// SPDX-License-Identifier: GPL-2.0
|
#include <linux/module.h>
|
#include <asm/alternative.h>
|
#include <asm/facility.h>
|
#include <asm/nospec-branch.h>
|
|
#define MAX_PATCH_LEN (255 - 1)
|
|
static int __initdata_or_module alt_instr_disabled;
|
|
static int __init disable_alternative_instructions(char *str)
|
{
|
alt_instr_disabled = 1;
|
return 0;
|
}
|
|
early_param("noaltinstr", disable_alternative_instructions);
|
|
struct brcl_insn {
|
u16 opc;
|
s32 disp;
|
} __packed;
|
|
static u16 __initdata_or_module nop16 = 0x0700;
|
static u32 __initdata_or_module nop32 = 0x47000000;
|
static struct brcl_insn __initdata_or_module nop48 = {
|
0xc004, 0
|
};
|
|
static const void *nops[] __initdata_or_module = {
|
&nop16,
|
&nop32,
|
&nop48
|
};
|
|
static void __init_or_module add_jump_padding(void *insns, unsigned int len)
|
{
|
struct brcl_insn brcl = {
|
0xc0f4,
|
len / 2
|
};
|
|
memcpy(insns, &brcl, sizeof(brcl));
|
insns += sizeof(brcl);
|
len -= sizeof(brcl);
|
|
while (len > 0) {
|
memcpy(insns, &nop16, 2);
|
insns += 2;
|
len -= 2;
|
}
|
}
|
|
static void __init_or_module add_padding(void *insns, unsigned int len)
|
{
|
if (len > 6)
|
add_jump_padding(insns, len);
|
else if (len >= 2)
|
memcpy(insns, nops[len / 2 - 1], len);
|
}
|
|
static void __init_or_module __apply_alternatives(struct alt_instr *start,
|
struct alt_instr *end)
|
{
|
struct alt_instr *a;
|
u8 *instr, *replacement;
|
u8 insnbuf[MAX_PATCH_LEN];
|
|
/*
|
* The scan order should be from start to end. A later scanned
|
* alternative code can overwrite previously scanned alternative code.
|
*/
|
for (a = start; a < end; a++) {
|
int insnbuf_sz = 0;
|
|
instr = (u8 *)&a->instr_offset + a->instr_offset;
|
replacement = (u8 *)&a->repl_offset + a->repl_offset;
|
|
if (!__test_facility(a->facility,
|
S390_lowcore.alt_stfle_fac_list))
|
continue;
|
|
if (unlikely(a->instrlen % 2 || a->replacementlen % 2)) {
|
WARN_ONCE(1, "cpu alternatives instructions length is "
|
"odd, skipping patching\n");
|
continue;
|
}
|
|
memcpy(insnbuf, replacement, a->replacementlen);
|
insnbuf_sz = a->replacementlen;
|
|
if (a->instrlen > a->replacementlen) {
|
add_padding(insnbuf + a->replacementlen,
|
a->instrlen - a->replacementlen);
|
insnbuf_sz += a->instrlen - a->replacementlen;
|
}
|
|
s390_kernel_write(instr, insnbuf, insnbuf_sz);
|
}
|
}
|
|
void __init_or_module apply_alternatives(struct alt_instr *start,
|
struct alt_instr *end)
|
{
|
if (!alt_instr_disabled)
|
__apply_alternatives(start, end);
|
}
|
|
extern struct alt_instr __alt_instructions[], __alt_instructions_end[];
|
void __init apply_alternative_instructions(void)
|
{
|
apply_alternatives(__alt_instructions, __alt_instructions_end);
|
}
|
