From: Christophe LEROY <christophe.leroy@c-s.fr>
To: Paul Burton <paul.burton@mips.com>, linux-kbuild@vger.kernel.org
Cc: Mauro Carvalho Chehab <mchehab@kernel.org>,
linux-mips@linux-mips.org, Arnd Bergmann <arnd@arndb.de>,
Ingo Molnar <mingo@kernel.org>, Matthew Wilcox <matthew@wil.cx>,
Thomas Gleixner <tglx@linutronix.de>,
Douglas Anderson <dianders@chromium.org>,
Josh Poimboeuf <jpoimboe@redhat.com>,
Andrew Morton <akpm@linux-foundation.org>,
Matthias Kaehlcke <mka@chromium.org>,
He Zhe <zhe.he@windriver.com>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Michal Marek <michal.lkml@markovi.net>,
Khem Raj <raj.khem@gmail.com>, Al Viro <viro@zeniv.linux.org.uk>,
Stafford Horne <shorne@gmail.com>,
Gideon Israel Dsouza <gidisrael@gmail.com>,
Masahiro Yamada <yamada.masahiro@socionext.com>,
Kees Cook <keescook@chromium.org>,
Michael Ellerman <mpe@ellerman.id.au>,
Heiko Carstens <heiko.carstens@de.ibm.com>,
linux-kernel@vger.kernel.org, Paul Mackerras <paulus@samba.org>,
linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH 2/3] disable -Wattribute-alias warning for SYSCALL_DEFINEx()
Date: Mon, 18 Jun 2018 09:01:21 +0200 [thread overview]
Message-ID: <8b6f684a-38d4-c757-ce0f-fdb2e0a3476b@c-s.fr> (raw)
In-Reply-To: <20180616005323.7938-3-paul.burton@mips.com>
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 <paul.burton@mips.com>
> Cc: Michal Marek <michal.lkml@markovi.net>
> Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
> Cc: Douglas Anderson <dianders@chromium.org>
> Cc: Al Viro <viro@zeniv.linux.org.uk>
> Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
> Cc: Mauro Carvalho Chehab <mchehab@kernel.org>
> Cc: Matthew Wilcox <matthew@wil.cx>
> Cc: Matthias Kaehlcke <mka@chromium.org>
> Cc: Arnd Bergmann <arnd@arndb.de>
> Cc: Ingo Molnar <mingo@kernel.org>
> Cc: Josh Poimboeuf <jpoimboe@redhat.com>
> Cc: Kees Cook <keescook@chromium.org>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Gideon Israel Dsouza <gidisrael@gmail.com>
> Cc: Christophe Leroy <christophe.leroy@c-s.fr>
> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
> Cc: Paul Mackerras <paulus@samba.org>
> Cc: Michael Ellerman <mpe@ellerman.id.au>
> Cc: Stafford Horne <shorne@gmail.com>
> Cc: Khem Raj <raj.khem@gmail.com>
> Cc: He Zhe <zhe.he@windriver.com>
> 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 <christophe.leroy@c-s.fr>
> ---
>
> include/linux/compat.h | 8 +++++++-
> include/linux/syscalls.h | 4 ++++
> 2 files changed, 11 insertions(+), 1 deletion(-)
>
> diff --git a/include/linux/compat.h b/include/linux/compat.h
> index b1a5562b3215..c68acc47da57 100644
> --- a/include/linux/compat.h
> +++ b/include/linux/compat.h
> @@ -72,6 +72,9 @@
> */
> #ifndef COMPAT_SYSCALL_DEFINEx
> #define COMPAT_SYSCALL_DEFINEx(x, name, ...) \
> + __diag_push(); \
> + __diag_ignore(GCC, 8, "-Wattribute-alias", \
> + "Type aliasing is used to sanitize syscall arguments");\
> asmlinkage long compat_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__)); \
> asmlinkage long compat_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__)) \
> __attribute__((alias(__stringify(__se_compat_sys##name)))); \
> @@ -80,8 +83,11 @@
