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Commit 0bc11ed5 authored by Masami Hiramatsu's avatar Masami Hiramatsu Committed by Steven Rostedt (VMware)
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kprobes: Allow kprobes coexist with livepatch 

Allow kprobes which do not modify regs->ip, coexist with livepatch
by dropping FTRACE_OPS_FL_IPMODIFY from ftrace_ops.

User who wants to modify regs->ip (e.g. function fault injection)
must set a dummy post_handler to its kprobes when registering.
However, if such regs->ip modifying kprobes is set on a function,
that function can not be livepatched.

Link: http://lkml.kernel.org/r/156403587671.30117.5233558741694155985.stgit@devnote2



Acked-by: default avatarJoe Lawrence <joe.lawrence@redhat.com>
Signed-off-by: default avatarMasami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: default avatarSteven Rostedt (VMware) <rostedt@goodmis.org>
parent c68c9ec1

kernel/kprobes.c

+40 −16
Original line number Diff line number Diff line
@@ -961,9 +961,16 @@ static struct kprobe *alloc_aggr_kprobe(struct kprobe *p) 


#ifdef CONFIG_KPROBES_ON_FTRACE

static struct ftrace_ops kprobe_ftrace_ops __read_mostly = {

	.func = kprobe_ftrace_handler,

	.flags = FTRACE_OPS_FL_SAVE_REGS,

};



static struct ftrace_ops kprobe_ipmodify_ops __read_mostly = {

	.func = kprobe_ftrace_handler,

	.flags = FTRACE_OPS_FL_SAVE_REGS | FTRACE_OPS_FL_IPMODIFY,

};



static int kprobe_ipmodify_enabled;

static int kprobe_ftrace_enabled;



/* Must ensure p->addr is really on ftrace */
@@ -976,58 +983,75 @@ static int prepare_kprobe(struct kprobe *p) 
}



/* Caller must lock kprobe_mutex */

static int arm_kprobe_ftrace(struct kprobe *p)

static int __arm_kprobe_ftrace(struct kprobe *p, struct ftrace_ops *ops,

			       int *cnt)

{

	int ret = 0;



	ret = ftrace_set_filter_ip(&kprobe_ftrace_ops,

				   (unsigned long)p->addr, 0, 0);

	ret = ftrace_set_filter_ip(ops, (unsigned long)p->addr, 0, 0);

	if (ret) {

		pr_debug("Failed to arm kprobe-ftrace at %pS (%d)\n",

			 p->addr, ret);

		return ret;

	}



	if (kprobe_ftrace_enabled == 0) {

		ret = register_ftrace_function(&kprobe_ftrace_ops);

	if (*cnt == 0) {

		ret = register_ftrace_function(ops);

		if (ret) {

			pr_debug("Failed to init kprobe-ftrace (%d)\n", ret);

			goto err_ftrace;

		}

	}



	kprobe_ftrace_enabled++;

	(*cnt)++;

	return ret;



err_ftrace:

	/*

	 * Note: Since kprobe_ftrace_ops has IPMODIFY set, and ftrace requires a

	 * non-empty filter_hash for IPMODIFY ops, we're safe from an accidental

	 * empty filter_hash which would undesirably trace all functions.

	 * At this point, sinec ops is not registered, we should be sefe from

	 * registering empty filter.

	 */

	ftrace_set_filter_ip(&kprobe_ftrace_ops, (unsigned long)p->addr, 1, 0);

	ftrace_set_filter_ip(ops, (unsigned long)p->addr, 1, 0);

	return ret;

}



static int arm_kprobe_ftrace(struct kprobe *p)

{

	bool ipmodify = (p->post_handler != NULL);



	return __arm_kprobe_ftrace(p,

		ipmodify ? &kprobe_ipmodify_ops : &kprobe_ftrace_ops,

		ipmodify ? &kprobe_ipmodify_enabled : &kprobe_ftrace_enabled);

}



/* Caller must lock kprobe_mutex */

static int disarm_kprobe_ftrace(struct kprobe *p)

static int __disarm_kprobe_ftrace(struct kprobe *p, struct ftrace_ops *ops,

				  int *cnt)

{

	int ret = 0;



	if (kprobe_ftrace_enabled == 1) {

		ret = unregister_ftrace_function(&kprobe_ftrace_ops);

	if (*cnt == 1) {

		ret = unregister_ftrace_function(ops);

		if (WARN(ret < 0, "Failed to unregister kprobe-ftrace (%d)\n", ret))

			return ret;

	}



	kprobe_ftrace_enabled--;

	(*cnt)--;



	ret = ftrace_set_filter_ip(&kprobe_ftrace_ops,

			   (unsigned long)p->addr, 1, 0);

	ret = ftrace_set_filter_ip(ops, (unsigned long)p->addr, 1, 0);

	WARN_ONCE(ret < 0, "Failed to disarm kprobe-ftrace at %pS (%d)\n",

		  p->addr, ret);

	return ret;

}



static int disarm_kprobe_ftrace(struct kprobe *p)

{

	bool ipmodify = (p->post_handler != NULL);



	return __disarm_kprobe_ftrace(p,

		ipmodify ? &kprobe_ipmodify_ops : &kprobe_ftrace_ops,

		ipmodify ? &kprobe_ipmodify_enabled : &kprobe_ftrace_enabled);

}

#else	/* !CONFIG_KPROBES_ON_FTRACE */

#define prepare_kprobe(p)	arch_prepare_kprobe(p)

#define arm_kprobe_ftrace(p)	(-ENODEV)