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* jump label: Make arch_jump_label_text_poke_early() optionalSteven Rostedt2010-10-291-0/+7
| | | | | | | | | | | | | | 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>
* jump label: Fix deadlock b/w jump_label_mutex vs. text_mutexJason Baron2010-10-281-12/+21
| | | | | | | | | | | | | | | | | | 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>
* jump label: Fix module __init section raceJason Baron2010-10-281-1/+40
| | | | | | | | | | | | | | | | | | | | | | | | | | | | 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>
* jump label: Add jump_label_text_reserved() to reserve jump pointsJason Baron2010-09-221-0/+83
| | | | | | | | | | | 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>
* jump label: Base patch for jump labelJason Baron2010-09-221-0/+346
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>