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
16 static 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 */
dump_stack_set_arch_desc(const char * fmt,...)28 void __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 */
dump_stack_print_info(const char * log_lvl)45 void 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 */
show_regs_print_info(const char * log_lvl)69 void show_regs_print_info(const char *log_lvl)
70 {
71 dump_stack_print_info(log_lvl);
72 }
73
__dump_stack(void)74 static void __dump_stack(void)
75 {
76 dump_stack_print_info(KERN_DEFAULT);
77 show_stack(NULL, NULL);
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
86 static atomic_t dump_lock = ATOMIC_INIT(-1);
87
dump_stack(void)88 asmlinkage __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 */
99 retry:
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
dump_stack(void)126 asmlinkage __visible void dump_stack(void)
127 {
128 __dump_stack();
129 }
130 #endif
131 EXPORT_SYMBOL(dump_stack);
132