Commit c7411a1a authored Oct 29, 2019 by Masami Hiramatsu Committed by Steven Rostedt (VMware) Nov 14, 2019

tracing/kprobe: Check whether the non-suffixed symbol is notrace

Check whether the non-suffixed symbol is notrace, since suffixed
symbols are generated by the compilers for optimization. Based on
these suffixed symbols, notrace check might not work because
some of them are just a partial code of the original function.
(e.g. cold-cache (unlikely) code is separated from original
 function as FUNCTION.cold.XX)

For example, without this fix,
  # echo p device_add.cold.67 > /sys/kernel/debug/tracing/kprobe_events
  sh: write error: Invalid argument

  # cat /sys/kernel/debug/tracing/error_log
  [  135.491035] trace_kprobe: error: Failed to register probe event
    Command: p device_add.cold.67
               ^
  # dmesg | tail -n 1
  [  135.488599] trace_kprobe: Could not probe notrace function device_add.cold.67

With this,
  # echo p device_add.cold.66 > /sys/kernel/debug/tracing/kprobe_events
  # cat /sys/kernel/debug/kprobes/list
  ffffffff81599de9  k  device_add.cold.66+0x0    [DISABLED]

Actually, kprobe blacklist already did similar thing,
see within_kprobe_blacklist().

Link: http://lkml.kernel.org/r/157233790394.6706.18243942030937189679.stgit@devnote2



Fixes: 45408c4f ("tracing: kprobes: Prohibit probing on notrace function")
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

parent 6ee40511

kernel/trace/trace_kprobe.c

+24 −3

Original line number	Diff line number	Diff line
		@@ -435,11 +435,10 @@ static int disable_trace_kprobe(struct trace_event_call *call,

		#if defined(CONFIG_KPROBES_ON_FTRACE) && \
		!defined(CONFIG_KPROBE_EVENTS_ON_NOTRACE)
		static bool within_notrace_func(struct trace_kprobe *tk)
		static bool __within_notrace_func(unsigned long addr)
		{
		unsigned long offset, size, addr;
		unsigned long offset, size;

		addr = trace_kprobe_address(tk);
		if (!addr \|\| !kallsyms_lookup_size_offset(addr, &size, &offset))
		return false;

		@@ -452,6 +451,28 @@ static bool within_notrace_func(struct trace_kprobe *tk)
		*/
		return !ftrace_location_range(addr, addr + size - 1);
		}

		static bool within_notrace_func(struct trace_kprobe *tk)
		{
		unsigned long addr = addr = trace_kprobe_address(tk);
		char symname[KSYM_NAME_LEN], *p;

		if (!__within_notrace_func(addr))
		return false;

		/* Check if the address is on a suffixed-symbol */
		if (!lookup_symbol_name(addr, symname)) {
		p = strchr(symname, '.');
		if (!p)
		return true;
		*p = '\0';
		addr = (unsigned long)kprobe_lookup_name(symname, 0);
		if (addr)
		return __within_notrace_func(addr);
		}

		return true;
		}
		#else
		#define within_notrace_func(tk) (false)
		#endif

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