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authorLinus Torvalds <torvalds@linux-foundation.org>2013-09-11 02:43:23 (GMT)
committerLinus Torvalds <torvalds@linux-foundation.org>2013-09-11 02:43:23 (GMT)
commit442e0973e9273ae8832abd70f52efde8b8326178 (patch)
treee2358f77f76143fe0f524c5a0e26cb940972e5c1 /arch/x86/kernel/jump_label.c
parent8d7551eb1916832f2a5b27346edf24e7b2382f67 (diff)
parentfb40d7a8994a3cc7a1e1c1f3258ea8662a366916 (diff)
Merge branch 'x86/jumplabel' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86 jumplabel changes from Peter Anvin: "One more x86 tree for this merge window. This tree improves the handling of jump labels, so that most of the time we don't have to do a massive initial patching run. Furthermore, we will error out of the jump label is not what is expected, eg if it has been corrupted or tampered with" * 'x86/jumplabel' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: x86/jump-label: Show where and what was wrong on errors x86/jump-label: Add safety checks to jump label conversions x86/jump-label: Do not bother updating nops if they are correct x86/jump-label: Use best default nops for inital jump label calls
Diffstat (limited to 'arch/x86/kernel/jump_label.c')
-rw-r--r--arch/x86/kernel/jump_label.c70
1 files changed, 66 insertions, 4 deletions
diff --git a/arch/x86/kernel/jump_label.c b/arch/x86/kernel/jump_label.c
index 460f5d9..ee11b7d 100644
--- a/arch/x86/kernel/jump_label.c
+++ b/arch/x86/kernel/jump_label.c
@@ -24,18 +24,57 @@ union jump_code_union {
} __attribute__((packed));
};
+static void bug_at(unsigned char *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_warning("Unexpected op at %pS [%p] (%02x %02x %02x %02x %02x) %s:%d\n",
+ ip, ip, ip[0], ip[1], ip[2], ip[3], ip[4], __FILE__, line);
+ BUG();
+}
+
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.
+ */
+ if (unlikely(memcmp((void *)entry->code, ideal_nop, 5) != 0))
+ bug_at((void *)entry->code, __LINE__);
+
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 };
+ if (unlikely(memcmp((void *)entry->code, default_nop, 5) != 0))
+ bug_at((void *)entry->code, __LINE__);
+ } else {
+ code.jump = 0xe9;
+ code.offset = entry->target -
+ (entry->code + JUMP_LABEL_NOP_SIZE);
+ if (unlikely(memcmp((void *)entry->code, &code, 5) != 0))
+ bug_at((void *)entry->code, __LINE__);
+ }
memcpy(&code, ideal_nops[NOP_ATOMIC5], JUMP_LABEL_NOP_SIZE);
+ }
/*
* Make text_poke_bp() a default fallback poker.
@@ -57,15 +96,38 @@ void arch_jump_label_transform(struct jump_entry *entry,
{
get_online_cpus();
mutex_lock(&text_mutex);
- __jump_label_transform(entry, type, NULL);
+ __jump_label_transform(entry, type, NULL, 0);
mutex_unlock(&text_mutex);
put_online_cpus();
}
+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)
{
- __jump_label_transform(entry, type, text_poke_early);
+ /*
+ * 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, text_poke_early, 1);
}
#endif

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