Le 16/06/2018 à 02:53, Paul Burton a écrit :

From: Arnd Bergmann <arnd@arndb.de>

gcc-8 warns for every single definition of a system call entry
point, e.g.:

include/linux/compat.h:56:18: error: 'compat_sys_rt_sigprocmask' alias between functions of incompatible types 'long int(int,  compat_sigset_t *, compat_sigset_t *, compat_size_t)' {aka 'long int(int,  struct <anonymous> *, struct <anonymous> *, unsigned int)'} and 'long int(long int,  long int,  long int,  long int)' [-Werror=attribute-alias]
   asmlinkage long compat_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__))\
                   ^~~~~~~~~~
include/linux/compat.h:45:2: note: in expansion of macro 'COMPAT_SYSCALL_DEFINEx'
   COMPAT_SYSCALL_DEFINEx(4, _##name, __VA_ARGS__)
   ^~~~~~~~~~~~~~~~~~~~~~
kernel/signal.c:2601:1: note: in expansion of macro 'COMPAT_SYSCALL_DEFINE4'
  COMPAT_SYSCALL_DEFINE4(rt_sigprocmask, int, how, compat_sigset_t __user *, nset,
  ^~~~~~~~~~~~~~~~~~~~~~
include/linux/compat.h:60:18: note: aliased declaration here
   asmlinkage long compat_SyS##name(__MAP(x,__SC_LONG,__VA_ARGS__))\
                   ^~~~~~~~~~

The new warning seems reasonable in principle, but it doesn't
help us here, since we rely on the type mismatch to sanitize the
system call arguments. After I reported this as GCC PR82435, a new
-Wno-attribute-alias option was added that could be used to turn the
warning off globally on the command line, but I'd prefer to do it a
little more fine-grained.

Interestingly, turning a warning off and on again inside of
a single macro doesn't always work, in this case I had to add
an extra statement inbetween and decided to copy the __SC_TEST
one from the native syscall to the compat syscall macro.  See
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83256 for more details
about this.

[paul.burton@mips.com:
   - Rebase atop current master.
   - Split GCC & version arguments to __diag_ignore() in order to match
     changes to the preceding patch.
   - Add the comment argument to match the preceding patch.]

Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82435
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Paul Burton <redacted>
Cc: Michal Marek <redacted>
Cc: Masahiro Yamada <redacted>
Cc: Douglas Anderson <dianders@chromium.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Heiko Carstens <redacted>
Cc: Mauro Carvalho Chehab <mchehab@kernel.org>
Cc: Matthew Wilcox <redacted>
Cc: Matthias Kaehlcke <mka@chromium.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Josh Poimboeuf <redacted>
Cc: Kees Cook <redacted>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Thomas Gleixner <redacted>
Cc: Gideon Israel Dsouza <redacted>
Cc: Christophe Leroy <redacted>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <redacted>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Stafford Horne <shorne@gmail.com>
Cc: Khem Raj <redacted>
Cc: He Zhe <redacted>
Cc: linux-kbuild@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: linux-mips@linux-mips.org
Cc: linuxppc-dev@lists.ozlabs.org

Tested-by: Christophe Leroy <redacted>