[PATCH 3/4] selftests: livepatch: Adapt mod_target module to pass on 4.12 kernels

[Marcos Paulo de Souza <mpdesouza@suse.com>]

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@suse.com>
---
 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