Documentation/kbuild: Document storage of symbol information

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>

diff --git a/Documentation/kbuild/modules.rst b/Documentation/kbuild/modules.rst
index 101de236cd0c9abe1f5684d80063ff3f9a7fc673..a42f00d8cb90ff6ee44677c1278287ef25a84c89 100644 (file)
--- a/Documentation/kbuild/modules.rst
+++ b/Documentation/kbuild/modules.rst
@@ -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
 ----------------------------