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Commit aa3d7e3d 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 x86_64 



This patch includes x86_64 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 417c8da6

arch/x86_64/kernel/kprobes.c

+62 −14
Original line number Diff line number Diff line
@@ -45,12 +45,10 @@ 


static DECLARE_MUTEX(kprobe_mutex);



/* 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_rflags, kprobe_saved_rflags;

static struct kprobe *kprobe_prev;

static unsigned long kprobe_status_prev, kprobe_old_rflags_prev, kprobe_saved_rflags_prev;

static struct pt_regs jprobe_saved_regs;

static long *jprobe_saved_rsp;

static kprobe_opcode_t *get_insn_slot(void);
@@ -240,6 +238,31 @@ void arch_remove_kprobe(struct kprobe *p) 
	down(&kprobe_mutex);

}



static inline void save_previous_kprobe(void)

{

	kprobe_prev = current_kprobe;

	kprobe_status_prev = kprobe_status;

	kprobe_old_rflags_prev = kprobe_old_rflags;

	kprobe_saved_rflags_prev = kprobe_saved_rflags;

}



static inline void restore_previous_kprobe(void)

{

	current_kprobe = kprobe_prev;

	kprobe_status = kprobe_status_prev;

	kprobe_old_rflags = kprobe_old_rflags_prev;

	kprobe_saved_rflags = kprobe_saved_rflags_prev;

}



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

{

	current_kprobe = p;

	kprobe_saved_rflags = kprobe_old_rflags

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

	if (is_IF_modifier(p->ainsn.insn))

		kprobe_saved_rflags &= ~IF_MASK;

}



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

{

	regs->eflags |= TF_MASK;
@@ -319,10 +342,30 @@ int kprobe_handler(struct pt_regs *regs) 
				regs->eflags |= kprobe_saved_rflags;

				unlock_kprobes();

				goto no_kprobe;

			}

			} else if (kprobe_status == KPROBE_HIT_SSDONE) {

				/* TODO: Provide re-entrancy from

				 * post_kprobes_handler() and avoid exception

				 * stack corruption while single-stepping on

				 * the instruction of the new probe.

				 */

				arch_disarm_kprobe(p);

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

				ret = 1;

			} else {

				/* We have reentered the kprobe_handler(), since

				 * another probe was hit while within the

				 * handler. We here save the original kprobe

				 * variables and just single step on 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)) {
@@ -352,11 +395,7 @@ int kprobe_handler(struct pt_regs *regs) 
	}



	kprobe_status = KPROBE_HIT_ACTIVE;

	current_kprobe = p;

	kprobe_saved_rflags = kprobe_old_rflags

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

	if (is_IF_modifier(p->ainsn.insn))

		kprobe_saved_rflags &= ~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 */
@@ -506,14 +545,23 @@ 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_rflags;



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

	if (kprobe_status == KPROBE_REENTER) {

		restore_previous_kprobe();

		goto out;

	} else {

		unlock_kprobes();

	}

out:

	preempt_enable_no_resched();



	/*