linux-kernel - [PATCH 4.9 32/33] turn off -Wattribute-alias

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Message-Id: <20180727100828.853992212@linuxfoundation.org>
Date:   Fri, 27 Jul 2018 12:09:13 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Arnd Bergmann <arnd@...db.de>
Subject: [PATCH 4.9 32/33] turn off -Wattribute-alias

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Arnd Bergmann <arnd@...db.de>

Starting with gcc-8.1, we get a warning about all system call definitions,
which use an alias between functions with incompatible prototypes, e.g.:

In file included from ../mm/process_vm_access.c:19:
../include/linux/syscalls.h:211:18: warning: 'sys_process_vm_readv' alias between functions of incompatible types 'long int(pid_t,  const struct iovec *, long unsigned int,  const struct iovec *, long unsigned int,  long unsigned int)' {aka 'long int(int,  const struct iovec *, long unsigned int,  const struct iovec *, long unsigned int,  long unsigned int)'} and 'long int(long int,  long int,  long int,  long int,  long int,  long int)' [-Wattribute-alias]
  asmlinkage long sys##name(__MAP(x,__SC_DECL,__VA_ARGS__)) \
                  ^~~
../include/linux/syscalls.h:207:2: note: in expansion of macro '__SYSCALL_DEFINEx'
  __SYSCALL_DEFINEx(x, sname, __VA_ARGS__)
  ^~~~~~~~~~~~~~~~~
../include/linux/syscalls.h:201:36: note: in expansion of macro 'SYSCALL_DEFINEx'
 #define SYSCALL_DEFINE6(name, ...) SYSCALL_DEFINEx(6, _##name, __VA_ARGS__)
                                    ^~~~~~~~~~~~~~~
../mm/process_vm_access.c:300:1: note: in expansion of macro 'SYSCALL_DEFINE6'
 SYSCALL_DEFINE6(process_vm_readv, pid_t, pid, const struct iovec __user *, lvec,
 ^~~~~~~~~~~~~~~
../include/linux/syscalls.h:215:18: note: aliased declaration here
  asmlinkage long SyS##name(__MAP(x,__SC_LONG,__VA_ARGS__)) \
                  ^~~
../include/linux/syscalls.h:207:2: note: in expansion of macro '__SYSCALL_DEFINEx'
  __SYSCALL_DEFINEx(x, sname, __VA_ARGS__)
  ^~~~~~~~~~~~~~~~~
../include/linux/syscalls.h:201:36: note: in expansion of macro 'SYSCALL_DEFINEx'
 #define SYSCALL_DEFINE6(name, ...) SYSCALL_DEFINEx(6, _##name, __VA_ARGS__)
                                    ^~~~~~~~~~~~~~~
../mm/process_vm_access.c:300:1: note: in expansion of macro 'SYSCALL_DEFINE6'
 SYSCALL_DEFINE6(process_vm_readv, pid_t, pid, const struct iovec __user *, lvec,

This is really noisy and does not indicate a real problem. In the latest
mainline kernel, this was addressed by commit bee20031772a ("disable
-Wattribute-alias warning for SYSCALL_DEFINEx()"), which seems too invasive
to backport.

This takes a much simpler approach and just disables the warning across the
kernel.

Signed-off-by: Arnd Bergmann <arnd@...db.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 Makefile |    1 +
 1 file changed, 1 insertion(+)

--- a/Makefile
+++ b/Makefile
@@ -635,6 +635,7 @@ KBUILD_CFLAGS	+= $(call cc-disable-warni
 KBUILD_CFLAGS	+= $(call cc-disable-warning, format-truncation)
 KBUILD_CFLAGS	+= $(call cc-disable-warning, format-overflow)
 KBUILD_CFLAGS	+= $(call cc-disable-warning, int-in-bool-context)
+KBUILD_CFLAGS	+= $(call cc-disable-warning, attribute-alias)
 
 ifdef CONFIG_LD_DEAD_CODE_DATA_ELIMINATION
 KBUILD_CFLAGS	+= $(call cc-option,-ffunction-sections,)