1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * Copyright (C) 2018 ARM Ltd, All Rights Reserved.
4 */
5
6 #include <linux/errno.h>
7 #include <linux/sched.h>
8 #include <linux/thread_info.h>
9
10 #include <asm/cpufeature.h>
11
12 /*
13 * prctl interface for SSBD
14 * FIXME: Drop the below ifdefery once merged in 4.18.
15 */
16 #ifdef PR_SPEC_STORE_BYPASS
ssbd_prctl_set(struct task_struct * task,unsigned long ctrl)17 static int ssbd_prctl_set(struct task_struct *task, unsigned long ctrl)
18 {
19 int state = arm64_get_ssbd_state();
20
21 /* Unsupported */
22 if (state == ARM64_SSBD_UNKNOWN)
23 return -EINVAL;
24
25 /* Treat the unaffected/mitigated state separately */
26 if (state == ARM64_SSBD_MITIGATED) {
27 switch (ctrl) {
28 case PR_SPEC_ENABLE:
29 return -EPERM;
30 case PR_SPEC_DISABLE:
31 case PR_SPEC_FORCE_DISABLE:
32 return 0;
33 }
34 }
35
36 /*
37 * Things are a bit backward here: the arm64 internal API
38 * *enables the mitigation* when the userspace API *disables
39 * speculation*. So much fun.
40 */
41 switch (ctrl) {
42 case PR_SPEC_ENABLE:
43 /* If speculation is force disabled, enable is not allowed */
44 if (state == ARM64_SSBD_FORCE_ENABLE ||
45 task_spec_ssb_force_disable(task))
46 return -EPERM;
47 task_clear_spec_ssb_disable(task);
48 clear_tsk_thread_flag(task, TIF_SSBD);
49 break;
50 case PR_SPEC_DISABLE:
51 if (state == ARM64_SSBD_FORCE_DISABLE)
52 return -EPERM;
53 task_set_spec_ssb_disable(task);
54 set_tsk_thread_flag(task, TIF_SSBD);
55 break;
56 case PR_SPEC_FORCE_DISABLE:
57 if (state == ARM64_SSBD_FORCE_DISABLE)
58 return -EPERM;
59 task_set_spec_ssb_disable(task);
60 task_set_spec_ssb_force_disable(task);
61 set_tsk_thread_flag(task, TIF_SSBD);
62 break;
63 default:
64 return -ERANGE;
65 }
66
67 return 0;
68 }
69
arch_prctl_spec_ctrl_set(struct task_struct * task,unsigned long which,unsigned long ctrl)70 int arch_prctl_spec_ctrl_set(struct task_struct *task, unsigned long which,
71 unsigned long ctrl)
72 {
73 switch (which) {
74 case PR_SPEC_STORE_BYPASS:
75 return ssbd_prctl_set(task, ctrl);
76 default:
77 return -ENODEV;
78 }
79 }
80
ssbd_prctl_get(struct task_struct * task)81 static int ssbd_prctl_get(struct task_struct *task)
82 {
83 switch (arm64_get_ssbd_state()) {
84 case ARM64_SSBD_UNKNOWN:
85 return -EINVAL;
86 case ARM64_SSBD_FORCE_ENABLE:
87 return PR_SPEC_DISABLE;
88 case ARM64_SSBD_KERNEL:
89 if (task_spec_ssb_force_disable(task))
90 return PR_SPEC_PRCTL | PR_SPEC_FORCE_DISABLE;
91 if (task_spec_ssb_disable(task))
92 return PR_SPEC_PRCTL | PR_SPEC_DISABLE;
93 return PR_SPEC_PRCTL | PR_SPEC_ENABLE;
94 case ARM64_SSBD_FORCE_DISABLE:
95 return PR_SPEC_ENABLE;
96 default:
97 return PR_SPEC_NOT_AFFECTED;
98 }
99 }
100
arch_prctl_spec_ctrl_get(struct task_struct * task,unsigned long which)101 int arch_prctl_spec_ctrl_get(struct task_struct *task, unsigned long which)
102 {
103 switch (which) {
104 case PR_SPEC_STORE_BYPASS:
105 return ssbd_prctl_get(task);
106 default:
107 return -ENODEV;
108 }
109 }
110 #endif /* PR_SPEC_STORE_BYPASS */
111
