René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Some DTrace probes are broken in 3.11","articleBody":"\u003c!--\r\n  Use this template for hard crashes of the interpreter, segmentation faults, failed C-level assertions, and similar.\r\n  Do not submit this form if you encounter an exception being unexpectedly raised from a Python function.\r\n  Most of the time, these should be filed as bugs, rather than crashes.\r\n\r\n  The CPython interpreter is itself written in a different programming language, C.\r\n  For CPython, a \"crash\" is when Python itself fails, leading to a traceback in the C stack.\r\n--\u003e\r\n\r\n# Crash report\r\nI've been using eBPF with the static markers in Python 3.10 and wanted to try out 3.11 now that it is released.\r\n\r\nBut it seems that the `function__entry` and `line` markers are broken in 3.11.\r\n\r\nThe `function__entry` probe simply does not fire into the eBPF program.\r\nThe `line` probe crashes the interpreter. \r\n\r\nI'm using BCC to load the eBPF program like this:\r\n```\r\n#!/usr/bin/python3\r\n\r\nimport argparse\r\nfrom bcc import BPF, USDT\r\n\r\nparser = argparse.ArgumentParser()\r\nparser.add_argument(\"pid\", type=int)\r\nargs = parser.parse_args()\r\n\r\nprogram = \"\"\"\r\nint trace_entry(struct pt_regs *ctx) {\r\n    bpf_trace_printk(\"Entry:\");\r\n\r\n    return 0;\r\n}\r\n\r\nint trace_return(struct pt_regs *ctx) {\r\n    bpf_trace_printk(\"Return:\");\r\n\r\n    return 0;\r\n}\r\n\r\nint trace_line(struct pt_regs *ctx) {\r\n    bpf_trace_printk(\"Line:\");\r\n\r\n    return 0;\r\n}\r\n\"\"\"\r\n\r\nusdt = USDT(pid=args.pid)\r\nusdt.enable_probe_or_bail(\"python:function__entry\", 'trace_entry')\r\nusdt.enable_probe_or_bail(\"python:function__return\", 'trace_return')\r\nusdt.enable_probe_or_bail(\"python:line\", 'trace_line')\r\n\r\nbpf = BPF(text=program, usdt_contexts=[usdt] if usdt else [], debug=0)\r\n\r\ntry:\r\n    bpf.trace_print()\r\nexcept KeyboardInterrupt:\r\n    exit()\r\n```\r\n\r\nIf I don't enable the `line` probe this is the output:\r\n\r\n```\r\n❯ sudo ./ebpf-test.py 80715\r\nb'          python-80715   [001] d...1  6539.145626: bpf_trace_printk: Return:'\r\n```\r\nThe entry message is never printed.\r\n\r\n\r\n# Error messages\r\nWith the  `line` probe enabled, this is the crash error:\r\n```\r\n❯ ./python\r\nPython 3.11.0+ (heads/3.11:57dd11038f, Oct 31 2022, 10:30:28) [GCC 11.3.0] on linux\r\nType \"help\", \"copyright\", \"credits\" or \"license\" for more information.\r\n\u003e\u003e\u003e print(\"Hello world!\")\r\npython: Python/ceval.c:5620: _PyEval_EvalFrameDefault: Assertion `cframe.use_tracing' failed.\r\n[1]    80398 IOT instruction (core dumped)  ./python\r\n```\r\n# Expected result\r\nRunning the same test in 3.10.6 I get this result, as expected:\r\n```\r\n❯ python3                      \r\nPython 3.10.6 (main, Aug 10 2022, 11:40:04) [GCC 11.3.0] on linux\r\nType \"help\", \"copyright\", \"credits\" or \"license\" for more information.\r\n\u003e\u003e\u003e print(\"Hello world!\")\r\nHello world!\r\n```\r\n```\r\n❯ sudo ./ebpf-test.py 81962\r\nb'         python3-81962   [003] d...1  6907.857690: bpf_trace_printk: Entry:'\r\nb'         python3-81962   [003] d...1  6907.857710: bpf_trace_printk: Line:'\r\nb'         python3-81962   [003] d...1  6907.857765: bpf_trace_printk: Return:'\r\n```\r\n\r\n\r\n# Your environment\r\n\r\nI used the head of the 3.11 branch with `./configure --with-dtrace --with-pydebug`\r\nOn Ubuntu 22.04.\r\n\n\n\u003c!-- gh-linked-prs --\u003e\n### Linked PRs\n* gh-125019\n* gh-139334\n* gh-142397\n\u003c!-- /gh-linked-prs --\u003e\n","author":{"url":"https://github.com/Elias-elastisys","@type":"Person","name":"Elias-elastisys"},"datePublished":"2022-10-31T09:50:10.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":7},"url":"https://github.com/98894/cpython/issues/98894"}