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

PATCH New Masami Hiramatsu 1 participant 1 message Oct 29, 2019 Tracing

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Masami Hiramatsu

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PATCH 1/1 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().

Fixes 45408c4f9250 ("tracing: kprobes: Prohibit probing on notrace function")
Signed-off-by Masami Hiramatsu <[email protected]>
---
 kernel/trace/trace_kprobe.c |   27 ++++++++++++++++++++++++---
 1 file changed, 24 insertions(+), 3 deletions(-)
kernel/trace/trace_kprobe.c +24 -3
index 1552a95c743b..7f890262c8a3 100644
@@ -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