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Patch "ARM: fix put_user() for gcc-8" has been added to the 4.4-stable tree

Message ID 15326847436103@kroah.com (mailing list archive)
State New, archived
Headers show
Series Patch "ARM: fix put_user() for gcc-8" has been added to the 4.4-stable tree | expand

Commit Message

Greg Kroah-Hartman July 27, 2018, 9:45 a.m. UTC
This is a note to let you know that I've just added the patch titled

    ARM: fix put_user() for gcc-8

to the 4.4-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     arm-fix-put_user-for-gcc-8.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


From arnd@arndb.de  Fri Jul 27 11:21:29 2018
From: Arnd Bergmann <arnd@arndb.de>
Date: Thu, 26 Jul 2018 10:13:23 +0200
Subject: ARM: fix put_user() for gcc-8
To: stable@vger.kernel.org
Cc: gregkh@linuxfoundation.org, Arnd Bergmann <arnd@arndb.de>, Russell King <linux@arm.linux.org.uk>, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org
Message-ID: <20180726081358.3829157-2-arnd@arndb.de>

From: Arnd Bergmann <arnd@arndb.de>

Building kernels before linux-4.7 with gcc-8 results in many build failures
when gcc triggers a check that was meant to catch broken compilers:

/tmp/ccCGMQmS.s:648: Error: .err encountered

According to the discussion in the gcc bugzilla, a local "register
asm()" variable is still supposed to be the correct way to force an
inline assembly to use a particular register, but marking it 'const'
lets the compiler do optimizations that break that, i.e the compiler is
free to treat the variable as either 'const' or 'register' in that case.

Upstream commit 9f73bd8bb445 ("ARM: uaccess: remove put_user() code
duplication") fixed this problem in linux-4.8 as part of a larger change,
but seems a little too big to be backported to 4.4.

Let's take the simplest fix and change only the one broken line in the
same way as newer kernels.

Suggested-by: Bernd Edlinger <bernd.edlinger@hotmail.de>
Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85745
Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86673
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 arch/arm/include/asm/uaccess.h |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)



Patches currently in stable-queue which might be from arnd@arndb.de are

queue-4.4/arm-fix-put_user-for-gcc-8.patch
queue-4.4/turn-off-wattribute-alias.patch
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Patch

--- a/arch/arm/include/asm/uaccess.h
+++ b/arch/arm/include/asm/uaccess.h
@@ -251,7 +251,7 @@  extern int __put_user_8(void *, unsigned
 	({								\
 		unsigned long __limit = current_thread_info()->addr_limit - 1; \
 		const typeof(*(p)) __user *__tmp_p = (p);		\
-		register const typeof(*(p)) __r2 asm("r2") = (x);	\
+		register typeof(*(p)) __r2 asm("r2") = (x);	\
 		register const typeof(*(p)) __user *__p asm("r0") = __tmp_p; \
 		register unsigned long __l asm("r1") = __limit;		\
 		register int __e asm("r0");				\