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With -fpatchable-function-entry (or the patchable_function_entry function attribute), we emit records of patchable entry locations to the __patchable_function_entries section. Add an additional parameter to the command line option that allows one to specify a different default section name for the records, and an identical parameter to the function attribute that allows one to override the section used. The main use case for this change is the Linux kernel using prefix NOPs for ftrace, and thus depending on__patchable_function_entries to locate traceable functions. Functions that are not traceable currently disable entry NOPs using the function attribute, but this creates a compatibility issue with -fsanitize=kcfi, which expects all indirectly callable functions to have a type hash prefix at the same offset from the function entry. Adding a section parameter would allow the kernel to distinguish between traceable and non-traceable functions by adding entry records to separate sections while maintaining a stable function prefix layout for all functions. LKML discussion: https://lore.kernel.org/lkml/Y1QEzk%2FA41PKLEPe@hirez.programming.kicks-ass.net/
The LLVM Compiler Infrastructure
Welcome to the LLVM project!
This repository contains the source code for LLVM, a toolkit for the construction of highly optimized compilers, optimizers, and run-time environments.
The LLVM project has multiple components. The core of the project is itself called "LLVM". This contains all of the tools, libraries, and header files needed to process intermediate representations and convert them into object files. Tools include an assembler, disassembler, bitcode analyzer, and bitcode optimizer.
C-like languages use the Clang frontend. This component compiles C, C++, Objective-C, and Objective-C++ code into LLVM bitcode -- and from there into object files, using LLVM.
Other components include: the libc++ C++ standard library, the LLD linker, and more.
Getting the Source Code and Building LLVM
Consult the Getting Started with LLVM page for information on building and running LLVM.
For information on how to contribute to the LLVM project, please take a look at the Contributing to LLVM guide.
Getting in touch
Join the LLVM Discourse forums, Discord chat, LLVM Office Hours or Regular sync-ups.
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