4 Commits

Author SHA1 Message Date
Fangrui Song
73d01a80ce [ELF] Sort by input order within an input section description
According to
https://sourceware.org/binutils/docs/ld/Input-Section-Basics.html#Input-Section-Basics
for `*(.a .b)`, the order should match the input order:

* for `ld 1.o 2.o`, sections from 1.o precede sections from 2.o
* within a file, `.a` and `.b` appear in the section header table order

This patch implements the behavior. The interaction with `SORT*` and --sort-section is:

Matched sections are ordered by radix sort with the keys being `(SORT*, --sort-section, input order)`,
where `SORT*` (if present) is most significant.

> Note, multiple `SORT*` within an input section description has undocumented and
> confusing behaviors in GNU ld:
> https://sourceware.org/pipermail/binutils/2020-November/114083.html
> Therefore multiple `SORT*` is not the focus for this patch but
> this patch still strives to have an explainable behavior.

As an example, we partition `SORT(a.*) b.* c.* SORT(d.*)`, into
`SORT(a.*) | b.* c.* | SORT(d.*)` and perform sorting within groups. Sections
matched by patterns between two `SORT*` are sorted by input order.  If
--sort-alignment is given, they are sorted by --sort-alignment, breaking tie by
input order.

This patch also allows a section to be matched by multiple patterns, previously
duplicated sections could occupy more space in the output and had erroneous zero bytes.

The patch is in preparation for support for
`*(SORT_BY_INIT_PRIORITY(.init_array.* .ctors.*)) *(.init_array .ctors)`,
which will allow LLD to mix .ctors*/.init_array* like GNU ld (gold's --ctors-in-init-array)
PR44698 and PR48096

Reviewed By: grimar, psmith

Differential Revision: https://reviews.llvm.org/D91127
2020-11-12 08:53:11 -08:00
Fangrui Song
2a9aed0e8b [ELF] Support multiple SORT in an input section description
The second `SORT` in `*(SORT(...) SORT(...))` is incorrectly parsed as a file pattern.
Fix the bug by stopping at `SORT*` in `readInputSectionsList`.

Reviewed By: grimar

Differential Revision: https://reviews.llvm.org/D91180
2020-11-12 08:46:53 -08:00
Rafael Espindola
317c339f61 Don't depend on lld creating space for the headers.
Currently lld will implicitly reserve space for the headers. This is
not the case is bfd, where it is the script responsibility to use
SIZEOF_HEADERS. This means that a script not using SIZEOF_HEADERS and
expecting the address of the first section to be 0 would fail with lld.

I am fixing that is the next commit. This one just makes the tests
explicitly use SIZEOF_HEADERS to avoid the dependency on the current
behaviour.

llvm-svn: 282814
2016-09-30 00:06:24 +00:00
George Rimar
07171f21d1 [ELF] - Linkerscript: support complex section pattern grammar.
This is PR30442.
Previously we were failed to parce complex expressions like:
foo : { *(SORT_BY_NAME(bar) zed) }

Main idea of patch that globs and excludes can be wrapped in a SORT.
There is a difference in semanics of ld/gold:
ld likes:
*(SORT(EXCLUDE_FILE (*file1.o) .foo.1))

gold likes:
*(EXCLUDE_FILE (*file1.o) SORT(.foo.1))

Patch implements ld grammar, complex expressions like 
next is not a problem anymore:
.abc : { *(SORT(.foo.* EXCLUDE_FILE (*file1.o) .bar.*) .bar.*) }


Differential revision: https://reviews.llvm.org/D24758

llvm-svn: 282078
2016-09-21 15:56:44 +00:00