1 #include <linux/module.h> 2 #include <asm/alternative.h> 3 #include <asm/facility.h> 4 5 #define MAX_PATCH_LEN (255 - 1) 6 7 static int __initdata_or_module alt_instr_disabled; 8 9 static int __init disable_alternative_instructions(char *str) 10 { 11 alt_instr_disabled = 1; 12 return 0; 13 } 14 15 early_param("noaltinstr", disable_alternative_instructions); 16 17 struct brcl_insn { 18 u16 opc; 19 s32 disp; 20 } __packed; 21 22 static u16 __initdata_or_module nop16 = 0x0700; 23 static u32 __initdata_or_module nop32 = 0x47000000; 24 static struct brcl_insn __initdata_or_module nop48 = { 25 0xc004, 0 26 }; 27 28 static const void *nops[] __initdata_or_module = { 29 &nop16, 30 &nop32, 31 &nop48 32 }; 33 34 static void __init_or_module add_jump_padding(void *insns, unsigned int len) 35 { 36 struct brcl_insn brcl = { 37 0xc0f4, 38 len / 2 39 }; 40 41 memcpy(insns, &brcl, sizeof(brcl)); 42 insns += sizeof(brcl); 43 len -= sizeof(brcl); 44 45 while (len > 0) { 46 memcpy(insns, &nop16, 2); 47 insns += 2; 48 len -= 2; 49 } 50 } 51 52 static void __init_or_module add_padding(void *insns, unsigned int len) 53 { 54 if (len > 6) 55 add_jump_padding(insns, len); 56 else if (len >= 2) 57 memcpy(insns, nops[len / 2 - 1], len); 58 } 59 60 static void __init_or_module __apply_alternatives(struct alt_instr *start, 61 struct alt_instr *end) 62 { 63 struct alt_instr *a; 64 u8 *instr, *replacement; 65 u8 insnbuf[MAX_PATCH_LEN]; 66 67 /* 68 * The scan order should be from start to end. A later scanned 69 * alternative code can overwrite previously scanned alternative code. 70 */ 71 for (a = start; a < end; a++) { 72 int insnbuf_sz = 0; 73 74 instr = (u8 *)&a->instr_offset + a->instr_offset; 75 replacement = (u8 *)&a->repl_offset + a->repl_offset; 76 77 if (!test_facility(a->facility)) 78 continue; 79 80 if (unlikely(a->instrlen % 2 || a->replacementlen % 2)) { 81 WARN_ONCE(1, "cpu alternatives instructions length is " 82 "odd, skipping patching\n"); 83 continue; 84 } 85 86 memcpy(insnbuf, replacement, a->replacementlen); 87 insnbuf_sz = a->replacementlen; 88 89 if (a->instrlen > a->replacementlen) { 90 add_padding(insnbuf + a->replacementlen, 91 a->instrlen - a->replacementlen); 92 insnbuf_sz += a->instrlen - a->replacementlen; 93 } 94 95 s390_kernel_write(instr, insnbuf, insnbuf_sz); 96 } 97 } 98 99 void __init_or_module apply_alternatives(struct alt_instr *start, 100 struct alt_instr *end) 101 { 102 if (!alt_instr_disabled) 103 __apply_alternatives(start, end); 104 } 105 106 extern struct alt_instr __alt_instructions[], __alt_instructions_end[]; 107 void __init apply_alternative_instructions(void) 108 { 109 apply_alternatives(__alt_instructions, __alt_instructions_end); 110 } 111