diff options
Diffstat (limited to 'arch/x86/kernel/jump_label.c')
| -rw-r--r-- | arch/x86/kernel/jump_label.c | 157 |
1 files changed, 157 insertions, 0 deletions
diff --git a/arch/x86/kernel/jump_label.c b/arch/x86/kernel/jump_label.c new file mode 100644 index 000000000..5ba8477c2 --- /dev/null +++ b/arch/x86/kernel/jump_label.c @@ -0,0 +1,157 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * 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> +#include <asm/text-patching.h> + +static void bug_at(const void *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_crit("jump_label: Fatal kernel bug, unexpected op at %pS [%p] (%5ph) %d\n", ip, ip, ip, line); + BUG(); +} + +static const void * +__jump_label_set_jump_code(struct jump_entry *entry, enum jump_label_type type, int init) +{ + const unsigned char default_nop[] = { STATIC_KEY_INIT_NOP }; + const unsigned char *ideal_nop = ideal_nops[NOP_ATOMIC5]; + const void *expect, *code; + const void *addr, *dest; + int line; + + addr = (void *)jump_entry_code(entry); + dest = (void *)jump_entry_target(entry); + + code = text_gen_insn(JMP32_INSN_OPCODE, addr, dest); + + if (init) { + expect = default_nop; line = __LINE__; + } else if (type == JUMP_LABEL_JMP) { + expect = ideal_nop; line = __LINE__; + } else { + expect = code; line = __LINE__; + } + + if (memcmp(addr, expect, JUMP_LABEL_NOP_SIZE)) + bug_at(addr, line); + + if (type == JUMP_LABEL_NOP) + code = ideal_nop; + + return code; +} + +static inline void __jump_label_transform(struct jump_entry *entry, + enum jump_label_type type, + int init) +{ + const void *opcode = __jump_label_set_jump_code(entry, type, init); + + /* + * As long as only a single processor is running and the code is still + * not marked as RO, text_poke_early() can be used; Checking that + * system_state is SYSTEM_BOOTING guarantees it. It will be set to + * SYSTEM_SCHEDULING before other cores are awaken and before the + * code is write-protected. + * + * 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 (init || system_state == SYSTEM_BOOTING) { + text_poke_early((void *)jump_entry_code(entry), opcode, + JUMP_LABEL_NOP_SIZE); + return; + } + + text_poke_bp((void *)jump_entry_code(entry), opcode, JUMP_LABEL_NOP_SIZE, NULL); +} + +static void __ref jump_label_transform(struct jump_entry *entry, + enum jump_label_type type, + int init) +{ + mutex_lock(&text_mutex); + __jump_label_transform(entry, type, init); + mutex_unlock(&text_mutex); +} + +void arch_jump_label_transform(struct jump_entry *entry, + enum jump_label_type type) +{ + jump_label_transform(entry, type, 0); +} + +bool arch_jump_label_transform_queue(struct jump_entry *entry, + enum jump_label_type type) +{ + const void *opcode; + + if (system_state == SYSTEM_BOOTING) { + /* + * Fallback to the non-batching mode. + */ + arch_jump_label_transform(entry, type); + return true; + } + + mutex_lock(&text_mutex); + opcode = __jump_label_set_jump_code(entry, type, 0); + text_poke_queue((void *)jump_entry_code(entry), + opcode, JUMP_LABEL_NOP_SIZE, NULL); + mutex_unlock(&text_mutex); + return true; +} + +void arch_jump_label_transform_apply(void) +{ + mutex_lock(&text_mutex); + text_poke_finish(); + mutex_unlock(&text_mutex); +} + +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, 1); +} |