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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 | // SPDX-License-Identifier: GPL-2.0
/*
* Copyright (C) 2018 ARM Ltd, All Rights Reserved.
*/
#include <linux/errno.h>
#include <linux/prctl.h>
#include <linux/sched.h>
#include <linux/thread_info.h>
#include <asm/cpufeature.h>
/*
* prctl interface for SSBD
*/
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);
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);
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);
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;
}
}
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