linux-kernel - [PATCH 2/2] x86/mm: Fix sparse warnings in untagged

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Message-Id: <20221116004353.15052-3-kirill.shutemov@linux.intel.com>
Date:   Wed, 16 Nov 2022 03:43:53 +0300
From:   "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To:     kirill@...temov.name
Cc:     dave.hansen@...el.com, dave.hansen@...ux.intel.com,
        jejb@...ux.ibm.com, kirill.shutemov@...ux.intel.com,
        linux-kernel@...r.kernel.org, lkp@...el.com,
        martin.petersen@...cle.com, oe-kbuild-all@...ts.linux.dev,
        x86@...nel.org
Subject: [PATCH 2/2] x86/mm: Fix sparse warnings in untagged_ptr()

Linear Address Masking patchset triggered a lot of sparse warnings.

The root cause is that casting pointer to '__typeof__(*(ptr)) *' will
strip all sparse tags. The type has to be defined based on the pointer
type, not based on what the pointer points to.

Fix cast in untagged_ptr() and avoid __typeof__() usage in
get/put_user().

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
Reported-by: kernel test robot <lkp@...el.com>
---
 arch/x86/include/asm/uaccess.h | 10 +++-------
 1 file changed, 3 insertions(+), 7 deletions(-)

diff --git a/arch/x86/include/asm/uaccess.h b/arch/x86/include/asm/uaccess.h
index 1d2c79246681..bd92e1ee1c1a 100644
--- a/arch/x86/include/asm/uaccess.h
+++ b/arch/x86/include/asm/uaccess.h
@@ -43,7 +43,7 @@ DECLARE_STATIC_KEY_FALSE(tagged_addr_key);
 #define untagged_ptr(mm, ptr)	({					\
 	u64 __ptrval = (__force u64)(ptr);				\
 	__ptrval = untagged_addr(mm, __ptrval);				\
-	(__force __typeof__(*(ptr)) *)__ptrval;				\
+	(__force __typeof__(ptr))__ptrval;				\
 })
 #else
 #define untagged_addr(mm, addr)	(addr)
@@ -158,10 +158,8 @@ extern int __get_user_bad(void);
  */
 #define get_user(x,ptr)							\
 ({									\
-	__typeof__(*(ptr)) __user *__ptr_clean;				\
-	__ptr_clean = untagged_ptr(current->mm, ptr);			\
 	might_fault();							\
-	do_get_user_call(get_user,x,__ptr_clean);			\
+	do_get_user_call(get_user,x,untagged_ptr(current->mm, ptr));	\
 })
 
 /**
@@ -263,10 +261,8 @@ extern void __put_user_nocheck_8(void);
  * Return: zero on success, or -EFAULT on error.
  */
 #define put_user(x, ptr) ({						\
-	__typeof__(*(ptr)) __user *__ptr_clean;				\
-	__ptr_clean = untagged_ptr(current->mm, ptr);			\
 	might_fault();							\
-	do_put_user_call(put_user,x,__ptr_clean);			\
+	do_put_user_call(put_user,x,untagged_ptr(current->mm, ptr));	\
 })
 
 /**
-- 
2.38.0