// SPDX-License-Identifier: GPL-2.0
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/*
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* Copyright (C) 2018 ARM Ltd, All Rights Reserved.
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*/
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#include <linux/errno.h>
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#include <linux/prctl.h>
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#include <linux/sched.h>
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#include <linux/thread_info.h>
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#include <asm/cpufeature.h>
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/*
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* prctl interface for SSBD
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*/
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static int ssbd_prctl_set(struct task_struct *task, unsigned long ctrl)
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{
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int state = arm64_get_ssbd_state();
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/* Unsupported */
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if (state == ARM64_SSBD_UNKNOWN)
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return -EINVAL;
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/* Treat the unaffected/mitigated state separately */
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if (state == ARM64_SSBD_MITIGATED) {
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switch (ctrl) {
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case PR_SPEC_ENABLE:
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return -EPERM;
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case PR_SPEC_DISABLE:
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case PR_SPEC_FORCE_DISABLE:
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return 0;
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}
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}
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/*
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* Things are a bit backward here: the arm64 internal API
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* *enables the mitigation* when the userspace API *disables
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* speculation*. So much fun.
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*/
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switch (ctrl) {
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case PR_SPEC_ENABLE:
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/* If speculation is force disabled, enable is not allowed */
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if (state == ARM64_SSBD_FORCE_ENABLE ||
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task_spec_ssb_force_disable(task))
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return -EPERM;
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task_clear_spec_ssb_disable(task);
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clear_tsk_thread_flag(task, TIF_SSBD);
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break;
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case PR_SPEC_DISABLE:
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if (state == ARM64_SSBD_FORCE_DISABLE)
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return -EPERM;
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task_set_spec_ssb_disable(task);
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set_tsk_thread_flag(task, TIF_SSBD);
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break;
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case PR_SPEC_FORCE_DISABLE:
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if (state == ARM64_SSBD_FORCE_DISABLE)
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return -EPERM;
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task_set_spec_ssb_disable(task);
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task_set_spec_ssb_force_disable(task);
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set_tsk_thread_flag(task, TIF_SSBD);
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break;
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default:
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return -ERANGE;
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}
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return 0;
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}
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int arch_prctl_spec_ctrl_set(struct task_struct *task, unsigned long which,
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unsigned long ctrl)
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{
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switch (which) {
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case PR_SPEC_STORE_BYPASS:
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return ssbd_prctl_set(task, ctrl);
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default:
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return -ENODEV;
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}
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}
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static int ssbd_prctl_get(struct task_struct *task)
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{
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switch (arm64_get_ssbd_state()) {
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case ARM64_SSBD_UNKNOWN:
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return -EINVAL;
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case ARM64_SSBD_FORCE_ENABLE:
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return PR_SPEC_DISABLE;
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case ARM64_SSBD_KERNEL:
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if (task_spec_ssb_force_disable(task))
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return PR_SPEC_PRCTL | PR_SPEC_FORCE_DISABLE;
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if (task_spec_ssb_disable(task))
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return PR_SPEC_PRCTL | PR_SPEC_DISABLE;
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return PR_SPEC_PRCTL | PR_SPEC_ENABLE;
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case ARM64_SSBD_FORCE_DISABLE:
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return PR_SPEC_ENABLE;
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default:
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return PR_SPEC_NOT_AFFECTED;
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}
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}
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int arch_prctl_spec_ctrl_get(struct task_struct *task, unsigned long which)
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{
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switch (which) {
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case PR_SPEC_STORE_BYPASS:
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return ssbd_prctl_get(task);
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default:
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return -ENODEV;
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}
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}
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