| Message ID | 20171205160651.2920270-1-arnd@arndb.de |
|---|---|
| State | New |
| Headers | show |
| Series | [1/2,RFC] kbuild: add macro for controlling warnings to linux/compiler.h | expand |
On Tue, Dec 05, 2017 at 05:06:31PM +0100, Arnd Bergmann wrote: > 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. > > Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82435 > Signed-off-by: Arnd Bergmann <arnd@arndb.de> Hi Arnd, What ever happened to this patch? I am compiline the kernel with the new OpenRISC GCC backend port https://github.com/stffrdhrn/gcc/commits/or1k-port, which is based on gcc 9.0.0 and seeing similar 'alias between functions of incompatible types' warnings. I found this old patch which seems will fix the issue, but it seems to not have been merged. Did we find another solution? Case in point, when I build x86 64 on gcc 8.1.1, I am not seeing the warnings. Is this not an issue for x86? -Stafford
diff --git a/include/linux/compat.h b/include/linux/compat.h index 1165036d091f..27b4a429df77 100644 --- a/include/linux/compat.h +++ b/include/linux/compat.h @@ -49,14 +49,19 @@ COMPAT_SYSCALL_DEFINEx(6, _##name, __VA_ARGS__) #define COMPAT_SYSCALL_DEFINEx(x, name, ...) \ + __diag_push(); \ + __diag_ignore(GCC_8, "-Wattribute-alias"); \ asmlinkage long compat_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__))\ __attribute__((alias(__stringify(compat_SyS##name)))); \ static inline long C_SYSC##name(__MAP(x,__SC_DECL,__VA_ARGS__));\ asmlinkage long compat_SyS##name(__MAP(x,__SC_LONG,__VA_ARGS__));\ asmlinkage long compat_SyS##name(__MAP(x,__SC_LONG,__VA_ARGS__))\ { \ - return C_SYSC##name(__MAP(x,__SC_DELOUSE,__VA_ARGS__)); \ + long ret = C_SYSC##name(__MAP(x,__SC_DELOUSE,__VA_ARGS__));\ + __MAP(x,__SC_TEST,__VA_ARGS__); \ + return ret; \ } \ + __diag_pop(); \ static inline long C_SYSC##name(__MAP(x,__SC_DECL,__VA_ARGS__)) #ifdef CONFIG_COMPAT diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h index 4df16a70b0d7..dcf6ceabda44 100644 --- a/include/linux/syscalls.h +++ b/include/linux/syscalls.h @@ -208,6 +208,8 @@ static inline int is_syscall_trace_event(struct trace_event_call *tp_event) #define __PROTECT(...) asmlinkage_protect(__VA_ARGS__) #define __SYSCALL_DEFINEx(x, name, ...) \ + __diag_push(); \ + __diag_ignore(GCC_8, "-Wattribute-alias"); \ asmlinkage long sys##name(__MAP(x,__SC_DECL,__VA_ARGS__)) \ __attribute__((alias(__stringify(SyS##name)))); \ static inline long SYSC##name(__MAP(x,__SC_DECL,__VA_ARGS__)); \ @@ -219,6 +221,7 @@ 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 SYSC##name(__MAP(x,__SC_DECL,__VA_ARGS__)) /*
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. Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82435 Signed-off-by: Arnd Bergmann <arnd@arndb.de> --- include/linux/compat.h | 7 ++++++- include/linux/syscalls.h | 3 +++ 2 files changed, 9 insertions(+), 1 deletion(-) -- 2.9.0