| // 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, 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); |
| } |