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kallsyms: move declarations to internal header 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>
2022-05-17 00:05:07 +00:00
/* SPDX-License-Identifier: GPL-2.0-only */
#ifndef LINUX_KALLSYMS_INTERNAL_H_
#define LINUX_KALLSYMS_INTERNAL_H_
#include <linux/types.h>
/*
kallsyms: Avoid weak references for kallsyms symbols kallsyms is a directory of all the symbols in the vmlinux binary, and so creating it is somewhat of a chicken-and-egg problem, as its non-zero size affects the layout of the binary, and therefore the values of the symbols. For this reason, the kernel is linked more than once, and the first pass does not include any kallsyms data at all. For the linker to accept this, the symbol declarations describing the kallsyms metadata are emitted as having weak linkage, so they can remain unsatisfied. During the subsequent passes, the weak references are satisfied by the kallsyms metadata that was constructed based on information gathered from the preceding passes. Weak references lead to somewhat worse codegen, because taking their address may need to produce NULL (if the reference was unsatisfied), and this is not usually supported by RIP or PC relative symbol references. Given that these references are ultimately always satisfied in the final link, let's drop the weak annotation, and instead, provide fallback definitions in the linker script that are only emitted if an unsatisfied reference exists. While at it, drop the FRV specific annotation that these symbols reside in .rodata - FRV is long gone. Tested-by: Nick Desaulniers <ndesaulniers@google.com> # Boot Reviewed-by: Nick Desaulniers <ndesaulniers@google.com> Reviewed-by: Kees Cook <keescook@chromium.org> Acked-by: Arnd Bergmann <arnd@arndb.de> Link: https://lkml.kernel.org/r/20230504174320.3930345-1-ardb%40kernel.org Signed-off-by: Ard Biesheuvel <ardb@kernel.org> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2024-04-15 16:20:43 +00:00
* These will be re-linked against their real values during the second link
* stage. Preliminary values must be provided in the linker script using the
* PROVIDE() directive so that the first link stage can complete successfully.
kallsyms: move declarations to internal header 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>
2022-05-17 00:05:07 +00:00
*/
kallsyms: Avoid weak references for kallsyms symbols kallsyms is a directory of all the symbols in the vmlinux binary, and so creating it is somewhat of a chicken-and-egg problem, as its non-zero size affects the layout of the binary, and therefore the values of the symbols. For this reason, the kernel is linked more than once, and the first pass does not include any kallsyms data at all. For the linker to accept this, the symbol declarations describing the kallsyms metadata are emitted as having weak linkage, so they can remain unsatisfied. During the subsequent passes, the weak references are satisfied by the kallsyms metadata that was constructed based on information gathered from the preceding passes. Weak references lead to somewhat worse codegen, because taking their address may need to produce NULL (if the reference was unsatisfied), and this is not usually supported by RIP or PC relative symbol references. Given that these references are ultimately always satisfied in the final link, let's drop the weak annotation, and instead, provide fallback definitions in the linker script that are only emitted if an unsatisfied reference exists. While at it, drop the FRV specific annotation that these symbols reside in .rodata - FRV is long gone. Tested-by: Nick Desaulniers <ndesaulniers@google.com> # Boot Reviewed-by: Nick Desaulniers <ndesaulniers@google.com> Reviewed-by: Kees Cook <keescook@chromium.org> Acked-by: Arnd Bergmann <arnd@arndb.de> Link: https://lkml.kernel.org/r/20230504174320.3930345-1-ardb%40kernel.org Signed-off-by: Ard Biesheuvel <ardb@kernel.org> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2024-04-15 16:20:43 +00:00
extern const unsigned long kallsyms_addresses[];
extern const int kallsyms_offsets[];
extern const u8 kallsyms_names[];
kallsyms: move declarations to internal header 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>
2022-05-17 00:05:07 +00:00
