From: Hannes Frederic Sowa <hannes@stressinduktion.org>
To: netdev@vger.kernel.org
Cc: linux-kernel@vger.kernel.org,
Hannes Frederic Sowa <hannes@stressinduktion.org>,
Steven Rostedt <rostedt@goodmis.org>,
Peter Zijlstra <a.p.zijlstra@chello.nl>,
Andi Kleen <andi@firstfloor.org>
Subject: [PATCH net-next v4 3/9] static_key: WARN on usage before jump_label_init was called
Date: Sat, 19 Oct 2013 21:48:53 +0200 [thread overview]
Message-ID: <1382212139-20301-4-git-send-email-hannes@stressinduktion.org> (raw)
In-Reply-To: <1382212139-20301-1-git-send-email-hannes@stressinduktion.org>
Usage of the static key primitives to toggle a branch must not be used
before jump_label_init() is called from init/main.c. jump_label_init
reorganizes and wires up the jump_entries so usage before that could
have unforeseen consequences.
Following primitives are now checked for correct use:
* static_key_slow_inc
* static_key_slow_dec
* static_key_slow_dec_deferred
* jump_label_rate_limit
The x86 architecture already checks this by testing if the default_nop
was already replaced with an optimal nop or with a branch instruction. It
will panic then. Other architectures don't check for this.
Because we need to relax this check for the x86 arch to allow code to
transition from default_nop to the enabled state and other architectures
did not check for this at all this patch introduces checking on the
static_key primitives in a non-arch dependent manner.
All checked functions are considered slow-path so the additional check
does no harm to performance.
The warnings are best observed with earlyprintk.
Based on a patch from Andi Kleen.
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Andi Kleen <andi@firstfloor.org>
Signed-off-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
---
include/linux/jump_label.h | 10 ++++++++++
include/linux/jump_label_ratelimit.h | 2 ++
init/main.c | 7 +++++++
kernel/jump_label.c | 5 +++++
4 files changed, 24 insertions(+)
diff --git a/include/linux/jump_label.h b/include/linux/jump_label.h
index a507907..e96be72 100644
--- a/include/linux/jump_label.h
+++ b/include/linux/jump_label.h
@@ -48,6 +48,13 @@
#include <linux/types.h>
#include <linux/compiler.h>
+#include <linux/bug.h>
+
+extern bool static_key_initialized;
+
+#define STATIC_KEY_CHECK_USE() WARN(!static_key_initialized, \
+ "%s used before call to jump_label_init", \
+ __func__)
#if defined(CC_HAVE_ASM_GOTO) && defined(CONFIG_JUMP_LABEL)
@@ -128,6 +135,7 @@ struct static_key {
static __always_inline void jump_label_init(void)
{
+ static_key_initialized = true;
}
static __always_inline bool static_key_false(struct static_key *key)
@@ -146,11 +154,13 @@ static __always_inline bool static_key_true(struct static_key *key)
static inline void static_key_slow_inc(struct static_key *key)
{
+ STATIC_KEY_CHECK_USE();
atomic_inc(&key->enabled);
}
static inline void static_key_slow_dec(struct static_key *key)
{
+ STATIC_KEY_CHECK_USE();
atomic_dec(&key->enabled);
}
diff --git a/include/linux/jump_label_ratelimit.h b/include/linux/jump_label_ratelimit.h
index 1137883..089f70f 100644
--- a/include/linux/jump_label_ratelimit.h
+++ b/include/linux/jump_label_ratelimit.h
@@ -23,12 +23,14 @@ struct static_key_deferred {
};
static inline void static_key_slow_dec_deferred(struct static_key_deferred *key)
{
+ STATIC_KEY_CHECK_USE();
static_key_slow_dec(&key->key);
}
static inline void
jump_label_rate_limit(struct static_key_deferred *key,
unsigned long rl)
{
+ STATIC_KEY_CHECK_USE();
}
#endif /* HAVE_JUMP_LABEL */
#endif /* _LINUX_JUMP_LABEL_RATELIMIT_H */
diff --git a/init/main.c b/init/main.c
index af310af..27bbec1a 100644
--- a/init/main.c
+++ b/init/main.c
@@ -136,6 +136,13 @@ static char *execute_command;
static char *ramdisk_execute_command;
/*
+ * Used to generate warnings if static_key manipulation functions are used
+ * before jump_label_init is called.
