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013eb043f3
As reported by Namhyung Kim and acknowledged by Qiao Zhao (link: https://lore.kernel.org/linux-perf-users/20241206001436.1947528-1-namhyung@kernel.org/), on certain machines, perf trace failed to load the BPF program into the kernel. The verifier runs perf trace's BPF program for up to 1 million instructions, returning an E2BIG error, whereas the perf trace BPF program should be much less complex than that. This patch aims to fix the issue described above. The E2BIG problem from clang-15 to clang-16 is cause by this line: } else if (size < 0 && size >= -6) { /* buffer */ Specifically this check: size < 0. seems like clang generates a cool optimization to this sign check that breaks things. Making 'size' s64, and use } else if ((int)size < 0 && size >= -6) { /* buffer */ Solves the problem. This is some Hogwarts magic. And the unbounded access of clang-12 and clang-14 (clang-13 works this time) is fixed by making variable 'aug_size' s64. As for this: -if (aug_size > TRACE_AUG_MAX_BUF) - aug_size = TRACE_AUG_MAX_BUF; +aug_size = args->args[index] > TRACE_AUG_MAX_BUF ? TRACE_AUG_MAX_BUF : args->args[index]; This makes the BPF skel generated by clang-18 work. Yes, new clangs introduce problems too. Sorry, I only know that it works, but I don't know how it works. I'm not an expert in the BPF verifier. I really hope this is not a kernel version issue, as that would make the test case (kernel_nr) * (clang_nr), a true horror story. I will test it on more kernel versions in the future. Fixes: 395d38419f18: ("perf trace augmented_raw_syscalls: Add more check s to pass the verifier") Reported-by: Namhyung Kim <namhyung@kernel.org> Signed-off-by: Howard Chu <howardchu95@gmail.com> Tested-by: Namhyung Kim <namhyung@kernel.org> Link: https://lore.kernel.org/r/20241213023047.541218-1-howardchu95@gmail.com Signed-off-by: Namhyung Kim <namhyung@kernel.org> |
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| drivers | ||
| fs | ||
| include | ||
| init | ||
| io_uring | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| rust | ||
| samples | ||
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| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .clippy.toml | ||
| .cocciconfig | ||
| .editorconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| .rustfmt.toml | ||
| COPYING | ||
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| Kbuild | ||
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| README | ||
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.