cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
Log | Files | Refs | README | LICENSE | sfeed.txt

printk_safe.c (1156B)

      1// SPDX-License-Identifier: GPL-2.0-or-later
      2/*
      3 * printk_safe.c - Safe printk for printk-deadlock-prone contexts
      4 */
      5
      6#include <linux/preempt.h>
      7#include <linux/kdb.h>
      8#include <linux/smp.h>
      9#include <linux/cpumask.h>
     10#include <linux/printk.h>
     11#include <linux/kprobes.h>
     12
     13#include "internal.h"
     14
     15static DEFINE_PER_CPU(int, printk_context);
     16
     17/* Can be preempted by NMI. */
     18void __printk_safe_enter(void)
     19{
     20	this_cpu_inc(printk_context);
     21}
     22
     23/* Can be preempted by NMI. */
     24void __printk_safe_exit(void)
     25{
     26	this_cpu_dec(printk_context);
     27}
     28
     29asmlinkage int vprintk(const char *fmt, va_list args)
     30{
     31#ifdef CONFIG_KGDB_KDB
     32	/* Allow to pass printk() to kdb but avoid a recursion. */
     33	if (unlikely(kdb_trap_printk && kdb_printf_cpu < 0))
     34		return vkdb_printf(KDB_MSGSRC_PRINTK, fmt, args);
     35#endif
     36
     37	/*
     38	 * Use the main logbuf even in NMI. But avoid calling console
     39	 * drivers that might have their own locks.
     40	 */
     41	if (this_cpu_read(printk_context) || in_nmi()) {
     42		int len;
     43
     44		len = vprintk_store(0, LOGLEVEL_DEFAULT, NULL, fmt, args);
     45		defer_console_output();
     46		return len;
     47	}
     48
     49	/* No obstacles. */
     50	return vprintk_default(fmt, args);
     51}
     52EXPORT_SYMBOL(vprintk);