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11570da1c5
On boot up, the jump label init function scans all the jump label locations and converts them to the best nop for the machine. If the nop is already the ideal nop, do not bother with changing it. Cc: Jason Baron <jbaron@redhat.com> Cc: H. Peter Anvin <hpa@zytor.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
83 lines
2.1 KiB
C
83 lines
2.1 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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{
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union jump_code_union code;
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if (type == JUMP_LABEL_ENABLE) {
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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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memcpy(&code, ideal_nops[NOP_ATOMIC5], JUMP_LABEL_NOP_SIZE);
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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);
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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);
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}
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#endif
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