> asmlinkage long __se_compat_sys##name(__MAP(x,__SC_LONG,__VA_ARGS__)); \
> asmlinkage long __se_compat_sys##name(__MAP(x,__SC_LONG,__VA_ARGS__)) \
> { \
> - return __do_compat_sys##name(__MAP(x,__SC_DELOUSE,__VA_ARGS__));\
> + long ret = __do_compat_sys##name(__MAP(x,__SC_DELOUSE,__VA_ARGS__));\
> + __MAP(x,__SC_TEST,__VA_ARGS__); \
> + return ret; \
> } \
> + __diag_pop(); \
> static inline long __do_compat_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__))
> #endif /* COMPAT_SYSCALL_DEFINEx */
>
> diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
> index 73810808cdf2..a368a68cb667 100644
> --- a/include/linux/syscalls.h
> +++ b/include/linux/syscalls.h
> @@ -231,6 +231,9 @@ static inline int is_syscall_trace_event(struct trace_event_call *tp_event)
> */
> #ifndef __SYSCALL_DEFINEx
> #define __SYSCALL_DEFINEx(x, name, ...) \
> + __diag_push(); \
> + __diag_ignore(GCC, 8, "-Wattribute-alias", \
> + "Type aliasing is used to sanitize syscall arguments");\
> asmlinkage long sys##name(__MAP(x,__SC_DECL,__VA_ARGS__)) \
> __attribute__((alias(__stringify(__se_sys##name)))); \
> ALLOW_ERROR_INJECTION(sys##name, ERRNO); \
> @@ -243,6 +246,7 @@ static inline int is_syscall_trace_event(struct trace_event_call *tp_event)
> __PROTECT(x, ret,__MAP(x,__SC_ARGS,__VA_ARGS__)); \
> return ret; \
> } \
> + __diag_pop(); \
> static inline long __do_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__))
> #endif /* __SYSCALL_DEFINEx */
>
>
next prev parent reply other threads:[~2018-06-18 7:01 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-06-16 0:53 [PATCH 0/3] Resolve -Wattribute-alias warnings from SYSCALL_DEFINEx() Paul Burton
2018-06-16 0:53 ` [PATCH 1/3] kbuild: add macro for controlling warnings to linux/compiler.h Paul Burton
2018-06-18 7:01 ` Christophe LEROY
2018-06-19 17:34 ` Masahiro Yamada
2018-06-19 19:02 ` Paul Burton
2018-06-19 20:14 ` [PATCH v2 0/3] Resolve -Wattribute-alias warnings from SYSCALL_DEFINEx() Paul Burton
2018-06-19 20:14 ` [PATCH v2 1/3] kbuild: add macro for controlling warnings to linux/compiler.h Paul Burton
2018-06-20 23:17 ` Masahiro Yamada
2018-06-19 20:14 ` [PATCH v2 2/3] disable -Wattribute-alias warning for SYSCALL_DEFINEx() Paul Burton
2018-06-19 20:14 ` [PATCH v2 3/3] powerpc: Remove -Wattribute-alias pragmas Paul Burton
2018-06-20 13:40 ` Christophe LEROY
2018-06-23 8:40 ` [PATCH v2 0/3] Resolve -Wattribute-alias warnings from SYSCALL_DEFINEx() Masahiro Yamada
2018-06-20 23:21 ` [PATCH 1/3] kbuild: add macro for controlling warnings to linux/compiler.h Masahiro Yamada
2018-06-21 0:02 ` Paul Burton
2018-06-16 0:53 ` [PATCH 2/3] disable -Wattribute-alias warning for SYSCALL_DEFINEx() Paul Burton
2018-06-18 7:01 ` Christophe LEROY [this message]
2018-06-16 0:53 ` [PATCH 3/3] Revert "powerpc: fix build failure by disabling attribute-alias warning in pci_32" Paul Burton
2018-06-18 7:01 ` Christophe LEROY
2018-06-19 13:01 ` Michael Ellerman
2018-06-17 1:11 ` [PATCH 0/3] Resolve -Wattribute-alias warnings from SYSCALL_DEFINEx() Stafford Horne
2018-06-18 7:00 ` Christophe LEROY
2018-06-18 13:05 ` Arnd Bergmann
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