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llvm / lld / dedaaf91a97e74e267528f8f03b35442d8184008
commitdedaaf91a97e74e267528f8f03b35442d8184008[log] [tgz]
authorRyan Prichard <rprichard@google.com>Wed Jan 09 00:09:59 2019 +0000
committerRyan Prichard <rprichard@google.com>Wed Jan 09 00:09:59 2019 +0000
tree2dc8840121e6d0d9a332f7857a650f4a1357dbc4
parent0fcfd21b5ad3ffb0764b5a0cba49c0920adf7962 [diff]
[ARM][AArch64] Increase TLS alignment to reserve space for Android's TCB

ARM and AArch64 use TLS variant 1, where the first two words after the
thread pointer are reserved for the TCB, followed by the executable's TLS
segment. Both the thread pointer and the TLS segment are aligned to at
least the TLS segment's alignment.

Android/Bionic historically has not supported ELF TLS, and it has
allocated memory after the thread pointer for several Bionic TLS slots
(currently 9 but soon only 8). At least one of these allocations
(TLS_SLOT_STACK_GUARD == 5) is widespread throughout Android/AArch64
binaries and can't be changed.

To reconcile this disagreement about TLS memory layout, set the minimum
alignment for executable TLS segments to 8 words on ARM/AArch64, which
reserves at least 8 words of memory after the TP (2 for the ABI-specified
TCB and 6 for alignment padding). For simplicity, and because lld doesn't
know when it's targeting Android, increase the alignment regardless of
operating system.

Differential Revision: https://reviews.llvm.org/D53906

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@350681 91177308-0d34-0410-b5e6-96231b3b80d8
9 files changed
tree: 2dc8840121e6d0d9a332f7857a650f4a1357dbc4
  1. cmake/
  2. COFF/
  3. Common/
  4. docs/
  5. ELF/
  6. include/
  7. lib/
  8. MinGW/
  9. test/
  10. tools/
  11. unittests/
  12. utils/
  13. wasm/
  14. .arcconfig
  15. .clang-format
  16. .gitignore
  17. CMakeLists.txt
  18. CODE_OWNERS.TXT
  19. LICENSE.TXT
  20. README.md
README.md

LLVM Linker (lld)

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.

Benchmarking

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.