[RFC v1] copy_{to,from}_user(): only inline when !__CHECKER__

From: Tycho Andersen
Date: Sun Dec 09 2018 - 15:45:12 EST

While working on some additional copy_to_user() checks for sparse, I
noticed that sparse's current copy_to_user() checks are not triggered. This
is because copy_to_user() is declared as __always_inline, and sparse
specifically looks for a call instruction to copy_to_user() when it tries
to apply the checks.

A quick fix is to explicitly not inline when __CHECKER__ is defined, so
that sparse will be able to analyze all the copy_{to,from}_user calls.
There may be some refactoring in sparse that we can do to fix this,
although it's not immediately obvious to me how, hence the RFC-ness of this

Signed-off-by: Tycho Andersen <tycho@xxxxxxxx>
include/linux/uaccess.h | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/include/linux/uaccess.h b/include/linux/uaccess.h
index efe79c1cdd47..f20a2d173e1f 100644
--- a/include/linux/uaccess.h
+++ b/include/linux/uaccess.h
@@ -140,7 +140,13 @@ extern unsigned long
_copy_to_user(void __user *, const void *, unsigned long);

-static __always_inline unsigned long __must_check
+#ifdef __CHECKER__
+#define uaccess_inline __attribute__((__noinline__))
+#define uaccess_inline __always_inline
+static uaccess_inline unsigned long __must_check
copy_from_user(void *to, const void __user *from, unsigned long n)
if (likely(check_copy_size(to, n, false)))
@@ -148,7 +154,7 @@ copy_from_user(void *to, const void __user *from, unsigned long n)
return n;

-static __always_inline unsigned long __must_check
+static uaccess_inline unsigned long __must_check
copy_to_user(void __user *to, const void *from, unsigned long n)
if (likely(check_copy_size(from, n, true)))