From: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
It's not easy to understand what can be done by the vchecker.
This sample could explain it and help to understand the vchecker.
Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
---
lib/Kconfig.kasan | 9 ++++
lib/Makefile | 1 +
lib/vchecker_test.c | 117 ++++++++++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 127 insertions(+)
create mode 100644 lib/vchecker_test.c
diff --git a/lib/Kconfig.kasan b/lib/Kconfig.kasan
index 4b8e748..9983ec8 100644
--- a/lib/Kconfig.kasan
+++ b/lib/Kconfig.kasan
@@ -65,4 +65,13 @@ config VCHECKER
depends on KASAN && DEBUG_FS
select KALLSYMS
+config TEST_VCHECKER
+ tristate "Module for testing vchecker"
+ depends on m && KASAN
+ help
+ This is a test module doing memory over-write. If vchecker is
+ properly set up to check that over-write, memory over-written
+ problem would be detected. See the help text in the
+ lib/vchecker_test.c for vchecker sample run.
+
endif
diff --git a/lib/Makefile b/lib/Makefile
index d11c48e..cc1f5ec 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -244,6 +244,7 @@ clean-files += oid_registry_data.c
obj-$(CONFIG_UCS2_STRING) += ucs2_string.o
obj-$(CONFIG_UBSAN) += ubsan.o
+obj-$(CONFIG_TEST_VCHECKER) += vchecker_test.o
UBSAN_SANITIZE_ubsan.o := n
diff --git a/lib/vchecker_test.c b/lib/vchecker_test.c
new file mode 100644
index 0000000..fcb4b7f
--- /dev/null
+++ b/lib/vchecker_test.c
@@ -0,0 +1,117 @@
+#include <linux/kernel.h>
+#include <linux/printk.h>
+#include <linux/slab.h>
+#include <linux/module.h>
+#include <linux/workqueue.h>
+
+/*
+ * How to use this sample for vchecker sample-run
+ *
+ * 1. Insert this module
+ * 2. Do following command on debugfs directory
+ * # cd /sys/kernel/debug/vchecker
+ * # echo 0 0xffff 7 > vchecker_test/value # offset 0, mask 0xffff, value 7
+ * # echo 1 > vchecker_test/enable
+ * # echo workfn_kmalloc_obj > kmalloc-8/alloc_filter
+ * # echo "0 8" > kmalloc-8/callstack
+ * # echo on > kmalloc-8/callstack
+ * # echo 1 > kmalloc-8/enable
+ * 3. Check the error report due to invalid written value
+ */
+
+struct object {
+ volatile unsigned long v[1];
+};
+
+static struct kmem_cache *s;
+static void *old_obj;
+static struct delayed_work dwork_old_obj;
+static struct delayed_work dwork_new_obj;
+static struct delayed_work dwork_kmalloc_obj;
+
+static void workfn_old_obj(struct work_struct *work)
+{
+ struct object *obj = old_obj;
+ struct delayed_work *dwork = (struct delayed_work *)work;
+
+ obj->v[0] = 7;
+
+ mod_delayed_work(system_wq, dwork, HZ * 5);
+}
+
+static void workfn_new_obj(struct work_struct *work)
+{
+ struct object *obj;
+ struct delayed_work *dwork = (struct delayed_work *)work;
+
+ obj = kmem_cache_alloc(s, GFP_KERNEL);
+
+ obj->v[0] = 7;
+ /*
+ * Need one more access to detect wrong value since there is
+ * no proper infrastructure yet and the feature is just emulated.
+ */
+ obj->v[0] = 0;
+
+ kmem_cache_free(s, obj);
+ mod_delayed_work(system_wq, dwork, HZ * 5);
+}
+
+static void workfn_kmalloc_obj(struct work_struct *work)
+{
+ struct object *obj;
+ struct delayed_work *dwork = (struct delayed_work *)work;
+
+ obj = kmalloc(sizeof(*obj), GFP_KERNEL);
+
+ obj->v[0] = 7;
+ /*
+ * Need one more access to detect wrong value since there is
+ * no proper infrastructure yet and the feature is just emulated.
+ */
+ obj->v[0] = 0;
+
+ kfree(obj);
+ mod_delayed_work(system_wq, dwork, HZ * 5);
+}
+
+static int __init vchecker_test_init(void)
+{
+ s = kmem_cache_create("vchecker_test",
+ sizeof(struct object), 0, SLAB_NOLEAKTRACE, NULL);
+ if (!s)
+ return 1;
+
+ old_obj = kmem_cache_alloc(s, GFP_KERNEL);
+ if (!old_obj) {
+ kmem_cache_destroy(s);
+ return 1;
+ }
+
+ INIT_DELAYED_WORK(&dwork_old_obj, workfn_old_obj);
+ INIT_DELAYED_WORK(&dwork_new_obj, workfn_new_obj);
+ INIT_DELAYED_WORK(&dwork_kmalloc_obj, workfn_kmalloc_obj);
+
+ mod_delayed_work(system_wq, &dwork_old_obj, HZ * 5);
+ mod_delayed_work(system_wq, &dwork_new_obj, HZ * 5);
+ mod_delayed_work(system_wq, &dwork_kmalloc_obj, HZ * 5);
+
+ return 0;
+}
+
+static void __exit vchecker_test_fini(void)
+{
+ cancel_delayed_work_sync(&dwork_old_obj);
+ cancel_delayed_work_sync(&dwork_new_obj);
+ cancel_delayed_work_sync(&dwork_kmalloc_obj);
+
+ kmem_cache_free(s, old_obj);
+ kmem_cache_destroy(s);
+}
+
+
+module_init(vchecker_test_init);
+module_exit(vchecker_test_fini)
+
+MODULE_LICENSE("GPL");
+
--
2.7.4
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