[PATCH 0/2] ftrace/selftests: Fix registering kprobe on non-unique symbol

Hi All!

Commit 1870ddcd94b0 ("bpf: Prefer vmlinux symbols over module symbols
for unqualified kprobes") broke registering kprobe on non-unique symbol
test - fix and improve it.

Thanks!

Alexander Gordeev (2):
  ftrace/selftests: Fix regex pattern to match vmlinux symbol names only
  ftrace/selftests: Change non-unique test symbol to init_once

 .../selftests/ftrace/test.d/kprobe/kprobe_non_uniq_symbol.tc  | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

-- 
2.53.0

Commit 1870ddcd94b0 ("bpf: Prefer vmlinux symbols over module symbols
for unqualified kprobes") changed unqualified kprobe lookup to prefer
a unique vmlinux symbol even when modules export symbols with the same
name.

Reflect this change in the test and anchor the grep pattern at the end
of the line so it only counts vmlinux symbols and skips module ones.

Suggested-by: Sven Schnelle <svens@linux.ibm.com>
Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>
---
 .../selftests/ftrace/test.d/kprobe/kprobe_non_uniq_symbol.tc    | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/testing/selftests/ftrace/test.d/kprobe/kprobe_non_uniq_symbol.tc b/tools/testing/selftests/ftrace/test.d/kprobe/kprobe_non_uniq_symbol.tc
index bc9514428dba..07b1177c1634 100644
--- a/tools/testing/selftests/ftrace/test.d/kprobe/kprobe_non_uniq_symbol.tc
+++ b/tools/testing/selftests/ftrace/test.d/kprobe/kprobe_non_uniq_symbol.tc

@@ -6,7 +6,7 @@
 SYMBOL='name_show'
 
 # We skip this test on kernel where SYMBOL is unique or does not exist.
-if [ "$(grep -c -E "[[:alnum:]]+ t ${SYMBOL}" /proc/kallsyms)" -le '1' ]; then
+if [ "$(grep -c -E "[[:alnum:]]+ t ${SYMBOL}$" /proc/kallsyms)" -le '1' ]; then
 	exit_unsupported
 fi
 

-- 
2.53.0

The name_show symbol is not the best choise, because it often
appears only three times on s390 in kallsyms, with two of them
having module annotations [mdev] and [i2c_core].

Switch to init_once which has many more duplicate instances
all in vmlinux, making it a more reliable non-unique symbol
for testing kprobe registration failure.

Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>
---
 .../selftests/ftrace/test.d/kprobe/kprobe_non_uniq_symbol.tc    | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/testing/selftests/ftrace/test.d/kprobe/kprobe_non_uniq_symbol.tc b/tools/testing/selftests/ftrace/test.d/kprobe/kprobe_non_uniq_symbol.tc
index 07b1177c1634..03eb9e70b438 100644
--- a/tools/testing/selftests/ftrace/test.d/kprobe/kprobe_non_uniq_symbol.tc
+++ b/tools/testing/selftests/ftrace/test.d/kprobe/kprobe_non_uniq_symbol.tc

@@ -3,7 +3,7 @@
 # description: Test failure of registering kprobe on non unique symbol
 # requires: kprobe_events
 
-SYMBOL='name_show'
+SYMBOL='init_once'
 
 # We skip this test on kernel where SYMBOL is unique or does not exist.
 if [ "$(grep -c -E "[[:alnum:]]+ t ${SYMBOL}$" /proc/kallsyms)" -le '1' ]; then

-- 
2.53.0

Polite ping.