46f7c07ad2b897
parent 3041e47e8b08d51188b2cbdbd9c1e6f43314c8f1
author Andreas Gruenbacher <agruen@suse.de> 1147199850 +0200
committer Sam Ravnborg <sam@mars.ravnborg.org> 1151185366 +0200

kbuild: support for %.symtypes files

Here is a patch that adds a new -T option to genksyms for generating dumps of
the type definition that makes up the symbol version hashes. This allows to
trace modversion changes back to what caused them. The dump format is the
name of the type defined, followed by its definition (which is almost C):

  s#list_head struct list_head { s#list_head * next , * prev ; }

The s#, u#, e#, and t# prefixes stand for struct, union, enum, and typedef.
The exported symbols do not define types, and thus do not have an x# prefix:

  nfs4_acl_get_whotype int nfs4_acl_get_whotype ( char * , t#u32 )

The symbol type defintion of a single file can be generated with:

  make fs/jbd/journal.symtypes

If KBUILD_SYMTYPES is defined, all the *.symtypes of all object files that
export symbols are generated.

The single *.symtypes files can be combined into a single file after a kernel
build with a script like the following:

for f in $(find -name '*.symtypes' | sort); do
    f=${f#./}
    echo "/* ${f%.symtypes}.o */"
    cat $f
    echo
done \
| sed -e '\:UNKNOWN:d' \
      -e 's:[,;] }:}:g' \
      -e 's:\([[({]\) :\1:g' \
      -e 's: \([])},;]\):\1:g' \
      -e 's: $::' \
      $f \
| awk '
/^.#/   { if (defined[$1] == $0) {
            print $1
            next
          }
          defined[$1] = $0
        }
        { print }
'

When the kernel ABI changes, diffing individual *.symtype files, or the
combined files, against each other will show which symbol changes caused the
ABI changes. This can save a tremendous amount of time.

Dump the types that make up modversions

Signed-off-by: Andreas Gruenbacher <agruen@suse.de>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
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