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/*
* Copyright (c) 2023 Ian Marco Moffett and the Osmora Team.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* 1. Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of Hyra nor the names of its
* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
#include <machine/spectre.h>
#include <machine/cpuid.h>
#include <machine/msr.h>
#include <sys/syslog.h>
#include <sys/types.h>
__MODULE_NAME("spectre");
__KERNEL_META("$Hyra$: spectre.c, Ian Marco Moffett, "
"Spectre mitigation support");
#if __SPECTRE_MITIGATION == 1
/*
* Returns true if Indirect Branch Restricted Speculation (IBRS)
* is supported.
*/
__naked bool
__can_mitigate_spectre(void);
/*
* Returns EXIT_FAILURE if not supported, returns
* EXIT_SUCCESS if mitigation is now active.
*
* This function will be NULL if spectre mitigation isn't enabled;
* therefore it is wise to verify to prevent access violations and
* undefined behaviour.
*
* This behaviour is governed by the __SPECTRE_MITIGATION define
*
* TODO: Try to enable others, not just IBRS
*/
__weak int
try_spectre_mitigate(void)
{
uint64_t tmp;
if (!__can_mitigate_spectre()) {
KINFO("IBRS not supported; spectre mitigation NOT enabled\n");
return EXIT_FAILURE;
}
KINFO("IBRS supported; spectre mitigation enabled\n");
tmp = rdmsr(IA32_SPEC_CTL);
tmp |= __BIT(0); /* IBRS */
wrmsr(IA32_SPEC_CTL, tmp);
return EXIT_SUCCESS;
}
#endif /* __SPECTRE_MITIGATION == 1 */
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