111 lines
2.5 KiB
C
111 lines
2.5 KiB
C
#include <linux/module.h>
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#include <asm/alternative.h>
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#include <asm/facility.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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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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