+ */
+bool static_key_initialized __read_mostly = false;
+EXPORT_SYMBOL_GPL(static_key_initialized);
+
+/*
* If set, this is an indication to the drivers that reset the underlying
* device before going ahead with the initialization otherwise driver might
* rely on the BIOS and skip the reset operation.
diff --git a/kernel/jump_label.c b/kernel/jump_label.c
index 297a924..9019f15 100644
--- a/kernel/jump_label.c
+++ b/kernel/jump_label.c
@@ -58,6 +58,7 @@ static void jump_label_update(struct static_key *key, int enable);
void static_key_slow_inc(struct static_key *key)
{
+ STATIC_KEY_CHECK_USE();
if (atomic_inc_not_zero(&key->enabled))
return;
@@ -103,12 +104,14 @@ static void jump_label_update_timeout(struct work_struct *work)
void static_key_slow_dec(struct static_key *key)
{
+ STATIC_KEY_CHECK_USE();
__static_key_slow_dec(key, 0, NULL);
}
EXPORT_SYMBOL_GPL(static_key_slow_dec);
void static_key_slow_dec_deferred(struct static_key_deferred *key)
{
+ STATIC_KEY_CHECK_USE();
__static_key_slow_dec(&key->key, key->timeout, &key->work);
}
EXPORT_SYMBOL_GPL(static_key_slow_dec_deferred);
@@ -116,6 +119,7 @@ EXPORT_SYMBOL_GPL(static_key_slow_dec_deferred);
void jump_label_rate_limit(struct static_key_deferred *key,
unsigned long rl)
{
+ STATIC_KEY_CHECK_USE();
key->timeout = rl;
INIT_DELAYED_WORK(&key->work, jump_label_update_timeout);
}
@@ -212,6 +216,7 @@ void __init jump_label_init(void)
key->next = NULL;
#endif
}
+ static_key_initialized = true;
jump_label_unlock();
}
--
1.8.3.1
next prev parent reply other threads:[~2013-10-19 19:52 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-10-19 19:48 [PATCH net-next v4 0/9] Introduce support to lazy initialize mostly static keys Hannes Frederic Sowa
2013-10-19 19:48 ` [PATCH net-next v4 1/9] ipv4: split inet_ehashfn to hash functions per compilation unit Hannes Frederic Sowa
2013-10-19 19:48 ` [PATCH net-next v4 2/9] ipv6: split inet6_ehashfn " Hannes Frederic Sowa
2013-10-19 19:48 ` Hannes Frederic Sowa [this message]
2013-11-06 21:16 ` [PATCH net-next v4 3/9] static_key: WARN on usage before jump_label_init was called Steven Rostedt
2013-11-07 0:50 ` Hannes Frederic Sowa
2013-11-07 1:02 ` Steven Rostedt
2013-11-07 9:08 ` Ingo Molnar
2013-10-19 19:48 ` [PATCH net-next v4 4/9] x86/jump_label: expect default_nop if static_key gets enabled on boot-up Hannes Frederic Sowa
2013-10-19 19:48 ` [PATCH net-next v4 5/9] net: introduce new macro net_get_random_once Hannes Frederic Sowa
2013-10-19 19:48 ` [PATCH net-next v4 6/9] inet: split syncookie keys for ipv4 and ipv6 and initialize with net_get_random_once Hannes Frederic Sowa
2013-10-19 19:48 ` [PATCH net-next v4 7/9] inet: convert inet_ehash_secret and ipv6_hash_secret to net_get_random_once Hannes Frederic Sowa
2013-10-19 19:48 ` [PATCH net-next v4 8/9] tcp: switch tcp_fastopen key generation " Hannes Frederic Sowa
2013-10-19 19:48 ` [PATCH net-next v4 9/9] net: switch net_secret " Hannes Frederic Sowa
2013-10-19 23:46 ` [PATCH net-next v4 0/9] Introduce support to lazy initialize mostly static keys David Miller
2013-10-20 3:33 ` Hannes Frederic Sowa
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