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/uaccess.h> 8 #include <linux/stop_machine.h> 9 #include <linux/jump_label.h> 10 #include <asm/ipl.h> 11 12 #ifdef HAVE_JUMP_LABEL 13 14 struct insn { 15 u16 opcode; 16 s32 offset; 17 } __packed; 18 19 struct insn_args { 20 struct jump_entry *entry; 21 enum jump_label_type type; 22 }; 23 24 static void jump_label_make_nop(struct jump_entry *entry, struct insn *insn) 25 { 26 /* brcl 0,0 */ 27 insn->opcode = 0xc004; 28 insn->offset = 0; 29 } 30 31 static void jump_label_make_branch(struct jump_entry *entry, struct insn *insn) 32 { 33 /* brcl 15,offset */ 34 insn->opcode = 0xc0f4; 35 insn->offset = (entry->target - entry->code) >> 1; 36 } 37 38 static void jump_label_bug(struct jump_entry *entry, struct insn *expected, 39 struct insn *new) 40 { 41 unsigned char *ipc = (unsigned char *)entry->code; 42 unsigned char *ipe = (unsigned char *)expected; 43 unsigned char *ipn = (unsigned char *)new; 44 45 pr_emerg("Jump label code mismatch at %pS [%p]\n", ipc, ipc); 46 pr_emerg("Found: %6ph\n", ipc); 47 pr_emerg("Expected: %6ph\n", ipe); 48 pr_emerg("New: %6ph\n", ipn); 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_JMP) { 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, &orignop, &new); 73 } else { 74 if (memcmp((void *)entry->code, &old, sizeof(old))) 75 jump_label_bug(entry, &old, &new); 76 } 77 s390_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