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: %6ph\n", ipc); 48 pr_emerg("Expected: %6ph\n", ipe); 49 pr_emerg("New: %6ph\n", ipn); 50 panic("Corrupted kernel text"); 51 } 52 53 static struct insn orignop = { 54 .opcode = 0xc004, 55 .offset = JUMP_LABEL_NOP_OFFSET >> 1, 56 }; 57 58 static void __jump_label_transform(struct jump_entry *entry, 59 enum jump_label_type type, 60 int init) 61 { 62 struct insn old, new; 63 64 if (type == JUMP_LABEL_JMP) { 65 jump_label_make_nop(entry, &old); 66 jump_label_make_branch(entry, &new); 67 } else { 68 jump_label_make_branch(entry, &old); 69 jump_label_make_nop(entry, &new); 70 } 71 if (init) { 72 if (memcmp((void *)entry->code, &orignop, sizeof(orignop))) 73 jump_label_bug(entry, &orignop, &new); 74 } else { 75 if (memcmp((void *)entry->code, &old, sizeof(old))) 76 jump_label_bug(entry, &old, &new); 77 } 78 s390_kernel_write((void *)entry->code, &new, sizeof(new)); 79 } 80 81 static int __sm_arch_jump_label_transform(void *data) 82 { 83 struct insn_args *args = data; 84 85 __jump_label_transform(args->entry, args->type, 0); 86 return 0; 87 } 88 89 void arch_jump_label_transform(struct jump_entry *entry, 90 enum jump_label_type type) 91 { 92 struct insn_args args; 93 94 args.entry = entry; 95 args.type = type; 96 97 stop_machine(__sm_arch_jump_label_transform, &args, NULL); 98 } 99 100 void arch_jump_label_transform_static(struct jump_entry *entry, 101 enum jump_label_type type) 102 { 103 __jump_label_transform(entry, type, 1); 104 } 105 106 #endif 107