[PATCH 3/4] selftests: livepatch: Adapt mod_target module to pass on 4.12 kernels
From: Marcos Paulo de Souza
Date: Sun May 24 2026 - 19:52:02 EST
Use the stable module_param_cb API instead of proc_fs for exposing module
state. This approach is compatible with kernel 4.12 and later. The end
result is the same: the module has a function that shows a string, which
is later livepatched to show a different string. The only difference is
that the file being checked is now a module parameter instead of a
procfs entry.
Signed-off-by: Marcos Paulo de Souza <mpdesouza@xxxxxxxx>
---
tools/testing/selftests/livepatch/functions.sh | 1 +
.../testing/selftests/livepatch/test-livepatch.sh | 23 +++++++++++-----------
.../livepatch/test_modules/test_klp_mod_patch.c | 11 +++++------
.../livepatch/test_modules/test_klp_mod_target.c | 22 ++++++++++-----------
4 files changed, 27 insertions(+), 30 deletions(-)
diff --git a/tools/testing/selftests/livepatch/functions.sh b/tools/testing/selftests/livepatch/functions.sh
index 25f137003865..c8c99851c3a2 100644
--- a/tools/testing/selftests/livepatch/functions.sh
+++ b/tools/testing/selftests/livepatch/functions.sh
@@ -7,6 +7,7 @@
MAX_RETRIES=600
RETRY_INTERVAL=".1" # seconds
SYSFS_KERNEL_DIR="/sys/kernel"
+SYSFS_MODULE_DIR="/sys/module"
SYSFS_KLP_DIR="$SYSFS_KERNEL_DIR/livepatch"
SYSFS_DEBUG_DIR="$SYSFS_KERNEL_DIR/debug"
SYSFS_KPROBES_DIR="$SYSFS_DEBUG_DIR/kprobes"
diff --git a/tools/testing/selftests/livepatch/test-livepatch.sh b/tools/testing/selftests/livepatch/test-livepatch.sh
index c44c5341a2f1..06aacf0f4dc7 100755
--- a/tools/testing/selftests/livepatch/test-livepatch.sh
+++ b/tools/testing/selftests/livepatch/test-livepatch.sh
@@ -198,26 +198,25 @@ livepatch: '$MOD_REPLACE': unpatching complete
% rmmod $MOD_REPLACE"
-# - load a target module that provides /proc/test_klp_mod_target with
-# original output
-# - load a livepatch that patches the target module's show function
-# - verify the proc entry returns livepatched output
+# - load a target module with module_param_cb get data with original output
+# - load a livepatch that patches the target module's get function
+# - verify the parameter get function returns the livepatched output
# - disable and unload the livepatch
-# - verify the proc entry returns original output again
+# - verify the parameter get function returns the original output again
# - unload the target module
start_test "module function patching"
load_mod $MOD_TARGET
-if [[ "$(cat /proc/$MOD_TARGET)" != "$MOD_TARGET: original output" ]] ; then
+if [[ "$(cat $SYSFS_MODULE_DIR/$MOD_TARGET/parameters/klp_mod_arg)" != "$MOD_TARGET: original output" ]] ; then
echo -e "FAIL\n\n"
die "livepatch kselftest(s) failed"
fi
load_lp $MOD_TARGET_PATCH
-if [[ "$(cat /proc/$MOD_TARGET)" != "$MOD_TARGET_PATCH: this has been live patched" ]] ; then
+if [[ "$(cat $SYSFS_MODULE_DIR/$MOD_TARGET/parameters/klp_mod_arg)" != "$MOD_TARGET_PATCH: this has been live patched" ]] ; then
echo -e "FAIL\n\n"
die "livepatch kselftest(s) failed"
fi
@@ -225,7 +224,7 @@ fi
disable_lp $MOD_TARGET_PATCH
unload_lp $MOD_TARGET_PATCH
-if [[ "$(cat /proc/$MOD_TARGET)" != "$MOD_TARGET: original output" ]] ; then
+if [[ "$(cat $SYSFS_MODULE_DIR/$MOD_TARGET/parameters/klp_mod_arg)" != "$MOD_TARGET: original output" ]] ; then
echo -e "FAIL\n\n"
die "livepatch kselftest(s) failed"
fi
@@ -252,9 +251,9 @@ $MOD_TARGET: test_klp_mod_target_exit"
# - load a livepatch that targets a not-yet-loaded module
# - load the target module: klp_module_coming patches it immediately
-# - verify the proc entry returns livepatched output
