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Commit afd66255 authored by Masami Hiramatsu's avatar Masami Hiramatsu Committed by Ingo Molnar
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kprobes: Introduce kprobes jump optimization 



Introduce kprobes jump optimization arch-independent parts.
Kprobes uses breakpoint instruction for interrupting execution
flow, on some architectures, it can be replaced by a jump
instruction and interruption emulation code. This gains kprobs'
performance drastically.

To enable this feature, set CONFIG_OPTPROBES=y (default y if the
arch supports OPTPROBE).

Changes in v9:
 - Fix a bug to optimize probe when enabling.
 - Check nearby probes can be optimize/unoptimize when disarming/arming
   kprobes, instead of registering/unregistering. This will help
   kprobe-tracer because most of probes on it are usually disabled.

Changes in v6:
 - Cleanup coding style for readability.
 - Add comments around get/put_online_cpus().

Changes in v5:
 - Use get_online_cpus()/put_online_cpus() for avoiding text_mutex
   deadlock.

Signed-off-by: default avatarMasami Hiramatsu <mhiramat@redhat.com>
Cc: systemtap <systemtap@sources.redhat.com>
Cc: DLE <dle-develop@lists.sourceforge.net>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Jim Keniston <jkenisto@us.ibm.com>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Anders Kaseorg <andersk@ksplice.com>
Cc: Tim Abbott <tabbott@ksplice.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Jason Baron <jbaron@redhat.com>
Cc: Mathieu Desnoyers <compudj@krystal.dyndns.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
LKML-Reference: <20100225133407.6725.81992.stgit@localhost6.localdomain6>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 4610ee1d

arch/Kconfig

+13 −0
Original line number Diff line number Diff line
@@ -57,6 +57,17 @@ config KPROBES 
	  for kernel debugging, non-intrusive instrumentation and testing.

	  If in doubt, say "N".



config OPTPROBES

	bool "Kprobes jump optimization support (EXPERIMENTAL)"

	default y

	depends on KPROBES

	depends on !PREEMPT

	depends on HAVE_OPTPROBES

	select KALLSYMS_ALL

	help

	  This option will allow kprobes to optimize breakpoint to

	  a jump for reducing its overhead.



config HAVE_EFFICIENT_UNALIGNED_ACCESS

	bool

	help
@@ -99,6 +110,8 @@ config HAVE_KPROBES 
config HAVE_KRETPROBES

	bool



config HAVE_OPTPROBES

	bool

#

# An arch should select this if it provides all these things:

#

include/linux/kprobes.h

+36 −0
Original line number Diff line number Diff line
@@ -122,6 +122,11 @@ struct kprobe { 
/* Kprobe status flags */

#define KPROBE_FLAG_GONE	1 /* breakpoint has already gone */

#define KPROBE_FLAG_DISABLED	2 /* probe is temporarily disabled */

#define KPROBE_FLAG_OPTIMIZED	4 /*

				   * probe is really optimized.

				   * NOTE:

				   * this flag is only for optimized_kprobe.

				   */



/* Has this kprobe gone ? */

static inline int kprobe_gone(struct kprobe *p)
@@ -134,6 +139,12 @@ static inline int kprobe_disabled(struct kprobe *p) 
{

	return p->flags & (KPROBE_FLAG_DISABLED | KPROBE_FLAG_GONE);

}



/* Is this kprobe really running optimized path ? */

static inline int kprobe_optimized(struct kprobe *p)

{

	return p->flags & KPROBE_FLAG_OPTIMIZED;

}

/*

 * Special probe type that uses setjmp-longjmp type tricks to resume

 * execution at a specified entry with a matching prototype corresponding
@@ -249,6 +260,31 @@ extern kprobe_opcode_t *get_insn_slot(void); 
extern void free_insn_slot(kprobe_opcode_t *slot, int dirty);

extern void kprobes_inc_nmissed_count(struct kprobe *p);



#ifdef CONFIG_OPTPROBES

/*

 * Internal structure for direct jump optimized probe

 */

struct optimized_kprobe {

	struct kprobe kp;

	struct list_head list;	/* list for optimizing queue */

	struct arch_optimized_insn optinsn;

};



/* Architecture dependent functions for direct jump optimization */

extern int arch_prepared_optinsn(struct arch_optimized_insn *optinsn);

extern int arch_check_optimized_kprobe(struct optimized_kprobe *op);

extern int arch_prepare_optimized_kprobe(struct optimized_kprobe *op);

extern void arch_remove_optimized_kprobe(struct optimized_kprobe *op);

extern int  arch_optimize_kprobe(struct optimized_kprobe *op);

extern void arch_unoptimize_kprobe(struct optimized_kprobe *op);

extern kprobe_opcode_t *get_optinsn_slot(void);

extern void free_optinsn_slot(kprobe_opcode_t *slot, int dirty);

extern int arch_within_optimized_kprobe(struct optimized_kprobe *op,

					unsigned long addr);



extern void opt_pre_handler(struct kprobe *p, struct pt_regs *regs);

#endif /* CONFIG_OPTPROBES */



/* Get the kprobe at this addr (if any) - called with preemption disabled */

struct kprobe *get_kprobe(void *addr);

void kretprobe_hash_lock(struct task_struct *tsk,

kernel/kprobes.c

+410 −51

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