It is useful to manually copy metadata in order to describe the effects
of memmove()-like logic in uninstrumented code or inline asm. Introduce
kmsan_memmove_metadata() for this purpose.

Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
---
 include/linux/kmsan-checks.h | 14 ++++++++++++++
 mm/kmsan/hooks.c             | 11 +++++++++++
 2 files changed, 25 insertions(+)

diff --git a/include/linux/kmsan-checks.h b/include/linux/kmsan-checks.h
index c4cae333deec..5218973f0ad0 100644
--- a/include/linux/kmsan-checks.h
+++ b/include/linux/kmsan-checks.h
@@ -61,6 +61,17 @@ void kmsan_check_memory(const void *address, size_t size);
 void kmsan_copy_to_user(void __user *to, const void *from, size_t to_copy,
 			size_t left);
 
+/**
+ * kmsan_memmove_metadata() - Copy kernel memory range metadata.
+ * @dst: start of the destination kernel memory range.
+ * @src: start of the source kernel memory range.
+ * @n:   size of the memory ranges.
+ *
+ * KMSAN will treat the destination range as if its contents were memmove()d
+ * from the source range.
+ */
+void kmsan_memmove_metadata(void *dst, const void *src, size_t n);
+
 #else
 
 static inline void kmsan_poison_memory(const void *address, size_t size,
@@ -77,6 +88,9 @@ static inline void kmsan_copy_to_user(void __user *to, const void *from,
 				      size_t to_copy, size_t left)
 {
 }
+static inline void kmsan_memmove_metadata(void *dst, const void *src, size_t n)
+{
+}
 
 #endif
 
diff --git a/mm/kmsan/hooks.c b/mm/kmsan/hooks.c
index eafc45f937eb..4d477a0a356c 100644
--- a/mm/kmsan/hooks.c
+++ b/mm/kmsan/hooks.c
@@ -286,6 +286,17 @@ void kmsan_copy_to_user(void __user *to, const void *from, size_t to_copy,
 }
 EXPORT_SYMBOL(kmsan_copy_to_user);
 
+void kmsan_memmove_metadata(void *dst, const void *src, size_t n)
+{
+	if (!kmsan_enabled || kmsan_in_runtime())
+		return;
+
+	kmsan_enter_runtime();
+	kmsan_internal_memmove_metadata(dst, (void *)src, n);
+	kmsan_leave_runtime();
+}
+EXPORT_SYMBOL(kmsan_memmove_metadata);
+
 /* Helper function to check an URB. */
 void kmsan_handle_urb(const struct urb *urb, bool is_out)
 {
-- 
2.41.0

On Tue, Nov 21, 2023 at 11:07 PM Ilya Leoshkevich <iii@linux.ibm.com> wrote:
>
> It is useful to manually copy metadata in order to describe the effects
> of memmove()-like logic in uninstrumented code or inline asm. Introduce
> kmsan_memmove_metadata() for this purpose.
>
> Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
> ---
>  include/linux/kmsan-checks.h | 14 ++++++++++++++
>  mm/kmsan/hooks.c             | 11 +++++++++++
>  2 files changed, 25 insertions(+)
>
> diff --git a/include/linux/kmsan-checks.h b/include/linux/kmsan-checks.h
> index c4cae333deec..5218973f0ad0 100644
> --- a/include/linux/kmsan-checks.h
> +++ b/include/linux/kmsan-checks.h
> @@ -61,6 +61,17 @@ void kmsan_check_memory(const void *address, size_t size);
>  void kmsan_copy_to_user(void __user *to, const void *from, size_t to_copy,
>                         size_t left);
>
> +/**
> + * kmsan_memmove_metadata() - Copy kernel memory range metadata.
> + * @dst: start of the destination kernel memory range.
> + * @src: start of the source kernel memory range.
> + * @n:   size of the memory ranges.
> + *
> + * KMSAN will treat the destination range as if its contents were memmove()d
> + * from the source range.
> + */
> +void kmsan_memmove_metadata(void *dst, const void *src, size_t n);

As noted in patch 18/33, I am pretty sure we shouldn't need this function.