Re: [PATCH 3/4] xen: resolve MISRA C Rule 11.8 in xen_build_id_check()

[Jan Beulich <jbeulich@xxxxxxxx>]

On 03.11.2026 11:29, Dmytro Prokopchuk1 wrote:
> ELFNOTE_NAME() unconditionally casts its argument to 'char *', and
> ELFNOTE_DESC() is built on top of it. xen_build_id_check() passes a
> 'const Elf_Note *' to both of them, so the const qualifier is cast away,
> which is a violation of MISRA C Rule 11.8.
> 
> Introduce ELFNOTE_NAME_CONST() and ELFNOTE_DESC_CONST() for read-only
> access to the note, and use them in xen_build_id_check().
> 
> No functional changes.
> 
> Signed-off-by: Dmytro Prokopchuk <dmytro_prokopchuk1@xxxxxxxx>

It again would have been nice if it was mentioned that this is an alternative
proposal to an earlier posted patch, [1]. Personally here I prefer my variant
(with the adjustment as per review feedback, pending a v2 submission).

Jan

[1] https://lists.xen.org/archives/html/xen-devel/2026-09/msg00045.html

> --- a/xen/common/version.c
> +++ b/xen/common/version.c
> @@ -133,13 +133,13 @@ int xen_build_id_check(const Elf_Note *n, unsigned int 
> n_sz,
>          return -EINVAL;
>  
>      /* Sanity check, name should be "GNU" for ld-generated build-id. */
> -    if ( strncmp(ELFNOTE_NAME(n), "GNU", n->namesz) != 0 )
> +    if ( strncmp(ELFNOTE_NAME_CONST(n), "GNU", n->namesz) != 0 )
>          return -ENODATA;
>  
>      if ( len )
>          *len = n->descsz;
>      if ( p )
> -        *p = ELFNOTE_DESC(n);
> +        *p = ELFNOTE_DESC_CONST(n);
>  
>      return 0;
>  }
> diff --git a/xen/include/xen/elf.h b/xen/include/xen/elf.h
> index 4199b4d6e6..3337b8cabe 100644
> --- a/xen/include/xen/elf.h
> +++ b/xen/include/xen/elf.h
> @@ -34,4 +34,8 @@
>  #define ELFNOTE_DESC(_n_) (ELFNOTE_NAME(_n_) + ELFNOTE_ALIGN((_n_)->namesz))
>  #define ELFNOTE_NEXT(_n_) ((Elf_Note *)(ELFNOTE_DESC(_n_) + 
> ELFNOTE_ALIGN((_n_)->descsz)))
>  
> +#define ELFNOTE_NAME_CONST(_n_) ((const char *)(_n_) + sizeof(*(_n_)))
> +#define ELFNOTE_DESC_CONST(_n_) \
> +    (ELFNOTE_NAME_CONST(_n_) + ELFNOTE_ALIGN((_n_)->namesz))
> +
>  #endif /* __XEN_ELF_H__ */