kallsyms: Avoid weak references for kallsyms symbols kallsyms is a directory of all the symbols in the vmlinux binary, and so creating it is somewhat of a chicken-and-egg problem, as its non-zero size affects the layout of the binary, and therefore the values of the symbols. For this reason, the kernel is linked more than once, and the first pass does not include any kallsyms data at all. For the linker to accept this, the symbol declarations describing the kallsyms metadata are emitted as having weak linkage, so they can remain unsatisfied. During the subsequent passes, the weak references are satisfied by the kallsyms metadata that was constructed based on information gathered from the preceding passes. Weak references lead to somewhat worse codegen, because taking their address may need to produce NULL (if the reference was unsatisfied), and this is not usually supported by RIP or PC relative symbol references. Given that these references are ultimately always satisfied in the final link, let's drop the weak annotation, and instead, provide fallback definitions in the linker script that are only emitted if an unsatisfied reference exists. While at it, drop the FRV specific annotation that these symbols reside in .rodata - FRV is long gone. Tested-by: Nick Desaulniers <ndesaulniers@google.com> # Boot Reviewed-by: Nick Desaulniers <ndesaulniers@google.com> Reviewed-by: Kees Cook <keescook@chromium.org> Acked-by: Arnd Bergmann <arnd@arndb.de> Link: https://lkml.kernel.org/r/20230504174320.3930345-1-ardb%40kernel.org Signed-off-by: Ard Biesheuvel <ardb@kernel.org> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2024-04-15 16:20:43 +00:00
extern const unsigned int kallsyms_num_syms;
extern const unsigned long kallsyms_relative_base;
kallsyms: move declarations to internal header 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>
2022-05-17 00:05:07 +00:00
kallsyms: Avoid weak references for kallsyms symbols kallsyms is a directory of all the symbols in the vmlinux binary, and so creating it is somewhat of a chicken-and-egg problem, as its non-zero size affects the layout of the binary, and therefore the values of the symbols. For this reason, the kernel is linked more than once, and the first pass does not include any kallsyms data at all. For the linker to accept this, the symbol declarations describing the kallsyms metadata are emitted as having weak linkage, so they can remain unsatisfied. During the subsequent passes, the weak references are satisfied by the kallsyms metadata that was constructed based on information gathered from the preceding passes. Weak references lead to somewhat worse codegen, because taking their address may need to produce NULL (if the reference was unsatisfied), and this is not usually supported by RIP or PC relative symbol references. Given that these references are ultimately always satisfied in the final link, let's drop the weak annotation, and instead, provide fallback definitions in the linker script that are only emitted if an unsatisfied reference exists. While at it, drop the FRV specific annotation that these symbols reside in .rodata - FRV is long gone. Tested-by: Nick Desaulniers <ndesaulniers@google.com> # Boot Reviewed-by: Nick Desaulniers <ndesaulniers@google.com> Reviewed-by: Kees Cook <keescook@chromium.org> Acked-by: Arnd Bergmann <arnd@arndb.de> Link: https://lkml.kernel.org/r/20230504174320.3930345-1-ardb%40kernel.org Signed-off-by: Ard Biesheuvel <ardb@kernel.org> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2024-04-15 16:20:43 +00:00
extern const char kallsyms_token_table[];
extern const u16 kallsyms_token_index[];
kallsyms: move declarations to internal header 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>
2022-05-17 00:05:07 +00:00
kallsyms: Avoid weak references for kallsyms symbols kallsyms is a directory of all the symbols in the vmlinux binary, and so creating it is somewhat of a chicken-and-egg problem, as its non-zero size affects the layout of the binary, and therefore the values of the symbols. For this reason, the kernel is linked more than once, and the first pass does not include any kallsyms data at all. For the linker to accept this, the symbol declarations describing the kallsyms metadata are emitted as having weak linkage, so they can remain unsatisfied. During the subsequent passes, the weak references are satisfied by the kallsyms metadata that was constructed based on information gathered from the preceding passes. Weak references lead to somewhat worse codegen, because taking their address may need to produce NULL (if the reference was unsatisfied), and this is not usually supported by RIP or PC relative symbol references. Given that these references are ultimately always satisfied in the final link, let's drop the weak annotation, and instead, provide fallback definitions in the linker script that are only emitted if an unsatisfied reference exists. While at it, drop the FRV specific annotation that these symbols reside in .rodata - FRV is long gone. Tested-by: Nick Desaulniers <ndesaulniers@google.com> # Boot Reviewed-by: Nick Desaulniers <ndesaulniers@google.com> Reviewed-by: Kees Cook <keescook@chromium.org> Acked-by: Arnd Bergmann <arnd@arndb.de> Link: https://lkml.kernel.org/r/20230504174320.3930345-1-ardb%40kernel.org Signed-off-by: Ard Biesheuvel <ardb@kernel.org> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2024-04-15 16:20:43 +00:00
extern const unsigned int kallsyms_markers[];
extern const u8 kallsyms_seqs_of_names[];
kallsyms: move declarations to internal header 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>
2022-05-17 00:05:07 +00:00
#endif // LINUX_KALLSYMS_INTERNAL_H_
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