On Tue, Aug 27, 2024 at 1:33 AM Thomas Munro <thomas.mu...@gmail.com> wrote: > I am sure this requires changes for various LLVM versions. I tested > it with LLVM 14 on a Mac where I've never managed to reproduce the > original complaint, but ... ooooh, this might be exacerbated by ASLR, > and macOS only has a small ALSR slide window (16M or 256M apparently, > according to me in another thread), so I'd probably have to interpose > my own mmap() to choose some more interesting addresses, or run some > other OS, but that's quite enough rabbit holes for one morning.
I've tested the patch. I had to make sure the issue was triggered on master first. The issue didn't happen with 4GB shared_buffers and 64 partitions. However, increasing to 6GB and 128 partitions triggered the issue. The architecture check in the patch was incorrect (__arch64__ instead of __aarch64__, glad to see I'm not the only one being confused with aarch64 and arm64 :)) but once fixed, it worked and avoided the segfault. I've run some additional tests to try to test different parameters: - I've tried disabling randomize_va_space, the issue still happened even with ASLR disabled. - I've tested different PG versions. With 14 and 15, 4GB and 64 partitions were enough. Starting PG 16, I had to increase shared_buffers to 6GB and partitions to 128. I've been able to trigger the issue on all versions from 14 to master (which was expected but I wanted confirmation) - I haven't been able to reproduce this on a macOS either. I've tried to remove MemGroup.Near hint so mmap addresses would be more random and played with different shared_buffers and partition values without success I've modified the patch with 3 changes: - meson.build was using SectionMemoryManager.cpp file name, I've replaced with SafeSectionMemoryManager.cpp - Use __aarch64__ instead of __arch64__ - Moved the architecture switch to llvm_create_object_layer and go through the normal LLVMOrcCreateRTDyldObjectLinkingLayerWithSectionMemoryManager on non arm64 architectures. There's no need to use the custom memory manager for non arm64 so it looked better to avoid it entirely if there's no need for the reserve allocation.
v3-0001-XXX-LLVM-ARM-relocation-bug-mitigation.patch
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