+# - verify the parameter get function returns the livepatched output
# - disable and unload the livepatch
-# - verify the proc entry returns original output again
+# - verify the parameter get function returns the original output again
# - unload the target module
start_test "module function patching (livepatch first)"
@@ -262,7 +261,7 @@ start_test "module function patching (livepatch first)"
load_lp $MOD_TARGET_PATCH
load_mod $MOD_TARGET
-if [[ "$(cat /proc/$MOD_TARGET)" != "$MOD_TARGET_PATCH: this has been live patched" ]] ; then
+if [[ "$(cat $SYSFS_MODULE_DIR/$MOD_TARGET/parameters/klp_mod_arg)" != "$MOD_TARGET_PATCH: this has been live patched" ]] ; then
echo -e "FAIL\n\n"
die "livepatch kselftest(s) failed"
fi
@@ -270,7 +269,7 @@ fi
disable_lp $MOD_TARGET_PATCH
unload_lp $MOD_TARGET_PATCH
-if [[ "$(cat /proc/$MOD_TARGET)" != "$MOD_TARGET: original output" ]] ; then
+if [[ "$(cat $SYSFS_MODULE_DIR/$MOD_TARGET/parameters/klp_mod_arg)" != "$MOD_TARGET: original output" ]] ; then
echo -e "FAIL\n\n"
die "livepatch kselftest(s) failed"
fi
diff --git a/tools/testing/selftests/livepatch/test_modules/test_klp_mod_patch.c b/tools/testing/selftests/livepatch/test_modules/test_klp_mod_patch.c
index 6725b4720365..ab56e57c02a8 100644
--- a/tools/testing/selftests/livepatch/test_modules/test_klp_mod_patch.c
+++ b/tools/testing/selftests/livepatch/test_modules/test_klp_mod_patch.c
@@ -8,17 +8,16 @@
#include <linux/livepatch.h>
#include <linux/seq_file.h>
-static int livepatch_mod_target_show(struct seq_file *m, void *v)
+static int livepatch_mod_target_get(char *buffer, const struct kernel_param *kp)
{
- seq_printf(m, "%s: %s\n", THIS_MODULE->name,
- "this has been live patched");
- return 0;
+ return sprintf(buffer, "%s: %s\n", THIS_MODULE->name,
+ "this has been live patched");
}
static struct klp_func funcs[] = {
{
- .old_name = "test_klp_mod_target_show",
- .new_func = livepatch_mod_target_show,
+ .old_name = "test_klp_mod_target_get",
+ .new_func = livepatch_mod_target_get,
},
{},
};
diff --git a/tools/testing/selftests/livepatch/test_modules/test_klp_mod_target.c b/tools/testing/selftests/livepatch/test_modules/test_klp_mod_target.c
index 9643984d2402..1382a266825f 100644
--- a/tools/testing/selftests/livepatch/test_modules/test_klp_mod_target.c
+++ b/tools/testing/selftests/livepatch/test_modules/test_klp_mod_target.c
@@ -5,31 +5,29 @@
#include <linux/module.h>
#include <linux/kernel.h>
-#include <linux/proc_fs.h>
-#include <linux/seq_file.h>
+#include <linux/moduleparam.h>
-static struct proc_dir_entry *pde;
-
-static noinline int test_klp_mod_target_show(struct seq_file *m, void *v)
+static noinline int test_klp_mod_target_get(char *buffer, const struct kernel_param *kp)
{
- seq_printf(m, "%s: %s\n", THIS_MODULE->name, "original output");
- return 0;
+ return sprintf(buffer, "%s: %s\n", THIS_MODULE->name, "original output");
}
+static const struct kernel_param_ops test_klp_mod_target_ops = {
+ .get = test_klp_mod_target_get,
+};
+
+module_param_cb(klp_mod_arg, &test_klp_mod_target_ops, NULL, 0444);
+MODULE_PARM_DESC(klp_mod_arg, "The value of this argument will be livepatched");
+
static int test_klp_mod_target_init(void)
{
pr_info("%s\n", __func__);
- pde = proc_create_single("test_klp_mod_target", 0, NULL,
- test_klp_mod_target_show);
- if (!pde)
- return -ENOMEM;
return 0;
}
static void test_klp_mod_target_exit(void)
{
pr_info("%s\n", __func__);
- proc_remove(pde);
}
module_init(test_klp_mod_target_init);
--
2.54.0