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Commit 417c8da6 authored by Prasanna S Panchamukhi's avatar Prasanna S Panchamukhi Committed by Linus Torvalds
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[PATCH] kprobes: Temporary disarming of reentrant probe for i386 



This patch includes i386 architecture specific changes to support temporary
disarming on reentrancy of probes.

Signed-of-by: default avatarPrasanna S Panchamukhi <prasanna@in.ibm.com>

Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent ea32c65c

arch/i386/kernel/kprobes.c

+49 −13
Original line number Diff line number Diff line
@@ -37,12 +37,10 @@ 
#include <asm/kdebug.h>

#include <asm/desc.h>



/* kprobe_status settings */

#define KPROBE_HIT_ACTIVE	0x00000001

#define KPROBE_HIT_SS		0x00000002



static struct kprobe *current_kprobe;

static unsigned long kprobe_status, kprobe_old_eflags, kprobe_saved_eflags;

static struct kprobe *kprobe_prev;

static unsigned long kprobe_status_prev, kprobe_old_eflags_prev, kprobe_saved_eflags_prev;

static struct pt_regs jprobe_saved_regs;

static long *jprobe_saved_esp;

/* copy of the kernel stack at the probe fire time */
@@ -93,6 +91,31 @@ void arch_remove_kprobe(struct kprobe *p) 
{

}



static inline void save_previous_kprobe(void)

{

	kprobe_prev = current_kprobe;

	kprobe_status_prev = kprobe_status;

	kprobe_old_eflags_prev = kprobe_old_eflags;

	kprobe_saved_eflags_prev = kprobe_saved_eflags;

}



static inline void restore_previous_kprobe(void)

{

	current_kprobe = kprobe_prev;

	kprobe_status = kprobe_status_prev;

	kprobe_old_eflags = kprobe_old_eflags_prev;

	kprobe_saved_eflags = kprobe_saved_eflags_prev;

}



static inline void set_current_kprobe(struct kprobe *p, struct pt_regs *regs)

{

	current_kprobe = p;

	kprobe_saved_eflags = kprobe_old_eflags

		= (regs->eflags & (TF_MASK | IF_MASK));

	if (is_IF_modifier(p->opcode))

		kprobe_saved_eflags &= ~IF_MASK;

}



static inline void prepare_singlestep(struct kprobe *p, struct pt_regs *regs)

{

	regs->eflags |= TF_MASK;
@@ -184,9 +207,18 @@ static int kprobe_handler(struct pt_regs *regs) 
				unlock_kprobes();

				goto no_kprobe;

			}

			arch_disarm_kprobe(p);

			regs->eip = (unsigned long)p->addr;

			ret = 1;

			/* We have reentered the kprobe_handler(), since

			 * another probe was hit while within the handler.

			 * We here save the original kprobes variables and

			 * just single step on the instruction of the new probe

			 * without calling any user handlers.

			 */

			save_previous_kprobe();

			set_current_kprobe(p, regs);

			p->nmissed++;

			prepare_singlestep(p, regs);

			kprobe_status = KPROBE_REENTER;

			return 1;

		} else {

			p = current_kprobe;

			if (p->break_handler && p->break_handler(p, regs)) {
@@ -221,11 +253,7 @@ static int kprobe_handler(struct pt_regs *regs) 
	}



	kprobe_status = KPROBE_HIT_ACTIVE;

	current_kprobe = p;

	kprobe_saved_eflags = kprobe_old_eflags

	    = (regs->eflags & (TF_MASK | IF_MASK));

	if (is_IF_modifier(p->opcode))

		kprobe_saved_eflags &= ~IF_MASK;

	set_current_kprobe(p, regs);



	if (p->pre_handler && p->pre_handler(p, regs))

		/* handler has already set things up, so skip ss setup */
@@ -370,14 +398,22 @@ static inline int post_kprobe_handler(struct pt_regs *regs) 
	if (!kprobe_running())

		return 0;



	if (current_kprobe->post_handler)

	if ((kprobe_status != KPROBE_REENTER) && current_kprobe->post_handler) {

		kprobe_status = KPROBE_HIT_SSDONE;

		current_kprobe->post_handler(current_kprobe, regs, 0);

	}



	if (current_kprobe->post_handler != trampoline_post_handler)

		resume_execution(current_kprobe, regs);

	regs->eflags |= kprobe_saved_eflags;



	/*Restore back the original saved kprobes variables and continue. */

	if (kprobe_status == KPROBE_REENTER) {

		restore_previous_kprobe();

		goto out;

	}

	unlock_kprobes();

out:

	preempt_enable_no_resched();



	/*