[PATCH] trace/kprobe: Display the actual notrace function when rejecting a probe

[PATCH] trace/kprobe: Display the actual notrace function when rejecting a probe

[Naveen N Rao]

Trying to probe update_sd_lb_stats() using perf results in the below
message in the kernel log:
	trace_kprobe: Could not probe notrace function _text

This is because 'perf probe' specifies the kprobe location as an offset
from '_text':
	$ sudo perf probe -D update_sd_lb_stats
	p:probe/update_sd_lb_stats _text+1830728

However, the error message is misleading and doesn't help convey the
actual notrace function that is being probed. Fix this by looking up the
actual function name that is being probed. With this fix, we now get the
below message in the kernel log:
	trace_kprobe: Could not probe notrace function update_sd_lb_stats.constprop.0

Signed-off-by: Naveen N Rao <naveen@kernel.org>
---
 kernel/trace/trace_kprobe.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
index 74adb82331dd81..975daa66fcef59 100644
--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c
@@ -449,9 +449,8 @@ static bool __within_notrace_func(unsigned long addr)
 	return !ftrace_location_range(addr, addr + size - 1);
 }
 
-static bool within_notrace_func(struct trace_kprobe *tk)
+static bool within_notrace_func(struct trace_kprobe *tk, unsigned long addr)
 {
-	unsigned long addr = trace_kprobe_address(tk);
 	char symname[KSYM_NAME_LEN], *p;
 
 	if (!__within_notrace_func(addr))
@@ -477,6 +476,8 @@ static bool within_notrace_func(struct trace_kprobe *tk)
 /* Internal register function - just handle k*probes and flags */
 static int __register_trace_kprobe(struct trace_kprobe *tk)
 {
+	unsigned long addr = trace_kprobe_address(tk);
+	char symname[KSYM_NAME_LEN];
 	int i, ret;
 
 	ret = security_locked_down(LOCKDOWN_KPROBES);
@@ -486,9 +487,9 @@ static int __register_trace_kprobe(struct trace_kprobe *tk)
 	if (trace_kprobe_is_registered(tk))
 		return -EINVAL;
 
-	if (within_notrace_func(tk)) {
+	if (within_notrace_func(tk, addr)) {
 		pr_warn("Could not probe notrace function %s\n",
-			trace_kprobe_symbol(tk));
+			lookup_symbol_name(addr, symname) ? trace_kprobe_symbol(tk) : symname);
 		return -EINVAL;
 	}
 

base-commit: e46ad59233cf16daf4f3b9dd080003f01ac940fe
-- 
2.40.1

Re: [PATCH] trace/kprobe: Display the actual notrace function when rejecting a probe

[kernel test robot]

Hi Naveen,

kernel test robot noticed the following build errors:

[auto build test ERROR on e46ad59233cf16daf4f3b9dd080003f01ac940fe]

url:    https://github.com/intel-lab-lkp/linux/commits/Naveen-N-Rao/trace-kprobe-Display-the-actual-notrace-function-when-rejecting-a-probe/20230609-125904
base:   e46ad59233cf16daf4f3b9dd080003f01ac940fe
patch link:    https://lore.kernel.org/r/20230609045545.418677-1-naveen%40kernel.org
patch subject: [PATCH] trace/kprobe: Display the actual notrace function when rejecting a probe
config: mips-allyesconfig (https://download.01.org/0day-ci/archive/20230609/202306091507.njZTnqSN-lkp@intel.com/config)
compiler: mips-linux-gcc (GCC) 12.3.0
reproduce (this is a W=1 build):
        mkdir -p ~/bin
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        git checkout e46ad59233cf16daf4f3b9dd080003f01ac940fe
        b4 shazam https://lore.kernel.org/r/20230609045545.418677-1-naveen@kernel.org
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-12.3.0 ~/bin/make.cross W=1 O=build_dir ARCH=mips olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-12.3.0 ~/bin/make.cross W=1 O=build_dir ARCH=mips SHELL=/bin/bash kernel/

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202306091507.njZTnqSN-lkp@intel.com/

All errors (new ones prefixed by >>):

   kernel/trace/trace_kprobe.c: In function '__register_trace_kprobe':
>> kernel/trace/trace_kprobe.c:490:41: error: macro "within_notrace_func" passed 2 arguments, but takes just 1
     490 |         if (within_notrace_func(tk, addr)) {
         |                                         ^
   kernel/trace/trace_kprobe.c:473: note: macro "within_notrace_func" defined here
     473 | #define within_notrace_func(tk) (false)
         | 
>> kernel/trace/trace_kprobe.c:490:13: error: 'within_notrace_func' undeclared (first use in this function)
     490 |         if (within_notrace_func(tk, addr)) {
         |             ^~~~~~~~~~~~~~~~~~~
   kernel/trace/trace_kprobe.c:490:13: note: each undeclared identifier is reported only once for each function it appears in


vim +/within_notrace_func +490 kernel/trace/trace_kprobe.c

   475	
   476	/* Internal register function - just handle k*probes and flags */
   477	static int __register_trace_kprobe(struct trace_kprobe *tk)
   478	{
   479		unsigned long addr = trace_kprobe_address(tk);
   480		char symname[KSYM_NAME_LEN];
   481		int i, ret;
   482	
   483		ret = security_locked_down(LOCKDOWN_KPROBES);
   484		if (ret)
   485			return ret;
   486	
   487		if (trace_kprobe_is_registered(tk))
   488			return -EINVAL;
   489	
 > 490		if (within_notrace_func(tk, addr)) {
   491			pr_warn("Could not probe notrace function %s\n",
   492				lookup_symbol_name(addr, symname) ? trace_kprobe_symbol(tk) : symname);
   493			return -EINVAL;
   494		}
   495	
   496		for (i = 0; i < tk->tp.nr_args; i++) {
   497			ret = traceprobe_update_arg(&tk->tp.args[i]);
   498			if (ret)
   499				return ret;
   500		}
   501	
   502		/* Set/clear disabled flag according to tp->flag */
   503		if (trace_probe_is_enabled(&tk->tp))
   504			tk->rp.kp.flags &= ~KPROBE_FLAG_DISABLED;
   505		else
   506			tk->rp.kp.flags |= KPROBE_FLAG_DISABLED;
   507	
   508		if (trace_kprobe_is_return(tk))
   509			ret = register_kretprobe(&tk->rp);
   510		else
   511			ret = register_kprobe(&tk->rp.kp);
   512	
   513		return ret;
   514	}
   515	

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki