Re: [PATCH v2] vdso: Remove struct getcpu_cache

[H. Peter Anvin]

On October 13, 2025 7:06:55 AM PDT, Dave Hansen <dave.hansen@xxxxxxxxx> wrote:
>On 10/13/25 02:20, Thomas Weißschuh wrote:
>> -int __vdso_getcpu(unsigned int *cpu, unsigned int *node, struct getcpu_cache *unused);
>> -int __vdso_getcpu(unsigned int *cpu, unsigned int *node, struct getcpu_cache *unused)
>> +int __vdso_getcpu(unsigned int *cpu, unsigned int *node, void *unused);
>> +int __vdso_getcpu(unsigned int *cpu, unsigned int *node, void *unused)
>>  {
>>  	int cpu_id;
>
>It would ideally be nice to have a _bit_ more history on this about
>how it became unused any why there is such high confidence that
>userspace never tries to use it.
>
>Let's say someone comes along in a few years and wants to use this
>'unused' parameter. Could they?

I believe it was a private storage area for the kernel to use... which it doesn't. Not doing anything at all with the pointer is perfectly legitimate.