Re: [PATCH v3 5/5] selftests/ftrace: Update fprobe test to check enabled_functions file
From: Heiko Carstens <hca@linux.ibm.com>
Date: 2025-02-26 10:50:48
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Subsystem:
kernel selftest framework, the rest, tracing · Maintainers:
Shuah Khan, Shuah Khan, Linus Torvalds, Steven Rostedt, Masami Hiramatsu
On Thu, Feb 20, 2025 at 03:20:14PM -0500, Steven Rostedt wrote:
quoted hunk ↗ jump to hunk
From: Steven Rostedt <rostedt@goodmis.org> A few bugs were found in the fprobe accounting logic along with it using the function graph infrastructure. Update the fprobe selftest to catch those bugs in case they or something similar shows up in the future. The test now checks the enabled_functions file which shows all the functions attached to ftrace or fgraph. When enabling a fprobe, make sure that its corresponding function is also added to that file. Also add two more fprobes to enable to make sure that the fprobe logic works properly with multiple probes. Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org> Tested-by: Heiko Carstens <hca@linux.ibm.com> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org> --- .../test.d/dynevent/add_remove_fprobe.tc | 54 +++++++++++++++++++ 1 file changed, 54 insertions(+)diff --git a/tools/testing/selftests/ftrace/test.d/dynevent/add_remove_fprobe.tc b/tools/testing/selftests/ftrace/test.d/dynevent/add_remove_fprobe.tc index dc25bcf4f9e2..449f9d8be746 100644 --- a/tools/testing/selftests/ftrace/test.d/dynevent/add_remove_fprobe.tc +++ b/tools/testing/selftests/ftrace/test.d/dynevent/add_remove_fprobe.tc@@ -7,12 +7,38 @@ echo 0 > events/enable echo > dynamic_events PLACE=$FUNCTION_FORK +PLACE2="kmem_cache_free" +PLACE3="schedule_timeout" echo "f:myevent1 $PLACE" >> dynamic_events + +# Make sure the event is attached and is the only one +grep -q $PLACE enabled_functions +cnt=`cat enabled_functions | wc -l` +if [ $cnt -ne 1 ]; then + exit_fail +fi
Bah.. :) this doesn't work always, since at least with Fedora 41 the
assumption that there are zero enabled functions before this test is
executed is not necessarily true:
# cat tracing/enabled_functions
free_user_ns (1) R
bpf_lsm_path_mkdir (1) R D M tramp: ftrace_regs_caller+0x0/0x68 (call_direct_funcs+0x0/0x20)
direct-->bpf_trampoline_6442505669+0x0/0x148
bpf_lsm_path_mknod (1) R D M tramp: ftrace_regs_caller+0x0/0x68 (call_direct_funcs+0x0/0x20)
direct-->bpf_trampoline_6442505671+0x0/0x14e
...
I didn't stumble across this before, since I tried a monolithic kernel
without modules when verifying your series; and then there aren't any
enabled functions. But with modules there are.
This could be worked around for example with something like the patch
below (against linux-next). But no idea what your preferred way to
handle this would be.
diff --git a/tools/testing/selftests/ftrace/test.d/dynevent/add_remove_fprobe.tc b/tools/testing/selftests/ftrace/test.d/dynevent/add_remove_fprobe.tc
index 449f9d8be746..b0f24c57b8e1 100644
--- a/tools/testing/selftests/ftrace/test.d/dynevent/add_remove_fprobe.tc
+++ b/tools/testing/selftests/ftrace/test.d/dynevent/add_remove_fprobe.tc@@ -10,12 +10,14 @@ PLACE=$FUNCTION_FORK PLACE2="kmem_cache_free" PLACE3="schedule_timeout" +ocnt=`cat enabled_functions | wc -l` + echo "f:myevent1 $PLACE" >> dynamic_events # Make sure the event is attached and is the only one grep -q $PLACE enabled_functions cnt=`cat enabled_functions | wc -l` -if [ $cnt -ne 1 ]; then +if [ $cnt -ne $((ocnt + 1)) ]; then exit_fail fi
@@ -23,7 +25,7 @@ echo "f:myevent2 $PLACE%return" >> dynamic_events # It should till be the only attached function cnt=`cat enabled_functions | wc -l` -if [ $cnt -ne 1 ]; then +if [ $cnt -ne $((ocnt + 1)) ]; then exit_fail fi
@@ -32,7 +34,7 @@ echo "f:myevent3 $PLACE2" >> dynamic_events grep -q $PLACE2 enabled_functions cnt=`cat enabled_functions | wc -l` -if [ $cnt -ne 2 ]; then +if [ $cnt -ne $((ocnt + 2)) ]; then exit_fail fi
@@ -49,7 +51,7 @@ grep -q myevent1 dynamic_events # should still have 2 left cnt=`cat enabled_functions | wc -l` -if [ $cnt -ne 2 ]; then +if [ $cnt -ne $((ocnt + 2)) ]; then exit_fail fi
@@ -57,7 +59,7 @@ echo > dynamic_events # Should have none left cnt=`cat enabled_functions | wc -l` -if [ $cnt -ne 0 ]; then +if [ $cnt -ne $ocnt ]; then exit_fail fi
@@ -65,7 +67,7 @@ echo "f:myevent4 $PLACE" >> dynamic_events # Should only have one enabled cnt=`cat enabled_functions | wc -l` -if [ $cnt -ne 1 ]; then +if [ $cnt -ne $((ocnt + 1)) ]; then exit_fail fi
@@ -73,7 +75,7 @@ echo > dynamic_events # Should have none left cnt=`cat enabled_functions | wc -l` -if [ $cnt -ne 0 ]; then +if [ $cnt -ne $ocnt ]; then exit_fail fi