linux-kernel - [PATCH] sparse: use static inline for __chk_{user,io}

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Message-Id: <20200628072019.67107-1-luc.vanoostenryck@gmail.com>
Date:   Sun, 28 Jun 2020 09:20:19 +0200
From:   Luc Van Oostenryck <luc.vanoostenryck@...il.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     linux-kernel@...r.kernel.org,
        Luc Van Oostenryck <luc.vanoostenryck@...il.com>
Subject: [PATCH] sparse: use static inline for __chk_{user,io}_ptr()

__chk_user_ptr() & __chk_io_ptr() are dummy extern functions which
only exist to enforce the typechecking of __user or __iomem pointers
in macros when using sparse.

This typechecking is done by inserting a call to these functions.
But the presence of these calls can inhibit some simplifications
and so influence the result of sparse's analysis of context/locking.

Fix this by changing these calls into static inline calls with
an empty body.

Signed-off-by: Luc Van Oostenryck <luc.vanoostenryck@...il.com>
---
 include/linux/compiler_types.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/linux/compiler_types.h b/include/linux/compiler_types.h
index b67930216e45..a9b6699f3934 100644
--- a/include/linux/compiler_types.h
+++ b/include/linux/compiler_types.h
@@ -11,8 +11,8 @@
 # define __iomem	__attribute__((noderef, address_space(__iomem)))
 # define __percpu	__attribute__((noderef, address_space(__percpu)))
 # define __rcu		__attribute__((noderef, address_space(__rcu)))
-extern void __chk_user_ptr(const volatile void __user *);
-extern void __chk_io_ptr(const volatile void __iomem *);
+static inline void __chk_user_ptr(const volatile void __user *ptr) { }
+static inline void __chk_io_ptr(const volatile void __iomem *ptr) { }
 /* context/locking */
 # define __must_hold(x)	__attribute__((context(x,1,1)))
 # define __acquires(x)	__attribute__((context(x,0,1)))
-- 
2.27.0