname during task
24 * dumps.  Usually used to add arch-specific system identifiers.  If an
25 * arch wants to make use of such an ID string, it should initialize this
26 * as soon as possible during boot.
27 */
28void __init dump_stack_set_arch_desc(const char *fmt, ...)
29{
30	va_list args;
31
32	va_start(args, fmt);
33	vsnprintf(dump_stack_arch_desc_str, sizeof(dump_stack_arch_desc_str),
34		  fmt, args);
35	va_end(args);
36}
37
38/**
39 * dump_stack_print_info - print generic debug info for dump_stack()
40 * @log_lvl: log level
41 *
42 * Arch-specific dump_stack() implementations can use this function to
43 * print out the same debug information as the generic dump_stack().
44 */
45void dump_stack_print_info(const char *log_lvl)
46{
47	printk("%sCPU: %d PID: %d Comm: %.20s %s%s %s %.*s\n",
48	       log_lvl, raw_smp_processor_id(), current->pid, current->comm,
49	       kexec_crash_loaded() ? "Kdump: loaded " : "",
50	       print_tainted(),
51	       init_utsname()->release,
52	       (int)strcspn(init_utsname()->version, " "),
53	       init_utsname()->version);
54
55	if (dump_stack_arch_desc_str[0] != '\0')
56		printk("%sHardware name: %s\n",
57		       log_lvl, dump_stack_arch_desc_str);
58
59	print_worker_info(log_lvl, current);
60}
61
62/**
63 * show_regs_print_info - print generic debug info for show_regs()
64 * @log_lvl: log level
65 *
66 * show_regs() implementations can use this function to print out generic
67 * debug information.
68 */
69void show_regs_print_info(const char *log_lvl)
70{
71	dump_stack_print_info(log_lvl);
72}
73
74static void __dump_stack(void)
75{
76	dump_stack_print_info(KERN_DEFAULT);
77	show_stack(NULL, NULL, KERN_DEFAULT);
78}
79
80/**
81 * dump_stack - dump the current task information and its stack trace
82 *
83 * Architectures can override this implementation by implementing its own.
84 */
85#ifdef CONFIG_SMP
86static atomic_t dump_lock = ATOMIC_INIT(-1);
87
88asmlinkage __visible void dump_stack(void)
89{
90	unsigned long flags;
91	int was_locked;
92	int old;
93	int cpu;
94
95	/*
96	 * Permit this cpu to perform nested stack dumps while serialising
97	 * against other CPUs
98	 */
99retry:
100	local_irq_save(flags);
101	cpu = smp_processor_id();
102	old = atomic_cmpxchg(&dump_lock, -1, cpu);
103	if (old == -1) {
104		was_locked = 0;
105	} else if (old == cpu) {
106		was_locked = 1;
107	} else {
108		local_irq_restore(flags);
109		/*
110		 * Wait for the lock to release before jumping to
111		 * atomic_cmpxchg() in order to mitigate the thundering herd
112		 * problem.
113		 */
114		do { cpu_relax(); } while (atomic_read(&dump_lock) != -1);
115		goto retry;
116	}
117
118	__dump_stack();
119
120	if (!was_locked)
121		atomic_set(&dump_lock, -1);
122
123	local_irq_restore(flags);
124}
125#else
126asmlinkage __visible void dump_stack(void)
127{
128	__dump_stack();
129}
130#endif
131EXPORT_SYMBOL(dump_stack);
132