1 /* 2 * Jump label s390 support 3 * 4 * Copyright IBM Corp. 2011 5 * Author(s): Jan Glauber <jang@linux.vnet.ibm.com> 6 */ 7 #include <linux/module.h> 8 #include <linux/uaccess.h> 9 #include <linux/stop_machine.h> 10 #include <linux/jump_label.h> 11 #include <asm/ipl.h> 12 13 #ifdef HAVE_JUMP_LABEL 14 15 struct insn { 16 u16 opcode; 17 s32 offset; 18 } __packed; 19 20 struct insn_args { 21 struct jump_entry *entry; 22 enum jump_label_type type; 23 }; 24 25 static void jump_label_make_nop(struct jump_entry *entry, struct insn *insn) 26 { 27 /* brcl 0,0 */ 28 insn->opcode = 0xc004; 29 insn->offset = 0; 30 } 31 32 static void jump_label_make_branch(struct jump_entry *entry, struct insn *insn) 33 { 34 /* brcl 15,offset */ 35 insn->opcode = 0xc0f4; 36 insn->offset = (entry->target - entry->code) >> 1; 37 } 38 39 static void jump_label_bug(struct jump_entry *entry, struct insn *expected, 40 struct insn *new) 41 { 42 unsigned char *ipc = (unsigned char *)entry->code; 43 unsigned char *ipe = (unsigned char *)expected; 44 unsigned char *ipn = (unsigned char *)new; 45 46 pr_emerg("Jump label code mismatch at %pS [%p]\n", ipc, ipc); 47 pr_emerg("Found: %02x %02x %02x %02x %02x %02x\n", 48 ipc[0], ipc[1], ipc[2], ipc[3], ipc[4], ipc[5]); 49 pr_emerg("Expected: %02x %02x %02x %02x %02x %02x\n", 50 ipe[0], ipe[1], ipe[2], ipe[3], ipe[4], ipe[5]); 51 pr_emerg("New: %02x %02x %02x %02x %02x %02x\n", 52 ipn[0], ipn[1], ipn[2], ipn[3], ipn[4], ipn[5]); 53 panic("Corrupted kernel text"); 54 } 55 56 static struct insn orignop = { 57 .opcode = 0xc004, 58 .offset = JUMP_LABEL_NOP_OFFSET >> 1, 59 }; 60 61 static void __jump_label_transform(struct jump_entry *entry, 62 enum jump_label_type type, 63 int init) 64 { 65 struct insn old, new; 66 67 if (type == JUMP_LABEL_ENABLE) { 68 jump_label_make_nop(entry, &old); 69 jump_label_make_branch(entry, &new); 70 } else { 71 jump_label_make_branch(entry, &old); 72 jump_label_make_nop(entry, &new); 73 } 74 if (init) { 75 if (memcmp((void *)entry->code, &orignop, sizeof(orignop))) 76 jump_label_bug(entry, &orignop, &new); 77 } else { 78 if (memcmp((void *)entry->code, &old, sizeof(old))) 79 jump_label_bug(entry, &old, &new); 80 } 81 s390_kernel_write((void *)entry->code, &new, sizeof(new)); 82 } 83 84 static int __sm_arch_jump_label_transform(void *data) 85 { 86 struct insn_args *args = data; 87 88 __jump_label_transform(args->entry, args->type, 0); 89 return 0; 90 } 91 92 void arch_jump_label_transform(struct jump_entry *entry, 93 enum jump_label_type type) 94 { 95 struct insn_args args; 96 97 args.entry = entry; 98 args.type = type; 99 100 stop_machine(__sm_arch_jump_label_transform, &args, NULL); 101 } 102 103 void arch_jump_label_transform_static(struct jump_entry *entry, 104 enum jump_label_type type) 105 { 106 __jump_label_transform(entry, type, 1); 107 } 108 109 #endif 110