1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * Jump label s390 support 4 * 5 * Copyright IBM Corp. 2011 6 * Author(s): Jan Glauber <jang@linux.vnet.ibm.com> 7 */ 8 #include <linux/uaccess.h> 9 #include <linux/jump_label.h> 10 #include <linux/module.h> 11 #include <asm/text-patching.h> 12 #include <asm/ipl.h> 13 14 struct insn { 15 u16 opcode; 16 s32 offset; 17 } __packed; 18 19 static void jump_label_make_nop(struct jump_entry *entry, struct insn *insn) 20 { 21 /* brcl 0,offset */ 22 insn->opcode = 0xc004; 23 insn->offset = (jump_entry_target(entry) - jump_entry_code(entry)) >> 1; 24 } 25 26 static void jump_label_make_branch(struct jump_entry *entry, struct insn *insn) 27 { 28 /* brcl 15,offset */ 29 insn->opcode = 0xc0f4; 30 insn->offset = (jump_entry_target(entry) - jump_entry_code(entry)) >> 1; 31 } 32 33 static void jump_label_bug(struct jump_entry *entry, struct insn *expected, 34 struct insn *new) 35 { 36 unsigned char *ipc = (unsigned char *)jump_entry_code(entry); 37 unsigned char *ipe = (unsigned char *)expected; 38 unsigned char *ipn = (unsigned char *)new; 39 40 pr_emerg("Jump label code mismatch at %pS [%px]\n", ipc, ipc); 41 pr_emerg("Found: %6ph\n", ipc); 42 pr_emerg("Expected: %6ph\n", ipe); 43 pr_emerg("New: %6ph\n", ipn); 44 panic("Corrupted kernel text"); 45 } 46 47 static struct insn orignop = { 48 .opcode = 0xc004, 49 .offset = JUMP_LABEL_NOP_OFFSET >> 1, 50 }; 51 52 static void jump_label_transform(struct jump_entry *entry, 53 enum jump_label_type type, 54 int init) 55 { 56 void *code = (void *)jump_entry_code(entry); 57 struct insn old, new; 58 59 if (type == JUMP_LABEL_JMP) { 60 jump_label_make_nop(entry, &old); 61 jump_label_make_branch(entry, &new); 62 } else { 63 jump_label_make_branch(entry, &old); 64 jump_label_make_nop(entry, &new); 65 } 66 if (init) { 67 if (memcmp(code, &orignop, sizeof(orignop))) 68 jump_label_bug(entry, &orignop, &new); 69 } else { 70 if (memcmp(code, &old, sizeof(old))) 71 jump_label_bug(entry, &old, &new); 72 } 73 s390_kernel_write(code, &new, sizeof(new)); 74 } 75 76 void arch_jump_label_transform(struct jump_entry *entry, 77 enum jump_label_type type) 78 { 79 jump_label_transform(entry, type, 0); 80 text_poke_sync(); 81 } 82 83 bool arch_jump_label_transform_queue(struct jump_entry *entry, 84 enum jump_label_type type) 85 { 86 jump_label_transform(entry, type, 0); 87 return true; 88 } 89 90 void arch_jump_label_transform_apply(void) 91 { 92 text_poke_sync(); 93 } 94 95 void __init_or_module arch_jump_label_transform_static(struct jump_entry *entry, 96 enum jump_label_type type) 97 { 98 jump_label_transform(entry, type, 1); 99 text_poke_sync(); 100 } 101