linux-kernel - [PATCH AUTOSEL 4.9 28/29] s390/uaccess: avoid (false positive) compiler warnings

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Message-Id: <20191018220920.10545-28-sashal@kernel.org>
Date:   Fri, 18 Oct 2019 18:09:19 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Christian Borntraeger <borntraeger@...ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Sasha Levin <sashal@...nel.org>, linux-s390@...r.kernel.org
Subject: [PATCH AUTOSEL 4.9 28/29] s390/uaccess: avoid (false positive) compiler warnings

From: Christian Borntraeger <borntraeger@...ibm.com>

[ Upstream commit 062795fcdcb2d22822fb42644b1d76a8ad8439b3 ]

Depending on inlining decisions by the compiler, __get/put_user_fn
might become out of line. Then the compiler is no longer able to tell
that size can only be 1,2,4 or 8 due to the check in __get/put_user
resulting in false positives like

./arch/s390/include/asm/uaccess.h: In function ‘__put_user_fn’:
./arch/s390/include/asm/uaccess.h:113:9: warning: ‘rc’ may be used uninitialized in this function [-Wmaybe-uninitialized]
  113 |  return rc;
      |         ^~
./arch/s390/include/asm/uaccess.h: In function ‘__get_user_fn’:
./arch/s390/include/asm/uaccess.h:143:9: warning: ‘rc’ may be used uninitialized in this function [-Wmaybe-uninitialized]
  143 |  return rc;
      |         ^~

These functions are supposed to be always inlined. Mark it as such.

Signed-off-by: Christian Borntraeger <borntraeger@...ibm.com>
Signed-off-by: Vasily Gorbik <gor@...ux.ibm.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 arch/s390/include/asm/uaccess.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/s390/include/asm/uaccess.h b/arch/s390/include/asm/uaccess.h
index a7ef702201260..31b2913372b56 100644
--- a/arch/s390/include/asm/uaccess.h
+++ b/arch/s390/include/asm/uaccess.h
@@ -151,7 +151,7 @@ unsigned long __must_check __copy_to_user(void __user *to, const void *from,
 	__rc;							\
 })
 
-static inline int __put_user_fn(void *x, void __user *ptr, unsigned long size)
+static __always_inline int __put_user_fn(void *x, void __user *ptr, unsigned long size)
 {
 	unsigned long spec = 0x810000UL;
 	int rc;
@@ -181,7 +181,7 @@ static inline int __put_user_fn(void *x, void __user *ptr, unsigned long size)
 	return rc;
 }
 
-static inline int __get_user_fn(void *x, const void __user *ptr, unsigned long size)
+static __always_inline int __get_user_fn(void *x, const void __user *ptr, unsigned long size)
 {
 	unsigned long spec = 0x81UL;
 	int rc;
-- 
2.20.1