On 01/05/23 at 10:17am, Eric DeVolder wrote:
......
> @@ -394,10 +409,37 @@ int crash_load_segments(struct kimage *image)
>       if (ret)
>               return ret;
>  
> -     image->elf_headers = kbuf.buffer;
> -     image->elf_headers_sz = kbuf.bufsz;
> +     image->elf_headers      = kbuf.buffer;
> +     image->elf_headers_sz   = kbuf.bufsz;
> +     kbuf.memsz              = kbuf.bufsz;
> +
> +     if (IS_ENABLED(CONFIG_CRASH_HOTPLUG)) {
> +             /*
> +              * Ensure the elfcorehdr segment large enough for hotplug 
> changes.
> +              * Start with VMCOREINFO and kernel_map.
> +              */
> +             unsigned long pnum = 2;
> +
> +             if (IS_ENABLED(CONFIG_HOTPLUG_CPU))
> +                     pnum += CONFIG_NR_CPUS_DEFAULT;
> +
> +             if (IS_ENABLED(CONFIG_MEMORY_HOTPLUG))
> +                     pnum += CRASH_MAX_MEMORY_RANGES;

Logic of pnum calculating is a little confusing to me. If I only enable
one of CONFIG_HOTPLUG_CPU and CONFIG_MEMORY_HOTPLUG, is it OK? Say I
only enable CONFIG_HOTPLUG_CPU and CONFIG_SMP, on x86_64,
CONFIG_NR_CPUS_DEFAULT will be 64. pnum will be 64, is it OK. Am I miss
anything?

> +
> +             if (pnum < (unsigned long)PN_XNUM) {
> +                     kbuf.memsz = pnum * sizeof(Elf64_Phdr);
> +                     kbuf.memsz += sizeof(Elf64_Ehdr);
> +
> +                     image->elfcorehdr_index = image->nr_segments;
> +                     image->elfcorehdr_index_valid = true;
> +
> +                     /* Mark as usable to crash kernel, else crash kernel 
> fails on boot */
> +                     image->elf_headers_sz = kbuf.memsz;
> +             } else {
> +                     pr_err("number of Phdrs %lu exceeds max\n", pnum);
> +             }
> +     }
>  
> -     kbuf.memsz = kbuf.bufsz;
>       kbuf.buf_align = ELF_CORE_HEADER_ALIGN;
>       kbuf.mem = KEXEC_BUF_MEM_UNKNOWN;
>       ret = kexec_add_buffer(&kbuf);
> @@ -412,3 +454,67 @@ int crash_load_segments(struct kimage *image)
>       return ret;
>  }
>  #endif /* CONFIG_KEXEC_FILE */


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