Commit graph

5 commits

Author SHA1 Message Date
Steven Rostedt
95bcd683fb jump label: Make arch_jump_label_text_poke_early() optional
Some archs do not need to do anything special for jump labels on
startup (like MIPS).  This patch adds a weak function stub for
arch_jump_label_text_poke_early();

Cc: Jason Baron <jbaron@redhat.com>
Cc: David Miller <davem@davemloft.net>
Cc: David Daney <ddaney@caviumnetworks.com>
Suggested-by: Thomas Gleixner <tglx@linutronix.de>
LKML-Reference: <1286218615-24011-2-git-send-email-ddaney@caviumnetworks.com>
LKML-Reference: <20101015201037.703989993@goodmis.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2010-10-29 12:56:13 -04:00
Jason Baron
91bad2f8d3 jump label: Fix deadlock b/w jump_label_mutex vs. text_mutex
register_kprobe() downs the 'text_mutex' and then calls
jump_label_text_reserved(), which downs the 'jump_label_mutex'.
However, the jump label code takes those mutexes in the reverse
order.

Fix by requiring the caller of jump_label_text_reserved() to do
the jump label locking via the newly added: jump_label_lock(),
jump_label_unlock(). Currently, kprobes is the only user
of jump_label_text_reserved().

Reported-by: Ingo Molnar <mingo@elte.hu>
Acked-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Signed-off-by: Jason Baron <jbaron@redhat.com>
LKML-Reference: <759032c48d5e30c27f0bba003d09bffa8e9f28bb.1285965957.git.jbaron@redhat.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2010-10-28 09:17:40 -04:00
Jason Baron
b842f8faf6 jump label: Fix module __init section race
Jump label uses is_module_text_address() to ensure that the module
__init sections are valid before updating them. However, between the
check for a valid module __init section and the subsequent jump
label update, the module's __init section could be freed out from under
us.

We fix this potential race by adding a notifier callback to the
MODULE_STATE_LIVE state. This notifier is called *after* the __init
section has been run but before it is going to be freed. In the
callback, the jump label code zeros the key value for any __init jump
code within the module, and we add a check for a non-zero key value when
we update jump labels. In this way we require no additional data
structures.

Thanks to Mathieu Desnoyers for pointing out this race condition.

Reported-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Signed-off-by: Jason Baron <jbaron@redhat.com>
LKML-Reference: <c6f037b7598777668025ceedd9294212fd95fa34.1285965957.git.jbaron@redhat.com>

[ Renamed remove_module_init() to remove_jump_label_module_init()
  as suggested by Masami Hiramatsu. ]

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2010-10-28 09:17:02 -04:00
Jason Baron
4c3ef6d793 jump label: Add jump_label_text_reserved() to reserve jump points
Add a jump_label_text_reserved(void *start, void *end), so that other
pieces of code that want to modify kernel text, can first verify that
jump label has not reserved the instruction.

Acked-by: Masami Hiramatsu <mhiramat@redhat.com>
Signed-off-by: Jason Baron <jbaron@redhat.com>
LKML-Reference: <06236663a3a7b1c1f13576bb9eccb6d9c17b7bfe.1284733808.git.jbaron@redhat.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2010-09-22 16:30:46 -04:00
Jason Baron
bf5438fca2 jump label: Base patch for jump label
base patch to implement 'jump labeling'. Based on a new 'asm goto' inline
assembly gcc mechanism, we can now branch to labels from an 'asm goto'
statment. This allows us to create a 'no-op' fastpath, which can subsequently
be patched with a jump to the slowpath code. This is useful for code which
might be rarely used, but which we'd like to be able to call, if needed.
Tracepoints are the current usecase that these are being implemented for.

Acked-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Jason Baron <jbaron@redhat.com>
LKML-Reference: <ee8b3595967989fdaf84e698dc7447d315ce972a.1284733808.git.jbaron@redhat.com>

[ cleaned up some formating ]

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2010-09-22 16:29:41 -04:00