llvm/llvm-project

Check for `__unw_add_dynamic_eh_frame_section` in non-ORC-runtime exception registration paths.

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#55,681 opened on May 24, 2022

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good first issueorcjit

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Description

Background:

LLVM JIT clients using libunwind on Linux have historically encountered "FDE is really a CIE" errors and associated issues with exception handling (see e.g. https://github.com/llvm/llvm-project/issues/86).

To address these issues @housel added new dynamic registration functions for eh-frame-sections to libunwind in bab39816085d7 (__unw_add_dynamic_eh_frame_section registers a section, __unw_remove_dynamic_eh_frame_section deregisters it), and updated the ORC runtime was updated to check for and use these registration functions in 981523b2e4675d4be496a333583b2f728c057d02.

@housel's patch fixes the issue for JIT clients who use the ORC runtime, but the LLVM-only registration paths are still hardcoded to use the __register_frame and __deregister_frame functions. We should update the LLVM-only paths to check and use these functions too.

Contributor guide

Research direction
Identify all non ORC registration paths in LLVM (e.g., in ExecutionEngine or JIT) that use register frame/ deregister frame and update them to check for and use unw add dynamic eh frame section/ unw remove dynamic eh frame section. Ensure proper fallback if the dynamic functions are not available.
Tech stack
cpp
Domain
backend
Issue type
Feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
Half day
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
C++Git
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
60