This reduces the amount of memory that needs to be allocated while
writing the ELF file to disk.
Note: We're abusing #:page-aligned? in 'link-elf' to choose whether to
return a bytevector or a procedure.
* module/system/vm/linker.scm (process-reloc): Subtract SECTION-OFFSET
when writing to BV.
(write-linker-object): Pass BV directly to the linker object writer.
(link-elf): When PAGE-ALIGNED? is false, call 'bytevector-slice' from
here. When it is true, return a procedure that takes a port and writes
to it, without having to allocate a bytevector for the whole ELF
container.
* module/language/bytecode/spec.scm (bytecode->value): Handle X being a
procedure instead of a bytevector.
(bytecode) <#:printer>: Likewise.
* test-suite/tests/linker.test (link-elf-with-one-main-section): Pass
#:page-aligned? #f.
This reduces the amount of memory used during linking and reduces the
number of copies to be done between bytevectors.
* module/system/vm/linker.scm (<linker-object>): Remove 'bv' field and
add 'size' and 'writer'.
(make-linker-object): Adjust accordingly.
(string-table-size): New procedure.
(link-string-table!): Remove.
(string-table-writer): New procedure.
(allocate-segment): Adjust 'make-linker-object' call.
(find-shstrndx): Call the 'linker-object-writer' of O.
(add-elf-objects): Adjust 'make-linker-object' call. Remove
'make-bytevector' allocations and move serialization to lazy 'writer'
procedures. Define 'segments' and 'add-header-segment!'. Return the
latter as the first value.
* module/system/vm/assembler.scm (make-object): Remove 'bv' parameter
and add 'size' and 'writer'.
(link-data): Remove 'make-bytevector' call and move serialization to
a lazy 'writer' procedure.
(link-text-object): Likewise.
(link-frame-maps): Likewise.
(link-dynamic-section): Likewise.
(link-shstrtab): Likewise.
(link-symtab): Likewise.
(link-arities): Likewise, and remove 'bytevector-append'.
(link-docstrs): Likewise.
(link-procprops): Likewise.
(link-debug): Likewise, and define 'copy-writer'.
* test-suite/tests/linker.test (link-elf-with-one-main-section): Adjust
accordingly.
* 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.
(relocate-section-header, allocate-segment): 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.
(link-elf): Refactor to use the new interfaces.
* test-suite/tests/linker.test: Update to expect the additional sections
for the header and section table.
* module/system/vm/elf.scm: Add commentary.
(make-elf): Add a constructor similar to make-elf-segment and
make-elf-section.
(write-elf32-header, write-elf64-header, write-elf-header): Take an
<elf> instead of all the fields separately.
(<elf-segment>, <elf-section>): Add "index" property. Adapt
constructors accordingly.
* module/language/objcode/elf.scm (bytecode->elf): Arrange to set the
section indexes when creating ELF sections.
* module/system/vm/linker.scm (fold-values): New helper.
(alloc-segment, relocate-section-header): Arrange to set segment and
section indexes.
(find-shstrndx): New helper, replaces compute-sections-by-name. Now
that sections know their indexes, this is easier.
(allocate-elf, write-elf): New helpers, factored out of link-elf.
Easier now that sections have indexes.
(link-elf): Simplify. Check that the incoming objects have sensible
numbers.
* test-suite/tests/linker.test: Update to set #:index on the linker
objects.
* module/Makefile.am:
* module/system/vm/linker.scm: New file, split out of (system vm elf).
(make-string-table, string-table-intern): Export under their bare
names, instead of make-elf-string-table and elf-string-table-intern.
* module/system/vm/elf.scm: Remove linking capabilities.
(string-table-ref): Export.
* module/language/objcode/elf.scm (bytecode->elf): Adapt to use (system
vm linker).
* test-suite/tests/linker.test: New test.
