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71f8c15565
Patch series "Expose kallsyms data in vmcoreinfo note". The kernel can be configured to contain a lot of introspection or debugging information built-in, such as ORC for unwinding stack traces, BTF for type information, and of course kallsyms. Debuggers could use this information to navigate a core dump or live system, but they need to be able to find it. This patch series adds the necessary symbols into vmcoreinfo, which would allow a debugger to find and interpret the kallsyms table. Using the kallsyms data, the debugger can then lookup any symbol, allowing it to find ORC, BTF, or any other useful data. This would allow a live kernel, or core dump, to be debugged without any DWARF debuginfo. This is useful for many cases: the debuginfo may not have been generated, or you may not want to deploy the large files everywhere you need them. I've demonstrated a proof of concept for this at LSF/MM+BPF during a lighting talk. Using a work-in-progress branch of the drgn debugger, and an extended set of BTF generated by a patched version of dwarves, I've been able to open a core dump without any DWARF info and do basic tasks such as enumerating slab caches, block devices, tasks, and doing backtraces. I hope this series can be a first step toward a new possibility of "DWARFless debugging". Related discussion around the BTF side of this: https://lore.kernel.org/bpf/586a6288-704a-f7a7-b256-e18a675927df@oracle.com/T/#u Some work-in-progress branches using this feature: https://github.com/brenns10/dwarves/tree/remove_percpu_restriction_1 https://github.com/brenns10/drgn/tree/kallsyms_plus_btf This patch (of 2): To include kallsyms data in the vmcoreinfo note, we must make the symbol declarations visible outside of kallsyms.c. Move these to a new internal header file. Link: https://lkml.kernel.org/r/20220517000508.777145-1-stephen.s.brennan@oracle.com Link: https://lkml.kernel.org/r/20220517000508.777145-2-stephen.s.brennan@oracle.com Signed-off-by: Stephen Brennan <stephen.s.brennan@oracle.com> Acked-by: Baoquan He <bhe@redhat.com> Cc: Nick Desaulniers <ndesaulniers@google.com> Cc: Dave Young <dyoung@redhat.com> Cc: Kees Cook <keescook@chromium.org> Cc: Jiri Olsa <jolsa@kernel.org> Cc: Stephen Boyd <swboyd@chromium.org> Cc: Bixuan Cui <cuibixuan@huawei.com> Cc: David Vernet <void@manifault.com> Cc: Vivek Goyal <vgoyal@redhat.com> Cc: Sami Tolvanen <samitolvanen@google.com> Cc: "Eric W. Biederman" <ebiederm@xmission.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
31 lines
858 B
C
31 lines
858 B
C
/* SPDX-License-Identifier: GPL-2.0-only */
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#ifndef LINUX_KALLSYMS_INTERNAL_H_
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#define LINUX_KALLSYMS_INTERNAL_H_
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#include <linux/types.h>
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/*
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* These will be re-linked against their real values
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* during the second link stage.
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*/
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extern const unsigned long kallsyms_addresses[] __weak;
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extern const int kallsyms_offsets[] __weak;
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extern const u8 kallsyms_names[] __weak;
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/*
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* Tell the compiler that the count isn't in the small data section if the arch
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* has one (eg: FRV).
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*/
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extern const unsigned int kallsyms_num_syms
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__section(".rodata") __attribute__((weak));
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extern const unsigned long kallsyms_relative_base
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__section(".rodata") __attribute__((weak));
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extern const char kallsyms_token_table[] __weak;
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extern const u16 kallsyms_token_index[] __weak;
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extern const unsigned int kallsyms_markers[] __weak;
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#endif // LINUX_KALLSYMS_INTERNAL_H_
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