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 #include <linux/stop_machine.h>
  16
  17 static char dump_stack_arch_desc_str[128];
  18
  19 /**
  20  * dump_stack_set_arch_desc - set arch-specific str to show with task dumps
  21  * @fmt: printf-style format string
  22  * @...: arguments for the format string
  23  *
  24  * The configured string will be printed right after utsname during task
  25  * dumps.  Usually used to add arch-specific system identifiers.  If an
  26  * arch wants to make use of such an ID string, it should initialize this
  27  * as soon as possible during boot.
  28  */
  29 void __init dump_stack_set_arch_desc(const char *fmt, ...)
  30 {
  31         va_list args;
  32
  33         va_start(args, fmt);
  34         vsnprintf(dump_stack_arch_desc_str, sizeof(dump_stack_arch_desc_str),
  35                   fmt, args);
  36         va_end(args);
  37 }
  38
  39 /**
  40  * dump_stack_print_info - print generic debug info for dump_stack()
  41  * @log_lvl: log level
  42  *
  43  * Arch-specific dump_stack() implementations can use this function to
  44  * print out the same debug information as the generic dump_stack().
  45  */
  46 void dump_stack_print_info(const char *log_lvl)
  47 {
  48         printk("%sCPU: %d PID: %d Comm: %.20s %s%s %s %.*s\n",
  49                log_lvl, raw_smp_processor_id(), current->pid, current->comm,
  50                kexec_crash_loaded() ? "Kdump: loaded " : "",
  51                print_tainted(),
  52                init_utsname()->release,
  53                (int)strcspn(init_utsname()->version, " "),
  54                init_utsname()->version);
  55
  56         if (dump_stack_arch_desc_str[0] != '\0')
  57                 printk("%sHardware name: %s\n",
  58                        log_lvl, dump_stack_arch_desc_str);
  59
  60         print_worker_info(log_lvl, current);
  61         print_stop_info(log_lvl, current);
  62 }
  63
  64 /**
  65  * show_regs_print_info - print generic debug info for show_regs()
  66  * @log_lvl: log level
  67  *
  68  * show_regs() implementations can use this function to print out generic
  69  * debug information.
  70  */
  71 void show_regs_print_info(const char *log_lvl)
  72 {
  73         dump_stack_print_info(log_lvl);
  74 }
  75
  76 static void __dump_stack(void)
  77 {
  78         dump_stack_print_info(KERN_DEFAULT);
  79         show_stack(NULL, NULL, KERN_DEFAULT);
  80 }
  81
  82 /**
  83  * dump_stack - dump the current task information and its stack trace
  84  *
  85  * Architectures can override this implementation by implementing its own.
  86  */
  87 #ifdef CONFIG_SMP
  88 static atomic_t dump_lock = ATOMIC_INIT(-1);
  89
  90 asmlinkage __visible void dump_stack(void)
  91 {
  92         unsigned long flags;
  93         int was_locked;
  94         int old;
  95         int cpu;
  96
  97         /*
  98          * Permit this cpu to perform nested stack dumps while serialising
  99          * against other CPUs
 100          */
 101 retry:
 102         local_irq_save(flags);
 103         cpu = smp_processor_id();
 104         old = atomic_cmpxchg(&dump_lock, -1, cpu);
 105         if (old == -1) {
 106                 was_locked = 0;
 107         } else if (old == cpu) {
 108                 was_locked = 1;
 109         } else {
 110                 local_irq_restore(flags);
 111                 /*
 112                  * Wait for the lock to release before jumping to
 113                  * atomic_cmpxchg() in order to mitigate the thundering herd
 114                  * problem.
 115                  */
 116                 do { cpu_relax(); } while (atomic_read(&dump_lock) != -1);
 117                 goto retry;
 118         }
 119
 120         __dump_stack();
 121
 122         if (!was_locked)
 123                 atomic_set(&dump_lock, -1);
 124
 125         local_irq_restore(flags);
 126 }
 127 #else
 128 asmlinkage __visible void dump_stack(void)
 129 {
 130         __dump_stack();
 131 }
 132 #endif
 133 EXPORT_SYMBOL(dump_stack);