Line data    Source code

       1             : // SPDX-License-Identifier: GPL-2.0
       2             : /*
       3             :  *  NMI backtrace support
       4             :  *
       5             :  * Gratuitously copied from arch/x86/kernel/apic/hw_nmi.c by Russell King,
       6             :  * with the following header:
       7             :  *
       8             :  *  HW NMI watchdog support
       9             :  *
      10             :  *  started by Don Zickus, Copyright (C) 2010 Red Hat, Inc.
      11             :  *
      12             :  *  Arch specific calls to support NMI watchdog
      13             :  *
      14             :  *  Bits copied from original nmi.c file
      15             :  */
      16             : #include <linux/cpumask.h>
      17             : #include <linux/delay.h>
      18             : #include <linux/kprobes.h>
      19             : #include <linux/nmi.h>
      20             : #include <linux/cpu.h>
      21             : #include <linux/sched/debug.h>
      22             : 
      23             : #ifdef arch_trigger_cpumask_backtrace
      24             : /* For reliability, we're prepared to waste bits here. */
      25             : static DECLARE_BITMAP(backtrace_mask, NR_CPUS) __read_mostly;
      26             : 
      27             : /* "in progress" flag of arch_trigger_cpumask_backtrace */
      28             : static unsigned long backtrace_flag;
      29             : 
      30             : /*
      31             :  * When raise() is called it will be passed a pointer to the
      32             :  * backtrace_mask. Architectures that call nmi_cpu_backtrace()
      33             :  * directly from their raise() functions may rely on the mask
      34             :  * they are passed being updated as a side effect of this call.
      35             :  */
      36           0 : void nmi_trigger_cpumask_backtrace(const cpumask_t *mask,
      37             :                                    bool exclude_self,
      38             :                                    void (*raise)(cpumask_t *mask))
      39             : {
      40           0 :         int i, this_cpu = get_cpu();
      41             : 
      42           0 :         if (test_and_set_bit(0, &backtrace_flag)) {
      43             :                 /*
      44             :                  * If there is already a trigger_all_cpu_backtrace() in progress
      45             :                  * (backtrace_flag == 1), don't output double cpu dump infos.
      46             :                  */
      47           0 :                 put_cpu();
      48           0 :                 return;
      49             :         }
      50             : 
      51           0 :         cpumask_copy(to_cpumask(backtrace_mask), mask);
      52           0 :         if (exclude_self)
      53           0 :                 cpumask_clear_cpu(this_cpu, to_cpumask(backtrace_mask));
      54             : 
      55             :         /*
      56             :          * Don't try to send an NMI to this cpu; it may work on some
      57             :          * architectures, but on others it may not, and we'll get
      58             :          * information at least as useful just by doing a dump_stack() here.
      59             :          * Note that nmi_cpu_backtrace(NULL) will clear the cpu bit.
      60             :          */
      61           0 :         if (cpumask_test_cpu(this_cpu, to_cpumask(backtrace_mask)))
      62           0 :                 nmi_cpu_backtrace(NULL);
      63             : 
      64           0 :         if (!cpumask_empty(to_cpumask(backtrace_mask))) {
      65           0 :                 pr_info("Sending NMI from CPU %d to CPUs %*pbl:\n",
      66             :                         this_cpu, nr_cpumask_bits, to_cpumask(backtrace_mask));
      67           0 :                 raise(to_cpumask(backtrace_mask));
      68             :         }
      69             : 
      70             :         /* Wait for up to 10 seconds for all CPUs to do the backtrace */
      71           0 :         for (i = 0; i < 10 * 1000; i++) {
      72           0 :                 if (cpumask_empty(to_cpumask(backtrace_mask)))
      73             :                         break;
      74           0 :                 mdelay(1);
      75           0 :                 touch_softlockup_watchdog();
      76             :         }
      77             : 
      78             :         /*
      79             :          * Force flush any remote buffers that might be stuck in IRQ context
      80             :          * and therefore could not run their irq_work.
      81             :          */
      82           0 :         printk_safe_flush();
      83             : 
      84           0 :         clear_bit_unlock(0, &backtrace_flag);
      85           0 :         put_cpu();
      86             : }
      87             : 
      88             : // Dump stacks even for idle CPUs.
      89             : static bool backtrace_idle;
      90             : module_param(backtrace_idle, bool, 0644);
      91             : 
      92           0 : bool nmi_cpu_backtrace(struct pt_regs *regs)
      93             : {
      94           0 :         int cpu = smp_processor_id();
      95             : 
      96           0 :         if (cpumask_test_cpu(cpu, to_cpumask(backtrace_mask))) {
      97           0 :                 if (!READ_ONCE(backtrace_idle) && regs && cpu_in_idle(instruction_pointer(regs))) {
      98           0 :                         pr_warn("NMI backtrace for cpu %d skipped: idling at %pS\n",
      99             :                                 cpu, (void *)instruction_pointer(regs));
     100             :                 } else {
     101           0 :                         pr_warn("NMI backtrace for cpu %d\n", cpu);
     102           0 :                         if (regs)
     103           0 :                                 show_regs(regs);
     104             :                         else
     105           0 :                                 dump_stack();
     106             :                 }
     107           0 :                 cpumask_clear_cpu(cpu, to_cpumask(backtrace_mask));
     108           0 :                 return true;
     109             :         }
     110             : 
     111             :         return false;
     112             : }
     113             : NOKPROBE_SYMBOL(nmi_cpu_backtrace);
     114             : #endif