[PATCH 01/17] mm/ksw: add build system support

[Jinchao Wang <wangjinchao600@gmail.com>]

Add Kconfig and Makefile infrastructure for KStackWatch, a real-time tool
for debugging kernel stack corruption.

The implementation is located under `mm/kstackwatch/`.

Signed-off-by: Jinchao Wang <wangjinchao600@gmail.com>
---
 mm/Kconfig.debug             | 10 ++++++++++
 mm/Makefile                  |  1 +
 mm/kstackwatch/Makefile      |  2 ++
 mm/kstackwatch/kernel.c      | 24 ++++++++++++++++++++++++
 mm/kstackwatch/kstackwatch.h |  5 +++++
 mm/kstackwatch/stack.c       |  1 +
 mm/kstackwatch/watch.c       |  1 +
 7 files changed, 44 insertions(+)
 create mode 100644 mm/kstackwatch/Makefile
 create mode 100644 mm/kstackwatch/kernel.c
 create mode 100644 mm/kstackwatch/kstackwatch.h
 create mode 100644 mm/kstackwatch/stack.c
 create mode 100644 mm/kstackwatch/watch.c

diff --git a/mm/Kconfig.debug b/mm/Kconfig.debug
index 32b65073d0cc..c2cc8c7b595f 100644
--- a/mm/Kconfig.debug
+++ b/mm/Kconfig.debug
@@ -309,3 +309,13 @@ config PER_VMA_LOCK_STATS
 	  overhead in the page fault path.
 
 	  If in doubt, say N.
+
+config KSTACK_WATCH
+	tristate "Kernel Stack Watch"
+	depends on STACKPROTECTOR && HAVE_HW_BREAKPOINT && KPROBES && FPROBE
+	help
+	  A lightweight real-time debugging tool to detect stack corruption.
+	  It can watch either the canary or local variable and tracks
+	  the recursive depth of the monitored function.
+
+	  If unsure, say N.
diff --git a/mm/Makefile b/mm/Makefile
index ef54aa615d9d..665c9f2bf987 100644
--- a/mm/Makefile
+++ b/mm/Makefile
@@ -92,6 +92,7 @@ obj-$(CONFIG_PAGE_POISONING) += page_poison.o
 obj-$(CONFIG_KASAN)	+= kasan/
 obj-$(CONFIG_KFENCE) += kfence/
 obj-$(CONFIG_KMSAN)	+= kmsan/
+obj-$(CONFIG_KSTACK_WATCH)	+= kstackwatch/
 obj-$(CONFIG_FAILSLAB) += failslab.o
 obj-$(CONFIG_FAIL_PAGE_ALLOC) += fail_page_alloc.o
 obj-$(CONFIG_MEMTEST)		+= memtest.o
diff --git a/mm/kstackwatch/Makefile b/mm/kstackwatch/Makefile
new file mode 100644
index 000000000000..84a46cb9a766
--- /dev/null
+++ b/mm/kstackwatch/Makefile
@@ -0,0 +1,2 @@
+obj-$(CONFIG_KSTACK_WATCH)	+= kstackwatch.o
+kstackwatch-y := kernel.o stack.o watch.o
diff --git a/mm/kstackwatch/kernel.c b/mm/kstackwatch/kernel.c
new file mode 100644
index 000000000000..93379a0a0f7e
--- /dev/null
+++ b/mm/kstackwatch/kernel.c
@@ -0,0 +1,24 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/module.h>
+
+MODULE_AUTHOR("Jinchao Wang");
+MODULE_DESCRIPTION("Kernel Stack Watch");
+MODULE_LICENSE("GPL");
+
+static int __init kstackwatch_init(void)
+{
+	pr_info("KSW: module loaded\n");
+	pr_info("KSW: usage:\n");
+	pr_info("KSW: echo 'function+ip_offset[+depth] [local_var_offset:local_var_len]' > /proc/kstackwatch\n");
+
+	return 0;
+}
+
+static void __exit kstackwatch_exit(void)
+{
+	pr_info("KSW: Module unloaded\n");
+}
+
+module_init(kstackwatch_init);
+module_exit(kstackwatch_exit);
diff --git a/mm/kstackwatch/kstackwatch.h b/mm/kstackwatch/kstackwatch.h
new file mode 100644
index 000000000000..0273ef478a26
--- /dev/null
+++ b/mm/kstackwatch/kstackwatch.h
@@ -0,0 +1,5 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _KSTACKWATCH_H
+#define _KSTACKWATCH_H
+
+#endif /* _KSTACKWATCH_H */
diff --git a/mm/kstackwatch/stack.c b/mm/kstackwatch/stack.c
new file mode 100644
index 000000000000..cec594032515
--- /dev/null
+++ b/mm/kstackwatch/stack.c
@@ -0,0 +1 @@
+// SPDX-License-Identifier: GPL-2.0
diff --git a/mm/kstackwatch/watch.c b/mm/kstackwatch/watch.c
new file mode 100644
index 000000000000..cec594032515
--- /dev/null
+++ b/mm/kstackwatch/watch.c
@@ -0,0 +1 @@
+// SPDX-License-Identifier: GPL-2.0
-- 
2.43.0