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    Subject[PATCH v7 00/11] kallsyms: Optimizes the performance of lookup symbols
    Date
    v6 --> v7:
    1. Improve the performance of kallsyms_lookup_name() when CONFIG_LTO_CLANG=y
    To achieve this, restrict '.' to be at the beginning of a substring, not in
    the middle or end.
    2. kallsyms_selftest.c adds support for CONFIG_LTO_CLANG=y.
    3. Patches 4-6 are rearranged, centralize implementations of the same
    functionality in one patch, rather than split it based on whether it
    belongs to the tool or kernel.
    4. Due to the impact of the following patches, some adaptations are made.
    aa221f2ea58655f kallsyms: take the input file instead of reading stdin
    73bbb94466fd3f8 kallsyms: support "big" kernel symbols
    dfb352ab1162f73 kallsyms: Drop CONFIG_CFI_CLANG workarounds


    v5 --> v6:
    1. Add patch 6/11, kallsyms: Add helper kallsyms_lookup_clang_name()
    2. Update commit message of patch 9/11.

    v4 --> v5:
    1. In scripts/kallsyms.c, we use an extra field to hold type and eventually
    put it together with name in write_src().
    2. Generate a new table kallsyms_best_token_table[], so that we compress a
    symbol in the kernel using a process similar to compress_symbol().
    3. Remove helper sym_name(), and rename field 'sym[]' to 'name[]' in
    scripts/kallsyms.c
    4. Add helper __kallsyms_lookup_compressed_name() to avoid duplicate code in
    functions kallsyms_lookup_name() and kallsyms_on_each_match_symbol().
    5. Add a new parameter "const char *modname" to module_kallsyms_on_each_symbol(),
    this makes the code logic clearer.
    6. Delete the parameter 'struct module *' in the hook function associated with
    kallsyms_on_each_symbol(), it's unused now.

    v3 --> v4:
    1. Move the declaration of function kallsyms_sym_address() to linux/kallsyms.h,
    fix a build warning.

    v2 --> v3:
    1. Improve test cases, perform complete functional tests on functions
    kallsyms_lookup_name(), kallsyms_on_each_symbol() and
    kallsyms_on_each_match_symbol().
    2. Add patch [PATCH v3 2/8] scripts/kallsyms: ensure that all possible
    combinations are compressed.
    3. The symbol type is not compressed regardless of whether
    CONFIG_KALLSYMS_ALL is set or not. The memory overhead is increased
    by less than 20KiB if CONFIG_KALLSYMS_ALL=n.
    4. Discard [PATCH v2 3/8] kallsyms: Adjust the types of some local variables

    v1 --> v2:
    Add self-test facility

    v1:
    Currently, to search for a symbol, we need to expand the symbols in
    'kallsyms_names' one by one, and then use the expanded string for
    comparison. This is very slow.

    In fact, we can first compress the name being looked up and then use
    it for comparison when traversing 'kallsyms_names'.

    This patch series optimizes the performance of function kallsyms_lookup_name(),
    and function klp_find_object_symbol() in the livepatch module. Based on the
    test results, the performance overhead is reduced to 5%. That is, the
    performance of these functions is improved by 20 times.

    To avoid increasing the kernel size in non-debug mode, the optimization is only
    for the case CONFIG_KALLSYMS_ALL=y.

    Zhen Lei (11):
    scripts/kallsyms: rename build_initial_tok_table()
    scripts/kallsyms: don't compress symbol types
    scripts/kallsyms: remove helper sym_name() and cleanup
    kallsyms: Add helper kallsyms_compress_symbol_name()
    kallsyms: Improve the performance of kallsyms_lookup_name()
    kallsyms: Improve the performance of kallsyms_lookup_name() when
    CONFIG_LTO_CLANG=y
    kallsyms: Add helper kallsyms_on_each_match_symbol()
    livepatch: Use kallsyms_on_each_match_symbol() to improve performance
    livepatch: Improve the search performance of
    module_kallsyms_on_each_symbol()
    kallsyms: Delete an unused parameter related to
    kallsyms_on_each_symbol()
    kallsyms: Add self-test facility

    include/linux/kallsyms.h | 12 +-
    include/linux/module.h | 4 +-
    init/Kconfig | 13 ++
    kernel/Makefile | 1 +
    kernel/kallsyms.c | 197 ++++++++++++++--
    kernel/kallsyms_internal.h | 1 +
    kernel/kallsyms_selftest.c | 464 +++++++++++++++++++++++++++++++++++++
    kernel/livepatch/core.c | 31 ++-
    kernel/module/kallsyms.c | 15 +-
    kernel/trace/ftrace.c | 3 +-
    scripts/kallsyms.c | 161 ++++++++++---
    scripts/link-vmlinux.sh | 4 +
    12 files changed, 837 insertions(+), 69 deletions(-)
    create mode 100644 kernel/kallsyms_selftest.c

    --
    2.25.1

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