| /* |
| * jump label x86 support |
| * |
| * Copyright (C) 2009 Jason Baron <jbaron@redhat.com> |
| * |
| */ |
| #include <linux/jump_label.h> |
| #include <linux/memory.h> |
| #include <linux/uaccess.h> |
| #include <linux/module.h> |
| #include <linux/list.h> |
| #include <linux/jhash.h> |
| #include <linux/cpu.h> |
| #include <asm/kprobes.h> |
| #include <asm/alternative.h> |
| |
| #ifdef HAVE_JUMP_LABEL |
| |
| union jump_code_union { |
| char code[JUMP_LABEL_NOP_SIZE]; |
| struct { |
| char jump; |
| int offset; |
| } __attribute__((packed)); |
| }; |
| |
| static void bug_at(unsigned char *ip, int line) |
| { |
| /* |
| * The location is not an op that we were expecting. |
| * Something went wrong. Crash the box, as something could be |
| * corrupting the kernel. |
| */ |
| pr_warning("Unexpected op at %pS [%p] (%02x %02x %02x %02x %02x) %s:%d\n", |
| ip, ip, ip[0], ip[1], ip[2], ip[3], ip[4], __FILE__, line); |
| BUG(); |
| } |
| |
| static void __jump_label_transform(struct jump_entry *entry, |
| enum jump_label_type type, |
| void *(*poker)(void *, const void *, size_t), |
| int init) |
| { |
| union jump_code_union code; |
| const unsigned char *ideal_nop = ideal_nops[NOP_ATOMIC5]; |
| |
| if (type == JUMP_LABEL_ENABLE) { |
| /* |
| * We are enabling this jump label. If it is not a nop |
| * then something must have gone wrong. |
| */ |
| if (unlikely(memcmp((void *)entry->code, ideal_nop, 5) != 0)) |
| bug_at((void *)entry->code, __LINE__); |
| |
| code.jump = 0xe9; |
| code.offset = entry->target - |
| (entry->code + JUMP_LABEL_NOP_SIZE); |
| } else { |
| /* |
| * We are disabling this jump label. If it is not what |
| * we think it is, then something must have gone wrong. |
| * If this is the first initialization call, then we |
| * are converting the default nop to the ideal nop. |
| */ |
| if (init) { |
| const unsigned char default_nop[] = { STATIC_KEY_INIT_NOP }; |
| if (unlikely(memcmp((void *)entry->code, default_nop, 5) != 0)) |
| bug_at((void *)entry->code, __LINE__); |
| } else { |
| code.jump = 0xe9; |
| code.offset = entry->target - |
| (entry->code + JUMP_LABEL_NOP_SIZE); |
| if (unlikely(memcmp((void *)entry->code, &code, 5) != 0)) |
| bug_at((void *)entry->code, __LINE__); |
| } |
| memcpy(&code, ideal_nops[NOP_ATOMIC5], JUMP_LABEL_NOP_SIZE); |
| } |
| |
| /* |
| * Make text_poke_bp() a default fallback poker. |
| * |
| * At the time the change is being done, just ignore whether we |
| * are doing nop -> jump or jump -> nop transition, and assume |
| * always nop being the 'currently valid' instruction |
| * |
| */ |
| if (poker) |
| (*poker)((void *)entry->code, &code, JUMP_LABEL_NOP_SIZE); |
| else |
| text_poke_bp((void *)entry->code, &code, JUMP_LABEL_NOP_SIZE, |
| (void *)entry->code + JUMP_LABEL_NOP_SIZE); |
| } |
| |
| void arch_jump_label_transform(struct jump_entry *entry, |
| enum jump_label_type type) |
| { |
| get_online_cpus(); |
| mutex_lock(&text_mutex); |
| __jump_label_transform(entry, type, NULL, 0); |
| mutex_unlock(&text_mutex); |
| put_online_cpus(); |
| } |
| |
| static enum { |
| JL_STATE_START, |
| JL_STATE_NO_UPDATE, |
| JL_STATE_UPDATE, |
| } jlstate __initdata_or_module = JL_STATE_START; |
| |
| __init_or_module void arch_jump_label_transform_static(struct jump_entry *entry, |
| enum jump_label_type type) |
| { |
| /* |
| * This function is called at boot up and when modules are |
| * first loaded. Check if the default nop, the one that is |
| * inserted at compile time, is the ideal nop. If it is, then |
| * we do not need to update the nop, and we can leave it as is. |
| * If it is not, then we need to update the nop to the ideal nop. |
| */ |
| if (jlstate == JL_STATE_START) { |
| const unsigned char default_nop[] = { STATIC_KEY_INIT_NOP }; |
| const unsigned char *ideal_nop = ideal_nops[NOP_ATOMIC5]; |
| |
| if (memcmp(ideal_nop, default_nop, 5) != 0) |
| jlstate = JL_STATE_UPDATE; |
| else |
| jlstate = JL_STATE_NO_UPDATE; |
| } |
| if (jlstate == JL_STATE_UPDATE) |
| __jump_label_transform(entry, type, text_poke_early, 1); |
| } |
| |
| #endif |