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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thumbee.c (1402B)

      1// SPDX-License-Identifier: GPL-2.0-only
      2/*
      3 * arch/arm/kernel/thumbee.c
      4 *
      5 * Copyright (C) 2008 ARM Limited
      6 */
      7
      8#include <linux/kernel.h>
      9#include <linux/init.h>
     10
     11#include <asm/cputype.h>
     12#include <asm/system_info.h>
     13#include <asm/thread_notify.h>
     14
     15/*
     16 * Access to the ThumbEE Handler Base register
     17 */
     18static inline unsigned long teehbr_read(void)
     19{
     20	unsigned long v;
     21	asm("mrc	p14, 6, %0, c1, c0, 0\n" : "=r" (v));
     22	return v;
     23}
     24
     25static inline void teehbr_write(unsigned long v)
     26{
     27	asm("mcr	p14, 6, %0, c1, c0, 0\n" : : "r" (v));
     28}
     29
     30static int thumbee_notifier(struct notifier_block *self, unsigned long cmd, void *t)
     31{
     32	struct thread_info *thread = t;
     33
     34	switch (cmd) {
     35	case THREAD_NOTIFY_FLUSH:
     36		teehbr_write(0);
     37		break;
     38	case THREAD_NOTIFY_SWITCH:
     39		current_thread_info()->thumbee_state = teehbr_read();
     40		teehbr_write(thread->thumbee_state);
     41		break;
     42	}
     43
     44	return NOTIFY_DONE;
     45}
     46
     47static struct notifier_block thumbee_notifier_block = {
     48	.notifier_call	= thumbee_notifier,
     49};
     50
     51static int __init thumbee_init(void)
     52{
     53	unsigned long pfr0;
     54	unsigned int cpu_arch = cpu_architecture();
     55
     56	if (cpu_arch < CPU_ARCH_ARMv7)
     57		return 0;
     58
     59	pfr0 = read_cpuid_ext(CPUID_EXT_PFR0);
     60	if ((pfr0 & 0x0000f000) != 0x00001000)
     61		return 0;
     62
     63	pr_info("ThumbEE CPU extension supported.\n");
     64	elf_hwcap |= HWCAP_THUMBEE;
     65	thread_register_notifier(&thumbee_notifier_block);
     66
     67	return 0;
     68}
     69
     70late_initcall(thumbee_init);