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// SPDX-License-Identifier: GPL-2.0
/*
* Copyright (C) 2018 ARM Ltd, All Rights Reserved.
*/
#include <linux/compat.h>
#include <linux/errno.h>
#include <linux/prctl.h>
#include <linux/sched.h>
#include <linux/sched/task_stack.h>
#include <linux/thread_info.h>
#include <asm/cpufeature.h>
static void ssbd_ssbs_enable(struct task_struct *task)
{
u64 val = is_compat_thread(task_thread_info(task)) ?
PSR_AA32_SSBS_BIT : PSR_SSBS_BIT;
task_pt_regs(task)->pstate |= val;
}
static void ssbd_ssbs_disable(struct task_struct *task)
{
u64 val = is_compat_thread(task_thread_info(task)) ?
PSR_AA32_SSBS_BIT : PSR_SSBS_BIT;
task_pt_regs(task)->pstate &= ~val;
}
/*
* prctl interface for SSBD
* FIXME: Drop the below ifdefery once merged in 4.18.
*/
#ifdef PR_SPEC_STORE_BYPASS
static int ssbd_prctl_set(struct task_struct *task, unsigned long ctrl)
{
int state = arm64_get_ssbd_state();
/* Unsupported */
if (state == ARM64_SSBD_UNKNOWN)
return -EINVAL;
/* Treat the unaffected/mitigated state separately */
if (state == ARM64_SSBD_MITIGATED) {
switch (ctrl) {
case PR_SPEC_ENABLE:
return -EPERM;
case PR_SPEC_DISABLE:
case PR_SPEC_FORCE_DISABLE:
return 0;
}
}
/*
* Things are a bit backward here: the arm64 internal API
* *enables the mitigation* when the userspace API *disables
* speculation*. So much fun.
*/
switch (ctrl) {
case PR_SPEC_ENABLE:
/* If speculation is force disabled, enable is not allowed */
if (state == ARM64_SSBD_FORCE_ENABLE ||
task_spec_ssb_force_disable(task))
return -EPERM;
task_clear_spec_ssb_disable(task);
clear_tsk_thread_flag(task, TIF_SSBD);
ssbd_ssbs_enable(task);
break;
case PR_SPEC_DISABLE:
if (state == ARM64_SSBD_FORCE_DISABLE)
return -EPERM;
task_set_spec_ssb_disable(task);
set_tsk_thread_flag(task, TIF_SSBD);
ssbd_ssbs_disable(task);
break;
case PR_SPEC_FORCE_DISABLE:
if (state == ARM64_SSBD_FORCE_DISABLE)
return -EPERM;
task_set_spec_ssb_disable(task);
task_set_spec_ssb_force_disable(task);
set_tsk_thread_flag(task, TIF_SSBD);
ssbd_ssbs_disable(task);
break;
default:
return -ERANGE;
}
return 0;
}
int arch_prctl_spec_ctrl_set(struct task_struct *task, unsigned long which,
unsigned long ctrl)
{
switch (which) {
case PR_SPEC_STORE_BYPASS:
return ssbd_prctl_set(task, ctrl);
default:
return -ENODEV;
}
}
static int ssbd_prctl_get(struct task_struct *task)
{
switch (arm64_get_ssbd_state()) {
case ARM64_SSBD_UNKNOWN:
return -EINVAL;
case ARM64_SSBD_FORCE_ENABLE:
return PR_SPEC_DISABLE;
case ARM64_SSBD_KERNEL:
if (task_spec_ssb_force_disable(task))
return PR_SPEC_PRCTL | PR_SPEC_FORCE_DISABLE;
if (task_spec_ssb_disable(task))
return PR_SPEC_PRCTL | PR_SPEC_DISABLE;
return PR_SPEC_PRCTL | PR_SPEC_ENABLE;
case ARM64_SSBD_FORCE_DISABLE:
return PR_SPEC_ENABLE;
default:
return PR_SPEC_NOT_AFFECTED;
}
}
int arch_prctl_spec_ctrl_get(struct task_struct *task, unsigned long which)
{
switch (which) {
case PR_SPEC_STORE_BYPASS:
return ssbd_prctl_get(task);
default:
return -ENODEV;
}
}
#endif /* PR_SPEC_STORE_BYPASS */
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