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 *insn) 40 { 41 unsigned char *ipc = (unsigned char *)entry->code; 42 unsigned char *ipe = (unsigned char *)insn; 43 44 pr_emerg("Jump label code mismatch at %pS [%p]\n", ipc, ipc); 45 pr_emerg("Found: %02x %02x %02x %02x %02x %02x\n", 46 ipc[0], ipc[1], ipc[2], ipc[3], ipc[4], ipc[5]); 47 pr_emerg("Expected: %02x %02x %02x %02x %02x %02x\n", 48 ipe[0], ipe[1], ipe[2], ipe[3], ipe[4], ipe[5]); 49 panic("Corrupted kernel text"); 50 } 51 52 static struct insn orignop = { 53 .opcode = 0xc004, 54 .offset = JUMP_LABEL_NOP_OFFSET >> 1, 55 }; 56 57 static void __jump_label_transform(struct jump_entry *entry, 58 enum jump_label_type type, 59 int init) 60 { 61 struct insn old, new; 62 63 if (type == JUMP_LABEL_ENABLE) { 64 jump_label_make_nop(entry, &old); 65 jump_label_make_branch(entry, &new); 66 } else { 67 jump_label_make_branch(entry, &old); 68 jump_label_make_nop(entry, &new); 69 } 70 if (init) { 71 if (memcmp((void *)entry->code, &orignop, sizeof(orignop))) 72 jump_label_bug(entry, &old); 73 } else { 74 if (memcmp((void *)entry->code, &old, sizeof(old))) 75 jump_label_bug(entry, &old); 76 } 77 probe_kernel_write((void *)entry->code, &new, sizeof(new)); 78 } 79 80 static int __sm_arch_jump_label_transform(void *data) 81 { 82 struct insn_args *args = data; 83 84 __jump_label_transform(args->entry, args->type, 0); 85 return 0; 86 } 87 88 void arch_jump_label_transform(struct jump_entry *entry, 89 enum jump_label_type type) 90 { 91 struct insn_args args; 92 93 args.entry = entry; 94 args.type = type; 95 96 stop_machine(__sm_arch_jump_label_transform, &args, NULL); 97 } 98 99 void arch_jump_label_transform_static(struct jump_entry *entry, 100 enum jump_label_type type) 101 { 102 __jump_label_transform(entry, type, 1); 103 } 104 105 #endif 106