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Yonghong Song bb899e081c kallsyms: Fix kallsyms_selftest failure commit `33f0467fe0` upstream. Kernel test robot reported a kallsyms_test failure when clang lto is enabled (thin or full) and CONFIG_KALLSYMS_SELFTEST is also enabled. I can reproduce in my local environment with the following error message with thin lto: [ 1.877897] kallsyms_selftest: Test for 1750th symbol failed: (tsc_cs_mark_unstable) addr=ffffffff81038090 [ 1.877901] kallsyms_selftest: abort It appears that commit `8cc32a9bbf` ("kallsyms: strip LTO-only suffixes from promoted global functions") caused the failure. Commit `8cc32a9bbf` changed cleanup_symbol_name() based on ".llvm." instead of '.' where ".llvm." is appended to a before-lto-optimization local symbol name. We need to propagate such knowledge in kallsyms_selftest.c as well. Further more, compare_symbol_name() in kallsyms.c needs change as well. In scripts/kallsyms.c, kallsyms_names and kallsyms_seqs_of_names are used to record symbol names themselves and index to symbol names respectively. For example: kallsyms_names: ... __amd_smn_rw._entry <== seq 1000 __amd_smn_rw._entry.5 <== seq 1001 __amd_smn_rw.llvm.<hash> <== seq 1002 ... kallsyms_seqs_of_names are sorted based on cleanup_symbol_name() through, so the order in kallsyms_seqs_of_names actually has index 1000: seq 1002 <== __amd_smn_rw.llvm.<hash> (actual symbol comparison using '__amd_smn_rw') index 1001: seq 1000 <== __amd_smn_rw._entry index 1002: seq 1001 <== __amd_smn_rw._entry.5 Let us say at a particular point, at index 1000, symbol '__amd_smn_rw.llvm.<hash>' is comparing to '__amd_smn_rw._entry' where '__amd_smn_rw._entry' is the one to search e.g., with function kallsyms_on_each_match_symbol(). The current implementation will find out '__amd_smn_rw._entry' is less than '__amd_smn_rw.llvm.<hash>' and then continue to search e.g., index 999 and never found a match although the actual index 1001 is a match. To fix this issue, let us do cleanup_symbol_name() first and then do comparison. In the above case, comparing '__amd_smn_rw' vs '__amd_smn_rw._entry' and '__amd_smn_rw._entry' being greater than '__amd_smn_rw', the next comparison will be > index 1000 and eventually index 1001 will be hit an a match is found. For any symbols not having '.llvm.' substr, there is no functionality change for compare_symbol_name(). Fixes: `8cc32a9bbf` ("kallsyms: strip LTO-only suffixes from promoted global functions") Reported-by: kernel test robot <oliver.sang@intel.com> Closes: https://lore.kernel.org/oe-lkp/202308232200.1c932a90-oliver.sang@intel.com Signed-off-by: Yonghong Song <yonghong.song@linux.dev> Reviewed-by: Song Liu <song@kernel.org> Reviewed-by: Zhen Lei <thunder.leizhen@huawei.com> Link: https://lore.kernel.org/r/20230825034659.1037627-1-yonghong.song@linux.dev Cc: stable@vger.kernel.org Signed-off-by: Kees Cook <keescook@chromium.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>		History 2023-09-02 09:14:38 +02:00
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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 Restructured Text 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.