lib/dump_stack.c

   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  */
  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  */
  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  */
  69 void show_regs_print_info(const char *log_lvl)
  70 {
  71         dump_stack_print_info(log_lvl);
  72 }
  73
  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
  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
 126 asmlinkage __visible void dump_stack(void)
 127 {
 128         __dump_stack();
 129 }
 130 #endif
 131 EXPORT_SYMBOL(dump_stack);