[Windows] Search for the closest free page for allocate jit memory in x64#122
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lucianopa-msft wants to merge 1 commit intomicrosoft:mainfrom
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[Windows] Search for the closest free page for allocate jit memory in x64#122lucianopa-msft wants to merge 1 commit intomicrosoft:mainfrom
lucianopa-msft wants to merge 1 commit intomicrosoft:mainfrom
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Hi @lucianopa-msft , thanks for providing the fix! Would you mind adding some tests to cover the change. Ideally, those tests should fail on main branch but pass with your changes. Thanks! |
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I really tried to but couldn't get a repro testing repro that mimics the exact crash. So there may be special conditions for the repro I am still not sure. |
mazong1123
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The old x86_64 Windows implementation of allocate_jit_memory scanned linearly from func_addr - 2GB upward, which often allocated memory ~2GB away from the function. This could land in/near the stack region, disrupting the stack guard page and causing STATUS_STACK_OVERFLOW (0xc00000fd) during parallel test execution. This change replaces the linear scan with a bidirectional closest-first search (matching the existing aarch64 Windows and Unix implementations). The allocator now searches outward from the function address at +offset and -offset, finding the closest available page first. This is an improved version of PR #122 that fixes two additional issues: - Searches both directions (not just downward) for robustness - Avoids an infinite loop when checked_sub fails by keeping offset increment outside the inner direction loop Also adds tests: - Unit test verifying JIT allocation is close to source (<128MB, not ~2GB) - Unit test verifying JIT allocation is not near the stack region - Integration test for stack growth after patching - Integration test for concurrent patching with deep stack usage (8 threads) Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
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Thanks @lucianopa-msft ! I have created a separate PR and added tests: #124 based on this PR. |
mazong1123
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…124) The old x86_64 Windows implementation of allocate_jit_memory scanned linearly from func_addr - 2GB upward, which often allocated memory ~2GB away from the function. This could land in/near the stack region, disrupting the stack guard page and causing STATUS_STACK_OVERFLOW (0xc00000fd) during parallel test execution. This change replaces the linear scan with a bidirectional closest-first search (matching the existing aarch64 Windows and Unix implementations). The allocator now searches outward from the function address at +offset and -offset, finding the closest available page first. This is an improved version of PR #122 that fixes two additional issues: - Searches both directions (not just downward) for robustness - Avoids an infinite loop when checked_sub fails by keeping offset increment outside the inner direction loop Also adds tests: - Unit test verifying JIT allocation is close to source (<128MB, not ~2GB) - Unit test verifying JIT allocation is not near the stack region - Integration test for stack growth after patching - Integration test for concurrent patching with deep stack usage (8 threads) Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
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Previous algorithm would take the base address compute 2GB up and start searching for a free page there (starting from furtherst from base address). Depending on the base address this could cause
VirtualAllocto try access an invalid memory range (stack memory) causing a crash. This changes the implementation to look instead for the closest free page.This also makes it consistent with other implementations such as
allocate_jit_memory_unix