Re: [Xen-devel] [livepatch-build-tools part3 v2 2/3] create-diff-object: Extend patchability verification: STN_UNDEF

[Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>]

On 8/8/19 1:48 PM, Pawel Wieczorkiewicz wrote:
> During verification check if all sections do not contain any entries
> with undefined symbols (STN_UNDEF). This situation can happen when a
> section is copied over from its original object to a patched object,
> but various symbols related to the section are not copied along.
> This scenario happens typically during stacked hotpatches creation
> (between 2 different hotpatch modules).
>
> Signed-off-by: Pawel Wieczorkiewicz <wipawel@xxxxxxxxx>
> Reviewed-by: Martin Pohlack <mpohlack@xxxxxxxxx>
> Reviewed-by: Bjoern Doebel <doebel@xxxxxxxxx>
> Reviewed-by: Norbert Manthey <nmanthey@xxxxxxxxx>
> Reviewed-by: Andra-Irina Paraschiv <andraprs@xxxxxxxxxx>
... snip
> +static int kpatch_section_has_undef_symbols(struct kpatch_elf *kelf,
> +                                           const struct section *sec)
> +{
> +       int offset, entry_size;
> +       struct rela *rela;
> +       size_t d_size;
> +
> +       entry_size = get_section_entry_size(sec, kelf);
> +       if (entry_size == 0)
> +               return false;
> +
> +       d_size = sec->base->data->d_size;
> +       for ( offset = 0; offset < d_size; offset += entry_size ) {
The coding style doesn't use spaces inside the for loop parentheses.

> +               list_for_each_entry(rela, &sec->relas, list) {
> +                       if (rela->offset < offset ||
> +                           rela->offset >= offset + entry_size) {
> +                               continue;
> +                       }
> +
> +                       if ((GELF_R_SYM(rela->rela.r_info) == STN_UNDEF) ||
> +                           (!rela->sym->include && rela->sym->status == SAME)) 
> {
> +                               log_normal("section %s has an entry with a STN_UNDEF 
> symbol: %s\n",
> +                                          sec->name, rela->sym->name ?: 
> "none");
Perhaps this log message is a bit misleading if only the second 
condition is true? Maybe something slightly more general like "has an 
entry with an undefined symbol".
Otherwise looks OK to me.

Thanks,
--
Ross Lagerwall

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