gh-144563: Fix remote debugging with duplicate libpython mappings from ctypes #144595
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…gs from ctypes When _ctypes is imported, it may call dlopen on the libpython shared library, causing the dynamic linker to load a second mapping of the library into the process address space. The remote debugging code iterates memory regions from low addresses upward and returns the first mapping whose filename matches libpython. After _ctypes is imported, it finds the dlopen'd copy first, but that copy's PyRuntime section was never initialized, so reading debug offsets from it fails. Fix this by validating each candidate PyRuntime address before accepting it. The validation reads the first 8 bytes and checks for the "xdebugpy" cookie that is only present in an initialized PyRuntime. Uninitialized duplicate mappings will fail this check and be skipped, allowing the search to continue to the real, initialized PyRuntime.
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@johnslavik wanna make a review pass? |
johnslavik
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Misc/NEWS.d/next/Core_and_Builtins/2026-02-08-18-13-38.gh-issue-144563.hb3kpp.rst
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Co-authored-by: Bartosz Sławecki <bartosz@ilikepython.com>
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Thanks @pablogsal for the PR 🌮🎉.. I'm working now to backport this PR to: 3.14. |
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Sorry, @pablogsal, I could not cleanly backport this to |
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… mappings from ctypes (pythonGH-144595) When _ctypes is imported, it may call dlopen on the libpython shared library, causing the dynamic linker to load a second mapping of the library into the process address space. The remote debugging code iterates memory regions from low addresses upward and returns the first mapping whose filename matches libpython. After _ctypes is imported, it finds the dlopen'd copy first, but that copy's PyRuntime section was never initialized, so reading debug offsets from it fails. Fix this by validating each candidate PyRuntime address before accepting it. The validation reads the first 8 bytes and checks for the "xdebugpy" cookie that is only present in an initialized PyRuntime. Uninitialized duplicate mappings will fail this check and be skipped, allowing the search to continue to the real, initialized PyRuntime. (cherry picked from commit 2c1ca6b) Co-authored-by: Pablo Galindo Salgado <Pablogsal@gmail.com>
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…gs from ctypes (python#144595) When _ctypes is imported, it may call dlopen on the libpython shared library, causing the dynamic linker to load a second mapping of the library into the process address space. The remote debugging code iterates memory regions from low addresses upward and returns the first mapping whose filename matches libpython. After _ctypes is imported, it finds the dlopen'd copy first, but that copy's PyRuntime section was never initialized, so reading debug offsets from it fails. Fix this by validating each candidate PyRuntime address before accepting it. The validation reads the first 8 bytes and checks for the "xdebugpy" cookie that is only present in an initialized PyRuntime. Uninitialized duplicate mappings will fail this check and be skipped, allowing the search to continue to the real, initialized PyRuntime. (cherry picked from commit 2c1ca6b)
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GH-144655 is a backport of this pull request to the 3.14 branch. |
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When _ctypes is imported, it may call dlopen on the libpython shared library, causing the dynamic linker to load a second mapping of the library into the process address space. The remote debugging code iterates memory regions from low addresses upward and returns the first mapping whose filename matches libpython. After _ctypes is imported, it finds the dlopen'd copy first, but that copy's PyRuntime section was never initialized, so reading debug offsets from it fails.
Fix this by validating each candidate PyRuntime address before accepting it. The validation reads the first 8 bytes and checks for the "xdebugpy" cookie that is only present in an initialized PyRuntime. Uninitialized duplicate mappings will fail this check and be skipped, allowing the search to continue to the real, initialized PyRuntime.
_ctypesimported #144563