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authorArnd Bergmann <arnd@arndb.de>2018-06-19 13:14:57 -0700
committerMasahiro Yamada <yamada.masahiro@socionext.com>2018-06-25 23:21:13 +0900
commitbee20031772af3debe8cbaa234528f24c7892e8f (patch)
tree89dda7f20d8320f1c93f20d2adae124c3133cff7
parent8793bb7f4a9dd1396575d2e9337d331662cb7555 (diff)
disable -Wattribute-alias warning for SYSCALL_DEFINEx()
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> Tested-by: Christophe Leroy <christophe.leroy@c-s.fr> Tested-by: Stafford Horne <shorne@gmail.com> Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
-rw-r--r--include/linux/compat.h8
-rw-r--r--include/linux/syscalls.h4
2 files changed, 11 insertions, 1 deletions
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 */