commit | f3d3b4d50a33fc279e6e600901f19f9311ea7f9b | [log] [tgz] |
---|---|---|
author | Fangrui Song <i@maskray.me> | Wed Nov 01 22:35:28 2023 -0700 |
committer | Copybara-Service <copybara-worker@google.com> | Wed Nov 01 22:41:16 2023 -0700 |
tree | f3334d3b1f0b7b275b3877392e0f11a4c6d6d453 | |
parent | c453e54930e8967b975096855a008cf3daa6cc25 [diff] |
[ELF] adjustOutputSections: don't copy SHF_EXECINSTR when an output does not contain input sections (#70911) For an output section with no input section, GNU ld eliminates the output section when there are only symbol assignments (e.g. `.foo : { symbol = 42; }`) but not for `.foo : { . += 42; }` (`SHF_ALLOC|SHF_WRITE`). We choose to retain such an output section with a symbol assignment (unless unreferenced `PROVIDE`). We copy the previous section flag (see https://reviews.llvm.org/D37736) to hopefully make the current PT_LOAD segment extend to the current output section: * decrease the number of PT_LOAD segments * If a new PT_LOAD segment is introduced without a page-size alignment as a separator, there may be a run-time crash. However, this `flags` copying behavior is not suitable for `.foo : { . += 42; }` when `flags` contains `SHF_EXECINSTR`. The executable bit is surprising (https://discourse.llvm.org/t/lld-output-section-flag-assignment-behavior/74359). I think we should drop SHF_EXECINSTR when copying `flags`. The risk is a code section followed by `.foo : { symbol = 42; }` will be broken, which I believe is unrelated as such uses are almost always related to data sections. For data-command-only output sections (e.g. `.foo : { QUAD(42) }`), we keep allowing copyable SHF_WRITE. Some tests are updated to drop the SHF_EXECINSTR flag. GNU ld doesn't set SHF_EXECINSTR as well, though it sets SHF_WRITE for some tests while we don't. GitOrigin-RevId: a40f651a065ef28fee17bc1f22cce08247eff950
This directory and its subdirectories contain source code for the LLVM Linker, a modular cross platform linker which is built as part of the LLVM compiler infrastructure project.
lld is open source software. You may freely distribute it under the terms of the license agreement found in LICENSE.txt.
In order to make sure various developers can evaluate patches over the same tests, we create a collection of self contained programs.
It is hosted at https://s3-us-west-2.amazonaws.com/linker-tests/lld-speed-test.tar.xz
The current sha256 is 10eec685463d5a8bbf08d77f4ca96282161d396c65bd97dc99dbde644a31610f
.