1 // SPDX-License-Identifier: GPL-2.0
3 * Copyright (C) 2018 ARM Ltd, All Rights Reserved.
6 #include <linux/errno.h>
7 #include <linux/sched.h>
8 #include <linux/thread_info.h>
10 #include <asm/cpufeature.h>
13 * prctl interface for SSBD
14 * FIXME: Drop the below ifdefery once merged in 4.18.
16 #ifdef PR_SPEC_STORE_BYPASS
17 static int ssbd_prctl_set(struct task_struct *task, unsigned long ctrl)
19 int state = arm64_get_ssbd_state();
22 if (state == ARM64_SSBD_UNKNOWN)
25 /* Treat the unaffected/mitigated state separately */
26 if (state == ARM64_SSBD_MITIGATED) {
31 case PR_SPEC_FORCE_DISABLE:
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.
43 /* If speculation is force disabled, enable is not allowed */
44 if (state == ARM64_SSBD_FORCE_ENABLE ||
45 task_spec_ssb_force_disable(task))
47 task_clear_spec_ssb_disable(task);
48 clear_tsk_thread_flag(task, TIF_SSBD);
51 if (state == ARM64_SSBD_FORCE_DISABLE)
53 task_set_spec_ssb_disable(task);
54 set_tsk_thread_flag(task, TIF_SSBD);
56 case PR_SPEC_FORCE_DISABLE:
57 if (state == ARM64_SSBD_FORCE_DISABLE)
59 task_set_spec_ssb_disable(task);
60 task_set_spec_ssb_force_disable(task);
61 set_tsk_thread_flag(task, TIF_SSBD);
70 int arch_prctl_spec_ctrl_set(struct task_struct *task, unsigned long which,
74 case PR_SPEC_STORE_BYPASS:
75 return ssbd_prctl_set(task, ctrl);
81 static int ssbd_prctl_get(struct task_struct *task)
83 switch (arm64_get_ssbd_state()) {
84 case ARM64_SSBD_UNKNOWN:
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;
97 return PR_SPEC_NOT_AFFECTED;
101 int arch_prctl_spec_ctrl_get(struct task_struct *task, unsigned long which)
104 case PR_SPEC_STORE_BYPASS:
105 return ssbd_prctl_get(task);
110 #endif /* PR_SPEC_STORE_BYPASS */