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// SPDX-License-Identifier: GPL-2.0-or-later
#include "../../special.h"
#include "../../builtin.h"
#define X86_FEATURE_POPCNT (4 * 32 + 23)
#define X86_FEATURE_SMAP (9 * 32 + 20)
void arch_handle_alternative(unsigned short feature, struct special_alt *alt)
{
switch (feature) {
case X86_FEATURE_SMAP:
/*
* If UACCESS validation is enabled; force that alternative;
* otherwise force it the other way.
*
* What we want to avoid is having both the original and the
* alternative code flow at the same time, in that case we can
* find paths that see the STAC but take the NOP instead of
* CLAC and the other way around.
*/
if (uaccess)
alt->skip_orig = true;
else
alt->skip_alt = true;
break;
case X86_FEATURE_POPCNT:
/*
* It has been requested that we don't validate the !POPCNT
* feature path which is a "very very small percentage of
* machines".
*/
alt->skip_orig = true;
break;
default:
break;
}
}
bool arch_support_alt_relocation(struct special_alt *special_alt,
struct instruction *insn,
struct reloc *reloc)
{
/*
* The x86 alternatives code adjusts the offsets only when it
* encounters a branch instruction at the very beginning of the
* replacement group.
*/
return insn->offset == special_alt->new_off &&
(insn->type == INSN_CALL || is_static_jump(insn));
}
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