[PATCH v2 1/2] kunit: add ability to run tests after boot using debugfs

[Rae Moar <rmoar@google.com>]

Add functionality to run built-in tests after boot by writing to a
debugfs file.

Add a new debugfs file labeled "run" for each test suite to use for
this purpose.

As an example, write to the file using the following:

echo "any string" > /sys/kernel/debugfs/kunit/<testsuite>/run

This will trigger the test suite to run and will print results to the
kernel log.

Note that what you "write" to the debugfs file will not be saved.

To guard against running tests concurrently with this feature, add a
mutex lock around running kunit. This supports the current practice of
not allowing tests to be run concurrently on the same kernel.

This functionality may not work for all tests.

This new functionality could be used to design a parameter
injection feature in the future.

Signed-off-by: Rae Moar <rmoar@google.com>
---

Changes since v1:
- Removed second patch as this problem has been fixed
- Added Documentation patch
- Made changes to work with new dynamically-extending log feature

Note that these patches now rely on (and are rebased on) the patch series:
https://lore.kernel.org/all/20230828104111.2394344-1-rf@opensource.cirrus.com/

 lib/kunit/debugfs.c | 66 +++++++++++++++++++++++++++++++++++++++++++++
 lib/kunit/test.c    | 13 +++++++++
 2 files changed, 79 insertions(+)

diff --git a/lib/kunit/debugfs.c b/lib/kunit/debugfs.c
index 270d185737e6..8c0a970321ce 100644
--- a/lib/kunit/debugfs.c
+++ b/lib/kunit/debugfs.c
@@ -8,12 +8,14 @@
 #include <linux/module.h>
 
 #include <kunit/test.h>
+#include <kunit/test-bug.h>
 
 #include "string-stream.h"
 #include "debugfs.h"
 
 #define KUNIT_DEBUGFS_ROOT             "kunit"
 #define KUNIT_DEBUGFS_RESULTS          "results"
+#define KUNIT_DEBUGFS_RUN              "run"
 
 /*
  * Create a debugfs representation of test suites:
@@ -21,6 +23,8 @@
  * Path						Semantics
  * /sys/kernel/debug/kunit/<testsuite>/results	Show results of last run for
  *						testsuite
+ * /sys/kernel/debug/kunit/<testsuite>/run	Write to this file to trigger
+ *						testsuite to run
  *
  */
 
@@ -99,6 +103,51 @@ static int debugfs_results_open(struct inode *inode, struct file *file)
 	return single_open(file, debugfs_print_results, suite);
 }
 
+/*
+ * Print a usage message to the debugfs "run" file
+ * (/sys/kernel/debug/kunit/<testsuite>/run) if opened.
+ */
+static int debugfs_print_run(struct seq_file *seq, void *v)
+{
+	struct kunit_suite *suite = (struct kunit_suite *)seq->private;
+
+	seq_puts(seq, "Write to this file to trigger the test suite to run.\n");
+	seq_printf(seq, "usage: echo \"any string\" > /sys/kernel/debugfs/kunit/%s/run\n",
+			suite->name);
+	return 0;
+}
+
+/*
+ * The debugfs "run" file (/sys/kernel/debug/kunit/<testsuite>/run)
+ * contains no information. Write to the file to trigger the test suite
+ * to run.
+ */
+static int debugfs_run_open(struct inode *inode, struct file *file)
+{
+	struct kunit_suite *suite;
+
+	suite = (struct kunit_suite *)inode->i_private;
+
+	return single_open(file, debugfs_print_run, suite);
+}
+
+/*
+ * Trigger a test suite to run by writing to the suite's "run" debugfs
+ * file found at: /sys/kernel/debug/kunit/<testsuite>/run
+ *
+ * Note: what is written to this file will not be saved.
+ */
+static ssize_t debugfs_run(struct file *file,
+		const char __user *buf, size_t count, loff_t *ppos)
+{
+	struct inode *f_inode = file->f_inode;
+	struct kunit_suite *suite = (struct kunit_suite *) f_inode->i_private;
+
+	__kunit_test_suites_init(&suite, 1);
+
+	return count;
+}
+
 static const struct file_operations debugfs_results_fops = {
 	.open = debugfs_results_open,
 	.read = seq_read,
@@ -106,10 +155,23 @@ static const struct file_operations debugfs_results_fops = {
 	.release = debugfs_release,
 };
 
+static const struct file_operations debugfs_run_fops = {
+	.open = debugfs_run_open,
+	.read = seq_read,
+	.write = debugfs_run,
+	.llseek = seq_lseek,
+	.release = debugfs_release,
+};
+
 void kunit_debugfs_create_suite(struct kunit_suite *suite)
 {
 	struct kunit_case *test_case;
 
+	if (suite->log) {
+		/* Clear the suite log that's leftover from a previous run. */
+		string_stream_clear(suite->log);
+		return;
+	}
 	/* Allocate logs before creating debugfs representation. */
 	suite->log = alloc_string_stream(GFP_KERNEL);
 	string_stream_set_append_newlines(suite->log, true);
@@ -124,6 +186,10 @@ void kunit_debugfs_create_suite(struct kunit_suite *suite)
 	debugfs_create_file(KUNIT_DEBUGFS_RESULTS, S_IFREG | 0444,
 			    suite->debugfs,
 			    suite, &debugfs_results_fops);
+
+	debugfs_create_file(KUNIT_DEBUGFS_RUN, S_IFREG | 0644,
+			    suite->debugfs,
+			    suite, &debugfs_run_fops);
 }
 
 void kunit_debugfs_destroy_suite(struct kunit_suite *suite)
diff --git a/lib/kunit/test.c b/lib/kunit/test.c
index 651cbda9f250..d376b886d72d 100644
--- a/lib/kunit/test.c
+++ b/lib/kunit/test.c
@@ -13,6 +13,7 @@
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/moduleparam.h>
+#include <linux/mutex.h>
 #include <linux/panic.h>
 #include <linux/sched/debug.h>
 #include <linux/sched.h>
@@ -22,6 +23,8 @@
 #include "string-stream.h"
 #include "try-catch-impl.h"
 
+static struct mutex kunit_run_lock;
+
 /*
  * Hook to fail the current test and print an error message to the log.
  */
@@ -668,6 +671,11 @@ int __kunit_test_suites_init(struct kunit_suite * const * const suites, int num_
 		return 0;
 	}
 
+	/* Use mutex lock to guard against running tests concurrently. */
+	if (mutex_lock_interruptible(&kunit_run_lock)) {
+		pr_err("kunit: test interrupted\n");
+		return -EINTR;
+	}
 	static_branch_inc(&kunit_running);
 
 	for (i = 0; i < num_suites; i++) {
@@ -676,6 +684,7 @@ int __kunit_test_suites_init(struct kunit_suite * const * const suites, int num_
 	}
 
 	static_branch_dec(&kunit_running);
+	mutex_unlock(&kunit_run_lock);
 	return 0;
 }
 EXPORT_SYMBOL_GPL(__kunit_test_suites_init);
@@ -836,6 +845,10 @@ static int __init kunit_init(void)
 	kunit_install_hooks();
 
 	kunit_debugfs_init();
+
+	/* Initialize lock to guard against running tests concurrently. */
+	mutex_init(&kunit_run_lock);
+
 #ifdef CONFIG_MODULES
 	return register_module_notifier(&kunit_mod_nb);
 #else

base-commit: b754593274e04fc840482a658b29791bc8f8b933
-- 
2.42.0.283.g2d96d420d3-goog