From: Arnd Bergmann <a...@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.bur...@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 <a...@arndb.de>
Signed-off-by: Paul Burton <paul.bur...@mips.com>
Cc: Michal Marek <michal.l...@markovi.net>
Cc: Masahiro Yamada <yamada.masah...@socionext.com>
Cc: Douglas Anderson <diand...@chromium.org>
Cc: Al Viro <v...@zeniv.linux.org.uk>
Cc: Heiko Carstens <heiko.carst...@de.ibm.com>
Cc: Mauro Carvalho Chehab <mche...@kernel.org>
Cc: Matthew Wilcox <matt...@wil.cx>
Cc: Matthias Kaehlcke <m...@chromium.org>
Cc: Arnd Bergmann <a...@arndb.de>
Cc: Ingo Molnar <mi...@kernel.org>
Cc: Josh Poimboeuf <jpoim...@redhat.com>
Cc: Kees Cook <keesc...@chromium.org>
Cc: Andrew Morton <a...@linux-foundation.org>
Cc: Thomas Gleixner <t...@linutronix.de>
Cc: Gideon Israel Dsouza <gidisr...@gmail.com>
Cc: Christophe Leroy <christophe.le...@c-s.fr>
Cc: Benjamin Herrenschmidt <b...@kernel.crashing.org>
Cc: Paul Mackerras <pau...@samba.org>
Cc: Michael Ellerman <m...@ellerman.id.au>
Cc: Stafford Horne <sho...@gmail.com>
Cc: Khem Raj <raj.k...@gmail.com>
Cc: He Zhe <zhe...@windriver.com>
Cc: linux-kbu...@vger.kernel.org
Cc: linux-ker...@vger.kernel.org
Cc: linux-m...@linux-mips.org
Cc: linuxppc-dev@lists.ozlabs.org
---
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 */
--
2.17.1
