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...

From: Nathan Chancellor

Date: Thu May 28 2026 - 12:52:14 EST

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@xxxxxxxxx/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@xxxxxxxxx/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@xxxxxxxxx>
> > | Closes: https://lore.kernel.org/oe-kbuild-all/202605281540.qUDQmxib-lkp@xxxxxxxxx/
> >
> > 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