linux-kernel - [PATCH v2 6/6] ARM: uaccess: remove const to avoid duplicate specifier

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Date:   Sun, 25 Mar 2018 20:09:59 +0200
From:   Stefan Agner <stefan@...er.ch>
To:     linux@...linux.org.uk, ard.biesheuvel@...aro.org, arnd@...db.de
Cc:     robin.murphy@....com, nicolas.pitre@...aro.org,
        marc.zyngier@....com, behanw@...verseincode.com,
        keescook@...omium.org, Bernhard.Rosenkranzer@...aro.org,
        mka@...omium.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, Stefan Agner <stefan@...er.ch>
Subject: [PATCH v2 6/6] ARM: uaccess: remove const to avoid duplicate specifier

Some users of get_user use the macro with an argument p which
is already specified as static. When using clang this leads to
a duplicate specifier:
    CC      arch/arm/kernel/process.o
  In file included from init/do_mounts.c:15:
  In file included from ./include/linux/tty.h:7:
  In file included from ./include/uapi/linux/termios.h:6:
  In file included from ./arch/arm/include/generated/uapi/asm/termios.h:1:
  ./include/asm-generic/termios.h:25:6: warning: duplicate 'const' declaration
          specifier [-Wduplicate-decl-specifier]
          if (get_user(tmp, &termio->c_iflag) < 0)
              ^
  ./arch/arm/include/asm/uaccess.h:195:3: note: expanded from macro 'get_user'
                  __get_user_check(x, p);                                 \
                  ^
  ./arch/arm/include/asm/uaccess.h:155:12: note: expanded from macro
          '__get_user_check'
                  register const typeof(*(p)) __user *__p asm("r0") = (p);\

Remove the const attribute from the register declaration
to avoid the duplicate const specifier. In a test with ptrace.c
and traps.c (both using get_user with non-const arguments for p)
the generated code was exactly the same.

Signed-off-by: Stefan Agner <stefan@...er.ch>
---
Similar issue has already been discussed here:
https://patchwork.kernel.org/patch/9693821/

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

diff --git a/arch/arm/include/asm/uaccess.h b/arch/arm/include/asm/uaccess.h
index 0bf2347495f1..3d614e90c19f 100644
--- a/arch/arm/include/asm/uaccess.h
+++ b/arch/arm/include/asm/uaccess.h
@@ -152,7 +152,7 @@ extern int __get_user_64t_4(void *);
 #define __get_user_check(x, p)						\
 	({								\
 		unsigned long __limit = current_thread_info()->addr_limit - 1; \
-		register const typeof(*(p)) __user *__p asm("r0") = (p);\
+		register typeof(*(p)) __user *__p asm("r0") = (p);	\
 		register typeof(x) __r2 asm("r2");			\
 		register unsigned long __l asm("r1") = __limit;		\
 		register int __e asm("r0");				\
-- 
2.16.2