diff options
| author | Steven Rostedt <srostedt@redhat.com> | 2012-01-26 18:38:07 -0500 |
|---|---|---|
| committer | Steven Rostedt <rostedt@goodmis.org> | 2013-08-06 21:43:20 -0400 |
| commit | 9c85f3bdf400665eecf62658a9106501f6a77a13 (patch) | |
| tree | 75de123db1e0deecaa0743c5dcd17bd6db81f261 /arch/x86/kernel/jump_label.c | |
| parent | 11570da1c5b1dee1dc1439159e967ee44214a78b (diff) | |
x86/jump-label: Add safety checks to jump label conversions
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>
Diffstat (limited to 'arch/x86/kernel/jump_label.c')
| -rw-r--r-- | arch/x86/kernel/jump_label.c | 32 |
1 files changed, 28 insertions, 4 deletions
diff --git a/arch/x86/kernel/jump_label.c b/arch/x86/kernel/jump_label.c index ae3d8fb8039f..24cf2b25ce73 100644 --- a/arch/x86/kernel/jump_label.c +++ b/arch/x86/kernel/jump_label.c @@ -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 |