9c85f3bdf4
As with all modifying of kernel text, we need to be very paranoid. When converting the jump label locations to and from nops to jumps a check has been added to make sure what we are replacing is what we expect, otherwise we bug. Cc: H. Peter Anvin <hpa@zytor.com> Cc: Jason Baron <jbaron@redhat.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
107 lines
2.8 KiB
C
107 lines
2.8 KiB
C
/*
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* jump label x86 support
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*
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* Copyright (C) 2009 Jason Baron <jbaron@redhat.com>
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*
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*/
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#include <linux/jump_label.h>
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#include <linux/memory.h>
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#include <linux/uaccess.h>
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#include <linux/module.h>
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#include <linux/list.h>
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#include <linux/jhash.h>
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#include <linux/cpu.h>
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#include <asm/kprobes.h>
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#include <asm/alternative.h>
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#ifdef HAVE_JUMP_LABEL
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union jump_code_union {
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char code[JUMP_LABEL_NOP_SIZE];
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struct {
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char jump;
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int offset;
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} __attribute__((packed));
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};
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static void __jump_label_transform(struct jump_entry *entry,
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enum jump_label_type type,
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void *(*poker)(void *, const void *, size_t),
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int init)
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{
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union jump_code_union code;
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const unsigned char *ideal_nop = ideal_nops[NOP_ATOMIC5];
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if (type == JUMP_LABEL_ENABLE) {
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/*
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* We are enabling this jump label. If it is not a nop
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* then something must have gone wrong.
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*/
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BUG_ON(memcmp((void *)entry->code, ideal_nop, 5) != 0);
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code.jump = 0xe9;
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code.offset = entry->target -
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(entry->code + JUMP_LABEL_NOP_SIZE);
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} else {
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/*
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* We are disabling this jump label. If it is not what
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* we think it is, then something must have gone wrong.
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* If this is the first initialization call, then we
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* are converting the default nop to the ideal nop.
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*/
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if (init) {
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const unsigned char default_nop[] = { STATIC_KEY_INIT_NOP };
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BUG_ON(memcmp((void *)entry->code, default_nop, 5) != 0);
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} else {
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code.jump = 0xe9;
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code.offset = entry->target -
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(entry->code + JUMP_LABEL_NOP_SIZE);
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BUG_ON(memcmp((void *)entry->code, &code, 5) != 0);
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}
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memcpy(&code, ideal_nops[NOP_ATOMIC5], JUMP_LABEL_NOP_SIZE);
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}
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(*poker)((void *)entry->code, &code, JUMP_LABEL_NOP_SIZE);
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}
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void arch_jump_label_transform(struct jump_entry *entry,
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enum jump_label_type type)
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{
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get_online_cpus();
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mutex_lock(&text_mutex);
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__jump_label_transform(entry, type, text_poke_smp, 0);
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mutex_unlock(&text_mutex);
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put_online_cpus();
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}
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static enum {
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JL_STATE_START,
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JL_STATE_NO_UPDATE,
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JL_STATE_UPDATE,
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} jlstate __initdata_or_module = JL_STATE_START;
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__init_or_module void arch_jump_label_transform_static(struct jump_entry *entry,
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enum jump_label_type type)
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{
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/*
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* This function is called at boot up and when modules are
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* first loaded. Check if the default nop, the one that is
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* inserted at compile time, is the ideal nop. If it is, then
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* we do not need to update the nop, and we can leave it as is.
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* If it is not, then we need to update the nop to the ideal nop.
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*/
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if (jlstate == JL_STATE_START) {
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const unsigned char default_nop[] = { STATIC_KEY_INIT_NOP };
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const unsigned char *ideal_nop = ideal_nops[NOP_ATOMIC5];
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if (memcmp(ideal_nop, default_nop, 5) != 0)
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jlstate = JL_STATE_UPDATE;
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else
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jlstate = JL_STATE_NO_UPDATE;
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}
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if (jlstate == JL_STATE_UPDATE)
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__jump_label_transform(entry, type, text_poke_early, 1);
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}
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#endif
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