Re: [PATCH 1/5] include/linux: Add instrumented.h infrastructure

On Mon, Jan 20, 2020 at 3:45 PM Dmitry Vyukov [off-list ref] wrote:

On Mon, Jan 20, 2020 at 3:19 PM Marco Elver [off-list ref] wrote:

quoted

This adds instrumented.h, which provides generic wrappers for memory
access instrumentation that the compiler cannot emit for various
sanitizers. Currently this unifies KASAN and KCSAN instrumentation. In
future this will also include KMSAN instrumentation.

Note that, copy_{to,from}_user require special instrumentation,
providing hooks before and after the access, since we may need to know
the actual bytes accessed (currently this is relevant for KCSAN, and is
also relevant in future for KMSAN).

Suggested-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Marco Elver <elver@google.com>
---
 include/linux/instrumented.h | 153 +++++++++++++++++++++++++++++++++++
 1 file changed, 153 insertions(+)
 create mode 100644 include/linux/instrumented.h

diff --git a/include/linux/instrumented.h b/include/linux/instrumented.h
new file mode 100644
index 000000000000..9f83c8520223
--- /dev/null
+++ b/include/linux/instrumented.h

@@ -0,0 +1,153 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+/*
+ * This header provides generic wrappers for memory access instrumentation that
+ * the compiler cannot emit for: KASAN, KCSAN.
+ */
+#ifndef _LINUX_INSTRUMENTED_H
+#define _LINUX_INSTRUMENTED_H
+
+#include <linux/compiler.h>
+#include <linux/kasan-checks.h>
+#include <linux/kcsan-checks.h>
+#include <linux/types.h>
+
+/**
+ * instrument_read - instrument regular read access
+ *
+ * Instrument a regular read access. The instrumentation should be inserted
+ * before the actual read happens.
+ *
+ * @ptr address of access
+ * @size size of access
+ */

Based on offline discussion, that's what we add for KMSAN:

quoted

+static __always_inline void instrument_read(const volatile void *v, size_t size)
+{
+       kasan_check_read(v, size);
+       kcsan_check_read(v, size);

KMSAN: nothing

KMSAN also has instrumentation in
copy_to_user_page/copy_from_user_page. Do we need to do anything for
KASAN/KCSAN for these functions?