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As per the ABI at https://github.com/ARM-software/abi-aa/blob/main/memtagabielf64/memtagabielf64.rst, this patch interprets the SHT_AARCH64_MEMTAG_GLOBALS_STATIC section, which contains R_NONE relocations to tagged globals, and emits a SHT_AARCH64_MEMTAG_GLOBALS_DYNAMIC section, with the correct DT_AARCH64_MEMTAG_GLOBALS and DT_AARCH64_MEMTAG_GLOBALSSZ dynamic entries. This section describes, in a uleb-encoded stream, global memory ranges that should be tagged with MTE. We are also out of bits to spare in the LLD Symbol class. As a result, I've reused the 'needsTocRestore' bit, which is a PPC64 only feature. Now, it's also used for 'isTagged' on AArch64. An entry in SHT_AARCH64_MEMTAG_GLOBALS_STATIC is practically a guarantee from an objfile that all references to the linked symbol are through the GOT, and meet correct alignment requirements. As a result, we go through all symbols and make sure that, for all symbols $SYM, all object files that reference $SYM also have a SHT_AARCH64_MEMTAG_GLOBALS_STATIC entry for $SYM. If this isn't the case, we demote the symbol to being untagged. Symbols that are imported from other DSOs should always be fine, as they're GOT-referenced (and thus the GOT entry either has the correct tag or not, depending on whether it's tagged in the defining DSO or not). Additionally hand-tested by building {libc, libm, libc++, libm, and libnetd} on Android with some experimental MTE globals support in the linker/libc. Reviewed By: MaskRay, peter.smith Differential Revision: https://reviews.llvm.org/D152921 |
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| COFF | ||
| Common | ||
| docs | ||
| ELF | ||
| include/lld/Common | ||
| MachO | ||
| MinGW | ||
| test | ||
| tools/lld | ||
| unittests | ||
| utils | ||
| wasm | ||
| .clang-format | ||
| .clang-tidy | ||
| .gitignore | ||
| CMakeLists.txt | ||
| CODE_OWNERS.TXT | ||
| LICENSE.TXT | ||
| 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.