Better unwind table support + unwind protection in _start() and clone()
#22035
Conversation
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
alexrp
commented
Nov 20, 2024
jacobly0
approved these changes
Dec 6, 2024
|
Sent the musl patch upstream: https://www.openwall.com/lists/musl/2024/12/06/4 Going to wait a bit and see if there are any comments on it before merging this. |
The goal here is to support both levels of unwind tables (sync and async) in zig cc and zig build. Previously, the LLVM backend always used async tables while zig cc was partially influenced by whatever was Clang's default.
The function is not marked .cantunwind for Arm/Thumb because of an LLVM assembler bug: llvm/llvm-project#115891
Whatever was in the frame pointer register prior to clone() will no longer be valid in the child process, so zero it to protect FP-based unwinders. Similarly, mark the link register as undefined to protect DWARF-based unwinders. This is only zeroing the frame pointer(s) on Arm/Thumb because of an LLVM assembler bug: llvm/llvm-project#115891
Whatever was in the frame pointer register prior to clone() will no longer be valid in the child process, so zero it to protect FP-based unwinders. This is just an extension of what was already done for i386 and x86_64. Only applied to architectures where the _start() code also zeroes the frame pointer.
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
No description provided.