Hi Jinjie,
On Wed, Jul 29, 2026 at 11:12:35AM +0800, Jinjie Ruan wrote:
> +/**
> + * update_crash_elfcorehdr() - Recreate the elfcorehdr and replace it with
> old
> + * elfcorehdr in the kexec segment array.
> + * @image: the active struct kimage
> + */
> +static void update_crash_elfcorehdr(struct kimage *image)
> +{
> + void *elfbuf = NULL, *old_elfcorehdr;
> + unsigned long mem, memsz;
> + unsigned long elfsz = 0;
> +
> + /*
> + * Create the new elfcorehdr reflecting the changes to CPU and/or
> + * memory resources.
> + */
> + if (crash_prepare_headers(true, &elfbuf, &elfsz, NULL)) {
> + pr_err("unable to create new elfcorehdr");
> + goto out;
> + }
> +
> + /*
> + * Obtain address and size of the elfcorehdr segment, and
> + * check it against the new elfcorehdr buffer.
> + */
> + mem = image->segment[image->elfcorehdr_index].mem;
> + memsz = image->segment[image->elfcorehdr_index].memsz;
> + if (elfsz > memsz) {
> + pr_err("update elfcorehdr elfsz %lu > memsz %lu",
> + elfsz, memsz);
> + goto out;
> + }
> +
> + /*
> + * Copy new elfcorehdr over the old elfcorehdr at destination.
> + */
> + old_elfcorehdr = phys_to_virt(mem);
> +
> + /*
> + * Temporarily invalidate the crash image while the
> + * elfcorehdr is updated.
> + */
> + xchg(&kexec_crash_image, NULL);
> + memcpy(old_elfcorehdr, elfbuf, elfsz);
> + dcache_clean_inval_poc((unsigned long)old_elfcorehdr,
> + (unsigned long)(old_elfcorehdr + elfsz));
> + xchg(&kexec_crash_image, image);
> + pr_debug("updated elfcorehdr\n");
> +
> +out:
> + vfree(elfbuf);
> +}
> +
> +/**
> + * arch_crash_handle_hotplug_event() - Handle hotplug elfcorehdr changes
> + * @image: a pointer to kexec_crash_image
> + * @arg: struct memory_notify handler for memory hotplug case and
> + * NULL for CPU hotplug case.
> + *
> + * Update the kdump image based on the type of hotplug event:
> + * - CPU add and remove: No action is needed.
> + * - Memory add/remove: Update the elfcorehdr to reflect the current memory
> layout.
> + *
> + * Prepare the new elfcorehdr and replace the existing elfcorehdr.
> + */
> +void arch_crash_handle_hotplug_event(struct kimage *image, void *arg)
> +{
> + if (image->hp_action == KEXEC_CRASH_HP_ADD_CPU ||
> + image->hp_action == KEXEC_CRASH_HP_REMOVE_CPU)
> + return;
> +
> + update_crash_elfcorehdr(image);
> +}
Looking at powerpc, they pass the arg down to update_crash_elfcorehdr()
to handle the memory hot-unplug case. It looks like the notifier is
called before the memblock_remove(), so the update above will still
count the memory being removed.
There are a few Sashiko comments as well, though some might be about
existing issues (it would be nice to have them fixed ;)).
--
Catalin
