Commit 615d0ebb authored by Masami Hiramatsu's avatar Masami Hiramatsu Committed by Ingo Molnar
Browse files

kprobes: Disable booster when CONFIG_PREEMPT=y 



Disable kprobe booster when CONFIG_PREEMPT=y at this time,
because it can't ensure that all kernel threads preempted on
kprobe's boosted slot run out from the slot even using
freeze_processes().

The booster on preemptive kernel will be resumed if
synchronize_tasks() or something like that is introduced.

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: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jim Keniston <jkenisto@us.ibm.com>
Cc: Mathieu Desnoyers <compudj@krystal.dyndns.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
LKML-Reference: <20100202214904.4694.24330.stgit@dhcp-100-2-132.bos.redhat.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 57d81889

arch/ia64/kernel/kprobes.c

+1 −1
Original line number Diff line number Diff line
@@ -870,7 +870,7 @@ static int __kprobes pre_kprobes_handler(struct die_args *args) 
		return 1;



ss_probe:

#if !defined(CONFIG_PREEMPT) || defined(CONFIG_FREEZER)

#if !defined(CONFIG_PREEMPT)

	if (p->ainsn.inst_flag == INST_FLAG_BOOSTABLE && !p->post_handler) {

		/* Boost up -- we can execute copied instructions directly */

		ia64_psr(regs)->ri = p->ainsn.slot;

arch/x86/kernel/kprobes.c

+1 −1
Original line number Diff line number Diff line
@@ -429,7 +429,7 @@ void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri, 
static void __kprobes setup_singlestep(struct kprobe *p, struct pt_regs *regs,

				       struct kprobe_ctlblk *kcb)

{

#if !defined(CONFIG_PREEMPT) || defined(CONFIG_FREEZER)

#if !defined(CONFIG_PREEMPT)

	if (p->ainsn.boostable == 1 && !p->post_handler) {

		/* Boost up -- we can execute copied instructions directly */

		reset_current_kprobe();

kernel/kprobes.c

+2 −27
Original line number Diff line number Diff line
@@ -124,30 +124,6 @@ static LIST_HEAD(kprobe_insn_pages); 
static int kprobe_garbage_slots;

static int collect_garbage_slots(void);



static int __kprobes check_safety(void)

{

	int ret = 0;

#if defined(CONFIG_PREEMPT) && defined(CONFIG_FREEZER)

	ret = freeze_processes();

	if (ret == 0) {

		struct task_struct *p, *q;

		do_each_thread(p, q) {

			if (p != current && p->state == TASK_RUNNING &&

			    p->pid != 0) {

				printk("Check failed: %s is running\n",p->comm);

				ret = -1;

				goto loop_end;

			}

		} while_each_thread(p, q);

	}

loop_end:

	thaw_processes();

#else

	synchronize_sched();

#endif

	return ret;

}



/**

 * __get_insn_slot() - Find a slot on an executable page for an instruction.

 * We allocate an executable page if there's no room on existing ones.
@@ -235,9 +211,8 @@ static int __kprobes collect_garbage_slots(void) 
{

	struct kprobe_insn_page *kip, *next;



	/* Ensure no-one is preepmted on the garbages */

	if (check_safety())

		return -EAGAIN;

	/* Ensure no-one is interrupted on the garbages */

	synchronize_sched();



	list_for_each_entry_safe(kip, next, &kprobe_insn_pages, list) {

		int i;

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