kunit: Introduce param_init/exit for parameterized test context management

Add (*param_init) and (*param_exit) function pointers to
`struct kunit_case`. Users will be able to set them via the new
KUNIT_CASE_PARAM_WITH_INIT() macro.

param_init/exit will be invoked by kunit_run_tests() once before and once
after the parameterized test, respectively. They will receive the
`struct kunit` that holds the parameterized test context; facilitating
init and exit for shared state.

This patch also sets param_init/exit to None in rust/kernel/kunit.rs.

Link: https://lore.kernel.org/r/20250826091341.1427123-3-davidgow@google.com
Reviewed-by: Rae Moar <rmoar@google.com>
Reviewed-by: David Gow <davidgow@google.com>
Signed-off-by: Marie Zhussupova <marievic@google.com>
Signed-off-by: David Gow <davidgow@google.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

Author: Marie Zhussupova

include/kunit/test.h

@@ -92,6 +92,8 @@ struct kunit_attributes {
  * @name:     the name of the test case.
  * @generate_params: the generator function for parameterized tests.
  * @attr:     the attributes associated with the test
+ * @param_init: The init function to run before a parameterized test.
+ * @param_exit: The exit function to run after a parameterized test.
  *
  * A test case is a function with the signature,
  * ``void (*)(struct kunit *)``
@@ -128,6 +130,8 @@ struct kunit_case {
 	const char *name;
 	const void* (*generate_params)(const void *prev, char *desc);
 	struct kunit_attributes attr;
+	int (*param_init)(struct kunit *test);
+	void (*param_exit)(struct kunit *test);
 
 	/* private: internal use only. */
 	enum kunit_status status;
@@ -218,6 +222,27 @@ static inline char *kunit_status_to_ok_not_ok(enum kunit_status status)
 		  .generate_params = gen_params,				\
 		  .attr = attributes, .module_name = KBUILD_MODNAME}
 
+/**
+ * KUNIT_CASE_PARAM_WITH_INIT - Define a parameterized KUnit test case with custom
+ * param_init() and param_exit() functions.
+ * @test_name: The function implementing the test case.
+ * @gen_params: The function to generate parameters for the test case.
+ * @init: A reference to the param_init() function to run before a parameterized test.
+ * @exit: A reference to the param_exit() function to run after a parameterized test.
+ *
+ * Provides the option to register param_init() and param_exit() functions.
+ * param_init/exit will be passed the parameterized test context and run once
+ * before and once after the parameterized test. The init function can be used
+ * to add resources to share between parameter runs, and any other setup logic.
+ * The exit function can be used to clean up resources that were not managed by
+ * the parameterized test, and any other teardown logic.
+ */
+#define KUNIT_CASE_PARAM_WITH_INIT(test_name, gen_params, init, exit)		\
+		{ .run_case = test_name, .name = #test_name,			\
+		  .generate_params = gen_params,				\
+		  .param_init = init, .param_exit = exit,			\
+		  .module_name = KBUILD_MODNAME}
+
 /**
  * struct kunit_suite - describes a related collection of &struct kunit_case
  *

lib/kunit/test.c

@@ -641,6 +641,20 @@ static void kunit_accumulate_stats(struct kunit_result_stats *total,
 	total->total += add.total;
 }
 
+static void kunit_init_parent_param_test(struct kunit_case *test_case, struct kunit *test)
+{
+	if (test_case->param_init) {
+		int err = test_case->param_init(test);
+
+		if (err) {
+			kunit_err(test_case, KUNIT_SUBTEST_INDENT KUNIT_SUBTEST_INDENT
+				"# failed to initialize parent parameter test (%d)", err);
+			test->status = KUNIT_FAILURE;
+			test_case->status = KUNIT_FAILURE;
+		}
+	}
+}
+
 int kunit_run_tests(struct kunit_suite *suite)
 {
 	char param_desc[KUNIT_PARAM_DESC_SIZE];
@@ -678,6 +692,11 @@ int kunit_run_tests(struct kunit_suite *suite)
 			kunit_run_case_catch_errors(suite, test_case, &test);
 			kunit_update_stats(&param_stats, test.status);
 		} else {
+			kunit_init_parent_param_test(test_case, &test);
+			if (test_case->status == KUNIT_FAILURE) {
+				kunit_update_stats(&param_stats, test.status);
+				goto test_case_end;
+			}
 			/* Get initial param. */
 			param_desc[0] = '\0';
 			/* TODO: Make generate_params try-catch */
@@ -714,10 +733,16 @@ int kunit_run_tests(struct kunit_suite *suite)
 				param_desc[0] = '\0';
 				curr_param = test_case->generate_params(curr_param, param_desc);
 			}
+			/*
+			 * TODO: Put into a try catch. Since we don't need suite->exit
+			 * for it we can't reuse kunit_try_run_cleanup for this yet.
+			 */
+			if (test_case->param_exit)
+				test_case->param_exit(&test);
 			/* TODO: Put this kunit_cleanup into a try-catch. */
 			kunit_cleanup(&test);
 		}
-
+test_case_end:
 		kunit_print_attr((void *)test_case, true, KUNIT_LEVEL_CASE);
 
 		kunit_print_test_stats(&test, param_stats);

rust/kernel/kunit.rs

@@ -210,6 +210,8 @@ pub const fn kunit_case(
         status: kernel::bindings::kunit_status_KUNIT_SUCCESS,
         module_name: core::ptr::null_mut(),
         log: core::ptr::null_mut(),
+        param_init: None,
+        param_exit: None,
     }
 }
 
@@ -229,6 +231,8 @@ pub const fn kunit_case_null() -> kernel::bindings::kunit_case {
         status: kernel::bindings::kunit_status_KUNIT_SUCCESS,
         module_name: core::ptr::null_mut(),
         log: core::ptr::null_mut(),
+        param_init: None,
+        param_exit: None,
     }
 }