Commit fec8898d authored by Anton Arapov's avatar Anton Arapov Committed by Oleg Nesterov
Browse files

uretprobes: Return probe exit, invoke handlers 



Uretprobe handlers are invoked when the trampoline is hit, on completion
the trampoline is replaced with the saved return address and the uretprobe
instance deleted.

TODO: handle_trampoline() assumes that ->return_instances is always valid.
We should teach it to handle longjmp() which can invalidate the pending
return_instance's. This is nontrivial, we will try to do this in a separate
series.

Signed-off-by: default avatarAnton Arapov <anton@redhat.com>
Acked-by: default avatarSrikar Dronamraju <srikar@linux.vnet.ibm.com>
Signed-off-by: default avatarOleg Nesterov <oleg@redhat.com>
parent 0dfd0eb8

kernel/events/uprobes.c

+64 −1
Original line number Diff line number Diff line
@@ -1633,6 +1633,62 @@ static void handler_chain(struct uprobe *uprobe, struct pt_regs *regs) 
	up_read(&uprobe->register_rwsem);

}



static void

handle_uretprobe_chain(struct return_instance *ri, struct pt_regs *regs)

{

	struct uprobe *uprobe = ri->uprobe;

	struct uprobe_consumer *uc;



	down_read(&uprobe->register_rwsem);

	for (uc = uprobe->consumers; uc; uc = uc->next) {

		if (uc->ret_handler)

			uc->ret_handler(uc, ri->func, regs);

	}

	up_read(&uprobe->register_rwsem);

}



static bool handle_trampoline(struct pt_regs *regs)

{

	struct uprobe_task *utask;

	struct return_instance *ri, *tmp;

	bool chained;



	utask = current->utask;

	if (!utask)

		return false;



	ri = utask->return_instances;

	if (!ri)

		return false;



	/*

	 * TODO: we should throw out return_instance's invalidated by

	 * longjmp(), currently we assume that the probed function always

	 * returns.

	 */

	instruction_pointer_set(regs, ri->orig_ret_vaddr);



	for (;;) {

		handle_uretprobe_chain(ri, regs);



		chained = ri->chained;

		put_uprobe(ri->uprobe);



		tmp = ri;

		ri = ri->next;

		kfree(tmp);



		if (!chained)

			break;



		BUG_ON(!ri);

	}



	utask->return_instances = ri;



	return true;

}



/*

 * Run handler and ask thread to singlestep.

 * Ensure all non-fatal signals cannot interrupt thread while it singlesteps.
@@ -1644,8 +1700,15 @@ static void handle_swbp(struct pt_regs *regs) 
	int uninitialized_var(is_swbp);



	bp_vaddr = uprobe_get_swbp_addr(regs);

	uprobe = find_active_uprobe(bp_vaddr, &is_swbp);

	if (bp_vaddr == get_trampoline_vaddr()) {

		if (handle_trampoline(regs))

			return;



		pr_warn("uprobe: unable to handle uretprobe pid/tgid=%d/%d\n",

						current->pid, current->tgid);

	}



	uprobe = find_active_uprobe(bp_vaddr, &is_swbp);

	if (!uprobe) {

		if (is_swbp > 0) {

			/* No matching uprobe; signal SIGTRAP. */

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