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deepmind.google·6d ago
AI Engineering
Hacker News·Aug 29·5 min read
Indirect Calling of Nested Functions on GCC Without Executable Stack
TL;DR
A method for indirectly calling nested functions in older versions of GCC without requiring an executable stack has been discussed. This approach allows developers to maintain compatibility while avoiding potential security risks associated with executable stacks.
✦ Why It Matters
Implement this workaround to enhance compatibility with older GCC versions while maintaining security standards.
Key Takeaways
- Use trampolines to call nested functions in older GCC versions.
- Extract code address and static chain for direct calls.
- Mark the stack as non-executable to improve security.
- Explore using trampolines as function descriptors for simpler calls.
How It Works
The method uses a trampoline to load the static frame register and jump to the nested function. By extracting the code address and static chain from the trampoline, developers can call the nested function directly using built-in functions, avoiding the need for an executable stack.