cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
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nmi_backtrace.c (3386B)

      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. */
     25static DECLARE_BITMAP(backtrace_mask, NR_CPUS) __read_mostly;
     26
     27/* "in progress" flag of arch_trigger_cpumask_backtrace */
     28static 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 */
     36void nmi_trigger_cpumask_backtrace(const cpumask_t *mask,
     37				   bool exclude_self,
     38				   void (*raise)(cpumask_t *mask))
     39{
     40	int i, this_cpu = get_cpu();
     41
     42	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		put_cpu();
     48		return;
     49	}
     50
     51	cpumask_copy(to_cpumask(backtrace_mask), mask);
     52	if (exclude_self)
     53		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	if (cpumask_test_cpu(this_cpu, to_cpumask(backtrace_mask)))
     62		nmi_cpu_backtrace(NULL);
     63
     64	if (!cpumask_empty(to_cpumask(backtrace_mask))) {
     65		pr_info("Sending NMI from CPU %d to CPUs %*pbl:\n",
     66			this_cpu, nr_cpumask_bits, to_cpumask(backtrace_mask));
     67		raise(to_cpumask(backtrace_mask));
     68	}
     69
     70	/* Wait for up to 10 seconds for all CPUs to do the backtrace */
     71	for (i = 0; i < 10 * 1000; i++) {
     72		if (cpumask_empty(to_cpumask(backtrace_mask)))
     73			break;
     74		mdelay(1);
     75		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	printk_trigger_flush();
     83
     84	clear_bit_unlock(0, &backtrace_flag);
     85	put_cpu();
     86}
     87
     88// Dump stacks even for idle CPUs.
     89static bool backtrace_idle;
     90module_param(backtrace_idle, bool, 0644);
     91
     92bool nmi_cpu_backtrace(struct pt_regs *regs)
     93{
     94	int cpu = smp_processor_id();
     95	unsigned long flags;
     96
     97	if (cpumask_test_cpu(cpu, to_cpumask(backtrace_mask))) {
     98		/*
     99		 * Allow nested NMI backtraces while serializing
    100		 * against other CPUs.
    101		 */
    102		printk_cpu_sync_get_irqsave(flags);
    103		if (!READ_ONCE(backtrace_idle) && regs && cpu_in_idle(instruction_pointer(regs))) {
    104			pr_warn("NMI backtrace for cpu %d skipped: idling at %pS\n",
    105				cpu, (void *)instruction_pointer(regs));
    106		} else {
    107			pr_warn("NMI backtrace for cpu %d\n", cpu);
    108			if (regs)
    109				show_regs(regs);
    110			else
    111				dump_stack();
    112		}
    113		printk_cpu_sync_put_irqrestore(flags);
    114		cpumask_clear_cpu(cpu, to_cpumask(backtrace_mask));
    115		return true;
    116	}
    117
    118	return false;
    119}
    120NOKPROBE_SYMBOL(nmi_cpu_backtrace);
    121#endif