Re: [tip:timers/vdso 10/18] kernel/sys.c:2878:1: warning: alias and aliasee have different types 'long (unsigned int *, unsigned int *, void *)' and 'long (typeof (__builtin_choose_expr((__builtin_types_compatible_p(typeof ((unsigned int *)0), typeof (0LL)) || __builtin_types_compat...

[Nathan Chancellor <nathan@kernel.org>]

Hi Thomas,

On Thu, May 28, 2026 at 09:50:43AM +0200, Thomas Weißschuh wrote:
> On Thu, May 28, 2026 at 03:22:06PM +0800, kernel test robot wrote:
> > tree:   https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git timers/vdso
> > head:   034779fb06aba5bc45faf366922bd77e4d36543a
> > commit: 7158fc54b2c6f124eec0d7cd13bff69da0172e59 [10/18] vdso: Remove struct getcpu_cache
> > config: um-allnoconfig (https://download.01.org/0day-ci/archive/20260528/202605281540.qUDQmxib-lkp@intel.com/config)
> > compiler: clang version 23.0.0git (https://github.com/llvm/llvm-project 5bac06718f502014fade905512f1d26d578a18f3)
> > reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260528/202605281540.qUDQmxib-lkp@intel.com/reproduce)
> > 
> > If you fix the issue in a separate patch/commit (i.e. not just a new version of
> > the same patch/commit), kindly add following tags
> > | Reported-by: kernel test robot <lkp@intel.com>
> > | Closes: https://lore.kernel.org/oe-kbuild-all/202605281540.qUDQmxib-lkp@intel.com/
> > 
> > All warnings (new ones prefixed by >>):
> > 
> >    kernel/sys.c:1793:1: warning: alias and aliasee have different types 'long (unsigned int, struct rlimit *)' and 'long (typeof (__builtin_choose_expr((__builtin_types_compatible_p(typeof ((unsigned int)0), typeof (0LL)) || __builtin_types_compatible_p(typeof ((unsigned int)0), typeof (0ULL))), 0LL, 0L)), typeof (__builtin_choose_expr((__builtin_types_compatible_p(typeof ((struct rlimit *)0), typeof (0LL)) || __builtin_types_compatible_p(typeof ((struct rlimit *)0), typeof (0ULL))), 0LL, 0L)))' (aka 'long (long, long)') [-Wattribute-alias]
> 
> (...)
> 
> >    kernel/sys.c:1933:1: warning: alias and aliasee have different types 'long (int, struct rusage *)' and 'long (typeof (__builtin_choose_expr((__builtin_types_compatible_p(typeof ((int)0), typeof (0LL)) || __builtin_types_compatible_p(typeof ((int)0), typeof (0ULL))), 0LL, 0L)), typeof (__builtin_choose_expr((__builtin_types_compatible_p(typeof ((struct rusage *)0), typeof (0LL)) || __builtin_types_compatible_p(typeof ((struct rusage *)0), typeof (0ULL))), 0LL, 0L)))' (aka 'long (long, long)') [-Wattribute-alias]
> >    kernel/sys.c:1959:1: warning: alias and aliasee have different types 'long (int)' and 'long (typeof (__builtin_choose_expr((__builtin_types_compatible_p(typeof ((int)0), typeof (0LL)) || __builtin_types_compatible_p(typeof ((int)0), typeof (0ULL))), 0LL, 0L)))' (aka 'long (long)') [-Wattribute-alias]
> 
> (...)
> 
> >    kernel/sys.c:2517:1: warning: alias and aliasee have different types 'long (int, unsigned long, unsigned long, unsigned long, unsigned long)' and 'long (typeof (__builtin_choose_expr((__builtin_types_compatible_p(typeof ((int)0), typeof (0LL)) || __builtin_types_compatible_p(typeof ((int)0), typeof (0ULL))), 0LL, 0L)), typeof (__builtin_choose_expr((__builtin_types_compatible_p(typeof ((unsigned long)0), typeof (0LL)) || __builtin_types_compatible_p(typeof ((unsigned long)0), typeof (0ULL))), 0LL, 0L)), typeof (__builtin_choose_expr((__builtin_types_compatible_p(typeof ((unsigned long)0), typeof (0LL)) || __builtin_types_compatible_p(typeof ((unsigned long)0), typeof (0ULL))), 0LL, 0L)), typeof (__builtin_choose_expr((__builtin_types_compatible_p(typeof ((unsigned long)0), typeof (0LL)) || __builtin_types_compatible_p(typeof ((unsigned long)0), typeof (0ULL))), 0LL, 0L)), typeof (__builtin_choose_expr((__builtin_types_compatible_p(typeof ((unsigned long)0), typeof (0LL)) || __builtin_types_compatible_p(typeof ((unsigned long)0), typeof (0ULL))), 0LL, 0L)))' (aka 'long (long, long, long, long, long)') [-Wattribute-alias]
