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(v: 0);
37 break;
38 case THREAD_NOTIFY_SWITCH:
39 current_thread_info()->thumbee_state = teehbr_read();
40 teehbr_write(v: 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);
71

source code of linux/arch/arm/kernel/thumbee.c