From 8c8187d41b99acd4f2078d0fff6807e0eeb47407 Mon Sep 17 00:00:00 2001 From: Arnd Bergmann Date: Thu, 26 Jul 2018 10:13:23 +0200 Subject: [PATCH] ARM: fix put_user() for gcc-8 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 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 Signed-off-by: Greg Kroah-Hartman --- 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 292c3f88f..48decaa00 100644 --- a/arch/arm/include/asm/uaccess.h +++ b/arch/arm/include/asm/uaccess.h @@ -158,7 +158,7 @@ extern int __put_user_8(void *, unsigned long long); #define put_user(x,p) \ ({ \ unsigned long __limit = current_thread_info()->addr_limit - 1; \ - register const typeof(*(p)) __r2 asm("r2") = (x); \ + register typeof(*(p)) __r2 asm("r2") = (x); \ register const typeof(*(p)) __user *__p asm("r0") = (p);\ register unsigned long __l asm("r1") = __limit; \ register int __e asm("r0"); \