[PATCH AUTOSEL 4.19 148/177] tracing/kprobe: Check whether the non-suffixed symbol is notrace

Sasha Levin
2019-12-10T21:38:13Z

From: Masami Hiramatsu <mhiramat@kernel.org>

[ Upstream commit c7411a1a126f649be71526a36d4afac9e5aefa13 ]

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: 45408c4f9250 ("tracing: kprobes: Prohibit probing on notrace function")
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
kernel/trace/trace_kprobe.c | 27 ++++++++++++++++++++++++---
1 file changed, 24 insertions(+), 3 deletions(-)

diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
index f9a0cd094b810..c61b2b0a99e9c 100644
--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c
@@ -519,11 +519,10 @@ disable_trace_kprobe(struct trace_kprobe *tk, struct trace_event_file *file)

#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;

@@ -536,6 +535,28 @@ 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
--
2.20.1