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Commit b2be84df authored by Masami Hiramatsu's avatar Masami Hiramatsu Committed by Ingo Molnar
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kprobes: Jump optimization sysctl interface 



Add /proc/sys/debug/kprobes-optimization sysctl which enables
and disables kprobes jump optimization on the fly for debugging.

Changes in v7:
 - Remove ctl_name = CTL_UNNUMBERED for upstream compatibility.

Changes in v6:
- Update comments and coding style.

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: <20100225133415.6725.8274.stgit@localhost6.localdomain6>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent afd66255

include/linux/kprobes.h

+8 −0
Original line number Diff line number Diff line
@@ -283,6 +283,14 @@ 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);



#ifdef CONFIG_SYSCTL

extern int sysctl_kprobes_optimization;

extern int proc_kprobes_optimization_handler(struct ctl_table *table,

					     int write, void __user *buffer,

					     size_t *length, loff_t *ppos);

#endif



#endif /* CONFIG_OPTPROBES */



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

kernel/kprobes.c

+85 −3
Original line number Diff line number Diff line
@@ -42,6 +42,7 @@ 
#include <linux/freezer.h>

#include <linux/seq_file.h>

#include <linux/debugfs.h>

#include <linux/sysctl.h>

#include <linux/kdebug.h>

#include <linux/memory.h>

#include <linux/ftrace.h>
@@ -360,6 +361,9 @@ static inline void copy_kprobe(struct kprobe *old_p, struct kprobe *p) 
}



#ifdef CONFIG_OPTPROBES

/* NOTE: change this value only with kprobe_mutex held */

static bool kprobes_allow_optimization;



/*

 * Call all pre_handler on the list, but ignores its return value.

 * This must be called from arch-dep optimized caller.
@@ -428,7 +432,7 @@ static __kprobes void kprobe_optimizer(struct work_struct *work) 
	/* Lock modules while optimizing kprobes */

	mutex_lock(&module_mutex);

	mutex_lock(&kprobe_mutex);

	if (kprobes_all_disarmed)

	if (kprobes_all_disarmed || !kprobes_allow_optimization)

		goto end;



	/*
@@ -471,7 +475,7 @@ static __kprobes void optimize_kprobe(struct kprobe *p) 
	struct optimized_kprobe *op;



	/* Check if the kprobe is disabled or not ready for optimization. */

	if (!kprobe_optready(p) ||

	if (!kprobe_optready(p) || !kprobes_allow_optimization ||

	    (kprobe_disabled(p) || kprobes_all_disarmed))

		return;
@@ -588,6 +592,80 @@ static __kprobes void try_to_optimize_kprobe(struct kprobe *p) 
	optimize_kprobe(ap);

}



#ifdef CONFIG_SYSCTL

static void __kprobes optimize_all_kprobes(void)

{

	struct hlist_head *head;

	struct hlist_node *node;

	struct kprobe *p;

	unsigned int i;



	/* If optimization is already allowed, just return */

	if (kprobes_allow_optimization)

		return;



	kprobes_allow_optimization = true;

	mutex_lock(&text_mutex);

	for (i = 0; i < KPROBE_TABLE_SIZE; i++) {

		head = &kprobe_table[i];

		hlist_for_each_entry_rcu(p, node, head, hlist)

			if (!kprobe_disabled(p))

				optimize_kprobe(p);

	}

	mutex_unlock(&text_mutex);

	printk(KERN_INFO "Kprobes globally optimized\n");

}



static void __kprobes unoptimize_all_kprobes(void)

{

	struct hlist_head *head;

	struct hlist_node *node;

	struct kprobe *p;

	unsigned int i;



	/* If optimization is already prohibited, just return */

	if (!kprobes_allow_optimization)

		return;



	kprobes_allow_optimization = false;

	printk(KERN_INFO "Kprobes globally unoptimized\n");

	get_online_cpus();	/* For avoiding text_mutex deadlock */

	mutex_lock(&text_mutex);

	for (i = 0; i < KPROBE_TABLE_SIZE; i++) {

		head = &kprobe_table[i];

		hlist_for_each_entry_rcu(p, node, head, hlist) {

			if (!kprobe_disabled(p))

				unoptimize_kprobe(p);

		}

	}



	mutex_unlock(&text_mutex);

	put_online_cpus();

	/* Allow all currently running kprobes to complete */

	synchronize_sched();

}



int sysctl_kprobes_optimization;

int proc_kprobes_optimization_handler(struct ctl_table *table, int write,

				      void __user *buffer, size_t *length,

				      loff_t *ppos)

{

	int ret;



	mutex_lock(&kprobe_mutex);

	sysctl_kprobes_optimization = kprobes_allow_optimization ? 1 : 0;

	ret = proc_dointvec_minmax(table, write, buffer, length, ppos);



	if (sysctl_kprobes_optimization)

		optimize_all_kprobes();

	else

		unoptimize_all_kprobes();

	mutex_unlock(&kprobe_mutex);



	return ret;

}

#endif /* CONFIG_SYSCTL */



static void __kprobes __arm_kprobe(struct kprobe *p)

{

	struct kprobe *old_p;
@@ -1610,10 +1688,14 @@ static int __init init_kprobes(void) 
		}

	}



#if defined(CONFIG_OPTPROBES) && defined(__ARCH_WANT_KPROBES_INSN_SLOT)

#if defined(CONFIG_OPTPROBES)

#if defined(__ARCH_WANT_KPROBES_INSN_SLOT)

	/* Init kprobe_optinsn_slots */

	kprobe_optinsn_slots.insn_size = MAX_OPTINSN_SIZE;

#endif

	/* By default, kprobes can be optimized */

	kprobes_allow_optimization = true;

#endif



	/* By default, kprobes are armed */

	kprobes_all_disarmed = false;

kernel/sysctl.c

+12 −0
Original line number Diff line number Diff line
@@ -50,6 +50,7 @@ 
#include <linux/ftrace.h>

#include <linux/slow-work.h>

#include <linux/perf_event.h>

#include <linux/kprobes.h>



#include <asm/uaccess.h>

#include <asm/processor.h>
@@ -1449,6 +1450,17 @@ static struct ctl_table debug_table[] = { 
		.mode		= 0644,

		.proc_handler	= proc_dointvec

	},

#endif

#if defined(CONFIG_OPTPROBES)

	{

		.procname	= "kprobes-optimization",

		.data		= &sysctl_kprobes_optimization,

		.maxlen		= sizeof(int),

		.mode		= 0644,

		.proc_handler	= proc_kprobes_optimization_handler,

		.extra1		= &zero,

		.extra2		= &one,

	},

#endif

	{ }

};