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>
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@ -72,6 +72,9 @@
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*/
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#ifndef COMPAT_SYSCALL_DEFINEx
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#define COMPAT_SYSCALL_DEFINEx(x, name, ...) \
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__diag_push(); \
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__diag_ignore(GCC, 8, "-Wattribute-alias", \
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"Type aliasing is used to sanitize syscall arguments");\
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asmlinkage long compat_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__)); \
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asmlinkage long compat_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__)) \
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__attribute__((alias(__stringify(__se_compat_sys##name)))); \
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@ -80,8 +83,11 @@
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asmlinkage long __se_compat_sys##name(__MAP(x,__SC_LONG,__VA_ARGS__)); \
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asmlinkage long __se_compat_sys##name(__MAP(x,__SC_LONG,__VA_ARGS__)) \
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{ \
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return __do_compat_sys##name(__MAP(x,__SC_DELOUSE,__VA_ARGS__));\
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long ret = __do_compat_sys##name(__MAP(x,__SC_DELOUSE,__VA_ARGS__));\
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__MAP(x,__SC_TEST,__VA_ARGS__); \
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return ret; \
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} \
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__diag_pop(); \
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static inline long __do_compat_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__))
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#endif /* COMPAT_SYSCALL_DEFINEx */
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@ -231,6 +231,9 @@ static inline int is_syscall_trace_event(struct trace_event_call *tp_event)
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*/
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#ifndef __SYSCALL_DEFINEx
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#define __SYSCALL_DEFINEx(x, name, ...) \
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__diag_push(); \
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__diag_ignore(GCC, 8, "-Wattribute-alias", \
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"Type aliasing is used to sanitize syscall arguments");\
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asmlinkage long sys##name(__MAP(x,__SC_DECL,__VA_ARGS__)) \
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__attribute__((alias(__stringify(__se_sys##name)))); \
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ALLOW_ERROR_INJECTION(sys##name, ERRNO); \
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@ -243,6 +246,7 @@ static inline int is_syscall_trace_event(struct trace_event_call *tp_event)
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__PROTECT(x, ret,__MAP(x,__SC_ARGS,__VA_ARGS__)); \
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return ret; \
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} \
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__diag_pop(); \
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static inline long __do_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__))
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#endif /* __SYSCALL_DEFINEx */
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