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: Thomas Weißschuh

Date: Thu May 28 2026 - 03:55:18 EST

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?


Thomas