> 
> (...)
> 
> > >> kernel/sys.c:2878:1: warning: alias and aliasee have different types 'long (unsigned int *, unsigned int *, void *)' and 'long (typeof (__builtin_choose_expr((__builtin_types_compatible_p(typeof ((unsigned int *)0), typeof (0LL)) || __builtin_types_compatible_p(typeof ((unsigned int *)0), typeof (0ULL))), 0LL, 0L)), typeof (__builtin_choose_expr((__builtin_types_compatible_p(typeof ((unsigned int *)0), typeof (0LL)) || __builtin_types_compatible_p(typeof ((unsigned int *)0), typeof (0ULL))), 0LL, 0L)), typeof (__builtin_choose_expr((__builtin_types_compatible_p(typeof ((void *)0), typeof (0LL)) || __builtin_types_compatible_p(typeof ((void *)0), typeof (0ULL))), 0LL, 0L)))' (aka 'long (long, long, long)') [-Wattribute-alias]
> >     2878 | SYSCALL_DEFINE3(getcpu, unsigned __user *, cpup, unsigned __user *, nodep, void __user *, unused)
> >          | ^
> >    include/linux/syscalls.h:227:36: note: expanded from macro 'SYSCALL_DEFINE3'
> >      227 | #define SYSCALL_DEFINE3(name, ...) SYSCALL_DEFINEx(3, _##name, __VA_ARGS__)
> >          |                                    ^
> >    include/linux/syscalls.h:236:2: note: expanded from macro 'SYSCALL_DEFINEx'
> >      236 |         __SYSCALL_DEFINEx(x, sname, __VA_ARGS__)
> >          |         ^
> >    include/linux/syscalls.h:251:18: note: expanded from macro '__SYSCALL_DEFINEx'
> >      251 |                 __attribute__((alias(__stringify(__se_sys##name))));    \
> >          |                                ^
> >    kernel/sys.c:2878:1: note: aliasee is declared here
> >    include/linux/syscalls.h:227:36: note: expanded from macro 'SYSCALL_DEFINE3'
> >      227 | #define SYSCALL_DEFINE3(name, ...) SYSCALL_DEFINEx(3, _##name, __VA_ARGS__)
> >          |                                    ^
> >    include/linux/syscalls.h:236:2: note: expanded from macro 'SYSCALL_DEFINEx'
> >      236 |         __SYSCALL_DEFINEx(x, sname, __VA_ARGS__)
> >          |         ^
> >    include/linux/syscalls.h:255:18: note: expanded from macro '__SYSCALL_DEFINEx'
> >      255 |         asmlinkage long __se_sys##name(__MAP(x,__SC_LONG,__VA_ARGS__))  \
> >          |                         ^
> >    <scratch space>:132:1: note: expanded from here
> >      132 | __se_sys_getcpu
> >          | ^
> 
> (...)
> 
> > vim +2878 kernel/sys.c
> > 
> >   2877	
> > > 2878	SYSCALL_DEFINE3(getcpu, unsigned __user *, cpup, unsigned __user *, nodep, void __user *, unused)
> >   2879	{
> >   2880		int err = 0;
> >   2881		int cpu = raw_smp_processor_id();
> >   2882	
> >   2883		if (cpup)
> >   2884			err |= put_user(cpu, cpup);
> >   2885		if (nodep)
> >   2886			err |= put_user(cpu_to_node(cpu), nodep);
> >   2887		return err ? -EFAULT : 0;
> >   2888	}
> >   2889	
> 
> This warning is reported for  many/all system call definitions in this file.
> The *new* warning is reported as the prototype of the system call has
> changed and the warning is now slightly different from before.
> So this report can be disregarded in my opinion.
> 
> It might be good to figure out why this warning happens in general,
> but that shouldn't be urgent.
> 
> Also this patch is not in the current tip tree, but already released.
> Is there an issue with the bot testing the wrong code?

Sorry for the noise. This is from a compiler upgrade, as tip of tree
clang has implemented -Wattribute-alias like GCC, which means it needs
to be turned off in the same way:

  https://git.kernel.org/nathan/c/175db11786bde9061db526bf1ac5107d915f5163

I plan to send that to Linus soon.

-- 
Cheers,
Nathan