[PATCH v5][makedumpfile 6/9] Add makedumpfile extensions support

[Tao Liu]

Hi Stephen & Kazu,

On Tue, Jun 16, 2026 at 5:12 AM Stephen Brennan
<stephen.s.brennan at oracle.com> wrote:
>
> HAGIO KAZUHITO(萩尾　一仁)   <k-hagio-ab at nec.com> writes:
> > On 2026/04/14 19:26, Tao Liu wrote:
> >
> >> +static bool init_kallsyms_btf(void)
> >> +{
> >> +    int count;
> >> +    bool ret = false;
> >> +    /* We will load module's btf/kallsyms on demand */
> >> +    bool init_ksyms_module = false;
> >> +    bool init_ktypes_module = false;
> >> +
> >> +    if (check_ksyms_require_modname("vmlinux", &count)) {
> >
> > Thank you for the explanation [1].
> >
> > so which code path adds "vmlinux" to the mods array before this line?
> > I could not find it.
>
> Hello Kazu,
>
> In kallsyms.c from patch 2, there is the line:
>   INIT_MOD_SYM(vmlinux, _stext);
> This adds a struct ksym_info to the main makedumpfile executable's
> array, which requests symbol "_stext" from vmlinux.
>
> In kallsyms.c "init_kernel_kallsyms()", again from patch 2, the first
> step is to call:
>    register_ksym_section((char *)__start_init_ksyms,
>                          (char *)__stop_init_ksyms))
> Which is a function generated by the macro REGISTER_SECTION(). The
> implementation will use add_ksym_modname() whens it encounters this
> symbol, ensuring that "vmlinux" is part of the modname array.

Thanks for the detailed info, yes, it is exactly how "vmlinux" is
added to the array.

>
> Thanks,
> Stephen
>
> > [1] https://lore.kernel.org/kexec/CAO7dBbUa_8H0fe+9bTNTQWjMVy9qCPiu0fo3g8XamiDS_Mr8eA@mail.gmail.com/
> >
> >
> >> +
> >> +bool has_extension_loaded(void)
> >> +{
> >> +    return extension_opts_len > 0;
> >
> > If an extension is skipped, this looks > 0 with no extention.
> > handle_cbs_len is better?

Yeah, I agree, `has_extension_loaded()` should also be updated to
`has_extension_callback()`. I will fix it in v6.

Thanks,
Tao Liu

> >
> >
> > Thanks,
> > Kazu
>