Re: [PATCH v2 12/13] xen/device_tree: Introduce function to merge overlapping intervals

[Jan Beulich <jbeulich@xxxxxxxx>]

On 09.04.2024 13:45, Luca Fancellu wrote:
> --- a/xen/arch/x86/extable.c
> +++ b/xen/arch/x86/extable.c
> @@ -23,7 +23,8 @@ static inline unsigned long ex_cont(const struct 
> exception_table_entry *x)
>       return EX_FIELD(x, cont);
>  }
>  
> -static int init_or_livepatch cf_check cmp_ex(const void *a, const void *b)
> +static int init_or_livepatch cf_check cmp_ex(const void *a, const void *b,
> +                                             const void *data)
>  {
>       const struct exception_table_entry *l = a, *r = b;
>       unsigned long lip = ex_addr(l);
> @@ -53,7 +54,7 @@ void init_or_livepatch sort_exception_table(struct 
> exception_table_entry *start,
>                                   const struct exception_table_entry *stop)
>  {
>      sort(start, stop - start,
> -         sizeof(struct exception_table_entry), cmp_ex, swap_ex);
> +         sizeof(struct exception_table_entry), cmp_ex, swap_ex, NULL);
>  }

Not the least because of this addition of an entirely useless parameter / 
argument
I'm not in favor of ...

> --- a/xen/include/xen/sort.h
> +++ b/xen/include/xen/sort.h
> @@ -23,8 +23,8 @@
>  extern gnu_inline
>  #endif
>  void sort(void *base, size_t num, size_t size,
> -          int (*cmp)(const void *a, const void *b),
> -          void (*swap)(void *a, void *b, size_t size))
> +          int (*cmp)(const void *a, const void *b, const void *data),
> +          void (*swap)(void *a, void *b, size_t size), const void *cmp_data)
>  {

... this change. Consider you were doing this on a C library you cannot change.
You'd have to find a different solution anyway. And the way we have sort()
right now is matching the C spec. The change to do renders things unexpected to
anyone wanting to use this function in a spec-compliant way. One approach may
be to make an adjustment to data representation, such that the extra reference
data is accessible through the pointers already being passed.

Jan