Commit 45408c4f authored by Masami Hiramatsu's avatar Masami Hiramatsu Committed by Steven Rostedt (VMware)
Browse files

tracing: kprobes: Prohibit probing on notrace function 

Prohibit kprobe-events probing on notrace functions.  Since probing on a
notrace function can cause a recursive event call. In most cases those are just
skipped, but in some cases it falls into an infinite recursive call.

This protection can be disabled by the kconfig
CONFIG_KPROBE_EVENTS_ON_NOTRACE=y, but it is highly recommended to keep it
"n" for normal kernel builds.  Note that this is only available if "kprobes on
ftrace" has been implemented on the target arch and CONFIG_KPROBES_ON_FTRACE=y.

Link: http://lkml.kernel.org/r/153294601436.32740.10557881188933661239.stgit@devbox



Signed-off-by: default avatarMasami Hiramatsu <mhiramat@kernel.org>
Tested-by: default avatarFrancis Deslauriers <francis.deslauriers@efficios.com>
[ Slight grammar and spelling fixes ]
Signed-off-by: default avatarSteven Rostedt (VMware) <rostedt@goodmis.org>
parent 518eeca0

kernel/trace/Kconfig

+20 −0
Original line number Diff line number Diff line
@@ -456,6 +456,26 @@ config KPROBE_EVENTS 
	  This option is also required by perf-probe subcommand of perf tools.

	  If you want to use perf tools, this option is strongly recommended.



config KPROBE_EVENTS_ON_NOTRACE

	bool "Do NOT protect notrace function from kprobe events"

	depends on KPROBE_EVENTS

	depends on KPROBES_ON_FTRACE

	default n

	help

	  This is only for the developers who want to debug ftrace itself

	  using kprobe events.



	  If kprobes can use ftrace instead of breakpoint, ftrace related

	  functions are protected from kprobe-events to prevent an infinit

	  recursion or any unexpected execution path which leads to a kernel

	  crash.



	  This option disables such protection and allows you to put kprobe

	  events on ftrace functions for debugging ftrace by itself.

	  Note that this might let you shoot yourself in the foot.



	  If unsure, say N.



config UPROBE_EVENTS

	bool "Enable uprobes-based dynamic events"

	depends on ARCH_SUPPORTS_UPROBES

kernel/trace/trace_kprobe.c

+38 −9
Original line number Diff line number Diff line
@@ -87,6 +87,21 @@ static nokprobe_inline unsigned long trace_kprobe_nhit(struct trace_kprobe *tk) 
	return nhit;

}



static nokprobe_inline

unsigned long trace_kprobe_address(struct trace_kprobe *tk)

{

	unsigned long addr;



	if (tk->symbol) {

		addr = (unsigned long)

			kallsyms_lookup_name(trace_kprobe_symbol(tk));

		addr += tk->rp.kp.offset;

	} else {

		addr = (unsigned long)tk->rp.kp.addr;

	}

	return addr;

}



bool trace_kprobe_on_func_entry(struct trace_event_call *call)

{

	struct trace_kprobe *tk = (struct trace_kprobe *)call->data;
@@ -99,16 +114,8 @@ bool trace_kprobe_on_func_entry(struct trace_event_call *call) 
bool trace_kprobe_error_injectable(struct trace_event_call *call)

{

	struct trace_kprobe *tk = (struct trace_kprobe *)call->data;

	unsigned long addr;



	if (tk->symbol) {

		addr = (unsigned long)

			kallsyms_lookup_name(trace_kprobe_symbol(tk));

		addr += tk->rp.kp.offset;

	} else {

		addr = (unsigned long)tk->rp.kp.addr;

	}

	return within_error_injection_list(addr);

	return within_error_injection_list(trace_kprobe_address(tk));

}



static int register_kprobe_event(struct trace_kprobe *tk);
@@ -504,6 +511,22 @@ disable_trace_kprobe(struct trace_kprobe *tk, struct trace_event_file *file) 
	return ret;

}



#if defined(CONFIG_KPROBES_ON_FTRACE) && \

	!defined(CONFIG_KPROBE_EVENTS_ON_NOTRACE)

static bool within_notrace_func(struct trace_kprobe *tk)

{

	unsigned long offset, size, addr;



	addr = trace_kprobe_address(tk);

	if (!kallsyms_lookup_size_offset(addr, &size, &offset))

		return true;	/* Out of range. */



	return !ftrace_location_range(addr - offset, addr - offset + size);

}

#else

#define within_notrace_func(tk)	(false)

#endif



/* Internal register function - just handle k*probes and flags */

static int __register_trace_kprobe(struct trace_kprobe *tk)

{
@@ -512,6 +535,12 @@ static int __register_trace_kprobe(struct trace_kprobe *tk) 
	if (trace_probe_is_registered(&tk->tp))

		return -EINVAL;



	if (within_notrace_func(tk)) {

		pr_warn("Could not probe notrace function %s\n",

			trace_kprobe_symbol(tk));

		return -EINVAL;

	}



	for (i = 0; i < tk->tp.nr_args; i++)

		traceprobe_update_arg(&tk->tp.args[i]);

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