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