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x86/jump-label: Add safety checks to jump label conversions

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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>
This commit is contained in:
Steven Rostedt 2012-01-26 18:38:07 -05:00 committed by Steven Rostedt
parent 11570da1c5
commit 9c85f3bdf4
1 changed files with 28 additions and 4 deletions
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32
arch/x86/kernel/jump_label.c
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@ -26,16 +26,40 @@ union jump_code_union {
static void __jump_label_transform(struct jump_entry *entry,
enum jump_label_type type,
void *(*poker)(void *, const void *, size_t))
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.
*/
BUG_ON(memcmp((void *)entry->code, ideal_nop, 5) != 0);
code.jump = 0xe9;
code.offset = entry->target -
(entry->code + JUMP_LABEL_NOP_SIZE);
} else
} 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 };
BUG_ON(memcmp((void *)entry->code, default_nop, 5) != 0);
} else {
code.jump = 0xe9;
code.offset = entry->target -
(entry->code + JUMP_LABEL_NOP_SIZE);
BUG_ON(memcmp((void *)entry->code, &code, 5) != 0);
}
memcpy(&code, ideal_nops[NOP_ATOMIC5], JUMP_LABEL_NOP_SIZE);
}
(*poker)((void *)entry->code, &code, JUMP_LABEL_NOP_SIZE);
}
@ -45,7 +69,7 @@ void arch_jump_label_transform(struct jump_entry *entry,
{
get_online_cpus();
mutex_lock(&text_mutex);
__jump_label_transform(entry, type, text_poke_smp);
__jump_label_transform(entry, type, text_poke_smp, 0);
mutex_unlock(&text_mutex);
put_online_cpus();
}
@ -76,7 +100,7 @@ __init_or_module void arch_jump_label_transform_static(struct jump_entry *entry,
jlstate = JL_STATE_NO_UPDATE;
}
if (jlstate == JL_STATE_UPDATE)
__jump_label_transform(entry, type, text_poke_early);
__jump_label_transform(entry, type, text_poke_early, 1);
}
#endif