Re: [PATCH 4/6] refactor linker to lay out ELF files and memory in the same way

[ludo@gnu.org (Ludovic Courtès)]

This goes beyond my ELF capabilities, so can’t really comment on this.

Style comments:

Andy Wingo <wingo@pobox.com> skribis:

> * module/system/vm/linker.scm (make-linker-object):
>   (linker-object-section-symbol):
>   (linker-object-symbols*): Create a symbol to the start of a linker
>   object.  Hide it from the external linker-object-symbols* accessor.
>
>   (segment-kind, count-segments): Sections without SHF_ALLOC don't get
>   segments.
>   (collate-objects-into-segments): Allow for #f segment types.  If two
>   sections have the same type and flags, leave them in the same order.
>
>   (align): Allow for 0 alignment.
>
>   (add-elf-objects): New helper: puts the ELF data structures (header,
>   segment table, and section table) in sections of their own.  This
>   lends a nice clarity and conceptual unity to the linker.

Please move the descriptions as docstrings.

>   (relocate-section-header, alloc-objects): Lay out segments with
>   congruent, contiguous addresses, so that we can just mmap the file and
>   if debugging sections that are not in segments are present, they can
>   be lazily paged in if needed by the kernel's VM system.

Nice.  Could you move this comment in the code?

>  ;; objects ::= list of <linker-object>
> -;; => 3 values: ELF header, program headers, objects
> +;;
> +;; => 3 values:
> +;;   file size
> +;;   objects with allocated memory address and file offset
> +;;   symbol table
> +;;
>  (define (allocate-elf objects page-aligned? endianness word-size)

What does it do?

Ludo’.