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Documentation/kbuild: Document storage of symbol information

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Document where exported and imported symbols are kept, format options,
and limitations.

Signed-off-by: Matthew Maurer <mmaurer@google.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
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Matthew Maurer 2025-01-03 17:37:04 +00:00 committed by Masahiro Yamada
parent e8639b7ef0
commit 272f8a6d62
1 changed files with 20 additions and 0 deletions
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Documentation/kbuild/modules.rst
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@ -423,6 +423,26 @@ Symbols From the Kernel (vmlinux + modules)
1) It lists all exported symbols from vmlinux and all modules.
2) It lists the CRC if CONFIG_MODVERSIONS is enabled.
Version Information Formats
---------------------------
Exported symbols have information stored in __ksymtab or __ksymtab_gpl
sections. Symbol names and namespaces are stored in __ksymtab_strings,
using a format similar to the string table used for ELF. If
CONFIG_MODVERSIONS is enabled, the CRCs corresponding to exported
symbols will be added to the __kcrctab or __kcrctab_gpl.
If CONFIG_BASIC_MODVERSIONS is enabled (default with
CONFIG_MODVERSIONS), imported symbols will have their symbol name and
CRC stored in the __versions section of the importing module. This
mode only supports symbols of length up to 64 bytes.
If CONFIG_EXTENDED_MODVERSIONS is enabled (required to enable both
CONFIG_MODVERSIONS and CONFIG_RUST at the same time), imported symbols
will have their symbol name recorded in the __version_ext_names
section as a series of concatenated, null-terminated strings. CRCs for
these symbols will be recorded in the __version_ext_crcs section.
Symbols and External Modules
----------------------------